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THE JOURNAL 



OF 



PHYSICAL CHEMISTRY 



H. T. Barnes 

S. L. BiGELOW 

F. K. Cameron 
E. C. Frankun 



Editor 
Wilder D. Bancroft 

Associate Editors 
G. A. HULETT 
L. Kahlenberg 
W. L. Miller 
J. L. R. Morgan 



T. B. Robertson 

H. SCHLUNDT 
E. P. SCHOCH 

J. W. Walker 



VOLUME XV 



• . • 

• • » 



ITHACA, N. Y. 
The Editor 

LEIPZIG: Bbrnh. Liebisch (K. F. Koehler's Anliquariutn) 
for the continent of Europe 



J9n 



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l64S^ 



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CONTENTS OF VOLUME XV 
I JANUARY 

The Influence of Organic Liquids upon the In- 
teraction of Hydrogen Sulphide and Sul- 
phur Dioxide, .... 

On the Transference and Transformation of 
Energy with Applications to the Theory 
of Solutions, .... 

Crystallization through Membranes 

The Specific Heat of Carbon Tetrachloride and 
its Saturated Vapor, 

The Solubility of Lime in Aqueous Solutions of 
Sugar and Glycerol, 

The Use of the Dewar Flask in Measurements 
of Heats of Neutralization, 

2. FEBRUARY 

Charles Baldwin Gates, The Replacement of Metals in Non-aqueous 

Liquids and the Solubility of Metals in 
Oleic Acid, .... 



David Ellein, 
M. M. Garver, 



James H. Walton, Jr., 
J. W. Mills and Duncan 
MacRae, 

F. K. Cameron and H. 
£. Patten, 

J. Howard Mathews and 
A. F. 0. Germann, 

New Books, 



W. L. Perdue and G. A. 
Hulett, 

W. L. Perdue and G. A. 
Hulett, 

T. Brailsford Robert- 
son, 

T. Brailsford Robert- 
son, 



New Books, 

H. W. GUlett, 
New Books, 

Wilder D. Bancroft, 



An Exact Electrolytic Method for Determining 
Metals, ..... 

Cadmium Sulphate and the Atomic Weight of 
Cadmium ..... 



20 

45 



54 



67 



73 
83 



97 



147 



155 



Studies in the Electrochemistry of the Pro- 
teins, IV. The Dissociation in Solutions 
of the Globulinates of the Alkaline Earths, 166 



Studies in the Electrochemistry of the Pro- 
teins, V. The Electrochemical Equivalent 
of Casein and its Relations to the Combin- 
ing and Molecular Weights of Casein, 



3. MARCH 

Temperature Measurements in an Experimental 
Carborundum Furnace, 

4. APRIL 

The Photographic Plate V, . . . 



179 
197 



213 
306 

313 



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11 

S. L. Bigelow and F. 
W. Hunter, 

R. C. Palmer and Her- 
man Schlundt, 

T. Brailsford Robert- 
son, 



New Books, 
J. E. Mills, 

Frank K. Cameron and 
W.J. McCaughey, 

Louis Kahlenberg and 
David Klein, 

William Buell Meldrum, 

G. A. Perley, 
New Books, 

Edward C. Franklin, 
T. Brailsford Robert- 
son, 



Wilder D. Bancroft, 
James M. Bell, 

Alonzo Simpson Mc- 
Daniel, 

New Books, 

M. M. Garver, 

H. E. Patten, 

F. E. Bartcll, 

Edward C. Franklin, 



Contents of Volume XV 



The Function of the Walls in Capillary Phe- 
nomena, ..... 

The Dielectric Constants of Some Liquid Hyd- 
rides, ..... 

Studies in the Electrochemistry of the Pro- 
teins, VI. The Conductivities of Solutions 
of the Caseinates of Potassium, and of the 
Alkaline Earths in Mixtures of Water and 
Alcohol, ..... 

5. MAY 
Molecular Attracti(m, I X. Molecular Attrac 
tion and the Law of Gravitation, 

Apatite and Spodiosite, 

On the Interaction of Sodium and Mercury, 

The Influence of Alkyl Substituents on the 

Electrical Conductivity of Malonic Acids, 
The Treatment of Sulphatcd Storage Cells, 

6. JUNE 
Potassium Ammono Plumbiie, . 

Studies in the Electrochemistry of the Pro- 
teins, VII. The Mode of Formation and 
Ionization of the Compounds of Proteins 
with Inorganic Acids and Bases, 

The Photographic Plate, VI, 

The Composition of Solid Phases in Four 
Component Systems, 

The Absorption of Hydrocarbon Oases by Non 
aqueous Liquids, 



7. OCTOBER 

On the Laws of Energy and the Physical Sig- 
nificance of Entropy, 

Effect of Soluble Salts on the A])sor])tion of 
Phosphates by Soils, 

The Permeability of Porcelain and Co])per Fcrro- 
cyanide Membranes, 

The Electrical Conductivity of Liquid Sulphur 
Dioxide Solutions at —35. 5°, — ^0°. — i"°. 
o°and +10°, .... 



367 
381 



387 
414 



417 

4^S 

471 

474 
489 
508 

509 



5-^1 
55 » 

580 



587 
611 



<^i3 

^S9 
675 



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Contents of Volume XV 



111 



8. NOVEMBER 

A Contribution to the Subject of the Hygro- 
scopic Moisture of Soils, 
The Electrolytic Corrosion of Some Metals, 



New Books, 

Chas. B. Lipman and 
Leslie T. Sharp, 

G. R. White, 
New Books, 

9. DECEMBER 
Ralph Cuthbert Snow- 
don, The Electrolytic Reduction of Nitrobenzene, 
Louisa Stone Stevenson, The Fluorescence of Anthracene, 
Philip Blackman, A New and Simple Method for Comparing 

Molecular Weights, I, 
Philip Blackman, A New Method for Determining Vapor Densities, 

IX, 
Philip Blackman, A Simple Method for Vapor Density Determina 

tions, XI, .... 
Philip Blackman, The Thermodynamics of Compressibility and Ex 

pansion, I, . 
New Books, 
Name Index, 
Index to New Books, 
Subject Index, 



698 



709 
723 
793 



797 
845 

866 
869 
871 

874 

877 
883 
885 
887 



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THE INFLUENCE OF ORGANIC LIQUIDS UPON THE 

INTERACTION OF HYDROGEN SULPHIDE AND 

SULPHUR DIOXIDE 



BY DAVID KLEIN 

Introduction 

Numerous examples of the influence of slight amounts of 
water upon chemical changes of various kinds are on record. 
But similar studies of the effect of liquids other than water 
are few and fragmentary. So it has seemed that a systematic 
investigation of the influence of organic liquids upon a gaseous 
system, incapable of decomposition in the dry state, would be 
of considerable value in gaining an understanding of the 
mechanism of chemical change, as well as in formulating a 
theory of solutions. 

Because of its abundance, and its great solvent power 
(for some classes of substances), water is regarded by certain 
chemists as having exceptional properties. ** Water is a 
substance whose presence in at least minute amounts seems 
to be essential to the occurrence of most chemical reactions. 
Moreover, its method of action is probably unique, consisting 
either in a hydration or electrolytic dissociation of the re- 
acting substances. It is therefore not inappropriate that it 
alone constitutes a type of catalytic agent.'** However, the 
results of the present investigation clearly show, at least as 
far as one property of water is concerned, namely its ability 
to accelerate chemical changes, that other liquids have that 
characteristic in a no less marked degree. 

The action between hydrogen sulphide and sulphur 
dioxide was selected as suitable for an experimental investiga- 
tion. It is difficult to state who first studied this reaction; 
certainly, it was known a century and a quarter ago. In 
1812 Cluzel' discovered that the gaseous system would not be 
decomposed unless moisture is present. The gases after being 

* Noyes and Sammet: Jour. Am. Chem. Soc, 24, 498 (1902). 
'Cluzel: Ann. Chim. Phys., 84, 162 (1812). 



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2 David Klein 

dried by fused calcium chloride were mixed in varying pro- 
portions in a glass container over mercury. Depending upon 
the degree of desiccation, the period of no action varied from 
fifteen minutes to five hotu*s. Experiments conducted in the 
absence of sunlight, showed no difference in action, when 
compared with similar tests, performed in sunlight. Cluzel 
summarizes his work as follows: ''Qiie Vhydrogkne sulfur 6 
et Vacide sulfur eux peuvent r ester assez longtemps en contact 
sans se decomposer, quand ils sont bien sees et quHl est trks- 
probable qu'ils ne se dicomposeraient pas si on les faisait arriver 
trks-secs dans un appareil ou^ il ny eUt aucun corps qui exerg&t 
une affinity sur le sou f re/* 

Then, in 1868, Schmidt* published a note on the influence 
of moisture on the gaseous mixture: '' Nachdem ich die 
Angabe VogeVs (Gmelin, Handb, 643) , dass gewohnliche 
Schwefelsaiire von Schwefelwasserstoff zersetzt wird, bestdtigt, 
beobachtete ich die Bildung von schwefliger Saiire bei Ubergiessen 
fein gepulverier oder gefdllter Schwefelmetalle mit concentrirter 
Schwefelsaiire J so zwar, dass rauchende keinen oder nur ein 
Minimum von Schwefelwasserstoff auftreten Idsst. Die 
fraglichen beiden Agentien vollkommen trocken gemischt, 
reagiren nicht auf einander; fiihrt man in das Gefdss einen 
benetzten Glasstab, so zeichnen sich die beruhrten Stellen 
momentan durch ausgeschiedenen Schwefel und die Pentathion- 
saiire tritt auf.** 

Apparatus and Method 

The experimental parts of this investigation may be 
conveniently divided among several general heads; (i) the 
preparation, drying and storing of the pure gases, (2) the 
devising of a suitable reaction vessel, (3) the preparation of 
pure dry organic liquids. 

Hydrogen sulphide. — After many unsatisfactory trials 

» W. Schmidt: Zeit. fiir Chemie (Beilstein-Fittig). 11, 50 (1868). The 
University of Wisconsin does not possess this periodical; but a copy was kindly 
loaned by the Mass. Inst, of Technology, for which I herewith wish to express 
my gratitude. Since the article in question is not readily accessible, it was 
thought worth while to reprint it in full. 



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Action of Hydrogen Sulphide on Sulphur Dioxide. 3 

with various substances for the preparation of pure hydrogen 
sulphide, such as calcium sulphide and antimony sulphide, 
it was found that the action of hydrochloric acid upon zinc 
sulphide would yield a very pure gas in quantities that were 
readily controlled. The means for drying and storing the gas 
are represented in Fig. i. The generator A was constructed 
out of a dropping funnel and a Liebig condenser jacket. It 
was filled in the inverted position through a, which was then 
sealed off. B is an ordinary wash bottle, containing pure 
water, to free the gas from any hydrochloric acid vapors. 
C, a large calcium chloride tower, was constructed from a 




Liebig condenser jacket. D is a large U-tube, made by 
bending a glass tube 4' long and ^/^^ in diameter. After 
being filled with phosphorus pentoxide, it was sealed to C at 
E. The dried gas was stored in two 500 cc Drechsel wash 
bottles (F * G) containing some phosphorus pentoxide. Some 
connections were made by sealing the tubes together, while 
others consisted of heavy rubber tubing. The latter gave no 
trouble, but, if necessary, could be eliminated. 

The train was first exhausted by means of a water pump ; 
then filled with the gas, by allowing concentrated hydro- 
chloric acid to flow down from the dropping funnel. The 



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David Klein 



exhaustion and refilling were repeated until the issuing gas 
was completely absorbed by a caustic potash solution. 

Sulphur dioxide, — For the preparation of this gas con- 
centrated hydrochloric add was allowed to act on pin-e sodium 
acid sulphite, contained in the generator A (Fig. 2). Addi- 




Fig. 2 

tional parts of the train were a wash bottle B containing pure 
water, to remove hydrochloric acid; two Wetzel bottles 
(C-D) capacity 500 cc; containing cone, sulphuric acid; a 
large U-tube E made by bending a glass tube 3' X •/a'', and 
filled with phosphorus pentoxide. It might be well to state 
at this point that all the phosphorus pentoxide used in these 
experiments was the ordinary variety, supplied either by 
Merck or Schuchardt. 

Reaction vessel. — This was made out of a condenser jacket 
(300 cc) and stop-cocks (the ordinary two-way variety). 
(A. Fig. 3). Branch c was connected with the sulphur 




Fig. 3 



dioxide generator; branch a likewise with the hydrogen 
sulphide train. Through b a current of air, dried by sul- 



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Action of Hydrogen Sulphide on Sulphur Dioxide. 5 

phuric acid and phosphorus pentoxide, was slowly aspirated 
by means of a water pump. The exit tube d was protected 
from the moisttwe of the pump E by a six-inch Schwartz tube, 
containing phosphorus pentoxide. A second similar guard 
bulb was attached to the Sprengel pump F; while a third one 
was connected with the open manometer B. At e is a ground 
glass joint, acciwately fitted to the vessel G, which served as 
the receptacle for the piwe organic liquid. The bulb was an 
ordinary 25 cc acetylization flask, to which was sealed a stop- 
cock. Coimection of the reaction chamber to the various 
parts of the apparatus was made with thick-walled rubber 
tubing, the ends of the glass tubing being pushed as close to- 
gether as possible. 

The purification of the organic liquids was carried out as 
follows : In the first place, the ptwest sample of the particular 
liquid that the laboratory afforded, was subjected to ordinary 
fractional distillation. The desired portion was collected in an 
eight-ounce bottle (commonly known as a specimen bottle) pro- 
vided with an accurately ground stopper. Previous to use, 
these bottles were thoroughly cleaned, rinsed with very pure 
distilled water, and dried in an air bath at 160° C for 3-5 
hours. They were kept in a desiccator containing phosphorus 
pentoxide. The appropriate drying agent was added to the 
liquid, with which it remained in contact, with frequent 
shaking, for varying periods of time. 

After each experiment the reaction vessel was coated 
with a film of sulphiu*. For the rapid and complete removal 
of this layer, fuming nitric acid was found very efiicient. 
After being thoroughly rinsed with distilled water, the ap- 
paratus was steamed out, the steam being evolved from water 
to which sulphuric acid and potassium bichromate were 
added. Steam is a very dehcate test for grease, since the 
latter supplies nuclei for the condensation of water vapor, 
thus causing drops to form on any unclean portion of the 
vessel. All visible moisture was removed by aspirating warm 
air through the apparatus. The stop-cocks and bores were 



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6 David Klein 

carefully wiped with a clean, fat-free cloth, after which they 
were thinly coated with a rubber composition lubricant. 

The lubricant is the one recommended by Travers.* It 
was used in all experiments, excepting a few trials with phos- 
phoric acid, made by exposing phosphorus pentoxide to the 
air. However, it was found that this substance would cause 
the gases to react, and was therefore discarded. 

When the reaction vessel was cleaned, dried and set in 
position, the catalytic liquid was subjected to a final distilla- 
tion. This was accomplished in the special apparatus, shown 
in Fig. 4. It consisted of a 150 cc distilling flask A to which 



Fig. 4 

was sealed a limb of a Schwartz tube. A condenser was also 
sealed to the flask. As a receiver B a 25 cc acetylization flask 
was used, so chosen that its groimd joint would fit very closely 
the small flask to be attached to the reaction chamber. To 
suspend a thermometer in the flask, a piece of fusible glass was 
bent so that the head could be inserted in the glass stopper, 
if held at an angle, but was too large to slip out if held verti- 
cally. From this hook a suitable thermometer was suspended 
by a platinum wire. 

The distilling apparatus was thoroughly dried by draw- 
ing through it a current of air, that had passed through cone, 
sulphuric acid and phosphorus pentoxide. Tubes of the latter 
material also prevented the access of any moisture from the 
pump D. After the air had thus passed for several hours at 
ordinary temperatures, the apparatus was highly heated with 
a free Bunsen flame. Dry air was continually aspirated 
through C, until room temperature was again restored. Then 
the stopper was quickly removed, the liquid poured in, and 



"Study of Gases." 



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Action of Hydrogen Sulphide on Sulphur Dioxide, 7 

distilled. After the condenser had been thoroughly moistened 
with the distilled liquid, the receiver was quickly replaced by 
the bulb which up to this time was kept in a desiccator over 
phosphorus pentoxide. When filled with the liquid, the bulb 
was very quickly detached and fitted with its own stopper, 
which was described before. 

The bulb was attached to the reaction vessel. A current 
of dry air at room temperature, was drawn through the ap- 
paratus for hours (varying from 6 to 20), after which the 
drying was continued, while the apparatus was being highly 
heated with a free Bunsen flame. This last operation was 
continued for an hour. Then the reaction vessel was evacuated 
as far as possible by means of a water pump. To reduce the 
pressure as completely as possible, the final exhaustion was 
effected with a good Sprengel pump. The pressure was noted 
on a closed manometer on the pump and also on an open 
manometer (B Fig. 3). To fill the vessel with the reacting 
gases in the proper proportion, sulphur dioxide was allowed 
to slowly enter until the pressure had risen to one-third the 
atmospheric pressure as read on the open manometer. The 
hydrogen sulphide was admitted, to make up the other two- 
thirds. All stop-cocks were closed, so that the mixture was 
contained in an apparatus entirely of glass, except for the 
lubricant on the stop-cocks. 

The mixture was allowed to remain an hour or more, to be 
sure that no action occurred spontaneously. Then by open- 
ing the stop-cocks to the catalyzer bulb (G Fig. 3) and gently 
warming the latter, enough liquid (never more than a few cc) 
could be admitted into the reaction chamber. The detailed 
observations will be given below. 

Results. — ^Since the procedure in nearly all cases was 
essentially that given above, it is not necessary to repeat it in 
discussing the various liquids. 

Benzol. — Some of Kahlbaum's recrystallized thiophene- 
free product was dried with phosphorus pentoxide for four 
months. In the first trial there was no action in three hours. 
A few drops of water were poured into the reaction vessel by 



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8 David Klein 

quickly raising and replacing the catalyzer bulb. There was 
immediate action. Subsequently on opening tap d (Fig. 3) 
under water, the Hquid completely filled the vessel. In fact, 
this check upon the purity of the mixture was performed after 
each experiment. 

The experiment was repeated with a new, freshly dis- 
tilled sample of benzol, with the result that there was no 
action within an hour and thirty minutes.* 

Carbon tetrachloride. — ^The liquid was dried with phos- 
phorus pentoxide for two weeks. Not the slightest sign of 
action within an hour. Repeated experiment, with a freshly 
distilled sample of the same liquid, with similar results. 

Chloroform, — ^This was dried for three days with phos- 
phorus pentoxide. It produced no action within an hour. 
A second trial gave the same result. 

Ethyl alcohol, — Ordinary alcohol was treated with calcium 
carbide, by boiling under a reflux condenser. The acetylene 
was removed by distilling tmder diminished pressure, and 
then by treating with bromine. The product was twice 
fractionated after adding sodium. As soon as the first drop 
of this liquid entered the reaction vessel, there was intense 
action. 

A repetition of the experiment with a sample of this 
alcohol, after a third distillation with sodium, gave a similar 
result. After this experiment a very slight odor of acetylene 
was noticeable in the alcohol, so that the results were not 
conclusive, although, as will appear later, the action must be 
attributed to the alcohol. 

A new sample was prepared as follows : Ordinary alcohol 
was boiled under a reflux condenser with pure lime for six 
hours; then distilled. It was similarly treated with barium 
oxide. ^ A final distillation was made after treatment with 



^ It must not be inferred that action occurred after this period. Here 
and elsewhere in this paper, where a similar expression occurs, it means that the 
experiment was discontinued at this point. 

' I have found barium oxide a most efficient drying agent. The easiest 
way to prepare a suitable product was to heat anhydrous barium peroxide to 



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Action of Hydrogen Sulphide on Sulphur Dioxide, 9 

sodium. As in the two previous trials, the first drop caused 
instantaneous action. 

Amylene. — ^A Schuchardt preparation was dried for three 
days over fused calcium chloride. The portion boiling be- 
tween 4o°-4i ® was employed. There was no visible action in 
over an hour. A drop of water caused an immediate de- 
position of sulphur. 

Acetone. — Merck's C. P. product was dried for four days 
with anhydrous sodium sulphate, before redistilling. Im- 
mediate action occurred as soon as the first drop entered the 
apparatus. 

Repeated with a portion of the acetone that had remained 
in contact with the drying agent for two days longer. Similar 
results were obtained as in the preceding trial. 

A third experiment was performed with a sample of 
Kahlbaum's acetone, that had been standing over fused 
calcium chloride for seven weeks. As in the other trials, the 
reaction began immediately. 

Ether, — ^The material was obtained from Professor 
Koelker, who had rendered it absolute from the commercial 
variety by treatment with calcium chloride and then with 
sodium. It was further dried over sodium and distilled from 
a fresh portion of that metal. The reaction was rather slow 
at first, but in less than two minutes it proceeded rapidly, 
due in part at least, to autocatalysis. 

The experiment was repeated after continued treatment 
with sodium, with similar results, as in the first trial. 

Methyl cyanide. — Merck's product was redistilled after 
being dried with fused calcium chloride for five days. After 
treatment with phosphorus pentoxide for four days, it was 
again distilled. Throughout the manipulations, the liquid 
boiled very constantly. For thirty-five minutes, the liquid 
caused no action. Then the reaction vessel became coated 
with a light yellow deposit. 



redness for an hour and then cool the product in a desiccator over phosphorus 
pentoxide. The mass was quickly pulverized and sealed in small portions in 
test tubes. 



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lo David Klein 

Ethyl disulphide, — ^The sample was a Schuchardt pre- 
paration. It was a yellow, oily liquid with a very disagree- 
able odor. No attempt was made at purification. The 
liquid was simply poured into the dried catalyzer bulb. Even 
after an hoiu-'s contact, there was not the slightest sign of 
action. A few drops of water produced immediate reaction. 
After several hours a large portion of the sulphur had dis- 
solved in the ethyl disulphide. 

Carbon bisulphide, — Ordinary carbon bisulphide was 
purified by shaking for hours with mercury; then decanting 
and shaking with potassium permanganate. It was again 
decanted, and after further treatment with mercury, it was 
redistilled. In twenty-five minutes there was no visible 
change. Then the glass in the T tube around the stop-cocks 
became coated with sulphur, although the liquid remained 
perfectly colorless and transparent. Of course, the action 
finally continued to completion. 

The above experiment was repeated, after the carbon 
bisulphide had been further shaken with merciuy. The same 
phenomena were noted as in the previous trial. Diu-ing the 
first twenty-one minutes there was no action ; then a distinct 
clouding of the T tube occurred, but the liquid remained 
clear. 

A third trial with some carbon bisulphide that had been 
in contact with mercury for six months, gave no action in an 
hour and ten minutes. After that, the same clouding of the 
T tube was observed, while the liquid remained clear. 

From these experiments it was evident that the lubricant* 
was a disturbing factor. To eliminate this source of trouble, a 
reaction chamber was constructed, similar to the one used in 
all other cases with the exception that no stop-cocks were 
used. Instead the tubes were constricted in order to seal 
them off. 

The catalyzer was contained in a little glass bulb, which 
was placed in the apparatus before sealing on the T tube. 
The obtaining of the liquid was necessarily different from the 
usual method. A receiver was devised, consisting of a large 



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Action of Hydrogen Sulphide on Sulphur Dioxide. 1 1 

bulb and a small glass tube, each sealed to a branch of a T 
tube. The third branch was sealed to a large adapter, which 
fitted over a two-hole stopper, to accommodate the con- 
denser tube and a guard tube of phosphorus pentoxide. The 
condenser was pushed down into the adapter as far as possible, 
to avoid contact of the carbon bisulphide fumes with the 
rubber stopper. The receiver was packed in an ice-salt 
mixture. The idea of the peculiarly shaped receiver was that 
the distillate could first be collected in the large bulb, but 
when the desired fraction was obtained, it could be diverted 
into the small tube by slightly ttuning the receiver. When 
enough of the liquid was obtained, the small tube was sealed off. 

As to the drying and filling of the apparatus, the manipula- 
tion was the same as in the other cases. After admitting the 
sulphur dioxide, the tube connecting the reaction vessel with 
the sulphur dioxide train was sealed off. In like manner the 
other tubes were sealed. A very slight deposition of sulphur 
occurred when the tube leading to the hydrogen sulphide 
train was sealed; but there was no visible increase in this 
deposit in forty-five minutes, probably because of slowness of 
diffusion in so small a tube. 

The bulb containing the carbon bisulphide was broken by 
shaking the apparatus. There was no visible action in an 
hour and five minutes. Upon the supposition that the carbon 
bisulphide might have dissolved the sulphur as fast as it 
formed, the end of the apparatus was broken under mercury. 
There was no appreciable rise. Upon the admission of a few 
drops of water, immediate action ensued. 

Ethyl chloride, — The material was the usual liquid em- 
ployed for anaesthesia. It was contained in a sealed glass 
tube, which was broken and the contents were rapidly poured 
into the catalyzer container. A large portion of the liquid 
vaporized, but enough was secured for a fair trial. After 
forty-five minutes of contact, the liquid seemed not at all 
affected. A little more of it was forced into the reaction 
vessel, whereupon the pressure became so great as to violently 
force out the ground joint and break it. 



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12 David Klein 

Benzoyl chloride. — ^A fresh unopened bottle of Kahl- 
baum's make was used as the catalyzer, without any special 
purification. The liquid was simply poured into the dried 
catalyzer container. There was no action in forty-five 
minutes. Water caused an immediate deposition of sulphur. 

The experiment was repeated with the same liquid. 
There was no action in three and one-half hours. 

Methyl benzoate. — ^A Schuchardt preparation was dried 
over fused calcium chloride for four days and then distilled 
under diminished pressure. For the first twenty-five minutes 
there was no action; then sulphiw was rapidly deposited. 

Acetyl chloride, — ^An unopened bottle of Merck's product 
was used without any attempt at purification. There was no 
reaction in two hours and twenty minutes. Water caused an 
immediate precipitation of sulphur. 

Benzaldehyde. — ^A Schuchardt preparation was dried for 
four days over fused calcium chloride, after which it was dis- 
tilled in a current of carbon dioxide under diminished pressure. 
Immediately after the admission of the catalyzer it assumed 
a greenish color, then a yellow one, and in a few minutes, 
sulphur was deposited. 

Carvone. — ^This compound is of special interest, since it 
forms a definite crystalline compound with hydrogen sulphide. 
The material was labelled ** Chemically Pure Carvol" 
Schimmel & Company. The liquid was dried over anhydrous 
copper sulphate for three days. The portion boiling between 
222^-224° was used. It had a very slight yellow tinge. There 
was instantaneous action as soon as the liquid entered the 
reaction chamber. 

Benzyl cyanide. — ^A Schuchardt specimen was dried over 
anhydrous copper sulphate for four days. In less than two 
minutes, after it was admitted into the reaction vessel, there 
was formed a distinct yellow deposit. 

Propyl acetate. — ^A Schuchardt sample had been standing 
for years over fused calcium chloride. Reaction ensued as 
soon as the liquid entered the reaction vessel. 

Amyl alcohol. — ^A redistilled Kahlbaum preparation was 



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Action of Hydrogen Sulphide on Sulphur Dioxide. 13 

dried over calcium chloride for two days and over anhydrous 
copper sulphate for six days. It boiled very constantly. 
There was instantaneous action when the liquid entered the 
catalyzer vessel. 

The experiment was repeated with a diflferent sample of 
Kahlbaum's make, that was refractionated and then dried 
over barium oxide* for eight days. The barium oxide showed 
extremely little hydration, a state that was easy to detect, 
inasmuch as the anhydrous oxide was gray, while the hydrate 
was a pure white. As in the preceding trial, there was an 
instantaneous deposition of sulphur. The next morning many 
monoclinic sulphur crystals were noted in the amyl alcohol. 
This phenomenon is not anomalous, as other cases are on 
record of sulphtu- crystallizing in the monoclinic system at 
ordinary temperatures. 

Propionitrile. — A good sample was dried for eight days 
over barium oxide The drying material seemed imaffected. 
For the first seven minutes, after introducing the liquid, there 
was no visible action. Then the liquid became cloudy. 

Isobutyl alcohol, — A redistilled Kahlbaum product was 
dried for five days over barium oxide. It distilled quite 
constantly. The liquid caused immediate, vigorous action. 
The experiment was repeated, using the above sample of the 
alcohol after it had remained over barium oxide for three 
days longer, and had then been treated with sodium. The 
boiling point was imchanged. Reaction proceeded exactly 
as in the previous trial. 

Isobutyl acetate, — A redistilled Schuchardt preparation 
was dried over barium oxide for two weeks. For the first six 
minutes, after entering the reaction vessel the liquid re- 
mained transparent, then it became clouded, and soon a dense 
deposit of sulphur was formed. 

Nitrobenzene, — ^A Schuchardt product was redistilled. It 
caused no action in an hour and forty-five minutes. Water 
produced an instantaneous precipitation. 

Valeronitrile. — A good sample was refractionated; then 
dried for ten days over anhydrous copper sulphate and for two 



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14 



David Klein 



days over barium oxide. For the first fifteen minutes after 
admitting the liquid, there was no action. Then the liquid 
became cloudy. 

Methyl ethyl ketone. — A previously unopened bottle of 
Schuchardt's make was dried for two days over barium oxide. 
In less than two minutes after entering the reaction vessel, the 
liquid clouded. 

Table i 



Action 



] Dielec- 
tric 
constant 



Associa- 
tion 
factor 



Water 

Ethyl alcohol 

Isobutyl alcohol 

Isoamyl alcohol 

Acetone 

Methyl ethyl ketone 

Ace tonit rile 

Propionitrile 

Valeronitrile 

Benzyl cyanide 

Methyl benzoate 

Propyl acetate 

Isobutvl acetate 

Ether ' 

Benzaldehyde 

Carvone 

Carbon bisulphide 

Ethyl disulphide 

Benzol 

Amylene 

Chloroform 

Nitrobenzene 

Acetyl chloride 

Benzoyl chloride 

Ethyl chloride 

Carbon tetrachloride 



H,0 

C2H5OH 

CjH^OH 

C^H^jOH 

CH3COCH, 

CHgCOCjHg 

CH,CN 

CjHjCN 

C«H,CN 

CeH.CHjCN 

C.H,COOCH, 

CHjCOOCjH, 

CHjCOOCiH, 

(C,H,),0 

C,H,CHO 

(C2H5),S2 

CcHe 

CHCI3 

C,H,N03 

CH3COCI 

CeH.COCl 

C^H.Cl 

ecu 



immediate 



less than two min. 

after 15 min. 

after 7 min. 

after 15 min. 

after 2 min. 

after 25 min. 
j immediate 
! after 6 min. 
less than two min. 
immediate 

none 



80.0 
25.8 
20.0 
16.0 
25.0 
17.8 

36.4 
26.5 
17.4 
14.9 
6.58 

5.73 
5.26 

4.3 
17.7 

2.64 
7.2 
2.28 
2.20 
5.14 
36.45 
25.30 

6.29 
2.25 



3.60 
2.74 

1.95 
^.97 
1.26 

1. 15 
1.60 

1.77 



1.04 
0.97 

1.67 

I.OI 

0.96 
0.94 
0.93 
1.06 



I.OI 



Discussion 

The experiments have been reported in considerable 
detail, because the experience of the author with the work of 
other investigators along similar lines seemed to warrant it. 
Thus, the report of the classic work of Baker on ammonia 



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Action of Hydrogen Sulphide on Sulphur Dioxide. 15 

and hydrochloric acid contains so little of the necessary 
manipulating directions that a repetition of his experiment 
is an extremely difficult matter. 

Experimentation of the kind involved in this paper is 
always open to the general objection that the substances 
which induce action may not have been sufficiently dry or 
pure. Of course, this criticism is unanswerable. On the 
other hand, to maintain that the reacting substances were 
"absolutely dry,'' a phrase one frequently meets in the writ- 
ings of reputable chemists, would require proof that could not 
be furnished. The best that can be done is to give an accurate 
and detailed description of the apparatus and method, so that 
others may be able to repeat the work. 

The selection of methods employed in this investigation 
might be questioned by some who have had experience with 
reactions in moisture free media. For instance, the failure 
to use redistilled phosphorus pentoxide would seem to in- 
validate the results and conclusions. But arguments of this 
nature lose much of their force, when the fact is taken into 
consideration that both positive and negative results were 
obtained imder working conditions that were as similar as it 
was possible to make them. 

But another reason for confidence in the method lies in 
the fact that Baker has obtained similar results for ethyl 
alcohol and carbon tetrachloride. While no statement of his 
experimental methods has appeared, his results form the con- 
cluding paragraph of the Wilde lectiu-e for 1909.^ 

** Mr. J. C. Thomson has recently done some experiments 
for me on the hydrogen sulphide and sulphur dioxide mixture. 
He finds that liquid alcohol and Hquid sulphur dioxide (both 
having high specific inductive capacity) can bring about the 
decomposition in the mixture, while carbon tetrachloride, 
whose specific inductive capacity is low, is inert. Also, 
metallic aluminum and metallic mercury are apparently un- 
able to affect the change.'* 

While the dependence of chemical activity upon specific 

* Mem. and Proc. Manchester Lit. and Phil. Soc, Vol. 53, Part III. 



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1 6 David Klein 

inductive capacity is not expressly stated, it is certainly im- 
plied in Baker's statement. This is evidently the Nemst- 
Thomson rule in a slightly modified form. In view of the 
work of Kahlenberg and Lincoln/ Lincoln,' and Schlimdt,* 
which proved that the Nemst-Thomson rule did not even 
hold qualitatively, much less quantitatively, it is surprising 
that Baker should attribute the ability of a liquid to induce 
the reaction in question, to its specific inductive capactiy. 

In Table I there has been included the dielectric con- 
stants of the various liquids as given in the Landolt-Bom- 
stein Tabellen (1905). A prediction from the specific in- 
ductive capacity would lead us far from the truth, if it is 
maintained that any liquid possessing a high dielectric con- 
stant will produce a reaction. For nitrobenzene, with a 
value of 36.45 and acetyl chloride (25.3) have no effect on the 
gaseous mixture, whereas either should act even better than 
the alcohols. Or, if the "rule'' is modified to read **if any 
action occurs it will be caused by a liquid of high specific 
inductive capacity," then ether, which has a low value (4.3) 
forms an important exception. Nor do the esters employed 
have very high values; but the accuracy of the observations 
upon them in this investigation might be questioned, on the 
score of the ready decomposition of esters upon distillation. 
Moreover, it is not quite clear just where to draw the line be- 
tween a high and a low dielectric value. Cases in point are 
ethyl chloride (6.29) and ethyl disulphide (7.2). 

That association in the liquid state cannot be a deter- 
mining factor is clearly seen from the last column of the table. 
Most of these values are taken from the work of Ramsay and 
Shields. Liquids, such as ether and benzaldehyde, which are 
unassociated, and methyl ethyl ketone, which is slightly so 
if at all, are capable of affecting the mixture. Moreover, 
Baker found that liquid sulphur dioxide, also an unassociated 
liquid, will induce the change. 

* Jour. Phys. Chem., 3, 12 (1899). 

* Ibid.. 3, 457 (1899). 
' Ibid., 5, 157 (1901) 



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Action of Hydrogen Sulphide on Sulphur Dioxide. 17 

Of late years there have been included under the term 
** catalysis," many phenomena of apparently different char- 
acter. So the influence of traces of moisture or other sub- 
stances upon chemical reactions has been commonly ascribed 
to catalytic action. But this is no satisfactory explanation 
of the process, for it does not help us at all in gaining a clearer 
insight into the mechanism of chemical change. What 
essential difference is there between the action of ammonia 
and hydrochloric acid gases in the presence of a trace of 
moisture, and the neutralization of ammonium hydroxide by a 
solution of hydrochloric acid? In the latter case water is just 
as much a catalyzer as in the former. A satisfactory theory 
of catalysis will apply equally well as a theory of solutions and 
vice versa. 

From the study of reactions involving pure substances, 
there has arisen the idea that pure compounds cannot react 
except in the presence of a suitable additional reagent. The 
fimction of the solvent, according to the theory of electrolytic 
dissociation would be to separate the reacting substances into 
ions. However, Kahlenberg^ has demonstrated that in- 
stantaneous actions may proceed in non-ionizing media. 
Armstrong too, has always contended that the function of the 
solvent was not to dissociate but to associate; not to separate 
substances into ions, but to build them into complexes. The 
following quotation from one of his papers gives Armstrong's^ 
views on the subject. 

** Regarding the problem from the standpoint of Fara- 
day's electrolytic studies, and in view of the well-known ob- 
servations of De la Rive, Brereton Baker, Cowper, and Dixon, 
I assume, however, that no two molecules can interact directly; 
that in all cases of chemical interchange (including elec- 
trolysis) the necessary slope of potential can only be provided 
by the inclusion of the interacting substances in a triple or 
tripartite conducting system." 

The assumption that **no two molecules can interact 

* Jour. Phys. Cheni., 6, i (1902). 
2 Proc. Roy. Soc, 81, 83 (1908). 



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1 8 David Klein 

directly" is not warranted by the facts as we know them at 
present. Even in the case of the system, hydrogen sulphide 
and sulphur dioxide, Baker maintains that liquid sulphur 
dioxide can induce the reaction. 

But the question of the possibility of the direct inter- 
action of two molecules, in no way affects the idea that the 
solvent enters into combination with the solutes in cases of 
chemical action. On this basis, the liquid would form inter- 
mediate compoimds with the hydrogen sulphide and sulphur 
dioxide, which subsequently would rearrange to produce the 
final products. Now, as to the nature of these intermediate 
compounds, it is not necessary that they conform to the law of 
definite proportions. Slowly the idea of compounds in 
varying proportions is gaining favor. Nor is it to be expected 
that the intermediate compotmds be prepared step by step 
in the order of their occurrence during a reaction, for oiu" 
methods of isolation of substances are such as would contin- 
ually change the composition of the intermediate compoimds. 

It is therefore assumed, that the liquids which induced 
the reaction between hydrogen sulphide and sulphur dioxide, 
entered into a loose chemical combination with the gases; 
that in those cases, in which the organic liquid was tmable to 
initiate the chemical change, no such loose combination 
occurred. Many examples of the action of hydrogen sulphide 
or sulphur dioxide upon the organic liquids employed in this 
investigation are recorded in Beilstein. The contention is 
not made that these compounds are intermediary in the re- 
actions reported in this paper. They are inserted merely to 
emphasize the possibility of chemical combination between the 
gases and the liquid. Nitriles unite with hydrogen sulphide 
to form thioamides, CH3CN + H^S = CHCSNH^. Aldehydes 
exchange their oxygen for sulphur. C^jH^CHO -h H^S = 
CjHjCHS + H3O. Addition compounds may also form. 

/OH 
RCHO + H,S = RCH<^ 

Both aldehydes and ketones form addition products 
with salts of sulphurous acid, so it is likely that they would 



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Action of Hydrogen Sulphide on Sulphur Dioxide 19 

possess some attraction for sulphur dioxide. In fact, Boss- 
neck* has shown that sulphur dioxide enters into loose com- 
bination with acetone. Aldehydes are capable of similar 
action., Carvone yields a well defined crystalline product 
with hydrogen sulphide 2Cj,jHj^0.HjS. In the case of the 
alcohols, it is clearly the specific properties of the hydroxyl 
group that come into play. Whatever r61e is assigned to 
water, would apply equally well to the alcohols. 

Summary 
The main points contained in this paper are : 
I . An apparatus has been devised by means of which the 
effect of organic liquids upon the interaction of the gases, 
hydrogen sulphide and sulphur dioxide, could be determined. 
2. Water in its ability to accelerate chemical change is 
in no way exceptional or unique, since other liquids have been 
found that have the same power. Of those investigated, the 
following induce the reaction: ethyl, isobutyl and isoamyl 
alcohols; acetone; methyl ethyl ketone; acetonitrile; propio- 
nitrile; valeronitrile ; benzyl cyanide; methyl benzoate, propyl 
acetate; isobutyl acetate; ether; benzaldehyde and carvone. 

3. Some liquids are unable to accelerate the action. Of 
the liquids investigated, the following produced no action: 
carbon bisulphide; ethyl disulphide; benzol; amylene; chloro- 
form; carbon tetrachloride; ethyl chloride; acetyl chloride; 
benzoyl chloride and nitrobenzene. 

4. There is no rigorous parallelism between the specific 
inductive capacity or the association of the liquid solvent on 
the one hand and its ability to induce action on the other. 

5. A rational explanation of the phenomena lies in the 
view that chemical action occurs through the formation of 
intermediate compotmds. 

This investigation was carried out under the supervision of 
Professor Kahlenberg. I take this means of acknowledging my 
obligations for his interest in the work, and also for his generosity 
in placing at my disposal his private collection of chemicals. 

University of Wisconsin, 
June, jgio 

* D. R. Pat. 47093, Ber. chem. Ges. Berlin. 22, c; 303 (1889). 



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ON THE TRANSFERENCE AND TRANSFORMATIONS 

OF ENERGY WITH APPLICATIONS TO THE 

THEORY OF SOLUTIONS 



BY M. M. GARVBR 

To the practical, working chemist the conservation of 
mass, or matter, is the basis of all of his operations and de- 
ductions. He assumes as a matter of course, that if no ma- 
terial substance has entered or left his apparatus, he still has 
his original substance matter intact. And while in many- 
chemical processes he may not be able to comprehend the 
exact state of the material present, he nevertheless relies on his 
fundamental principle; the material is present in some form. 
Now those characteristics of conservation, so fundamental in 
the case of matter, must hold also in the case of energy, for it 
also is conserved, or is constant in amoimt so long as none 
enters or leaves a given inclosure or system of bodies. From 
the principle of conservation it follows of necessity that 
changes in amount of energy in a given system of bodies, or 
even in the different parts of the same system, can be due 
only to the transference of energy from one point to another. 

The object of the present paper is to attempt to correlate 
certain facts and to establish some criteria by means of which 
the direction of transfer of energy in certain cases may be rec- 
. ognized ; and from the direction of transfer, to deduce a rule 
that shall aid us in forming a judgment of changing energy- 
states in certain transformations and processes with a view to 
obtaining a better understanding of the energy relations of 
the phenomena we observe. 

In consequence of the transmission of energy by means of 
radiation and conduction through comipunicated motion, the 
study of energy transfer becomes more complicated and 
difficult than the transference of matter; but this difficulty 
furnishes no valid objection to making a careful analysis of the 
conditions and mechanism of transfer with a view to establish- 



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Transference and Transformations of Energy 21 

ing the general laws and underlying principles of energy 
transfers. 

While the principle of the conservation of energy may 
rightly be claimed to rest on an experimental basis, it is only 
partially expressed in the first law of thermodynamics, and 
its strongest proof is fomid in the fact that to assume its truth 
always leads to verifiable, or consistent, results. Hence if 
we can in a somewhat similar manner also extend and gen- 
eralize the second law of thermodynamics and find that we 
are led to results consistent with our limited experience we 
may then use such extension to aid us in those cases where our 
experience is insufficient to furnish a satisfactory basis for a 
conclusion. 

Suppose we assume as the natural law underlying the 
second law of thermodynamics, that: 

In an isolated system all spontaneous^ naturally occurring, 
processes are essentially equilibrating processes during which 
energy parses from points of higher to points of lower intensity 
of the type undergoing transfer, tending to produce a state in 
which each element of space gives out as much energy as it re- 
ceives, ^ 

The foregoing statement may be used as a basis for a more 
general entmciation of the second law of thermodynamics 
than that originally due to Clausius, as follows : 

All transformations into potential forms of energy, like 
the doing of mechanical work, take place during the transfer 
of some type of energy from points of higher to points of lower 
intensity of the type tmdergoing transfer. 

It should be observed that it will be necessary to dis- 
tinguish between states of equilibrium and steady states not 
in equiUbrium, like a battery circuit giving a steady current^ 
but in which a chemical transformation is taking place at a 
steady rate. 

The first most obvious objection to the above statement 

^ Since the above statement was formulated I have found a somewhat 
similar statement partially embodying the same idea in Professor Reeve's book 
on "Energy," p. 204. His point of view is otherwise, however, quite different. 



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22 M, M, Garver 

of the second law of energetics as a working rule is, that in 
addition to discontinuities in intensity during transformation 
of type, we have no general criterion of energy intensity except 
in the case of heat. Notwithstanding this objection we shall 
find that in another important class of cases a criterion as to 
direction of transfer can be established, while it is already 
established and accepted in the case of the most universal 
form of energy, heat. The notions, intensity and direction of 
transfer, may be made mutually to aid each other; we may 
establish either from a knowledge of the other when known. 
We may then use the information so gained in cases where 
there would otherwise be doubt. Thus we may in many 
instances gain important information as to intensity of energy 
from knowing the direction of transfer, the direction being 
determined from dynamical considerations more general than 
the special instance under observation. For instance, we 
know from dynamical principles that when mechanical work 
is done by the action of a force producing motion of its point of 
application, energy is transferred, or transmitted, in the 
direction of the resultant motion, only by a push, a com- 
pression, or a pressure, etc., while a pull, or a tension, trans- 
mits energy in a direction opposite to the direction of the 
motion produced by the tension. Example; the transmission 
of power by belting and the doing of work by means of cords 
and strings. 

Since fluids are not susceptible to appreciable tensions or 
pulls, but to pressures only, a spontaneous, natural, transfer 
of matter in the form of fluid indicates a transfer of energy in 
the direction of the transfer of material and from points of 
higher to points of lower intensity of energy. If the motion 
of the fluid is opposed by friction, heat is distributed along 
the path of motion. If the motion is resisted by attractive 
forces, work is done against the forces. By the first law of 
motion (Newton) the motion will continue until the energy 
due to the motion is absorbed in some manner and, in the 
absence of external eff'ects, the absorbing space gives out as 
much energy as it receives. We then have a state of equilib- 



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Transference and Transformations of Energy 23 

num. But the absorption and disappearance of energy of one 
t3rpe always necessarily involves the appearance of an equiv- 
alent amount of some other type. (The principle of con- 
servation.) Hence we can confirm the above generalized 
statement of the second law of energetics by the following 
reasoning : 

It is shown by Nemst* that instead of accepting the 
second law as limited by Clausius, it may be expressed more 
generally as follows : 

"All spontaneously occurring natural processes may, by 
appropriate devices, be utilized to do a finite amount of 
mechanical work.'* Accepting this as a fact of experience 
and combining it with the first statement that all spontaneously 
occurring processes in an isolated system are essentially 
equilibrating processes and we arrive at the conclusion that : 

In an isolated system, work or potential energy, appears 
only during the spontaneous transfer of energy from points of 
higher to points of lower intensity, accompanied by an equilibra- 
ting of the various energy intensities. Whether work be done 
or not depends upon whether or not the energy stream has had 
a portion, or, in the limit the whole, of the energy undergoing 
transfer diverted into the particular form called work, such as 
overcoming attractive forces as lifting a weight, etc. 

From the above stated point of view it is evident that the 
particular form of energy to us the most important, i, e,^ 
work, is but an incident, a mere episode, as it were, in the 
ceaseless ebb and flow of the energy tide. Every form, how- 
ever, of potential energy, such as mechanical work introduces 
a discontinuity in the intensity of the energy diverted from the 
course of its natural flow; for the work in disappearing may be 
transformed into energy of an intensity bearing no functional 
relation to the intensity of the energy from which the work was 
originally derived. But the law of conservation enables us to 
assert that notwithstanding the discontinuity in the intensity 
of energy in passing through the potential form, the intensity 



" Theoretische Chemie, 6th edition, 18 (1909). 



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24 M. M, Garver 

is nevertheless inversely proportional to the redistribution, or 
extensity, of the retransformed energy. For if a quantity of 
energy, Q be represented by the product of two factors, ex- 
tensity E, and intensity I the second law of energetics asserts 
that 

Q = E.I = W + Q' 

where W represents the transformed and Q' the transferred 
energy. If W be transformed back into energy of the same 
type, we must have 

E,I — E',r = Q' >o. 

This is a more general statement than that embodied in the 
entropy function,* 

for the latter refers to only one type of energy while the other 
asserts that transformations are dependent on transfers and 
that there must necessarily (except ideally) be some energy 
transferred, for transformations occur only during transfer. 
In addition this equation shows the discontinuity in the in- 
tensity factors I and I' which evidently bear no functional 
relation to each other so long as the extensities are independent 
and arbitrary. 

The foregoing may be taken as a concise outline of a point 
of view. If it is in opposition to, or inconsistent with, any 
well-established thermodynamic facts I have failed to observe 
them. Indeed many of the leading facts of thermodynanfics 
seem to follow directly as a consequence from the above 
assumptions. Without at present attempting a systematic 
comparison of the facts of thermodynamics with the suggested 
assumptions, perhaps the best way to present the subject as a 

* "It would be absurd to assume that the validity of the second law de- 
pends in any way on the skill of the physicist or chemist in observing or ex- 
perimenting. The gist of the second law has nothing to do with experiment; 
the law asserts briefly that there exists in nature a quantity which changes always 
in the same sense in all natural processes.*' Planck, Thermodynamics, translated 
by Ogg, p. 103. 



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Transference and Transformations of Energy 25 

whole without detailed analysis, will be to illustrate by a series 
of statements how some of the fundamental facts of ther- 
modynamics follow by simple non-mathematical deduction 
from the above general assumptions. But absence of conflict 
is not sufficient. Not only should we expect the general to 
include the special, but a general form is an unnecessary com- 
plication if it does not enable us to take a forward step and 
include phenomena that were previously isolated. 

1. Energy, like matter is conserved, and again like matter 
may vary in amount per unit volume or space. The variation 
of matter per unit volume is recognized as change in density. 
The variation of energy per unit volume is expressed as 
variations in intensity. 

Dropping the use of analogies, for they are only analogies, 
we may proceed : 

2. All natural processes taking place spontaneously in 
isolated systems are essentially equilibrating processes during 
which each type, of energy, independently, tends to become 
uniformly distributed, by the passage of energy from points of 
higher to points of lower intensity. 

3. During a transfer of energy due to the equilibrating 
process, transformations occur; (a) by distributions along the 
path producing molecular motions; (b) by overcoming at- 
tractive forces internal and external; (c) by communicating 
motion to masses against inertia or other resistance. All 
spontaneous transfers of energy in an isolated system must 
then result in an equilibrating redistribution of energy either 
molecular or molar, or in a partial redistribution and a partial 
transformation into potential energy constituting work either 
external or internal or both. 

4. Each type of energy can in general be equilibrated by in- 
tensities of its own type and by some potential form or forms ; 
but different types may have the same potential form and con- 
sequently may be equilibrated by a common potential. Hence 
actual equilibrium may co-exist with great energy heterogeneity. 

5. If a transfer of energy of any type results in equilibrium 
without change of type the process is finished, the incident is 



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26 M. M. Garver 

closed ; there remains no latent possibility that that particular 
redistribution can be made to take place again so as to produce 
a potential form, t. e., do work. (Irreversible processes.) 

6. Ability to control the rate of transfer of energy with- 
out lowering the intensity necessarily implies the ability to 
equilibrate one intensity against another. Hence, if the 
equilibrating intensity be of a type susceptible to control the 
transformation of the two types from one into the other may 
be made to take place slowly in either of two directions with 
but slight lowering of intensity of either type. (In the limit, 
no lowering.) Therefore if an energy transfer can be made 
to take place suflRciently slowly by equilibrating of intensities, 
energy that would otherwise be transferred may be trans- 
formed with a minimum of loss by transfer. (Reversible 
processes.) 

7. In all actual redistributions of energy due to sponta- 
neous motion by which energy is transferred from points of 
higher to points of lower intensity, some difference in in- 
tensity must exist or transfers will cease. Therefore trans- 
formations (which take place during transfer) are never com- 
plete; some energy necessarily being transferred and the re- 
mainder transformed. (Law of entropy.) 

8. An isolated energy system, free from external action, 
relatively at rest, and occupying a constant volume, can exist 
only with one-half of its energy kinetic and one-half potential. 
(Clausius* virial.) 

This last statement follows immediately from the first 
and third laws of Newton and is necessarily true in general 
unless strain may exist independent of motion in which case 
we can assert only that the kinetic energy cannot exceed the 
potential energy which reaches a minimum when it equals 
the kinetic energy of the system. As applied to a fluid 
system not subjected to external stresses, as in a free liquid, 
it merely specifies a condition of equilibrium which is evident 
from general principles; but those who require an analytic 
proof will find it in Clausius'* virial: 

* Phil. Mag., [4] 40, 122 (1870). 



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Transference and Transformations of Energy 27 

Each of the above statements might be made a text for a 
more extended discussion and comparison with experimental 
facts; but even in their present abridged form they will serve 
to show that the proposed extension of the second law of 
thermodynamics to include all iinds of energy transfers is, 
to say the least, not inconsistent with its present narrower 
interpretation. In addition, the proposed extension throws a 
light on the significance of irreversible and reversible processes 
and on entropy that cannot fail to be helpful in the applica- 
tion of the second law of energetics to the phenomena of 
solution. The facts seem to indicate that the phenomena of 
solutions are in a class by themselves and require a f tmdamental 
treatment. The thermodynamics of gases cannot be made to 
explain fundamental characteristics not found in connection 
with the phenomena of gases. Of course there are resem- 
blances but there are also diflferences. The resemblances are, 
however, superficial while the differences are fundamental. 
The warrant for this last statement, it is expected, will be 
evident from the result of a study of a few of the fundamental 
experimental facts of solutions. The first of the following 
examples will be discussed in more detail than the remainder 
because it illustrates simultaneously co-existing different 
types of energy and the conditions of their equilibrium and 
transfer as well as an instructive reversible transformation 
into work. We shall find the study much facilitated by the 
application of the rule that a spontaneous transfer of fluid 
matter indicates the relative energy intensities, as well as the 
direction of transfer of the energy. Of course the rule may be 
objected to but the objector may find it difficult to explain 
how the matter undergoing spontaneous transfer manages to 
leave its intrinsic energy behind. 

Application of the Preceding Principles 

If two vessels, one containing a volatile liquid and the 
other a solution of a non-volatile solid in the same liquid, be 
placed side by side in an inclosure from which the air is ex- 
hausted, the volume of the solution will increase at the ex- 



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28 M. M . Garver 

pense of that of the pure solvent so long as the temperatures 
of the liquids in the two vessels are equal. From the well- 
known relation of vapor-pressures to temperatures, we know 
that if the solution be at a certain temperature, somewhat 
above that of the pure solvent, the vapor of the solution will 
be in equilibrium with that of the pure solvent. The two 
liquids will then possess different temperatures and are 
consequently not in thermal equilibrium, yet their vapors are 
in equilibrium, we say, because they exert equal pressures; 
but heat will pass from the warmer to the cooler vessel both by 
radiation and conduction if the vessels are in thermal com- 
munication. If the temperature of the solution be higher 
than this equilibrating temperature, both radiant heat and 
vapor pass in the same direction, i. e., from the solution to the 
pure solvent. If the temperature of the solution lie between 
the equilibrating temperature and the temperature of the pure 
solvent, radiant heat and vapor pass in opposite directions. 
If the solution be cooler than the pure solvent both radiant 
heat and vapor pass from the pure solvent to the solution. 
Such are the experimental facts with a few obvious deduc- 
tions from the facts. In addition, experimental facts rela- 
ting vapor pressure to altitude, show that if the temperatures 
of the two liquids be the same, the vapors may be equilibrated 
by a difference in level of the two containing vessels — the 
solution occupying the higher level. If too high, vapor will 
pass from the solution; if too low, vapor will pass to it and be 
condensed. Other equilibrating devices employing semi- 
permeable partitions need not at present be considered, as 
they were discussed at some length in a former paper. * 

The point to which special attention is called is the co- 
existence of two types of molecular energy — heat and the 
ability to form vapor — either of which may be equilibrated 
independently, but not simultaneously without introducing 
a third element, or potential, a diflference in level. With a 
properly selected difference in level both temperature and 
vapor pressure may be simultaneously equilibrated. But 

* Jour. Phys. Chem., 14, 260 (1910). 



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Transference and Transformations of Energy 29 

with the vessels at the same level vapor equilibrium can be 
attained only when the solution is at a higher temperature 
than the pure solvent; and in producing this difference of 
temperature — thermal communication being prevented — the 
transferred vapor acts in the double capacity of lowering the 
temperature of the pure solvent and elevating that of the solu- 
tion. If communication of heat be prevented the vapors 
will reach equilibrium by producing the necessary difference 
in temperature. 

The ability of the pure solvent to raise the temperature 
of the solution at the expense of the heat in the pure solvent 
indicates the presence of ''free energy'' — ^the ability to do 
work — ^the energy being supplied by the pure solvent and being 
absorbed by the solution. Instead of being transferred to and 
absorbed by the solution, producing heat, it may be trans- 
ferred against gravity and made to do gravitation work. 
For details of a reversible process of accomplishing this a 
former paper may be consulted.* 

This peculiar example — a transfer of molecular energy, 
not heat, producing either heat or work at will is more nearly 
analogous to a battery circuit containing an electric motor 
than it is to gas expanding into additional solvent like a gas 
expanding into a vacuum. If the motor be allowed to run 
and lift a weight, gravitation work is done; if stopped, the 
entire energy is transformed into heat. At a certain definite 
speed of the motor, both the transfer of electricity and transfer 
of chemical material may be equilibrated; at a still higher 
speed both may be reversed in direction by the doing of ex- 
ternal work. If a reference to a gas be used at all to illustrate 
the redistribution of the energy, a better illustration is afforded 
by Joule's first experiment. Consider two equal masses of 
the same gas occupying different volumes, t. ^., subjected to 
different pressures. If they are placed in thermal com- 
munication they will come to the same temperature. Now 
if we have equal masses in the two portions we have equal 
numbers of molecules and each molecule, if we accept the 

* Loc. dt. 



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30 M . M. Garver 

kinetic theory of the molecule, possesses the same average 
kinetic energy of translation, so that the two portions of gas 
represent equal amounts of energy. The real difference be- 
tween the two portions is found in the energy per imit volume, 
or intensity. Together, the two parts constitute an energy 
system capable of producing a difference in temperature in 
the parts of the system or of doing external work instead. 
In this respect, such a gaseous system is very similar to a 
system composed of a solvent and solution such as we have 
been considering. The resemblance extends even to balancing 
the free energy by a temperature difference; but the free 
energy in the two systems is quite diflferently related to their 
respective systems. In the one we have a homogeneous gas, 
the equilibrium of the system being disturbed by, and the 
free energy arising from, a difference in externally applied 
pressure. In the other we have a compound Uquid system 
in which the equilibrium is disturbed by, and consequently 
the free energy arises from, the presence of a non-volatile 
substance dissolved in one portion of an otherwise homoge- 
neous liquid. The transfer of material from the pure solvent 
to the solution spontaneously, proves that the energy i>er 
unit volume of the pure solvent exceeds that of the solution 
when the temperatures are equal; therefore the free energy of 
such a system resides in the pure solvent during the sponta- 
neous transfer of which, to the solution, work is done. Strictly 
speaking, the free energy in the sense of ability to do external 
work, is a function of the system and not of either constituent 
alone, but may be said to be due to a disturbed equilibrium 
in consequence of which material is transported spontaneously 
from one part of the system to the other. The maximum 
quantity of work which may be done by such a system may be 
calculated by either of two processes and yields the same 
result when ambiguities are removed. The method by 
equilibrated vapors was given in the paper referred to above, 
but the same numerical results, when correctly interpreted, 
may be obtained by *' osmotic'* methods which may be 
termed the static (because dealing with pressures, or forces), 



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Transference and Transformations of Energy 31 

method as compared with the above which might be called 
the kinetic. It may not be amiss to offer, at this point, a 
few reflections on the above distinctions — the static and kinetic. 

The first law of Newton is really dual and opens the way 
to the two different methods of viewing things, the static and 
kinetic, (a) Matter at rest remains at rest, etc. (b) Matter 
in motion remains in motion, etc. The fact is, we are really 
dealing with two aspects of the same thing, energy, or, more 
properly speaking, matter in motion. (This last phrase 
shows the personal predilection of the writer.) But we 
should all recognize the fact that pressure may produce 
motion and motion, pressure as illustrated by the phenomena 
of gases. In many instances it is as difficult to determine 
which is antecedent and which consequent as in the proverbial 
case of the egg and the fowl. We may start from either 
point of view and obtain results that are consistent with 
themselves and with our general experience. Since, however, 
the kinetic view of fluid matter has so enlarged our con- 
ceptions of the activities and processes found in Nature, it 
seems but reasonable to postulate that the phenomena we 
observe arise from interchanges of matter in motion. Hence 
the proposed generalized second law of energetics is merely 
another way of saying that nothing can happen while every- 
thing is at rest. 

As the history of science proves, either of two hypotheses, 
or theories, may sometimes equally well account for all the 
known facts until the material for a crucial experimental test 
enables us to decide which of the two best represents the 
widest range of facts. The rival views inevitably lead to 
different interpretations of the same fact and experiment must 
be appealed to to decide between them. In the present 
instance the osmotic theory, as opposed to what we may call 
the chemical theory, requires that when work is done by a 
solution due to the expanding solute, it must be cooled in 
consequence of the external work done by the expanding 
solute.^ The experimental facts of the relation of vapor 

» Nernst, Theoretische Chemie., 6th Ed., 147 (1909). 



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32 M, M. Garver 

pressures to temperature require that the solution be warmed 
in order to produce equilibrium of the vapors. Hitherto the 
relation of the vapor pressures to the ability of a solvent-solu- 
tion system (for brevity) to do external work was not fully 
recognized; but since the maximum work by a reversible 
isothermal process may be obtained by the interaction of the 
vapors alone ^ it is evident from the principle that work or 
potential energy, is produced only by transformation occur- 
ring during transfer of energy, that the work actually done by 
the system must merely diminish the molecular energy, or 
heat, transferred from the pure solvent to the solution. This 
means that warming the solution until the equilibrating 
difference in temperature is produced should absolutely pre- 
vent the doing of work by the system because it prevents the 
transfer of energy and material which is the prerequisite to 
doing work. This deduction from the experimental evidence 
is easily tested experimentally. It has been proven fre- 
quently that a certain difference of temperature will equili- 
brate the vapors and prevent transfer of vapor; the same 
difference in temperature will undoubtedly also prevent the- 
transfer of liquid material through a semi-permeable mem- 
brane. 

The characteristic features of a solvent-solution system 
are that it may be equilibrated in three different ways, (a) 
by a temperature difference, (6) by a difference in external 
pressure, (c) by a difference in level equivalent to the differ- 
ence in pressure. This indicates plainly that the system will 
produce any one of the three differences when the other two 
are prevented, since all processes tend to produce equilibrium, 
ultimately. The system does work Because the solution is 
cooled, not the converse. By the second law, the transfer 
of heat is antecedent, the doing of work consequent. The 
doing of work can be prevented by preventing any transfer 
of heat; but if the vapors are in communication the solution 
will become warmer than the adjacent pure solvent. 

Query. What is the character of the energy in such a 

* Jour. Phys. Chem., 14, 260 (1910). 



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Transference and Transformations of Energy 33 

system? and where does it originate? It is not heat that 
may be indicated by a thermometer or a pressure that may be 
measured by a manometer; its transfer produces these char- 
acteristics of free energy. It is, from the evidence, a distinct 
type that may imdergo distribution without change of type 
(irreversibly) or may, during transfer, be transformed pro- 
ducing a temperature difference or do work while producing 
a less difference in temperature. If it produces a temperature 
difference it is, of course, distributed as heat and follows the 
thermodynamic laws found to hold in such distributions; 
but there is a persistent transfer of energy when both the 
temperatures and the externally applied pressures are uni- 
form throughout the system. It must then differ in type 
from heat, for heat transfer is accompanied by a difference in 
temperature. Otherwise, except as to temperature char- 
acteristics, it strongly resembles the molecular motion called 
heat and has a heat equivalent. 

Its origin is interesting and curious for it seems to orig- 
inate in the potential energy (chemism?) of solution just as 
heat originates in the chemism of combustion. 

When coal is burnt it can produce a perfectly definite 
amoimt of heat which may be distributed as heat, irreversibly, 
or may produce a difference in temperature which may be 
utilized to do work, the heat not being entirely distributed 
so long as any temperature difference, or work, remains in 
existence. The production and distribution are entirely 
distinct quantities; they may occur simultaneously or con- 
secutively. 

When a solute is dissolved, a perfectly definite amount of 
energy is set free and may be distributed at once by indefinite 
dilution, or, a concentrated solution may be diluted and 
additional work obtained during and by the process of dilu- 
tion, but the distribution of, the energy is not complete until 
the solution is infinitely diluted. The energy set free and the 
work obtainable by dissolving unit mass of a substance is 
equal lo mg h where m is the mass of the solvent and h is the 
height necessary to equilibrate the difference in vapor-ten- 



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34 M' Af- Garver 

sions.^ If h varies, m varies inversely, so that the total work 
is independent of the quantity of solvent used, so long as the 
solution is complete, and is just sufficient to lift the entire 
mass of solvent to a height h against gravity. It is evidently 
a definite potential and may be interpreted as indicating a 
definite chemical union uninfluenced by the excess of the 
solvent, just as any excess of air does not affect the quantity 
of heat diuing complete combustion, merely the distribution 
and temperature. The energy obtainable by solution is 
entirely independent of whether work is done or not just as 
in the case of combustion. It may be carried out so as to 
obtain work, but while the work exists as work, the molecular 
energy produced by the solution remains incompletely dis- 
tributed. 

The subject can be illustrated more strikingly and the 
significance of redistributions of matter and energy, and the 
resulting equilibrium shown better by two specific cases. 

Consider a piece of charcoal in a jar of oxygen. If the 
charcoal be above a certain temperature the system will not 
be in equilibrium and the process called combustion takes 
place with the result that the carbon is uniformly distributed 
throughout the oxygen and the oxygen throughout the carbon. 
The resulting heat can be used to do work; but if the com- 
bustion be conducted in the open air a simple irreversible 
distribution takes place. 

An exact parallel is seen when sugar is dissolved in water 
except that instead of a rise of temperature there is a drop, 
otherwise the redistribution takes place until the sugar is 
uniformly distributed throughout the water and the water 
throughout the sugar. During the process a definite amotmt 
of work is possible, but the energy distribution may take 
place either reversibly, or irreversibly without change of type. 
If reversibly, work may be done as during dilution, when part 
of the energy undergoing transfer may be transformed into 
work. If no mechanical work be done it may be entirely 
transformed into heat and be distributed as such, or, be 

^ Jour. Phys. Chem., 14, 263 (1910). 



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Transference and Transformaiions of Energy 35 

distributed without change of type directly without the pro- 
duction of heat, as on direct dilution by adding additional 
solvent to a dilute solution. 

For my part, I do not see how to identify the type of 
energy distributed in the case of the sugar and water with the 
type of energy called heat in the case of the carbon and oxygen. 
The conviction is forced on my mind that each separate sub- 
stance represents a distinct type of energy tending to uniform 
distribution irrespective of every other type as is so plainly 
manifested in the case of gases. 

To those who have thus far followed the deductions from 
the experimental facts as interpreted by means of the gen- 
eralized second law of energetics applied to the phenomena 
of solutions its great utility should be apparent. We have 
without recourse to the phenomena of osmosis isolated the 
hidden energy and traced it to a source, which, by the writer 
at least, has been hitherto unsuspected. And while osmosis, 
as such, is foxmd not to be the source of the energy, the energy 
is always present in the phenomena of osmosis, thus indicating 
that there was ample warrant for the conclusions of those who 
regarded osmotic pressure as representing an energy otherwise 
unidentified and which certainly is neither heat nor work but 
can be transformed into either. The regular thermodynamic 
treatment fails to do more than to express the conditions of 
equilibrium in terms of an entropy function and the ordinary 
variables of thermodynamics. But little insight into the 
energy relations is thus obtained; and energy relations are all- 
important to a rational comprehension of the phenomena. 
However, Planck distinctly states that the free energy of a 
solution after mixing with additional free solvent is less than 
the free energy of the materials existing separately, before 
mixing,* but he fails to give any indication that this is due to 
the presence of a distinct type of energy causing a transfer from 
the pure solvent to the solution. Since osmosis and osmotic 
pressure constitute its most characteristic phenomena, osmotic 
energy would not seem inappropriate but it could not approp- 

* Loc. dt., p. 204. 



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36 M. M. Garver 

riately be termed **the energy of a dissolved substance" 
although the energy arises from the presence of a dissolved sub- 
stance but only as it constitutes an "energy sink." Properly 
speaking it should be called solution energy. 

We have traced the solution energy that gives rise to the 
phenomena of osmotic pressure and osmosis to the potential 
energy of the solute set free by its union with a solvent, 
which union gives rise to a peculiar type of energy just as the 
union of carbon with oxygen gives rise to the peculiar type of 
energy called heat. Each type of energy may be trans- 
formed into work by processes applicable to the special tj^pe, 
but each necessarily involving the transference and partial 
distribution of the energy set free as a condition precedent 
to the transformation. The transference of solution energy is 
conditioned on dilution as the sine qua non of distribution 
during which mechanical work may, or may not, be done just 
as in the case of heat, work may or may not be done during 
distribution. The doing of work during dilution is con- 
ditioned on a depressed state of a solution as compared to the 
energy state of the pure solvent; for the transfer takes place 
spontaneously from the pure solvent to the solution. It 
remains to reconcile this latter deduction with the deduction 
from the kinetic theory that the average energy per molecule 
of a solution is the same as that of the solvent at the same 
temperature. That the two conclusions are not necessarily 
in contradiction is shown by the fact that equal average 
energy per molecule holds also for gases at the same tem- 
perature, but that a difference in pressure confers on such a 
system free energy. Hence we may admit that the average 
energy per molecule is the same in both solvent and solution 
without necessarily admitting that the free energy is the same 
in both. The problem, then, is to determine, if possible, 
how the free energy of a solution can be less than that of the 
solvent while the energy per molecule remains unchanged. 

As a preliminary, we may note that if the pressure of the 
vapor be taken as a criterion of free energy we can express 
the difference in the free energies in terms of a pressure, just 



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Transference and Transformations of Energy 37 

as in the case of two portions of a gas at different pressures. 
This pressure criterion may even be extended to the liquids as 
well as to the vapors by introducing the conditions of simulta- 
neous dynamic equilibrium between the vapors and liquids, 
namely : 

Pi Pi 

where p^ and p^ are the vapor pressures of pure solvent and 
solution resi>ectively and Pj and P^ are the intrinsic pressures 
of the respective Hquids.* The transfer of material, whether 
vapor or liquid will take place spontaneously if not prevented, 
from the higher to the lower pressure, and thus introduce a 
process expressible in terms of *' pressures*' diuing which 
external work may be done. In terms of energy, however, 
since "free energy'* is merely another expression for ability 
to do work, which ability disappears entirely when the differ- 
ence in vapor pressures disappears either by dilution or by a 
temp>eratiu:e difference, we may without doubt assume that 
the average molecular energy per molecule, Ei or Ej of the 
material which supplies the vapor, is proportional to the 
pressure />, or p^ of the vapor which it supplies. Therefore 

^» = ^1 = ?? 
Ex ^ Pi 

where the subscript i refers to pure solvent and 2 to the corre- 
sponding solution. 

Suppose N molecules of solution to consist of n molecules 
of solute and N-n molecules of solvent; the total free energy 
being E. The average free energy per molecule of solution 
will be E/N = E3 and of the solvent in the solution (since the 
non- volatile solute furnishes no vapor), E/(N~n) = E^ say. 
The ratio E^/E^ = (N-n)/N = p^/p^ whence 

P1 — P2 ^ V 
~'Pi N 

Raoult's experimentally observed law. Since the assumptions 

* Loc. cit., p. 265. 



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38 M. M, Garver 

lead to an experimental law, we may regard them, not only as 
warranted, but as indicating an interpretation of Raoult's 
law. 

The previous deduction, however, throws no light on the 
constitution of the molecule. The N molecules of solution 
are regarded as formed from n molecules of solute and N-n 
molecules of solvent; their actual number does not enter into 
the result. In order to obtain information on this point it 
will be necessary to proceed differently; we must consider the 
changes that take place on solution. 

When a solid, non- volatile solute is dissolved, three cases 
may arise : (a) a rise in temperature : (b) a fall in temperature : 
(c) no appreciable temi>erature change. Let us consider the 
last case first; a detailed consideration of the others will be 
found unnecessary. 

The absence of temperature change does not imply the 
absence of chemical action. It must be interpreted as mean- 
ing merely that the work done during solution is just equal 
to the work done on the solute n changing it from a free solid 
to a solute. Energy existed in potential has disappeared and 
in another form, has been transferred to the solute. If no 
energy enters or leaves the system and the solvent and solute 
imdergo no temperature change, the entire result consists in 
changing the state of the solute without taking any heat from 
the solvent. If we accept the kinetic theory, each molecule 
of the solution has an average energy equal to the average 
energy per molecule of the original solvent and to the mole- 
cules of free solvent in the solution when the temperatures are 
equal; but has the number of molecules changed? That is 
the question. 

In this connection it is important to remember the 
fundamental bearing of the second law of energetics that it is 
only during transfers of energy that transformations take 
place. We have here a transfer of energy and we may, or 
may not, have a change in type due to transformation during 
the transfer. It seems to me that the evidence indicates a 
definite change of type; but this evidence may be considered 
later. 



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Transference and Transformations of Energy 39 

It is evident on consideration that the separation and 
distribution of the molecules of the solid solute can be accom- 
plished only by the molecules of solvent entering between the 
molecules of solute; consequently the attractive forces of 
solvent for solute must exceed the attraction of solute for 
solute. Or, the tmion of the solvent with the solute can be 
comprehended from the energy viewpoint only by supposing 
a decrease in chemical potential with a corresponding pro- 
duction of heat, or a release of free energy, or both. If we 
consider the relative volumes of the solute before and after 
solution, the energy of its molecules and their separation 
against their molecular attractions, the energy required to 
dissolve it is comparable with the energy required to gasify it. 
Since we are supposedly dealing with an isolated system this 
increase in energy all comes from energy supplied by the 
solvent. We may therefore suppose that the total energy 
supplied by the solute is small as compared with the total 
energy supplied by the solvent in a moderately dilute solu- 
tion. From statement 8 (Clausius* virial) we may conclude 
that the kinetic energy in a free liquid is proportional to the 
absolute temperature T. Therefore if E represents the total 
energy of N molecules of solvent the average energy per mole- 
cule of the solvent is E/N = E^ (say). Likewise, the average 
energy per molecule of the solution will be (E + e)/N' = E,. 
Therefore 

E3 _ (E + e) V N _ / . 1\ N _ T, 
E, ~ N' ^ E "" V "^ E/ N' "" T; 

Now since e is small in comparison with E, f i + ^j ap- 
proximates to imity, and since T^/T^ is supposed to be nearly 
imity N/N' must also be not far from unity. When T^ is 
larger than T^ N', the number of molecules of solution, may be 
actually less than Nj the original number of molecules of pure 
solvent. 

As the observed lowering of the energy of a solution is 
apparently of such a nature that the thermometer does not 
show it (for at least one phase of the energy is lowered even 



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40 M. M. Garver 

when the temperature is not lowered) the temperatures T, 
and Tj probably do not correctly represent the relative en- 
ergies of the solution and piu'e solvent. If all the energy due 
to the union was transferred in the form of heat and none of it 
transformed, the temperatiu-e T, of the solution shotild be 
higher. But if the energy transferred during solution be partly 
transformed into a subtype — a molecular potential type 
analogous to work — ^in the doing of which heat disappears, 
the heat generated partly disappears and the temperature 
produced is less than we should otherwise expect. Therefore 
the estimate that 

E, T, \ ^ E/ N' 
is probably too low and we should have instead 

El Tj V ^ E/ N' 

so that probably N' < N. 

Suppose on the other hand that we assume the absence 
of union and of energy set free during solution, and that there- 
fore the energ>' E of the solvent is merely distributed among 
the N + n molecules of the solution, the energy contributed 
by the solute being negligible. We should then have E/N = 
El and E/(N 4- n) = E,. 
Whence 

E, ^ N -f n ^ r, 
E, " N tV 

If we test this formula with the results obtained with an 
aqueous solution of cane sugar we find that the solution of i 
gram molecule in a liter of water at 20° C should cause a drop 
in temperature of 5*^ C while the heat absorbed, as stated by 
Nemst is 800 calories, indicating a drop in temperature of 
less than 0.8 of a degree. 

Hence when viewed from one side we are led to conclude 
that in a solution the number of molecules must be less than 
the sum of the molecules in the components; and from the 
other side that the observed temperature change is not suffi- 



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Transference and Transformations of Energy 41 

cient to indicate that an xmchanged number of molecules was 
supplied with the requisite energy called for by the kinetic 
theory. These two indications moreover unite in confirming 
the deduction that the energy obtainable from dissolving a 
substance points to a definite chemical union with a decrease 
in the number of reacting molecules. In addition there are 
numerous other indications of a tmion of some sort between 
the solute and solvent. Osmotic pressure for instance, could 
be explained by a tmion of such a nature that the combined 
molecules could not pass the semi-permeable membrane.* 
It would also explain Pickering's experiment.' In simple 
cases like a solution of a non- volatile non -electrolyte **the 
action is as if each molecule of solute had removed from action 
one molecule of solvent.'* Let us then suppose that there is a 
loose but definite sort of molecular union between a solvent 
and its solute and see whether such assumption enables us to 
explain otherwise isolated phenomena. 

Let X represent the molecular mass of the solute and y 
that of the solvent. Then Ej = Vj y u{ will represent the 
average energy of translation of the molecules of the solvent, 
if ti\ is the average square of the velocity of the solvent mole- 
cules. Let E represent the total kinetic energy of N mole- 
cules of solvent and e the total kinetic energy of n molecules 
of the solute which we will assume to be a non-volatile non- 
electrolyte. In accordance with the assumption, a molecule 
of solution will have a mass {x + y) and an average energy of 
translation of Ej = V2 (^ + V) ^2 (say). The actual value 
of the average energy per molecule of the solution may be 
taken as lying between two limits. If we assume that the 
original energy e of the solute is negligible in comparison with 
the energy E of the solvent we get a lower limit. If we assume 
the kinetic energy of the solid solute before dissolving to be 
proportional to the absolute temperature and equal per mole- 
cule to the liquid solvent at the same temperature we will 
doubtless include the upper limit. Let us consider the lower 

* Jour. Phys. Chem., 14, 651 (1910). 

» Whetham: "Theory of Solutions," p. 97. 



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42 M. M. Garver 

limit first. In this case the average energy per molecule will 
be the same after dissolving as before for the same amoimt of 
energy E is divided among the same number of molecules N 
so that Ej = E, or, Va y ^i ^ Va (^ + y) ^l- M no molecular 
work were done during solution in separating the molecules 
of the solute there should be no temi>erature change during 
solution in consequence of such union for the mean kinetic 
energy of the molecules is proportional to the absolute tem- 
perature. The temjjerature change then should merely re- 
present the disgregation work done diuing solution and this 
is generally indicated by a fall in temi>erature. 

Now let us consider the second case in which the energy 
supplied by the solid solute is equal to the energy of the same 
number of molecules of solvent, still however, remembering 
that the number of molecules after solution is equal to the 
number of molecules of solvent. The energy now divided 
among the N molecules will be E + e and the energy i>er 
molecule 

The only effect of the increment e/N supplied by the 
energy of the solute will be to decrease the fall in temperatiu-e 
due to the disgregation work done by the solvent on the solute. 
Less heat then, will have to be supplied to restore the original 
temperature, if we include and take into account the energy 
supplied by the solute But entirely aside from the molecular 
work done which produces temperature effects it is seen that 
there is a large amount of molecular work done in imparting 
kinetic energy to the solute that has no heat equivalent^ for no 
fall in temperature results from the energy y, x u\, the 
entire kinetic energy imparted to the solute by the solvent. If 
the two parts of the molecule, V, x u\ and V, yu\ had sep- 
arately, before the union, had a surplus of energy it would 
have been given out as heat to the rest of the solvent and the 
fact would still remain that the energy ^l^xu\ is related to 
V, y ul as though the energy of the part V^ x wf had been 
raised from zero by the fall of V2 y ul to V^ y uj without any 



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Transference and Transformations of Energy 43 

temperature change. The reason for this apparently para- 
doxical result is seen when we remember that the energy per 
molecule is independent of the mass of the molecule and 
hence that the work done by the molecule goes to change the 
mass of the molecule. Therefore that kind of molecular work 
does not change the temperature of the molecule that does it. 
We are now in a position to see why the energy of the 
solution is depressed although the temperatiure is unchanged — 
why, although it has the same temperatiu-e and the same 
average energy per molecule as the piu-e solvent, the vapor 
persistently passes from the pure solvent to the solution and 
also why the liquid solvent passes through a semi-p>ermeable 
membrane into the solution unless prevented by either a 
temperatiu*e, or pressure, difference. In this connection, how- 
ever, it is necessary to remember that a transfer of energy is 
determined solely by relative intensities of the type under- 
going transfer and is independent of total energies except as they 
affect equiUbrium. Therefore the total energy in a solution 
may, or may not, be actually greater than in the original 
solvent, but if the intensity of any one type be less than the 
intensity of the same type at a nearby point and the conditions 
permit of transfer, energ>' of that type will pass spontaneously 
from the points of higher to points of lower intensity of that 
t3T>e and diuing the transfer work may be done. In the case 
of a solvent-solution system, the kinetic energy of the solvent 
in the solution is both depressed and divided beween the 
solute and solvent so that energy in the form of solvent passes 
freely to the solution where that type is depressed and diluted. 
The depression and dilution may be further analyzed from the 
equation 

V,(^ + >')^ = V.xul+W.yul = 'Uyv\. 

Here we have two t>'pes which united will equilibrate V , y Wj 
so far as heat is concerned when the temperatures are equal, 
but separately the part V2 y ^2 ^ less intense than */j y u\. 
Hence work may be done diuing the redistribution if con- 
ducted reversibly, or the type may be distributed directly 
and irreversibly without doing work or generating heat just 



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44 M. M. Garver 

as in the case of heat. By infinite dilution the difference 
upon which the transfer depends disapp>ears. 

In addition we have the type V2 ^ ^2> generally a heavy 
molecule with a depressed velocity so that it forms no vapor 
nor is it able to penetrate semi-permeable membranes with the 
facility shown by the more active free solvent. This V, x uj 
represents the "sub-type" of molecular energy the formation 
of which apparently takes no heat energy since it repays the 
energy it receives by adding mass to the molecule from which 
it receives its motion. 

R^sum^ of evidence indicating a definite chemical tmion 
of solute and solvent. 

(a) The definiteness of the energy, mgh, set free on solu- 
tion. 

(6) The energy set free indicates a tmion of molecules 
by which the number of molecules in a solution is less than the 
sum of the constituent molecules. 

(c) The energy, as indicated by temperature changes, is 
not sufficient to supply an aggregate equal to the sum of the 
constituent molecules. 

(d) The lowering of the energy of a solution although the 
temperatures of solution and solvent are equal. 

(e) The doing of molecular work with a disappearance of 
energy without lowering the temperature. 

(/) A union of the solute and solvent enables us to ex- 
plain satisfactorily the depression of vapor and intrinsic pres- 
sures, hence osmotic pressure. 

Finally the evidence and reasoning are not based on the 
kinetic molecular theory. The frequent references to the 
latter theory and the discussions generally were to show that 
the two views were not contradictory. They do, however 
mutually support each other. 

State College, Pa., 
September i6, igio 



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CRYSTALLIZATION THROUGH MEMBRANES 



BY JAMES H. WALTON, JR. 

In a previous communication^ it was shown by the author 
that if a supersaturated solution or an undercooled liquid is 
divided by a membrane and a crystal is added to one part, 
crystals will form in the other part, the crystallization being 
transmitted via the membrane. This was found to hold true 
with aqueous sup>ersaturated solutions of sodium sulphate, 
acetate, tetraborate, thiosulphate, potassium alum and lead 
acetate with parchment, collodion and gold-beater*s skin. 
Similarly, tmdercooled water and thymol were used with 
collodion and gold-beater's skin. 

An tmdercooled liquid of a type entirely different from 
any of those employed can be made by melting phosphorus 
in water to which a few crystals of urea have been added to 
facilitate the xmdercooling. A few experiments were carried 
out with this substance. .The apparatus used is shown in 
Fig. I. The membrane is fitted over the lower end of B, 
and this is slipped into A, which is made of a glass tube with a 
bore slightly larger than B. The phosphorus 
was melted in a beaker containing about 200 
cc of water to which about i gram of solid 
urea had been added. The hot liquid was then 
poured into a separatory funnel, and the clear 
liquid phosphorus with a little of the urea solu- 
tion was run into each of the arms A and B. 
On cooling to room temperature the phos- 
phorus still remained liquid. Two series of experiments were 
made in which gold-beater's skin and sheet rubber (0.005 hi. 
thick) respectively, were used as membranes. In neither case, 
however, was the crystallization transmitted through the 
membrane. The use of undercooled phosphorus is partic- 
ularly interesting, diflfering as it does from some of the other 



Fig. I 



* Jour. Phys. Chem., 13, 490 (1909). 



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46 



James H. Walton, Jr. 



substances used in the matter of speed of crystallization.* 
Phosphorus crystallizes with the velocity of 60,000 mm 

per minute, while salol, one of the substances used in the 

experiments already referred to, crystallizes at the rate of 

4 mm in one minute. 

This experiment confirms the conclusion already drawn 

in the preceding paper, viz, — that the crystallization through 

membranes depends primarily upon the nature of membrane 

and the dissolved substance. 

Supersaturated Aqueous Solutions with Rubber Membranes 

In the first paper on this subject, reference was made to 
some experiments which tended to show that if very thin 
rubber were substituted for the parchment and collodion 
membranes, crystallization would be transmitted through it. 
At that time it was not possible to definitely establish this 
point, which is obviously of great importance — ^involving as it 
does the question of whether actual contact with the solid 
phase is necessary for the separation of crystals from a super- 
saturated solution. 

A series of very carefully performed experiments was 
carried out in order to decide this question. The apparatus 
used is shown in Fig. 2, which is simply a 250 cc distilling 




Fig. 2 



flask connected with a manometer. About 25 cc of the super- 
saturated solution was placed in A; it was then boiled for a 

^ Friedlander and G. Tammann: Zeit. phys. Chem., 24, 152 (1897). 



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Crystallization through Membranes 47 

few minutes so that the steam would condense on the neck 
of the flask and wash down any solid particles which might by 
any chance be lodged there. The stopper C — carrying a 
glass tube, B over the end of which was tied a piece of sheet 
rubber, was then inserted in the neck of the flask, and the 
hquid allowed to cool to the room temperature, about 23°. 
The system was then connected with the manometer E, and 
suction applied at D. This caused the rubber on the tube B 
to become expanded, its thickness being reduced to 0.0003- 
0.0004 in. The manometer permits the pressure to be regu- 
lated, so that the rubber will not be disrupted by too great a 
pressure. By means of a pinch cock, D was then closed and 
the apparatus allowed to stand for an hour. Any leaks in the 
membrane could be detected by the change in the manometer 
reading during this time. The tube B was then partially 
filled with a supersaturated solution of the same concentration 
as that in the flask, and after a few minutes was inoculated. 

Experiments were carried out with the following sub- 
stances : 

Experiment i. — ^A supersaturated solution of sodium 
acetate made by heating 300 grams of the pure crystallized 
salt with 50 cc of water was used, the flask being filled in the 
manner described. The solution inside the expanded rubber 
was inoculated. On standing for 1-2 hours no separation of 
crystals occtured in the flask. Duplicates were carried out 
in this experiment. 

Experiment 2. — ^An experiment similar to the above was 
carried out with a supersaturated solution of potassium alum. 
The solution used was of no definite concentration. In its 
preparation a sample of alum consisting of crystals about the 
size of a pea, was used. About 30 grams were placed in the 
flask, enough distilled water added to just cover them, and the 
water heated until the crystals were dissolved, forming a 
solution supersaturated at room temperature. The rest of 
the experiment was carried out in a manner similar to that 
just described. In one experiment no change was noticed 
after two hours, at the end of which time the rubber film 



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48 James H, Walton^ Jr, 

broke. In a duplicate no crystallization was transmitted 
through the membrane even after twelve hours. 

Experiment 3. — A supersaturated solution of lead acetate 
was prepared by heating 200 grams of the crystals with 75 cc 
of water. Four experiments were conducted — the details 
being similar to the experiments just described. After 
fifteen hours no transmission of crystallization had occurred. 

These experiments indicate the necessity of actual con- 
tact of the supersaturated solution with the solid phase be- 
fore crystallization can occur. They show that with these 
salts whenever crystallization is transmitted through mem- 
branes it is brought about by the formation of the solid phase 
in the pores of the membrane. 

Experiments with Solutions Which Were Only Slightly 
Supersaturated 

In all of the experiments made with aqueous supersaturated 
solution it was found that whenever water could pass through a 
membrane crystallization could be transmitted through the mem- 
brane. As a result of these experiments, therefore, it might 
seem reasonable to state the above as a generalization. It 
must be remembered, however, that the experiments referred 
to were made with solutions which were very strongly super- 
saturated, and before any such generalization can be made it 
is necessary to make similar experiments with solutions which 
are only slightly supersaturated. 

To prove this point experiments were carried out as 
follows : 

A saturated solution of a given salt was prepared and 
kept at 30° C. It could be supersaturated and the degree of 
supersaturation controlled by either of the following methods : 

1. By lowering the temperature of the bath any desired 
amount. 

2. By measuring out a definite quantity of the saturated 
solution, raising its temperature fifteen or twenty degrees, 
dissolving a weighed quantity of the salt, and cooling the 
solution in the bath to 30° again. 



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Crystallization through Membranes 



49 



Method 2 was used in these experiments. The super- 
saturated solution was divided by a membrane, one-half was 
inoculated, and the other half examined from time to time to 
see whether or not crystals had formed. 

The following experiments were made : 

A saturated solution of potassium alum was prepared 
by saturating at 35°, then placing in a bath at 30° and shaking 
for several hours in contact with the solid phase. 

Twenty-five cc portions of the solution were removed by 
means of a pipette and placed in beakers containing weighed 
quantities of the alum. These beakers stood in a bath which 
was kept at a temperature of 45-50° C. After the alum had 
dissolved portions of the solution were removed and placed 
in each of the tubes A and B — shown in Fig. 3, which is simply 
a large test tube closed with a rubber stopper 
carrying a smaller tube which has its lower end 
covered with a membrane. When parchment was 
used as a membrane considerable difficulty was 
experienced in fastening it over A in such a manner 
that it would be perfectly tight. This was accom- 
plished by slipping a piece of rubber tubing over 
the tube, tying the wet parchment over the end 
in the usual manner, and allowing to dry. A 
cylinder of glass — C — of diameter large enough to 
leave a space of about 3 mm between it and the 
outer wall of A was slipped over the tube. Molten paraffine 
was poured into this space, and a suction was applied at 
the upper end of A to draw the paraffine into all the crevices. 
The portion of parchment at the immediate lower end of A 
was kept wet in order to prevent its becoming saturated with 
paraffine, and thus made water-proof. This makes a very 
tight joint. Instead of paraffine, sealing wax can be used. 
Collodion membranes can easily be fastened over the end of the 
tube by means of liquid collodion. 

After introducing the solutions into A and B, they were 
closed, and shaken so that the hot solution (at 50° C) would 
dissolve from the stopper or sides of the tube any particles 




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50 



James H, Walton, Jr, 



of the solid phase. The cell was then shaken for 1-2 hours in a 
thermostat which was kept at a temperature of 30°, to see if 
spontaneous crystallization would take place. It was then 
allowed to stand for 2-3 hours and examined for crystals in 
A or B. If no crystals had separated A was inoculated, and 
the cell allowed to stay in the bath with frequent shakings, 
and B examined for crystals from time to time. By holding 
to the light the separation of even a fraction of a gram of 
crystalline matter can readily be observed. 

The above precautions in filling the cell with warm solu- 
tion and allowing to stand before inoculating, are absolutely 
necessary owing to the fact that these supersaturated solutions 
are so sensitive to the slightest amount of the solid phase. In 
working in a laboratory in which these substances have been 
ground, weighed out, etc., it is almost impossible to keep the 
surfaces of the cell free from the solid phase but by the above 
precautions these diflBculties can be readily controlled. 

Experiment 4. — Supersaturated solutions of potassium 
alum were used with membranes of parchment and inoculated 
as described above. The degree of supersaturation and the 
results obtained are recorded in Table i. 

Table i 

Results of experiment 4, using supersaturated solutions of potassium 

alum. Temperature 30° in all cases 



Degree of super- 
saturation* 
Grams 




Transmission 




Membrane 


of crystals 


Length of time 


used 


through 
membrane 


in thermostat 


1.2 


Parchment 


No 


3 days 


2.0 


Parchment 


No 


3 davs 


4.0 


Parchment 


No 


24 hours 


4.0 


Parchment 


No 


4 davs 


8.0 


Parchment 


Yes 


30 min. 


8.0 


Parchment 


Yes 


30 min. 


2.0 


Collodion 


Yes 


12 hours 


2.0 


Collodion 


Yes 


I hour 



* Expressed as grams of substance in 100 cc beyond the amount necessary 
to saturate the solution at 30*^. 



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Crystallization through Membranes 



51 



It is evident that there is a minimum limit to super- 
satm-ation beyond which crystallization is not transmitted 
through membranes. 

With collodion and a supersaturated solution of potassium 
alum crystallization was transmitted through the membrane. 
It is of interest to note that with the same concentration, 
using parchment, no crystals separated in B. 

Experiment 5. — Experiments similar to 4 were carried 
out with solutions of sodium acetate supersaturated to various 
degrees. The results are shown in Table 2. With parch- 
ment, as in the case of the alum solution, there is a minimum 
limit of supersaturation beyond which crystallization will not 
pass through the membrane. 

Table 2 

Results of experiment 5, using supersaturated solutions of sodium 

acetate. Temperature 30° in all cases 



Degree of super- 
saturation^ 
Grains 



Membrane 
used 



Transmission 

of crystals 

through 

membrane 



Length of time 
in thermostat 



1 .2 
2.0 
4.0 
2.0 
2.0 
4.0 
40 



Parchment 

Parchment 

Parchment 

Collodion 

Collodion 

Collodion 

Collodion 



No 

No 

Yes 

No 

No 

No 

No 



5 days 
24 hours 
30 min. 
3 days 
7 days 
7 days 
7 days 



With sodium acetate and collodion membranes it is evi- 
dent that this limit is higher than with the parchment. That 
sodium acetate of greater supersaturation does pass through 
collodion was shown in experiment 3 in the preceding paper. 

To be perfectly sure that these collodion membranes 
which did not transmit crystallization were still permeable 
to solutions of salts, they were tested with potassium iodide 
solution. This was found to pass through immediately — a 

* Expressed as grams of substance in 100 cc beyond the amount necessary 
to saturate the solution at 30°. 



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52 James //. Walton, Jr, 

test for the iodide being obtained in the solution on the other 
side of the membrane. Moreover, in experiments in which 
crystallization did not pass through — on cooling the liquid 
in the cell a few degrees, the crystals separated in B at once. 

Conclusion 

Owing to the complex nature of membranes in general, 
it is not possible to state the direct cause of this lower limit at 
which crystals may be transmitted through membrane. 

It seems to the author, however, that the existence of this 
lower limit points to the fact that the solution within the mem- 
brane has a lower concentration than the solution which 
surrounds the membrane. According to this theory, with a 
strongly supersaturated solution crystals would be trans- 
mitted through the membrane. With a solution whose 
degree of supersaturation was equal to (or less than) the differ- 
ence between the concentration of the solution in the mem- 
brane and that surrounding the membrane, no transmission of 
crystallization could occur. 

Such a lowering of the concentration of the solution 
within the membrane could be explained by the formation of a 
compound of membrane and solute. In the membrane we 
would have, not only supersaturated solution, but also this 
compound (membrane + solute) in equilibrium with solution 
in the pores, and it is easy to conceive of a case in which the 
solution is supersaturated to such a slight extent that the 
amount taken up by the membrane leaves in the capillaries of 
the membrane a solution just saturated or even less than 
saturated. Such a solution in the membrane would of course 
not permit the transmission of crystals. 

Summary 

The results of the foregoing experiments may be sum- 
marized as follows : 

1 . The crystallization of under cooled phosphorus cannot 
be transmitted through rubber nor gold beater's skin. 

2. In the case of supersaturated aqueous solutions the 
transmission of crystallization through nienibrancs occurs only 



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Crystallization through Membranes 53 

in cases in which the membranes are permeable to water. This 
has been demonstrated by supersatm-ated solutions of potas- 
sium alum, sodium acetate and lead acetate, with rubber 
membranes 0.0003-0.0004 in. thick. In these cases no trans- 
mission took place, even after several hours. Contact with 
the solid phase is necessary. A new method is described by 
which rubber membranes of the above thickness may easily 
be obtained. 

3. A minimum limit of supersaturation exists, below 
which crystallization will no longer be transmitted through 
membranes which are p)ermeable to water. This phenomenon 
will be the subject of further investigation. 

University of Wisconsin 



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II. THE SPECIFIC HEAT OF CARBON TETRA- 
CHLORIDE AND OF ITS SATURATED VAPOR 



BY J. E. MILLS AND DUNCAN MacRAE 

The Purity of the Carbon Tetrachloride Used 

Some of Baker's *' analyzed'* C. P. carbon tetrachloride 
was fractionated over sodium through a Young's fractionating 
column and considerable trouble was experienced getting a 
perfectly constant boiling point. So additional commercial 
carbon tetrachloride was taken and purified as follows:* A 
small stick of potash was dissolved in its own weight of water 
and added to 200 cc of alcohol. 100 cc of this solution was 
added to 1000 cc of carbon tetrachloride, the mixture was 
heated to 50 or 60° C, and shaken for a half hour. The water 
was poured oflf and the shaking and heating repeated with 
50 cc of alcoholic potash This was repeated a third time. 
The carbon tetrachloride was then shaken up with 500 cc of 
water until the mixture rapidly cleared and separated. This 
was repeated. Water was removed by shaking first with 
potassium hydroxide and finally with metallic sodium. After 
standing over sodium for some days the carbon tetrachloride 
was fractionated until the following pure constant boiling 
fractions were obtained: 

75 . 90° under 743 . 7 mm pressure = 76 . 69° under 760 mm 
75.70 under 739.2 mm pressure = 76.68 under 760 mm 
75 . 99 under 745 . 9 mm pressure = 76 . 66 under 760 mm 
75.99 under 746.3 mm pressure = 76.64 under 760 mm 

These fractions amounting in all to about 1000 cc were 
mixed and constituted the sample tested. 

The Method Used 

In a former paper^ the method used was described, the 
determination of the calorimeter constant was given in detail, 



* Sammlung chemischer und chemisch-technischer Vortrage, Vol. lo, 
1906. 

' Jour. Phys. Chem., 14, 797 (1910). 



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specific Heat of Carbon Tetrachloride 55 

and the specific heat of benzol from its freezing point to 70° C 
was determined. We do not consider it necessary here to 
repeat any of the explanation there given. The details of the 
determination of the specific heat of carbon tetrachloride are 
given below in Table i. If these details are not immediately 
understood reference to the former paper will doubtless make 
them suflBciently clear. 

The Results Obtained 

The series of experiments 1-5 inclusive, see Table i, were 
made with two thermometers that were graduated only to 
tenths of a degree and were read to hundredths of a degree 
with a microscope. Experimen s 5-9 were made with a 
Beckmann thermometer. In experiments 6 and 7 the Beck- 
mann was set at 5.95° and no bath was used. In experiments 
8 and 9 the Beckmann was set at 60.02° and the calorimeter 
was surroimded by a bath held at 59.5°. As related in the 
previous paper already cited all corrections necessary to re- 
duce the thermometers to the correct hydrogen scale were 
known. The results are shown plotted in Diagram i. From 
the results obtained it appears that the specific heat of carbon 
tetrachloride from 0-70° C increases only very slightly with 
the temperatiu-e and can be represented by a straight line 
passing through the values 0.2010 at 0° and 0.2031 at 70° C. 
The actual values read from this line at intervals of 10° are 
given in Table 2. We believe that they are correct to one 
part in 200. 

Comparison of the Results with those Obtained by Other 

Observers 

The specific heat of carbon tetrachloride given by other 
observers* is shown in Diagram i. Calculating the specific 
heat from the formulae given by Winkelmann for the total 
heat and the latent heat of vaporization we find the straight 

* Saramlung chemischer und chemisch-technischer Vortrage, Vol. 10, 
1906. Him: Ann. chim. phys., [4] 10, 63 and 91 (1867). Winkelmann: Ann. 
der Physik., 9, 208, 358 (1880). Sutherland: Phil. Mag., [5] 26, 298 (1888). Reg- 
nault: M^m. de TAcad., 26, 761 (1862). 



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56 



J, E, Mills and Duncan MacRae 



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specific Heat of Carbon Tetrachloride 



57 



line shown in the diagram. Regnault determined the total 
heat of carbon tetrachloride to i6o°, finding at i6o^ the value 
71.00 calories, in good agreement with the value, 71.21 calories, 
obtained by Winkelmann. Using the value obtained by 
Regnault and the value of the heat of vaporization at this 
temperature, 37.95 calories,^ we find that the average specific 
heat of carbon tetrachloride from 0-160° is 0.2066 calories. 











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A 


^ 


66 


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k3 


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li 





M 


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e 








Fig. I 
Hirn. 

Winkelmann. 
Sutherland. 
From Regnault. 
Mills and MacRae. 



This average value is probably nearly correct though it is 
somewhat higher than the probable true value at 80° C. 
The values obtained by the authors for the specific heat of 
carbon tetrachloride are shown in the diagram and indicate 
that at low temperatures the specific heat of carbon tetra- 
chloride does not increase so rapidly with the temperature 
as has been supposed. 

The Specific Heat of the Saturated Vapor 

If the heat of vaporization of the liquid at intervals of 
10° and the specific heat of the liquid are known, the specific 
heat of the saturated vapor may be calculated. For the 
energy necessary to change the liquid at 0° into the saturated 
vapor at 10° is the same whatever may be the method pursued 
to effect the change. Letting the subscripts of L denote tem- 
perature, and letting a^ denote the total heat added to the 

* Sci. Proc. Roy. Dublin Soc, 12, 427 (1910). 



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58 y. E, Mills and Duncan MacRae 

liquid and a^ that added to the vapor between the temperature 
limits given, we have, 

1. l^^ -\- Ov = Lio -\- c^L, or Ov = Lio + ^L — Lq. 

By this method we have calculated the values for the 
specific heat of the saturated vapor at intervals of io° from 
5-65° from the data given in Table 2 and give the results in 
that table. 

The heats of vaporization marked *'Ther " were calculated 
by use of the thermodynamical equation, 

2. L == 0.O43183 - ^ T (V — v) calories, 

from the data^ given in Table 2. In this equation L is the heat 
of vaporization, T is absolute temperature, P is pressure in 
millimeters of mercury, and v and V are the volumes of a gram 
of the liquid and of its saturated vapor. 

The values of the heat of vaporization in the column 
marked *' Mills*' are obtained by using the equation, 

Here /i' is a constant for any particular substance and for 
carbon tetrachloride has the value 44.01. Eb is the energy 
expended in overcoming the external pressure as the liquid 
expands to the volume of the saturated vapor and is given by 
the equation, 

4. Eb = 0.O43183 P(V — v) calories. 

Equation 3 has been carefully and extensively studied^ and 
seems to hold accurately for non-associated liquids at all 
temperatures. 



* See Sd. Proc. Roy. Dublin Soc, 12, 427 (19 10), except the density and 
volume of the saturated vapor from 0-60° inclusive. At o® the values are the 
theoretical values. At 10-60 '^ they are obtained by extrapolating an equation 
given by Young: Journal de Physique, Jan., 1909. 

' See particularly Jour. Phys. Chem., 13, 512 (1909), and Jour. Am. 
Chem. Soc, 31, 1099 (1909), and references there given. 



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specific Heat of Carbon Tetrachloride 59 



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6o /. E, Mills and Duncan MacRae 

While equation 2 is correct if the data is absolutely 
accurate we have shown in the paper cited that slight in- 
accuracies in the data are often greatly multiplied in their 
proportionate effect upon the values of the heat of vaporiza- 
tion. For this reason we consider the smoothed values of the 
specific heat of the saturated vapor as given under the head- 
ing *' Mills *' in Table 2 to be the most accurate. 

Analysis of the Specific Heat of Benzol and of Carbon 
Tetrachloride 

The object of this research was to throw light upon the 
nature and cause of the energy changes involved during the 
rise in temperature of a liquid. So fa' as the writers are 
aware the specific heat of any substance is supposed to be due 
to the following energy changes : 

1. The energy necessary to overcome the external pressure 
as the substance expands, — ^This energy can be easily calculated 
if the external pressure and the volumes before {v) and after 
{v') expansion are known. If the pressure is given in milli- 
meters of mercury and the volumes of a gram in cubic centi- 
meters, the equation takes the form, 

5- EBxternai = Ee = 0.O43183 P(i;' — v) calories. 

2. The energy necessary to overcome the molecular attraction 
as the substance expands, — The investigation upon molecular 
attraction by one of the authors^ has led to the belief that 
this amount of energy can be calculated from the equation, 

6 Eattraction = Ea = //' ( ^^ — \50, 

where fx' is a constant characteristic of the substance, and d 
is the density of the substance before, and d' the density of 
the substance after, expansion. This equation is certainly 
applicable to the expansion of a liquid at constant tempera- 
ture and under constant pressure from its volume as a liquid 
to its volume as a saturated vapor. That it is likewise ap- 

' Jour. Phys. Chem., 6, 209 (1902): 8, 383 (1904); 8, 593 (1904); 9f 402 
(1905); 10, I (1906); II, 132 (1907); II, 594 (1907); I3f 51-2 (1909); Jour. Am, 
Chem. Soc., 31, 1099 (1909). 



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specific Heat of Carbon Tetrachloride 6i 

plicable to the expansion of a substance when both tempera- 
ture and pressure are variable has not been proved, but it 
seems to the authors Hkely to constitute at least one term of 
the energy necessary for such expansion. We expect the in- 
vestigation when completed to throw light upon this point. 

3. The energy necessary to increase the translational motion 
of the molecules as the temperature of the substance is raised, — 
If the substance is a perfect gas and the kinetic theory of gases 
is true, the total amount of this translational energy for i 
gram of substance is, at the absolute temperature T, simply 

~ — calories. Therefore, 
m 

7. Ekinetic = Uk = ~^^— calories, 

where m is the molecular weight of the substance. It is possi- 
ble that equation 7 does not apply to substances whose mole- 
cules are under the action of attractive forces, more particu- 
larly solids and liquids. To obtain further evidence upon this 
point was one of the objects in view in the present investiga- 
tion. 

4. An amount of energy which we propose to call ''internal 
energy '\ the office of the ^energy being^unknown. — ^This energy 
is roughly proportional to the number of atoms within the 
molecule, being zero for a monatomic molecule, such as 
mercury or argon. If from the specific heat of the substance 
as a perfect gas at constant volume, the kinetic energy neces- 
sary to raise the temperature of the substance i ° (see 3 above) 
be subtracted, the remainder is the internal energy as we have 
defined it. This "internal energy '* change is probably not a 
change of the chemical energy of the atoms within the mole- 
cule, but seems to be required for even the most stable poly- 
atomic molecule. It may have to do with the rotation of the 
molecule as a whole. Numerous attempts, of which particu- 
larly the efforts of Boltzmann may be mentioned, to give a 
satisfactory explanation of this internal energy have failed. 
For a perfect gas, while the gas is chemically stable, the 



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62 /. E. Mills and Duncan MacRae 

internal energy appears to be proportional to the translational 
energy and may be obtained from the equation, 

S. HinternAl = Ei = E*, 

r— I 

where y is the ratio of the specific heat of the gas at constant 
pressm-e to its specific heat at constant volume. 

5. The energy which binds the atoms together, — This energy 
might be called chemical energy. We are inclined to believe 
that for a stable chemical compotmd, far removed from its 
point of decomposition, the chemical energy of the body is 
not affected by changes in temperature. ' 

Hence except for a substance nearing the point of, or 
undergoing, decomposition, we think that, 

9- Echcmical = Ec = O. 

6. Other possible energy changes. — It is well to bear in 
mind that there may be other energy changes of which we 
know nothing. Thus the total heat added to a solid, probably 
monatomic, metal to raise its temperature from — 273° C 
to its melting point and bring it into the liquid condition is 
about 9T/W calories. This amotmt of energy is far greater 
than has yet been accoimted for. Therefore for the present 
we have called, 

10. Eunknown = Ei* = <7 — (E« H" Eo H" Ejk). 

Whether E,, will prove identical with E, is a very interesting 
point. 

We have in the manner indicated analyzed the specific 
heat of benzol and of carbon tetrachloride and give the re- 
sults in Tables 3 and 4. The data for benzol is given in the 
former paper already cited. The measurements have not yet 
been carried over a sufficient range of temperature, nor ex- 
tended to enough substances, to enable conclusions to be 
drawn with certainty. We would, however, call attention to 
the following points : 



* Trans. Am. Electrochem. Soc, 14, 35 (1908). 



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specific Heat of Carbon Tetrachloride 



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64 



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specific Heat of Carbon Tetrachloride 



65 



(a) The energy changes in the saturated vapor due to the 
molecular attraction are far greater than has usually been 
supposed. 

(6) The total energy change unaccounted for, which we 
have called the unknown energy, and designated E«, is a 
constant for carbon tetrachloride to within the limit of error 
of the measurements. It is not a constant for benzol. 

(c) If we compare the energy changes at o® C of mole- 
cules of benzol and carbon tetrachloride we find them similar 
to a remarkable degree as shown below. 

Liquid. 





aXm EkXfn 


EaX w 


EiXw 


Benzol 30 . 98 2 . 98 
Carbon tetrachloride 30.91 2.98 


3.22 
3 18 


24.78 
24 -74 


Saturated Vapor. 








aXm E^Xwe 




EuXn 


Benzol 

Carbon tetrachloride 


1 
22.17 I 95 
21.53 1-77 


—7.61 
—7.78 


24.84 
24 -55 



(d) y has been measured for benzol by Stevens* who ob- 
tained the value 1.105 at 99.7°, and by Wiedemann' who ob- 
tained the value i . 1 29. For carbon tetrachloride Capstick* 
obtained the value 1.130. For benzol using the value of 
Stevens we obtain 0.2044 for E, from equation 8. For carbon 
tetrachloride similarly we obtain 0.0800. When y is nearly 
equal to one slight errors in the measurement of ;- cause 
greatly increased errors in E, and it is unfortunate that for 
this reason no very great reliance can be placed upon these 
values. 

(e) The total heat necessary to raise 6.05 grams of hy- 
drogen from — 273® to 20^ C is 6740 calories.* The total heat 

* Stevens: Ann. der Physik., [4] 7, 285 (1902). 
' Wiedemann: Wied. Ann., 2, 195 (1877). 
'Capstick: Proc. Roy. Soc, 57, 322 (1895). 

* Trans. Am. Electrochem. Soc., 14, 35 (1908). 



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66 /. E, Mills and Duncan MacRae 

necessary to raise 72 grams of carbon as graphite from — 273® 
to 20® is approximately 1480 calories, and similarly as diamond 
800 calories. ^ Nordmeyer and Bemouilli' have determined the 
average specific heat of benzol from 20^ to — 185® C to be o. 1 76, 
allowing 30 calories for the heat of fusion. Estimating the 
average specific heat of benzol from — 185° to — 273® to be 
0.08 we find that 5707 calories of energy would be required to 
raise the temperature of 78.05 grams of benzol from — 273® 
to 20® C. If the carbon and hydrogen existed as elements 
the necessary energy for a similar rise in temperature would 
be 7540 calories if the carbon were in the form of diamond, 
and 8220 calories if the carbon were in the form of graphite. 
Since about 1745 calories of this energy is due to external 
work this amount might be subtracted, leaving 5795 and 6475 
calories respectively. Nearly as much energy is therefore 
required to raise the temperature of the carbon and hydrogen 
from — 273® to 20^ C when they are combined to form benzol 
as when they exist separately. 

Summary 

1. The specific heat of liquid carbon tetrachloride is 
foimd to vary linearly with the temperature between o® and 
70® C. The line passes through the values 0.2010 at o® and 
0.2031 at 70® C. 

2. The specific heat of the saturated vapor of carbon 
tetrachloride has been determined and the following values 
obtained, o® = 0.140, 10° = 0.138, 20^ = 0.135, 30^ = 0.132, 
40® = 0.128, 50° = 0.124, 60° = 0.119, 70° = 0.115. 

3. The results obtained both for carbon tetrachloride 
and for benzol have been discussed and certain facts con- 
cerning the energy changes involved have been pointed out. 

The above work was done in the chemical laboratory of 
the University of North Carolina. 

University of North Carolina, 
August II, 1 910 



* Dewar: Proc. Roy. Soc, 76a, 325 (1905). 

* Verh. der deutsch. Phys. Ges., 9, 175 (1907). 



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THE SOLUBILITY OF LIME IN AQUEOUS SOLUTIONS 
OF SUGAR AND OF GLYCEROL* 



BY F. K. CAMERON AND H. B. PATTEN 

Introduction 

In a previous publication from this laboratory^ a r&um^ 
was given of the extant data upon the solubility of lime in 
various solutions. It was concluded that when lime is brought 
into contact with sugar solutions, the ratio of lime to sugar 
in the solid varies continuously with the composition of the 
solution ; and . consequently the solid compound resulting 
when lime is added in excess to a sugar solution is one of a 
series of solid solutions. The data on record, however, 
possess the common defect that the quantities of sugar re- 
maining in solution after contact with the lime were not 
determined. The original sugar concentrations of the solu- 
tion were known, and the quantities of lime dissolved by it 
were determined; but the sugar in the resulting solution not 
being determined, there is a possibility that some of the sugar 
may have been precipitated in the solid (lime) phase. While 
the existence of a compound of lime with sugar is known, 
and this fact would indicate the strong probability that some 
sugar at least would be withdrawn from a sugar solution in 
contact with excess of lime, yet it is to be remembered that 
water breaks down the crystalline lime-sugar compound. 

The System, Lime-Sugrar-Water at ES'' 

Cane sugar solutions varying from 0.5-40 percent were 
prepared, and slaked lime added to each in slight excess. 
The physical properties of the system, lime-sugar- water, are 
such as to render difficult the attainment of equilibrium con- 
ditions. The lime compacts into balls and cakes and these 



* Published by permission of the Secretary of Agriculture. 

' The action of water and aqueous solutions upon soil carbonates. F. 
K. Cameron and J. M. Bell, Bull. No. 49, Bureau of Soils, U. 3. Dept. of Agri- 
culture (1907). 



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68 F. K, Cameron and H. E. Patten 

resist disintegration into a flocculent sediment, even under 
months of shaking in a thermostat. Consequently to ensure 
the formation of a soHd phase in final equilibrium with the 
solution, it was found desirable to saturate the sugar solution 
with lime at a low temperature — about o® C — where it is more 
soluble, and then pour off the supernatant solution. This 
saturated liquid was then allowed to warm up to 25^ with 
constant agitation in the thermostat. The solid phase which 
deposited from solution was finely d vided and showed no 
tendency to form aggregates. 

The sugar solutions are of course very viscous at room 
temperature. The viscosity decreases rapidly with rise in 
temperature, but the solubility of lime in these solutions also 
decreases. If the stiff solution be heated in order to stir it, 
then fine particles of solid phase appear throughout the 
liquid, and if these be allowed to settle while the solution is hot, 
then on cooling, the supernatant liquid — which has again 
become stiff — ^regains its higher solvent power for lime. It 
is well nigh impossible to bring this stiff liquid into intimate 
contact with a sufficient surface of solid phase to ensure 
equilibrium. Consequently it was found impracticable to 
study the lime-water-sugar system at high concentrations of 
sugar and lime. The fact that considerable lime will dissolve 
in these stiff syrups may of course be shown and is of interest 
in itself, but the main object of the present work is to deter- 
mine the character of the solid phase under equilibrium con- 
ditions, and the stiffer sugar solutions are not adapted to this 
purpose. 

The complete dry combustion of the solution was made in 
oxygen supplemented by copper oxide, the carbon of the sugar 
being weighed as carbon dioxide; and the solvent wate plus 
the constitutional water of the sugar were weighed together 
as water. Given the weight of carbon dioxide, the weight of 
constitutional water in the sugar can be computed, and 
deducting this leaves the water originally added to make up 
the solution. The lime in solution was determined separately 
by evaporating the solution in platinum, burning off the sugar 



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Sotubility of Lime in Sugar Solutions 69 

and igniting before the blast lamp. In the case of a solid 
phase rich in lime, the combustion was carried out at high 
temperature to decompose the calcium carbonate formed. 
Several combustions at lower temperature left a residue in the 
combustion boat rich in carbonate, but by using a higher tem- 
perature, not a trace of carbonate remained. For the solid 
phase the percentage of Hme is so high and the cafbon dioxide 
and water determinations so accurate, that the lime was in 
some cases taken by difference; but the solutions were analyzed 
for lime directly in every case. 

The solid phase obtained was in no case crystalline. 
Under the microscope it appeared as fine globular granules, 
consequently a sharp separation from the mother liquor was 
not feasible. To obviate this difficulty the solutions were 
allowed to settle in the thermostat for several weeks, and the 
clear Hquid phase poured off from the pasty sediment. This 
residual lime-paste was scraped into a glass-stoppered weigh- 
ing bottle, placed in a padded glass test tube and centrifuged 
at about'800 r. p. m. for two or three days imtil the solid showed 
no further signs of settling. The supernatant liquid was poured 
out of the bottle and the last few drops absorbed with clean 
filter paper. The weighing bottle was then weighed, the solid 
phase scooped out with a small platinum spoon and removed 
to a long combustion boat by means of a platinum scraper. 
Both spoon and scraper were placed in the combustion boat 
which was immediately transferred to the combustion tube in 
place in the furnace. The closely stoppered weighing bottle 
was again weighed and the difference from the former weight 
gave the weight of the solid phase and mother liquor taken for 
analysis. 

The compositions of the solutions are given in Table I. 
The lime present is reckoned as Ca(0H)2 for convenience, 
esi>ecially as it was anticipated that the solid phase might 
prove to be calcium hydroxide. On the other hand, there is 
no particular advantage in stating the results as calcium 
oxide. In Fig. i the calcium hydroxide in solution is plotted 
as a function of the sugar. The curve thus obtained is smooth. 



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70 



F. K. Cameron and H. E. Patten 



Table I 
Lime-sugar- water system at 25® C. Liquid phase. 



C.(OH), 
percent 



O.I17* 

0.188 

0.73 

I 355 

2.31 

3.21 

4-57 

5.38 

6.07 



CifH„0,| 
perceot 



O 
0.62 
4.82 
7 50 
9.87 
II .90 

15 I 

17.42 

19.86 



H,0 
percent 



99 


19 


94 


50 


91 


12 


87 


85 


84 


89 


80 


33 


76 


93 


73 


07 



Density 



0.983 
1 .000 
1 .021 

1.037 
1. 051 
1.067 
1 .092 
1 . 109 
1. 123 



.t 






















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Q 








^ 


^ 


^ 








^La 


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1 4 


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1 M 




lor 

1 i< 


• M 


1 M 


• to 



Fig. I 

showing no obvious breaks, and passing of course through the 
point for the solubility of calcium hydroxide in water alone. 
Consequently the solid phases in contact with the solutions 
represented by this isotherm must be either calcium hydroxide, 
or a series of solid solutions with calcium hydroxide, as a 
limiting solid solution at one end of the series. 

Attempts were made to determine the nature of the 
solid phases by the indirect method of Schreinemakers' and 
Bancroft,* employing the triangular diagram, but owing to 
the viscosity of the solutions, satisfactory separations of solid 
from mother liquor could not be obtained even under long 
centrifuging. Consequently the results were indeterminate 
and the method was abandoned. 

A solution was prepared containing 303.24 grams of water, 

* Cameron and Bell, 1. c. 

»Zeit. phys. Chem., II, 81 (1893). ' • 

* Jour. Phys. Chen^., 6, 178 (1903). . . 



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Solubility of Lime in Sugar Solutions 



71 



and 100 grams of sugar. To this solution was added 63.88 
grams of calcium hydroxide. After long standing with inter- 
mittent shakings at 25® C analysis of the supernatant solu- 
tion gave 21.97 percent sugar, 8.32 percent calcium hydroxide 
and 69.71 percent water (by difference). The ratio of water 
to sugar in the liquid phase was therefore increased by the 
addition of lime from 303-3. 17, showing that sugar entered 
the solid phase. Consequently the solid phases were a series 
of solid solutions. That the absorption of sugar in the solid 
phase may be considerable is shown by the fact that in this 
particular case just cited the solid contains about 10.8 percent 
sugar, assiuning that the ratio of lime to water remains that 
in calcium hydroxide. 

The System, Lime-Glycerol- Water at 25^ 

This system presents experimental difficulties similar to 
the one just described owing to the great viscosity of the more 
concentrated solutions. The solubility data are given in 
Table II. When plotted they give a straight line passing 
through the point representing the solubility of calcium 
hydroxide in water. 

Table II 
Lime-glycerol-water system at 25® C. Liquid phase 



Experiment 
number 



O 
a 

A 
B 
C 



Ca(OH), 
percent 



0.I17 
0.178 
0.413 

0.48 
0.88 
1-34 



CHsCOH), 
percent 



H,0 

percent 



3 
15 

17 
34 
55 



50 
59 

84 
32 
04 



96.32 
80.28 

81.68 
64.80 
43.62 



Density 



1.008 



1.042 
1.088 
1. 149 



A solution was prepared containing 35.9 percent glycerol, 
to which was added about 40 gt^ms calcium hydroxide. This 
system was agitated for several hours in an ice bath, then 
aUowed to come gradually to 25®. Analysis of the super- 
natant solution gave 36.2 percent glycerol and 0.93 percent 



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72 F, K. Cameron and H, E, Patten 

lime. Evidently no glycerol entered the solid phase, and the 
slight apparent increase in the liquid phase can most probably 
be attributed to the difficulties of analysis. It is apparent 
that the solid phase in contact with a water glycerol solution 
at 25° is always calcium hydroxide. Furthermore, the 
solubiUty of calcium hydroxide is increased proportionally to 
the concentration of glycerol. 

Summary 

(i) Solubility isotherms for lime in solutions of sugar and 
of glycerol at 25° have been determined by direct analysis 
of the liquid phases. 

(2) The solid phase in the system lime-sugar- water is 
one of a series of solid solutions, with calcium hydroxide a 
limiting case. 

(3) The solid phase in the system lime-glycerol-water at 
25® is always calcium hydroxide. 

(4) The increase in solubility of lime in aqueous solutions 
of glycerol over that in pure water is directly proportional to 
the concentration of glycerol. 

Bureau oj Soils^ 

V . S. Department oj Agriculture^ 

Oct. 3, J 9 JO 



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THE USE OF A DEWAR FLASK IN MEASUREMENTS OF 
HEATS OF NEUTRALIZATION 



BY J. HOWARD MATHEWS AND A. F. O. GERM ANN 

Many attempts have been made to devise a simple 
laboratory method for the accurate determination of heats of 
neutralization. The method in most common use is cumber- 
some, and has some other very serious objections. The chief 
of these is the necessity of removing one of the reacting 
liquids from its calorimeter and pouring into the other; an 
operation which introduces a temperature change the magni- 
tude of which cannot be estimated, and for which consequently 
no correction can be applied. Of importance also is the fact 
that two thermometers are required, which may introduce 
considerable error if they have not been accurately compared 
and standardized against each other. 

To overcome these objections various devices have been 
tried. Thus Julius Thomsen placed one calorimeter above 
the other and mixed the liquids after temperature equilibrium 
had been reached, by allowing the upper liquid to flow into the 
lower. Nemst tried to remove the necessity of the second 
thermometer and at the same time insure temperature equilib- 
rium before mixing by immersing the acid, contained in a large 
test tube, in the alkali, and breaking the tube when tempera- 
ture equilibrium had been reached. Kahlenberg has used a 
somewhat similar device in that he replaced the test tube by a 
thin glass flask open at both ends, over the bottom of which 
he placed paraffined paper. The latter could be broken 
without difficulty and was easily replaced. Rubber mem- 
branes have also been used. Still others have used a collap- 
sible cup for holding one of the reacting liquids until tempera- 
ture equilibrium was attained. 

In both the Thomsen and Berthelot methods, and their 
various modifications, the correction for radiation is often 
large and necessarily of somewhat uncertain value. Further- 
more, heat radiation is undesirable because it also accentuates 



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74 /• Howard Mathews and A. F. O, Gertnann 

the error due to thermometric lag/ The adiabatic method 
devised by Richards and Rowe,' is of course, the best method 
so far devised for the determination of heats of neutralization 
where very accurate results are required. 

The primary object of the present investigation was to 
devise an apparatus of simple construction which would 
be free from the more prominent sources of error in the Berthe- 
lot and Thomsen methods. Preliminary experiments in which 
two Dewar cylinders replaced the customary calorimeter and 
concentric polished cylinders of the Thomsen method or the 
calorimeter and surrounding water jacket of the Berthelot 
method showed a very great improvement, as the radiation 
.correction became very small because of the superior insulation 
afforded by the Dewar flasks. This makes the radiation 
correction more certain in value and reduces the error due to 
thermometric lag, although it does not entirely eliminate it. 

We then conceived the idea of replacing the large and 
cumbersome calorimeter in common use by a Dewar flask, 
and of using a cylindrical tube of thin glass whose lower end 
was closed by a rubber septum to separate the acid from the 
base; and, further, of determining the heats of neutralization 
of several acids with sodium hydroxide at different concentra- 
tions to ascertain the general applicability of the method. 

A silvered Dewar flask (see figure) of about 600 cc capacity 
constitutes the calorimeter. The glass cell B has a capacity 
of about 250 cc, and fits loosely into the flask. At the bottom 
is a flange over which a small piece of dentist's rubber dam 
may be tightly drawn, and held by a rubber band. The cell 
B is attached to a brass sleeve and eccentric, which gives it a 
vertical motion, guided by a central modified Witt stirring 
rod C, whose motion is rotary. By th s means the two solu- 
tions, both within and without the cell B, are well stirred. 
The flask is closed by a cork stopper containing two holes; 
one in the center to allow the passage of the central stirring 



* Richardson, Henderson and Forbes: Proc. Am. Acad., 41, 1; Zeit. 
phys. Chem., 52, 551 (1905). 

^ Zeit. phys. Chem., 64, 187 (1908). 



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The Use of a Dewar Flask 



75 



rod and the pitman attached to the crank, and the other at 
one side for the entrance of the thermometer. The latter 
dips into the Uquid contained in the eel! B. The cork is 
covered with bright tinfoil to reduce radiation. 




The thermometers used were a Beckmann and two others 
not of the differential type. One of the latter was graduated 
to twentieths of at degree, and read froni 15^-30^; and the 
other read from 18^-25^ and was graduated to hundredths 
of a degree, as was also the Beckmann. The instruments were 
all of Goetze's make and of the best grade. They were Hot 
standardized for this work, however, since we had in mind 
only the testing out of the methbd to ascertain its adaptability 
to general laboratory practice. Therefore the values here 
given are in no wise to be interpreted as a revision of Thomsen's 
values. Nevertheless we believe that we have demonstrated 
that by the method here described a high degree of accuracy 
may be attained. 

The acid solutions were made up in carbon dioxide free 
water,' and were carefully checked again3t each dther. Half 
normal hydrochloric acid, standardized gravimetrically by 
precipitation as silver chloride, was used as the starting point. 



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76 



/. Howard Mathews and A. F, O, Germann 



The sodium hydroxide was Merck's **from alcohol/* and was 
freed from carbonate by making up first a i : i solution, in 
which sodium carbonate is very insoluble, filtering, and 
making up to the required strength. For the half normal 
solutions sodium hydroxide prepared from metallic sodium, 
by allowing to stand in a platinum dish over water in a desic- 
cator protected with a soda-lime tube, was also used. The 
thermal data obtained by the use of the solutions prepared 
in these two ways checked so closely that the Merck product, 
purified as described, was used for the other concentrations. 




The initial temperature of the determinations for all but the 
twice normal solutions was 1 8 ^. For twice normal sulphuric acid 
the initial temperature was about 15^, and for the other twice 
normal solutions about 16^. The solutions after being 
brought to the desired temperature were measured from a 
200 cc pipette, the exact capacity of which had been deter- 
mined, and the excess of the acid or alkali was ascertained 
after each experiment by titration, using phenolphthalein as 
an indicator. The motor was run at such a rate that the cell 
B plunged up and down about once per second; while the 



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The Use of a Dewar Flask 



77 



central stirring rod was geared so as to make about four or 
five revolutions per second. The initial temperature of the 
base, which was always placed in the cell B, was always a 
little higher than that of the acid. This gave an opportunity 
to determine when temperature equiUbrium was established, 
for the thermometer, which was placed in B, at first showed a 
slow drop in temperature, came to a minimum, and then 
finally began to rise again due to communication of heat from 
without the apparatus. The minimum reading showed tem- 
perature equilibrium, and this was always reached in less than 



9U99d 

•1 socf 


: 1 


y 






o 

c 




/ 






Ckcetf 


• 










IS^Ctf 


3 


u i 
• / 

E / 


f 






^ / 










IT-.OMf 




Jll 


!• In MInut 


»• 






1 i 9 


1 






9 



(Curve II) 

five minutes. Temperature readings were made at intervals 
of one minute. When the thermometer seemed to be rising 
regularly the stirring rod, which was provided with two 
sharp copper points at the base, was lowered without inter- 
rupting the stirring, so that the points, coming in contact 
with the tightly stretched membrane, tore the latter and 
allowed the solutions to mix. At the same time the flask 
was raised, thus plunging the cell with its contents into it 
to such a depth that the solution could flow over the top of the 
cell B and thus insure thorough mixing in the least possible 



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78 /. Howard Mathews and A. F, O. Germann 

time. The time at which the mercury thread of the thermom- 
eter began to rise was noted and taken as the time of mixing. 
One minute was required for the thermometer to register 
the total rise in the case of the normal, half normal and twice 
normal solutions; thirty seconds for the quarter normal. 
The temperatures were plotted against the time, and by a 
slight extrapolation the exact temperature of the solution 
before and after mixing was found. It was found that about 
five minutes were necessary for the glass flask, etc., to assume 
the temperature of the solution; hence only those tempera- 
tures should be considered which were taken after the ex- 
piration of this time, i. e,, the time required for temperature 
equilibrium. 



Z4^0tf 



e^eso* 




Fig. 4 

(Curve III) 

The water equivalent of the apparatus could not be 
determined directly, but was found indirectly by allowing a 
reaction of known thermal value to take place in it, and from 
this calculating the water equivalent. The reaction em- 
ployed was the neutralization of half normal hydrochloric 
acid by sodium hydroxide. The heat of neutralization is 
given by Julius Thomsen in this case as 13,740 calories at 



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The Use of a Dewar Flask 79 

18^. The mean of two concordant determinations was taken 
as the true value, and was found to be 23.2 grams. The data 
and computations appear in the following table : 

I. To Determine the Heat Capacity of the Apparatus, as Ex- 
pressed IN Terms of the Water Equivalent 

Volume of measuring pipette 198.4 cc 

Weight of N/4 solution formed 402 .7 grams 
Specific heat of N/4 HCl solution (Thomsen) 0.980 

Rise of temperature (from Curve I) 

Final temperature 3 549° 

Initial temperature o . 286 ^ 



Rise in temperature during experiment 3 . 263® 

"Heat Capacity" of the solution: 

402.7 X 0.980 = 394.64 grams 

Total heat taken up by the solution : 

394.64 X 3263 = 1287.7 cal 

One gram equivalent of sodium hydroxide (at a dilution of 
N/2) should liberate 13,740 cals. (Thomsen). 
Then 198.4 cc of N/2 solution should liberate: 

.98.4 X 13,740 _ 6 ^ 
2000 

The difference divided by the rise, 

1363— 1287.7 _ ,, ^^ 

2 = 23.07 

3.263 

is the water equivalent of the apparatus. 

By a similar calculation we obtain from Curve II a rise of 
3.261^, and a water equivalent for the apparatus of 23.33 
grams. The mean of these two values is 23.2, and differs 
from each individual determination by but 0.6 percent. This 
reduces to a negligible quantity in the final calculations of 
heats of neutralization, viz,, o.i percent in the case of thie 
half normal solutions, 0.025 percent for the normal ones, and 
0.005 percent for the twice normal ones. 



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8o ./. Howard Mathews and A, F. O. Germann 

II. Method of Calculation of Heat of Neutralization. 
(Neutralization of Normal Hydrochloric Acid with 

Sodium Hydroxide) 
Temperature rise (from Curve III) 

Final temperature 24.678° 

Initial temperature 18 . 130 



Total rise in temperature during expt. 6.648° 

Specific heat of N/2 NaCl solution (Thomsen) 0.964 

Weight of NaCl solution formed 408.83 grams 
Water equivalent of NaCl solution formed: 

408.83 X 0.964 = 394 11 grams. 
Total water equivalent 394- n + 23.2 = 41731 grams 

Total heat liberated 4i7-3i X 6.548 = 2732.6 cal 

Volume of sodium hydroxide actually neutralized 198.1 cc 
1000 cc (containing one gram equivalent) would 
therefore liberate 

2732 X 1000 , . 

198 T"^ = 13.793 calories. 

The complete data for the determinations made on the 
four concentrations appear in the following table. 

The results obtained for half normal solutions are some- 
what lower than those given by Thomsen (Thermochemische 
Untersuchungsmethoden Vol. I) except in the case of nitric 
acid. The molecular heats of neutralization found at different 
dilutions exhibit little regularity of change; in the case of 
hydrochloric acid the value increases with the concentration; 
for nitric acid the value remains more nearly constant; for 
sulphuric acid it increases with the concentration; and for 
acetic acid the value diminishes from 13.2 + calories for 
fourth and half normal solutions to 12.9 + calories for twice 
normal solutions. Greater dilution than half normal seems 
to have little effect on the heat of neutralization. 

As shown by the curves, the absorption of heat when 
Working at even 10^-14^ below room temperature is very small, 
amounting to less than 1/100° per minute. All of these 
determinations were made under unfavorable conditions, as 
they were all made in July when the temperature of the room 
was generally about 30°. Under ordinary laboratory con- 
ditions much better results could undoubtedly be obtained. 



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The Use of a Dewar Flask 



8i 



Strength of acid used 


Heat of neutralization 1 
(in calories) 1 

1 


Average value 


N/4 HCl 
N/4 HCl 


i3»5o8 ; 
13,565 


13.536 


N/2 HCl 


— 


(13,740)' 


N HCl 
N HCl 


13.791 

13.785 i 


13.788 


2 NHCl 

2 N HCl 


13.923 
13.906 


13.915 


N/4 HNO, 
N/4 HNO, 


13.536 
13.561 


13.548 


N/2 HNO, 
N/2 HNO, 


13.648 
13.647 


13,647 


N HNO, 
N HNO, 


13,612 
13.616 


13.614 


2 N HNO, 
2 N HNO, 
2 N HNO, 


13.649 
13.633 
13.627 


13.636 


N/4 H,SO, 
N/4 H,SO, 


15.370 i 
15.353 


15,361 


N/2 HjSO, 
N/2 H,SO, 


15.585 i 
15.593 


15.589 


N H,SO, 
N H,SO, 


15.674 
15.667 


15.670 


2 N H,SO, 
2 N H,SO« 


15.817 
15.810 


15.813 


N/4 CHjCOOH 
N/4 CH,COOH 


13.219 
13.244 


'3.231 


N/2 CH,COOH 
N/2 CHjCOOH 
N/2 CHjCOOH 


13.231 
13.237 
13.233 


13.234 


N CHjCOOH 
N CH,COOH 


13.175 
13.162 


13.168 


2 N CH,COOH 
2 N CH,COOH 
2 N CH,COOH 


12,903 

12.943 
12,921 


12,922 



* Reaction chosen for determination of water equivalent of apparatus. 



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82 /. Howard Mathews and A, F, O, Germann 

It has been shown that the Dewar flask may be used 
successfully as a calorimeter for determining the heats of 
neutralization of acids and bases at widely diflferent concen- 
trations; heat radiation is very small, even when working 
considerably below room temperature, and results may be 
obtained which are concordant. By using but one vessel the 
acid and alkali acquire the same temperature and that tem- 
perature may be determined exactly. The working parts are 
simple, and if necessary can be made by a student of ordinary 
skill, thus making it both a convenient and reliable method for 
laboratory use in classes of physical and thermochemistry. 

Laboratory of Physical Chemistry ^ 
University of YVisconsin, Madison ^ 
Octoher^ igio 



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NEW BOOKS 



Descriptiye Meteorology. By Willis L. Moore. i6 X 23 cm; pp. xiii -f 
344. New York: D. Applelon and Company, igio. — "The object in writing 
this book was to provide, so far as possible, the young men entering the service 
of the U. S. weather Bureau with a comprehensive introduction to modern 
meteorology." 

The subject is discussed under the headings: the atmospheres of the earth 
and of the planets; atmospheric air; microorganisms and dust-motes of the air; 
physical conditions of the sun and its relation to the earth's atmosphere; heat, 
light, and temperature; thermometry; distribution of insolation and the re- 
sulting temperature of the atmosphere, the land, and the water; the isothermal 
layer; atmospheric pressure and circulation; the winds of the globe; the clouds; 
precipitation; forecasting the weather and the storms; optical phenomena in 
meteorology; climate. Concealed in one of these chapters — I will not say 
which — is a long and interesting dissertation on frost in cranberry bogs. 

The book is full of items of interest to the physical chemist and to the 
frequenter of receptions. After reading this book one sees marvelous and un- 
suspected possibilities in the weather as a topic of conversation. It is per- 
haps too much to urge that this book should be on every dinner table; but 
there are times when that would be useful. 

Among the briefer items of interest are: the variation in the amount of 
ozone, p. 14; the number of bacteria in the air, p. 27; the dust-motes in the air 
and how to count them, pp. 29, 37; the frost level in the free air, p. 93; our 
perplexity as to lightning, p. 169; the existence of supercooled water in clouds, 
p. 195; the limiting diameter of rain drops, about 0.3 inch, p. 208. 

The author has the following to say, p. 67, in regard to the placing of 
thermometers. "In order that thermometers may indicate the temperature of 
the free air it is necessary that they be exposed where they will not receive direct 
radiation from the sun or sky or from surrounding objects, and where the air can 
circulate freely. They also must be protected from rain and snow as far as 
possible. In large cities it is necessary to locate the shelter on the roof of a 
building, if possible on one higher than any surrounding it, care being taken to 
avoid the influence of chimneys, skylights, ventilators, etc. Thermometers 
that are exposed to direct radiation from any source, even though they are pro- 
tected from direct solar radiation, cannot indicate the true temperature of the 
air." 

There are some curious facts about the temperatures in lakes, seas, and 
oceans, p. 84. 

"Mill has shown that the lochs of Scotland, which are filled with sea water 
much freshened on the surface by numerous small mountain streams, cool on 
their surfaces as winter approaches, but, since the water is comparatively fresh, 
it continues to float on the wsumer sea water below. The latter, because of its 
salinity, maintains a greater specific gravity than the chilled fresh water above. 
Convection does not operate freely, as it would if the lighter water were below. 
In many cases the water of these lochs is prevented from circulating with the 
cold water of the deep ocean by bars or sills which rise, at the entrance to the 



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84 New Books 

lorh, nearly to the surface. In such cases the fresh water may freeze, while the 
salt water that is below the level of the bar retains a temperature of 45° or more. 

"Because of the displacement of oceanic isothermals by ocean currents, it is 
impossible to name a definite temperature as prevailing over oceans at all places 
on a given parallel of latitude. But in a general way it may be stated that at 
the equator there is a surface temperature of 82^-84° F, which changes less than 
a degree between day and night, and not over 5® between winter and summer; 
at a depth of 400 fathoms the temperature is 44® and unchangeable, and below 
i,ooo fathoms it is a little above the freezing point of fresh water — namely, 
% 1^-36°. In the middle latitudes the surface variation is from 50® in winter to 
68 '^ in summer. At latitude 70° N the surface temp^erature has but a small 
diurnal variation, and a yearly range of from 35° for winter to 45® for summer; 
at a depth of 4CX) fathoms it remains steady at 32°. From this level there is a 
gradual decrease to a depth of 1,000 fathoms, where a constant temperature of 
about 28° exists, and below this to the bottom there is no change. One may 
get an idea of the enormous volume of cold water that lies upon the surface of 
the earth from the statement that about three-fourths of the earth is covered 
with oceans, whose depths average about two miles, and in some places five 
miles, and whose temperatures below one mile are always close to the freezing 
point. 

"The temperature of enclosed seas is fairly well represented by the thermal 
conditions of the Red Sea, which extends in a nearly north and south direction, 
approximately one-half of it lying in the tropics, being 1,450 miles long and 
about 180 miles wide. It receives heat from the hot radiating land that confines 
it to a long channel, which is narrow in comparison with other inland seas. 
Only the surface water of the Indian Ocean on the south is able to enter to take 
the place of the large amount that evaporates, for at its southern extremity a 
bar or sill, which extends from the bottom to within 200 fathoms of the surface, 
separates the deep water of the sea from that of the outside ocean. Its siu*face 
temperature varies from 85° in summer to 70° in winter, which is about the 
same as that of the Indian Ocean. Both bodies decrease in temperature at about 
the same rate down to the level of the sill, where the temperattwe remains con- 
stant at 70® the year through. Here their thermal similarity ceases, for the 
Red Sea, which has a depth of 1,200 fathoms, maintains a temperature of 70® 
from the top of the sill all the way down to the bottom, while the ocean con- 
tinues to decrease in temperature down to a depth of at least 1,000 fathoms, 
where a temperature of 34°-36® F prevails without variation. 

"In a comparison between the Mediterranean and the basin of the Atlantic, 
a similar condition is found to exist. The sill at the entrance to the Mediterranean 
is 190 fathoms below the surface, at which level the temperature of both bodies 
is equal to 55° F. In the Mediterranean this temjjerature continues clear 
down to the bottom, while the temperatiwe of the Atlantic at the same level 
as that of the bottom of the Mediterranean is only 35°. 

"In Lake Superior, which has an average depth of 900 feet, the temperature 
below the level of 240 feet remains unchanged throughout the year at 39®." 

On p. 100 we learn that mountain tops are cooler than free air at the same 
level. 

"Wherever observations have been made they have shown that the tem- 



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New Books 85 

perature of the air on high mountain peaks and crests and for a distance of 
100-300 feet above them is appreciably cooler than adjacent free air of the 
same height, due to deflection of the winds and radiation of the peaks. It is, 
therefore, probable that the same conditions of coldness prevail over all moun- 
tains. Clayton, in an excellent series of observations at Blue Hill, Mass., has 
shown that even at this station, which is only a little over 600 feet above the 
sea level and 480 feet above the level of the valley, the temperature at night is 
lower than that of the free air at the same elevation over the valley, the differ- 
ence often being as much as 2 °, 5 °, or 7 ® F ; and when the decrease of tcmp^era- 
ture with elevation in the free air was less than the adiabatic rate, as it usually 
is, the cooling appeared above the top of Blue Hill in the daytime. When the 
kites were pulled in at night the kite-meteorograph generally showed a uniform 
rise of temperature with descent until it was within less than 150 feet of the 
top of the hill, when a sudden fall of temperature occurred. The mean tem- 
I>erature of the air above every peak that has been compared with the tem- 
perature of the free air of the same level has been found cooler than the free air, 
and it is probable that all mountains, by forcing the air to rise over them and to 
cool by expansion as it ascends — which cooling usually is at greater rate than the 
vertical decrease of temperature of the free air — produce a cooling effect that 
more than compensates for the heat given to the air by conduction and radiation 
from the mountain. This effect must be greater when the direction of the wind 
forms a considerable angle with the direction in which the mountain trends, 
and be greatest when the incident winds encounter mountains at right angles 
to their direction of movement. On clear nights mountains are abnormally 
cooled by radiation." 

On p. 105 the author compares the temperature changes for San Francisco, 
Denver, Chicago and New York. 

"San Francisco, being situated near the ocean and in the prevaiUng westerly 
winds of the middle latitudes, has a marine climate, the westerly wind usually 
bringing to that city the temperature, approximately, of the ocean. The range 
of the temperature of the water is not great, and consequently there is found 
on the Pacific Coast very even temperature. The range at New York should be 
greater because of its position farther north, but were the prevailing winds from 
the Atlantic on the eastern seaboard, the range in temperature would not be 
materially greater than along the Pacific Coast. Temperature conditions at 
New York are therefore affected somewhat by the proximity of the ocean, and 
the range is consequently considerably less than in the interior. Denver, Colo., 
located at a slightly lower latitude than New York City, has a much greater 
annual range in temperature, and it is even greater than Chics^go, the temp^erature 
in the latter city being affected by the great lake that washes its shores, but while 
its annual range is considerable, it is not as great, as a rule, as that observed 
on the great plains, immediately east of the Rocky Mountains, or on the same 
parallel of latitude, where it approaches close to the Pacific Ocean, but is partly 
protected from the modifying vapor of the ocean by intervening high mountain 
ranges." 

Some interesting facts in regard to marshes and bogs are brought out on p. 
108. 

"In order to ward off frost, progressive cranberry growers have resorted to 



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86 New Books 

three expedients, viz., cultivation, drainage, and sanding. Through cultivation 
the marsh may be kept clean and free from weeds, moss, or other rank growth, 
thus permitting the solar radiation to reach the soil and to increase its tempera- 
ture. The growth of thick vegetation screens the soil from the sun's rays, and 
there is consequently less heat in such a soil to be given off by radiation or con- 
duction in the nighttime. Drainage lowers the specific heat of the soil and de- 
creases the cooling effect of evaporation; therefore, under sunshine the dry soil 
becomes warmer than the wet and, whether or not it has more heat to give off 
at night, it has a higher temperature and therefore radiates more freely to the 
air above. A covering of sand likewise lowers the specific heat of the surface, 
and thereby conduces to a higher temperature during the day and increased 
radiation at night. In the Cape Cod cranberry marshes sand about half an 
inch in depth is spread over the surface of the bog each year, while in Wisconsin 
no such systematic method has been adopted; but several of the marshes have 
been sanded from time to time, usually to a depth of about 2 inches, at intervals 
of several years. These three methods of prevcntirtg low night temperatures 
have been so beneficial that where systematically carried out, there is practically 
no need of flooding to prevent frost, except in the spring or autumn. 

"The cold air, on nights when frost is imminent, settles gradually down the 
slopes to the bottom lands, and if all the conditions in these bottom lands or bogs 
were the same, there would be no differences in air temperatiu-es at the! sur- 
face; yet it is interesting to see how much the temperature varies at different 
places in the same bog, and often even wheri these places ate near together. 
The difference in temperature over these varidus surfaces disappears often at an 
elevation of 3 feet, while at the very surfaces there may be a difference of from 
5°-io°. The cold air, as it settles gradually through gravity, overspreads the 
marsh, but here and there we find warm places and cold places, atid still others 
having an intermediate value. This variation in temperature is due largely to 
the differences in temperature of the soil or covering. It is as if heaters of vary- 
ing power were scattered over the bog, giving off hedt to the air immediately 
above, some in greater quantity, others in less. In places where the heater was 
protected by vegetation and, therefore, not supplied with much fuel the previous 
day, or where, much heat being supplied, the specific heat of the heater was so 
great that but little gain in temperature was effected, or where the fuel was con- 
sumed in processes other than those of heating, such as evaporation, there is 
weak radiation at night; at those places the surface air temperatures remain 
relatively low. Right here it is important that a close distinctioh t)6 made 
between the effect on the air of weak radiation and conduction from a surface 
of great specific heat and moderate temperature and the effect of rapid trans- 
ference of heat from a good conductor having a surface of low specific heat and ' 
high temperature. In the first instance, a moderate amount of heat may be 
transmitted for a long time without addition to the original quantity; in the 
second case, comparatively high temperature is transmitted for a short' time, 
which period, however, may be sufficiently long to span the houfS at night Wh^n; 
frost is liable to occur." ' , • 

On p. 12 1 \te learn that " we therefore have two distinct strala in bur atmos-' 
phcrc that intermingle but slightly.' a lower or inner turbulent btib, Which iti- 
cludes the first two regions previously described, with a large negative tempers- 



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ture gradient, and an upper or outer one, with a small positive gradient, floating 
on the first, like oil on water. The lower stratum contains from two thirds to 
three fourths of the entire mass of such gases of the air as oxygen, nitrogen, and 
all the members, except helium, presumably, of the argon family; a still greater 
proportion of the carbon dioxide, and nearly all the water vapor. It is warm 
in its lowest portion, but cools, irregularly at first, then rapidly and nearly 
regularly, with increasing elevation to a minimum of from — 40° to — 70° C. 
The upper stratum contains extremely little water vapor, and its temperature 
rises, sometimes abruptly at the start and then slowly, but usually slowly all 
the way, with elevation from the place of inversion to an unknown temperature 
at a height not yet reached. Occasional observations indicate an isothermal 
condition, and for this reason the outer atmosphere is often called the isothermal 
layer, and a few observations have shown even a slow cooling with elevation^ 
but both these conditions are tmusual. 

"The region above the upper inversion cannot appreciably be penetrated 
by convection currents from the air below, since this would cause a cooUng by 
expansion of the rising mass to a temperature lower than that of the surrounding 
medium, so that under the same pressure or at the same level its density would 
be greater than that of the adjacent air; and therefore all storms, all condensa- 
tion, all abnormal and irregular moisture distribution, and virtually all dust, 
except that of meteors and of violent volcanic eruptions, are Umited to the 
lower atmosphere." 

It will perhaps be news to some to learn, p. 145, that North America is the 
principal breeding grotmd for storms. 

"Any theory to explain the origin of cyclones and anticyclones must account 
for the fact that Asia is singularly free from such disturbances. The great 
Himalayan range runs east and west near the southern part of this continent^ 
and, naturally, interferes with the flow of currents of air from the Indian Ocean 
to the interior. On the other hand, in North America the Rocky Mountains 
run north and south along its western portions, and, while they tend to check 
the eastward flow of air in the lower strata, they permit the flow of warm currents 
from the south and cold currents from the north over the United States. There- 
fore, in Asia the mountains tend to prevent the conflict of currents that seem 
to be necessary to the formation of cyclones, while in North America they aid 
it. Hence it is that North America is the region of the most vigorous mixing- 
processes in the northern hemisphere, and, in fact, in either hemisphere, and 
is the area upon which the most active cyclonic circulation takes place; for this 
reason it must be the special theater for meteorological studies upon the causes 
and efifects of the thermodynamic and hydrodynamic forces operating in the 
lower strata of the atmosphere." 

The author groups the winds of the globe, p. 177, under three general head- 
ings, as follows: permanent winds, periodic winds, and non-periodic winds. 

"To the permanent winds belong the trade winds, the antitrades, and the 
prevailing westerlies of high latitudes; to the periodic winds belong monsoons, 
land and sea breezes, and mountain and valley breezes; to the non -periodic 
winds belong the high winds that accompany cyclones and anticyclones, in- 
cluding the hurricane of the West Indies, the typhoon of the China Seas, the 
simoom of Arabia and Africa, the sirocco of Italy, the fohn winds of the Alps^ 



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88 New Books 

the Chinook winds of the northwestern part of the United States, the mistral of 
Europe, the Texas northers, the blizzards and the hot winds of our western 
plains, tornadoes, thunderstorm gusts, whirlwinds, and many others.** 

The author has the following in regard to the chinook winds, p. i86. 

"In North America when an area of low pressure crosses the Canadian 
Rockies, it causes winds from the Pacific to cross the mountains in its southern 
quadrant. These cause copious rains or snows on the western slopes of the 
mountains, and hot, dry winds to the east of them. Since the prevailing winds 
of this region arc from the west, these winds at certain seasons become almost 
permanent, and exert a marked influence on the climate, which is particularly 
noticeable in the Saskatchewan valley in Canada and in portions of Montana 
and Wyoming in the United States, where the winters are noticeably milder 
than on the corresponding parallels farther east. The valleys are generally 
free from snow, so that stock can live on the ranges practically the entire year. 

"While the effects of the chinook winds are most marked in the valleys on 
the eastern slopes of the Rocky Mountains, they are sometimes felt 500 miles to 
the east of them. They are also noticeable as far south as Colorado. We should 
expect to find traces of their influence in the vicinity of all extensive mountain 
ranges outside the tropics." 

There are apparently some clouds which puzzle the meteorologists a good 
deal, p. 197. 

"Certain clouds that are seen about midnight in summer have for twenty 
years past received considerable attention from Abbe and others, but as yet we 
do not know enough about them to give them a name; sometimes they are called 
nacreous, from their gentle, pearly luster, at other times noctilucent, because 
they shine at night; they have as yet only been observed in northern latitudes 
during the month of June and above the northern horizon. The most reason- 
able assumption is that they are so high up as to receive a little light from the 
twilight then prevailing over the Artie regions. Otherwise they may be self- 
luminous or phosphorescent. 

"A few measurements have given these clouds altitudes of between 20 and 
40 miles. But we believe that a more systematic search for such clouds and a 
more careful determination of their altitudes must be made before we can attempt 
to discuss the questions that will naturally arise in regard to them, for of course at 
present no one can understand how aqueous vapor can be carried up to those 
altitudes or exist there long enough to form a visible cloud. The eruption of 
Krakatoa did throw vapor particles up to middle altitudes, and these formed 
interesting optical phenomena, but not visible clouds. However, if such clouds 
do exist, and their motions can be determined, we shall hardly dare to assume 
that the motions represent any movement of the atmosphere as such, for the air 
is so rarefied that the cloud particles may be moving without reference to the 
wind." 

It is quite clear where the author stands in regard to rain making, p. 206. 

"The hypothesis suggested centuries ago that any loud noise, such as 
thunder or cannonading, or even the ringing of bells, jostled the small drops to- 
gether so as to form large ones and rain, was fully disproved by the experiments 
made at the United States Government's exf)ense in 1892. An appropriation 
for this work was made by Congress in deference to a widespread popular de- 



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mand that something be done to relieve the dryness of our arid regions and our 
droughty summers. Several popular writers had diffused the illogical con- 
clusion that since great battles are frequently followed by rain/ therefore the 
noise of the cannon or the clashing of swords against coats of mail had caused 
the formation of raindrops. 

"In the government tests heavy charges of explosives, such as dynamite 
and rosselite, were carried aloft and even into the interior of clouds by means of 
kites, and balloons, and exploded there, but with no resulting rain. Similar 
experiments were made by others, and some tried even the foolish method of the 
fakirs, who send small quantities of gas or vapor into the air. But the general 
result is that no rain has as yet been brought down from the clouds by any 
human agency. 

"The ringing of church bells has for ages been practiced in southern Europe 
as a method of preventing hail, although the foolish practice was forbidden 
long ago by papal decree. Of late years a form of hail cannon has been widely 
employed in i>arts of Europe for shooting vortex rings of smoke upward, under 
the impression that sucji rings w^ould break up the ascending or gyrating currents 
that are supposed to make hail. But it has been abundantly shown by Professor 
Pernter and others that such vortex rings have no appreciable influence on the 
formation and path of a hailstorm. 

"The lightning rod of Benjamin Franklin, originally intended to protect 
from destruction by lightning, was afterwards assumed to protect also from the 
hail which accompanies thunderstorms. But the collected statistics do not 
confirm this assumption." 

On p. 222 we read that the winter storms are general rather than local, 
whereas the reverse is more often the case in summer. "The summer typ>e of 
local storms gradually merges into general storms as the heat of summer wanes, 
the first general rain-storms usually occurring during the latter part of Septem- 
ber. This has given rise to the erroneous idea of an equinoctial storm." 

On p. 223 we find a statement of the conditions for forming a hot wave. 

"In summer there come periods of stagnation in the drift of the highs and 
the lows. At such times, if a high sluggishly rests over the South Atlantic 
Ocean between Bermuda and the coast of the United States and a low over the 
northern Rocky Mountain region, there will result what is popularly known as a 
warm wave, for the air will slowly and steadily flow from the southeast, where 
the pressure is greater, toward the northwest, where the pressure is less, and, 
receiving constant accretions of heat from the hot, radiating surface of the earth, 
without any cyclones to mix the upper and lower strata, will finally become 
abnormally heated. This superheated condition of the lower stratum continues 
until the high over the ocean dies out or drifts away to the east and the low- 
pressure area in the northwest begins to gyrate as a cyclone and moves eastward, 
mixing in its course strata of unequal temperatures and causing cool thunder- 
showers." 

It is interesting to learn, p. 233, that "four sevenths of all the storms of the 



* Probably because they usually begin on fair days, and rain falls one 
day in three at least, on the average, in any region populous enough to mobilize 
any considerable fighting force. 



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United States come from the north plateau region of the Rocky Mountains 
and pass from this subarid region eastward over the Lakes and New England, 
producing but scant precipitation. The greater number of the remaining three 
sevenths are first defined in the southwest States or territories. These neariy 
always can be relied on to cause bountiful precipitation as they move north- 
eastward over the lower Mississippi Valley and thence to New England. 

"Droughts in the great wheat and com belts and elsewhere eastward are 
broken only by cyclones that form in Arizona, New Mexico, or Texas. 

"Storms move faster in the northern part of the United States than they do 
in the southern portion, and their tracks migrate with the sun.'* 

Although most people use cyclone and tornado as synonymous terms, this is 
quite wrong, p. 238. "The cyclone is a horizontally revolving disk of air, prob- 
ably 1000 miles in diameter, while the tornado is a revolving mass of air of only 
about 1000 yards in diameter, and is simply an incident of the cyclone, nearly 
always occurring in its southeast quadrant. The cyclone may cause moderate 
or high winds through a vast expanse of territory, while the tornado, with a 
vortical motion almost unmeasurable, always leaves a trail of destruction in an 
area infinitesimal in comparison with the area covered by the cyclone." 

One pre-requisite for a tornado is an abnormal heating of a thin stratum of 
air next the earth, while the stratum next above still retains the cold of winter. 
This accounts for tornadoes occurring usually early in the afternoon of a spring 
day. This abnormal heating causes an unstable equilibrium, p. 239, which "is 
more often relieved by the breaking through, here and there, of masses of the 
heavier air and the ascent of the lighter together with a horizontal rolling along 
the surface of the earth ; these are thunderstorms. But at times a narrow vertical 
whirl is set up which develops great vortical energy; this is the tornado." 

"Tornadoes mostly occur between 2 and 5 in the afternoon, and generally 
move from the southwest to the northeast; their tracks may vary in width from 
a few hundred feet to one mile; their velocity of translation is usually about that 
of an express train; their speed of gyration can be measured only approximately, 
but it is sufficient often to drive straws into the bark of trees. A roaring sound 
like the sound of many express trains accompanies the tornado, whose track is 
usually 5 or 10 miles in length." 

The sky of the novelist may be blue or red or yellow or some other color; 
but it is rarely, |>erhaps never, green. The reviewer recalls distinctly being 
taken severely to task, many years ago, for saying that the sky was sometimes 
green. The Chief of the Weather Bureau is not so intolerant, p. 245. 

"In the lower half of the atmosphere there are frequently larger particles, 
probably of aqueous vapor, dust, and smoke that absorb the blue, but transmit 
the red, so that after sunset or before sunrise beams of reddish light permeate the 
atmosphere above our heads. When we look at this light directly above the 
sun and at an altitude of from io°-2o** above the horizon, while the sun is 10° or 
15° below the horizon, we see a pinkish blotch on the sky; on either side of this 
for a long distance we perceive a delicate green tint shading above into the blue 
and below into the yellows and reds. Lower down nearer the horizon, both be- 
fore and after sunset, we frequently ^e horizontal bailds of both red and yellow, 
the red being more prominent in warm, moist air, and the yellow in cold, dry air. 
In very dry air, such as occurs in areas of high barometric pressiuxi and cloud- 



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less skies, the color is a light lemon-yellow, but this is only seen in temperate 
and northern latitudes, while the deeper yellows and reds prevail in the tropical 
regions and in our moist summers and on the advancing fronts of areas of low 
pressures or storms." 

The section on the colors of clouds, p. 254, is worth quoting in full. 

"An observer inside a bank of fog usually reports that the sky is cloudy 
and of a gray tint, since this is about the character of the light that penetrates 
the bank of fog, unless it be a very light fog or haze, or he be near its surface. 
There is quite a distinction between the tints seen inside a wet fog or cloud and 
those seen inside a dry fog or haze, such as is always associated with the har- 
mattan on the west coast of Africa. In the latter case the sky has a chalky- 
white tint and the air is very dry. We attribute the whitish tint not to any 
moisture, but to the presence of innumerable fragments of microscopic diatoms 
or siliceous shells. The whitish color of the haze must be attributed to the 
reflection of light from their surfaces. A similar white haze occurs in air that is 
full of grains of pollen, or fine crystals of snow, or almost any other kind of small 
particles. 

"Although the clouds appear white in full sunlight, yet when illumined by 
the yellow and red rays that penetrate to them from the setting sun they form 
the most magnificient color displays that are to be found anywhere in nature. 

"The upper part of a tall cumulus is often a delicate pink, while the lower 
portion is ashen gray; and below that the blue and green sky tints may be visible. 
A decided pink, or straw-colored yellow is often seen when looking at the dazzling 
white on the sunny side of a cumulus cloud. Apparently the siu'face particles 
of the cloud are being evaporated in the sunshine, and the adjacent layer of air is 
supersaturated with moisture at a relatively high temperature; possibly minute 
particles of water are present and modify the orange and pink that are spread 
in spots over the cloud. The tints are only seen when cumuli are sending up 
great thunderheads like explosions of steam boilers. 

"Still another color phenomenon is associated with the under sides of 
cumulus clouds, as in approaching thunderstorms, when the landscape beyond 
the cloud is brilliantly lighted by the sunshine; in such cases the observer may 
see patches of yellow or green on the lower side of the cloud, being light from the 
bright landscape, reflected by the big drops." 

We are grieved to read, p. 266, that the Gulf Stream is not so important a 
factor in the English climate as we had always supposed. 

"In this connection the writer would correct what he believes to be an 
exaggerated popular idea relative to the effect of the Gulf Stream on the climate 
of Europe. The eastward extension of the Gulf Stream — generally known as 
the Gulf Stream Drift. — doubtless brings immense quantities of relatively warm 
water to the shores of western Europe; but that the latter region is warmer, 
more hui?ud, and less subject to radical changes in temperature than equal 
latitudes in North America, except on the Pacific coast, is due primarily to the 
mere presence .9f a great ocean to the westward and the prevalence of westerly 
winds. Without o<;ean currents of any description this body of water would give 
to the air that moves from it to Europe a mild and damp climate and a more 
equable temp^atiire than is possessed by the eastern part of the North American 
continenL" . . 



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92 New Books 

Those who are interested in mean temperatures as a test of climate should 
read the paragraphs, p. 268, on an equable climate. 

"Within the broad confines of the United States there are many, but not 
all, shades and varieties of climate. One of the questions most frequently asked 
is: "Where shall I find a climate possessing both dryness and equability of 
temperature?" To this interrogatory reply must be made that the ideal climate 
as regards equability of temperature and absence of moisture does not exist, but 
that a near approach to it will be found in the southwest part of the United 
States. 

"The temperature of the Southwest is not equable in the sense of having an 
extremely small daily range, but it possesses the quality of annual uniformity 
in a greater degree than will generally be found elsewhere, except on the sea- 
coast, and there the humidity is great. 

"The most equable temperature on the globe will be found on the high 
table lands and plateaus of the tropics. Bogotd, in the United States of Colom- 
bia, has an average temperature of about 59° F for all months of the year, and 
the range for the entire year is less than is often experienced in a single day in 
some parts of the middle latitudes. But while the ideal temperature may be 
found on the higher elevations of the tropics, the rainfall is much greater and 
more continuous than in this country. 

"At sea level in the tropics extreme conditions of heat and moisture produce 
great physical discomfort. But even under the equator it is possible to escape 
the tropical heat of low levels by ascending from 4,000-6,000 feet. In the 
economy of nature there is a certain limit beyond which the two extremes, 
dryness and equability of temperature, cannot coexist: thus we may find a 
region so deficient in moisture as to satisfy the requirements of the case, but the 
very lack of moisture is a condition that facilitates radiation and thus con- 
tributes to extremes of temperature. 

"Regions may be found, as on the lower Nile, where there is a lack of rain- 
fall coupled with a high and moderately uniform temperature. The mean 
winter temperature of Cairo, Egypt, is 56° F; mean summer temperature, 83"; 
a range from winter to summer of 27 ®. The mean winter temperature of Phoenix, 
Arizona, is 52®; mean summer temperature, 87°; a range of 35°. It is, there- 
fore, by no means difficult to find a counterpart of the far-famed Egyptian 
climate in the great Southwest." 

As a chemist, the reviewer protests against the term "atmosphere" being 
used, p. 14, as synonymous with "gas." "The earth is surrounded by four 
important atmospheres — nitrogen, oxygen, vapor of water, and carbon dioxide." 
The paragraph accounting for cyclonic action, p. 160, is so vague and unsatis- 
factory that it might well have been left out. Wilder D. Bancroft 

Essentials of Chemistry. Experimental, Desert pfive. Theoretical . By 
Ru'us Phillips Wi Hams, ij X 20 cm; pp. ix -\- 421. Boston: Ginn and 
Company, 7910. Price: $1.23, — The title of this book is an attractive one, but 
the author has been so careless in many of his statements that the value of the 
book is much impaired thereby. 

On the first page he says that "chemistry may be defined as that science 
which treats of matter in its simplest forms, and the various combinations of 



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those forms." While this definition may be justifiable, there is really no reason 
why the student should be made to memorize it at the start as a fundamental 
definition. Incidentally the definition of matter does not come until the next 
paragraph. 

At the bottom of the same page — the first one — we are told that "when- 
ever there is matter in motion — and it is everywhere — work is being done, and 
that which does the work we call energy, though it is a subtle, invisible worker, 
which we know only by its effects." It is not worth while to speculate as to 
what the author means by this, but it does seem cruel that any student should 
be asked to memorize this as a fundamen al definition. 

On page 4 we find the interesting statement that "a molecule is the smallest 
particle of an element or a compound which can be separated from a mass by 
physical means. It retains most of the pro|>crties of the mass of the substance." 

On page 6 the author says that '* When sugar is dissolved in water, the result 
is called a mixture of the two substances. If sulphur and iron particles are 
stirred together, the result is a mixture." It does not seem credible that any- 
body could treat these two cases as analogous. * 

Speaking of chemical affinity, p. 6, the author says that "at very high 
temperatures compounds are often broken up. At extremely low ones reactions 
scarcely take place." It seems probable that the author does not distinguish 
between chemical affinity and reaction velocity. 

On page 22, we read that "a molecule is a group of atoms held together 
by chemical affinity. The molecules of a given substance always contain the 
same kind of atoms and the same number, but those of different substances have 
usually different kinds of atoms and varying numbers." If one admits that red 
and white phosphorus, for instance, are different substances, this statement 
may stand; but if this statement is the criterion of a substance, why not say so? 

On page 154, the author tries to define saturation, and of course comes to 
grief. "When a solvent holds in solution all of a given solid or gas that it can 
retain, it is said to be saturated." This sounds well but how much gas can a 
solvent hold in solution? That depends entirely on the pressure, to which no 
reference has been made. 

Under efflorescence and deliquescence, page 155, there is nothing to show 
what the decisive factor is. On page 214 is the startling statement that "elec- 
trolytes of the first class are usually metals." The author does not distinguish 
between a conductor and an electrolyte. It is quite evident that he has never 
read Faraday, but if further proof were needed, it is to be found page 218, in 
the statement that the "metallic or positively charged ions are attracted to 
the cathode." 

On page 217, the author says that " the more dilute a solution, up to a certain 
point, the greater the conductivity." This is not true; the author means molec- 
ular conductivity. 

There is a most extraordinary statement on page 218. "In order to have 
equilibrium it is evident there must be the same number of negative as of positive 
ions in a solution. This serves to explain why a salt readily soluble in water 
is not so soluble in water containing other compounds having some of the same 
ions in solution; for example, on adding hydrochloric acid to a strong solution 
of barium chlorid, a precipitate of barium chlorid is formed. This is usually 



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94 iVew Books 

explained by saying that BaCi, is less soluble in HCl than in water; the ionic 
explanation is that there is an excess of chlorin ions when HCl is added to BaCl,, 
equilibrium is upset, and hence a precipitate continues to fall until equilibrium 
is again asserted." 

The author's definition of a reversible reaction seems to be page 219, a 
reaction which runs to an end in one direction at one temperature and to an end 
in the other direction at another temperature. 

When a sulphate is electrolyzed, the author states, pages 225, 228, that 
the SO4 ion breaks down into O and SO3, the sulphur trioxide combining with 
water to regenerate sulphuric acid. This is very possibly true, but it is not an 
accepted doctrine outside of France. If the author can prove his statement, 
he should present his evidence. 

The Moissan furnace, page 230, is not "a general type of most electric furnaces;" 
the temperature of the calcium carbide furnace is certainly not 3300° in any 
resistance type. In the Castner-Kellner process, page 232, the NaCl is not 
"fused by the current, +, +, of the anode." 

The reviewer doubts whether nowadays, page 323, "phosphorus is obtained 
mainly from bones of vertebrate animals." It certainly is never "made by the 
electrolytic process," page 324. 

On page 379, the author says that white lead " is a basic carbonate of varying 
composition, e. g., 2PbCO.,.Pb(OH)j". This is self-contradictory. If white 
lead were really a substance of varying composition, no definite formula could 
be written for it. 

It is certainly a desirable thing to include some physical chemistry among 
the essentials of chemistry, but it is a great pity that good intentions should be 
accompanied by such a painful degree of ignorance. It is better to have no 
physical chemistry at all than to have so much which is not so. 

IViider D. Bancroft 

Verhalten der wichtigsten seltenen Erden zu Reagentien. By Jos. v. 
Panayeff. 14 X 22 cm; pp. iv X 83. Halle: W Ihelm Kttapp, 1909. Price: 
paper, 3.60 marks. — What is a rare-earth? That is an interesting technical 
question, which has caused no little patento-legal perturbation. The term 
is applied to the oxides of certain elements which are classified into two groups, 
namely, the cerite metals and the yt trite metals, so classed according to the solu- 
bility of the double sulphates (with alkalies). The oxides of thorium and 
zirconium are often associated with these for reasons unnecessary to give here. 
The "rare-earths," about twenty five percent of the accepted list of chemical 
elements, whose names have some far-off meaning to a vast majority of chemists, 
are not so rare after all. In fact some are more common And apparently occur in 
greater abundance than many elements spoken of with the greatest intimacy. 
The cause of this is not difficult to find. The methods of separation and iden- 
tification are not easy nor over-definite, except with a few cases. A dependable 
manual would therefore be most acceptable. Several small books are available. 
Each has its worthy features, but none is satisfactory, hence the reviewer wel- 
comed this small book with hopes. Again there was disappointment. The 
authors- of the several books are not altogether at fault, because the methods are 
not yet worked out; but some have been worked out which are not incorporated. 



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New Books 95 

For instance one might wonder why the conduct of thorium with fumaric acid 
(Miller and Metzger), with potassium trinitride (Dennis), and the behavior of 
zirconium salts with sulphurous acid and their separation from titanium (Basker- 
villc) — ^methods developed in the United States with material found in quantity 
within its territory, are not mentioned, except for the fact that the author states 
that the minerals from which these elements are extracted are found in Norway 
Sweden, Brazil, Canada, Russia "und anderen Landern." In short, the liter- 
ature has not been covered. This resident of St. Petersburg starts out with 
the periodic classification, but he has not read Mendeljeff's "Principles," or 
if he has, it did not profit him much in preparing his booklet, for therein he 
would find not a few facts that he has failed to incorporate. In his revision, 
which, it is hoped, will develop an index, we commend a careful study of Bohm's 
excellent compendium. The book would then acquire real value, for it is quite 
good as far as it goes, but it doesn't go far enough. Charles BaskerviUe 

L'Energic. By W. Osiwald, Traduit de Vallemand, par E. Philippi. 
(Nouvelle Collection scientifique. Directeur: ^mile Borel). 12 X 18 cm; pp. 
^ + ^37' Paris: FSlix A lean, 19 jo. Price: paper, 3 fr. 50. — In the first chapter 
Ostwald takes up the preliminary work of Aristotle, Archimedes, Gahleo and 
Lagrange. The second chapter deals with perpetual motion and the third 
with motion. In this third chapter the references are chiefly to Galileo, Newton, 
Huyghens, and Leibnitz. The fourth chapter is devoted to the mechanical 
equivalent of heat, and Ostwald quotes Mayer's first paper in full. In the fifth 
chapter we get Sadi Carnot's work on the steam engine together with the formu- 
lation of the second law of thermodynamics by Clausius and by Thomson. 

Ostwald calls attention to the fact that Sadi Carnot was twenty-eight years 
old when his paper appeared and that Mayer, Joule, and Helmholtz were twenty- 
five, twenty-six, and twenty-five years old respectively, when the papers on the 
mechanical equivalent of heat and on the conservation of energy were published 
He uses these facts as an argument against extending the education in the 
secondary schools over too long a time. 

The remaining chapters are entitled: energy and entropy; energetics; 
the law of intensities; the capacity factors; life; psychological phenomena; 
energetics and sociology. 

Ostwald cannot resist a fling at the mechanical hypothesis, pp. 120, 127. 
"The mechanical hypothesis has two very serious disadvantages. It forces 
us to adopt a large number of secondary hypotheses which cannot be proved, 
and it is powerless to account for what our daily experience shows to be a fact, 
the relation between physical phenomena in the narrow sense of the word and 
psychological phenomena. 

"All the mechanical explanations of the different forms of energy have, 
sooner or later, proved insufficient. They are now abandoned in many branches 
of physics. People have begun to replace them by electrical hypotheses; but 
those who remember the fate of electrical hypotheses in chemistry will not be 
very sanguine as to what they may accomplish in physics." 

In the chapter on life, page 178, Ostwald says that "a constant manifesta- 
tion of energy is an essential characteristic of life, even though this may not 
serve as a complete characterization." 



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96 New Books 

On page i8i, he says: "It is important to note that the idea of conservation 
can be taken in two different ways, the conservation of the individual and the 
conservation of the race. Usually whatever is good for the individual is good 
for the race and vice versa y but sometimes the contrary is true. In such cases 
what assures the perpetuation of the race is more in harmony with the biological 
tendency than that which assures the perpetuation of the individual. Under 
some conditions the race may go on though the individual perishes, for instance 
if the individual dies after reproducing its kind. If the race disappears the 
biological goal has not been reached even though the life of the individual be 
prolonged." 

The translation has been done well enough, but it lacks the clearness and 
vivacity of Ostwald's prose. Wilder D. Bancroft 

Les Etats Physiques dc la Mati^re. By Ch. Maurain. {Nouvelle Collec- 
tion scieniipque. Directeur: ^mile Borel.) 12 X iS cm; pp. J2j. Paris: Felix 
Alcan, I ^10. Prxe: paper, j.50 francs. — The subject is treated under the follow- 
ing headings: the gaseous state and ionization in gases; the liquid state; crystals 
and the crystalline state; general structure of solids; inversions of solids, and 
solidification; anisotropism produced by external actions; flowing crystals, 
liquid crystals and crystalline liquids; properties of surface films and of thin layers 
of solids; homogeneous mixtures; heterogeneous mixtures; colloidal state. 

This book is merely a compilation and is noticeably lacking in inspiration. 

Wilder D. Bancroft 



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THE REPLACEMENT OF THE METALS IN NON- 
AQUEOUS LIQUIDS AND THE SOLUBILITY . 
OF METALS IN OLEIC ACID 



BY CHARLES BALDWIN GATES 

INTRODUCTION 

About four years ago, Sammis* showed that certain types 
of chemical reactions that take place in aqueous solutions 
that conduct electricity can be duplicated in non-conducting 
liquids. That this is true of most of the typical chemical 
reactions has been demonstrated by the work of Kahlenberg 
and others.' Even the replacement of one metal by another 
in a non-aqueous medium has been shown to take place in 
liquids that are the best of insulators. Thus it has been 
proven that chemical reactions do take place in non-con- 
ductors and that these reactions are in every respect the same 
as to type and rapidity as those occurring in aqueous solu- 
tions. 

The present research has for its aim the further investiga- 
tion of this new field of chemical replacement of the metals in 
non-conducting media. If a large number of such replace- 
ment experiments be performed, using all the more common 
metals, the relative frequency with which these will replace 
some one metal, as copper for instance, may fairly be used as a 
basis for the arrangement of the metals in a series analogous 
to the so-called electrochemical series. Such a series would 
throw some light on the question as to whether the relative 
basicity of the metals is always approximately the same and 
an inherent property of the individual metals, or whether the 
nature of the solution in which the replacement is effected 
must be considered.* 



* Jour. Phys. Chem., lo, 593 (1906). 

'Kahlenberg: Ibid., 6, 6 (1902); Kahlenberg and Schlundt: Ibid., 6, 
447 (1902); Mathews: Ibid., g, 641 (1905); Kahlenberg: Zeit. phys. Chem., 46, 

63 (1903). 

• Compare Kahlenberg: Science, 31, 41 (1910). 



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98 Charles Baldwin Gates 

It has been particularly emphasized by the adherents 
of the electrolytic dissociation hypothesis that there is a 
close connection between the electromotive forces set up by 
metals in contact with solutions of their salts on the one 
hand and their replacing power on the other hand. Un- 
fortimately, the experiments which seemingly confirm this 
view have been limited to electrolytic solutions in which water 
was the solvent, as a rule. A complete series of replace- 
ments, obtained in solutions that are insulators, would have 
a distinct bearing upon the question as to whethef the re- 
lationship between the replacing power of the metals and the 
electromotive forces which they may develop really exists. 
Accordingly, the following experimental work was imder- 
taken in order to determine in a large number of cases what 
metals will replace each other in non-conducting liquids. 

GENERAL PLAN OF THE WORK 

The replacement of copper by other metals was chosen for 
this investigation and consequently some pure copper salts 
were necessary. But as non-aqueous solvents were to be 
employed, inorganic copper salts could not be used, for they 
are insoluble in such liquids, as a rule. Organic salts were 
therefore taken and salts with considerable carbon content 
were preferred, in order that the large organic radical might 
more readily drag the copper into solution in the organic 
solvents* to be employed. 

Pure anhydrous solvents were then carefully prepared 
and the solubility of the copper salts determined in them. 
The conductance of the pure solvent and of the solution was 
measured in each case. In the concentrated solutions so ob- 
tained, strips of the metals were introduced and all replace- 
ment indications were carefully noted. The work was done 
at different temperatures and prolonged for various periods 
of time. The effect of small amounts of moisture upon the 
reaction was also duly investigated. 



Kahlenberg: Trans. Am. Electrochem. Soc., 6, II, 53 (1904). 



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Replacement of the Metals in N on- Aqueous Liquids 99 

The replacement of copper in non-conducting fused 
salts and the replacement of other metals in fused salts that 
do conduct was studied to determine whether the presence of 
water is necessary for chemical action to take place. These 
experiments also furnished a replacement series which could 
be compared with the ordinary electrochemical series of the 
metals and so aid in determining whether the relative re- 
placing power of each metal is constant. 

The accidental discovery of the solubility of metallic 
copper in oleic acid led to the preparation of some very piu-e 
oleic acid and the investigation of its ability to dissolve 
metals. This was an unexpected development on account 
of the fact that the higher fatty acids are complete insulators. 

EXPERIMENTAL WORK 
Preparation of Copper Salts 

The salts were all prepared in aqueous solutions by 
neutralization of the free acid with caustic potash and subse- 
quent precipitation of the copper salt with a solution of pure 
copper sulphate. These salts were then thoroughly washed 
and dried to constant weight at a temperature as close to 
120® C as the salt would bear without decomposing. 

Copper anisate— (C,H,(O.CH,)COO)2Cu— was green. 
Copper margarate — (CH3-(CHj),5-COO)jCu — was blue when 
first precipitated, but it changed to a dark green at about 
100^ C. Copper cinnamate— (C^jH^-CH = CH— COO),Cu— 
was bluish-green. Copper phthalate — C,H^(COO)jCu — was 
sky-blue and precipitated only on evaporating the solution 
to a small bulk. Copper abietate — (C,gH28COO)jCu(?) — was 
light green and was prepared from abietic acid extracted from 
Oregon balsam. Copper camphorate — Cj^^Hj^O^Cu — was 
bright green and in an exceedingly fine state of division. 

The following copper salts were fiunished by Professor 
Kahlenberg: copper palmitate— (CH,— (CH^)!,— COO)jCu— 
made by J. L. Sammis; copper laurate — (CH, — (CH,),^^ — 
C00)2Cu; copper capronate— (CHj—CCH,),— COO) ^Cu— made 



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loo Charles Baldwin Gates 

by J. L. Sammis and dried at 120® C; copper isovalerianate — 

(cH^x^^ — ^^2 — COOjjCu — ^made from the corresponding 

acid, b. p. 173-175^0, not entirely free from potassium 
sulphate; copper acetoacetic ester — (CH, — CO — CH — COO. 
C3H,)3Cu — of Schuchardt's manufacture. 

Replacement of Silver by Copper 

Silver abietate, citrate, tartrate and succinate were 
similarly prepared, but not used to any extent as yet in this 
investigation. They all dissolved in pyridine and silvered 
metallic copper — ^the coating of silver finally becoming gray. 
In time, the copper was completely disintegrated; the succinate 
solution in pyridine became almost black, while the others 
turned green. The experiments ran for several weeks. These 
preliminary trials suggest that silver salts in solution will 
be found to give results very much like those of copper salts. 

Solubility of Copper Salts 

Thirty-four representative organic liquids were made as 
pure and anhydrous as possible and the solubility of the 
above copper salts determined in them. The results are 
summarized in Table I. In no case was the solubility more 
than approximately 5 percent, with the exception of many 
of the copi>er acetoacetic ester solutions. In most cases, 
only small amounts of the copper salts could be dissolved, but 
always enough to give the solutions a good green or blue 
color. All solutions were made as concentrated as possible, 
before replacement was attempted. 



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Replacement of the Metals in Non^Aqueous Liquids loi 



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Replacement of the Metals in Non-Aquecms Liquids 103 



Conductance of Solvents 

The conductance of the pure solvent and of the con- 
centrated solution was determined in each case. This was 
done by the Kohlrausch bridge method; using a resistance 
box of one htmdred thousand ohms. Ten of the seventeen 
solvents measured and used had less conductance than could 
be measured by the apparatus. This meant a conductance 
of less than 2 X lo"**. When the copper salts were dis- 
solved in the solvents, it was not possible to predict how the 
conductance would be aflFected. In a few instances it was 
decreased, though the majority of cases showed a very slight 
increase. The conductance of all the solvents used in the 
following experiments is shown in Table 2. The figures 
indicate reciprocal ohms. 

Table 2 
Conductance of the pure solvents 



Solvents 


Conductance 


Temperature 


Oleic acid 


Less than 2 


X io-'» 


15° 


Acetaldehyde 


552 X lo"^ 




20.5° 


Benzaldehyde 


35 X IO-* 




195° 


Ethyl alcohol 


14 X 10-^ 




19.5° 


Amyl alcohol 


44 X lo"^ 




20° 


Pyridine 


43 X 10-^ 




21° 


Acetone 


10 X 10-^ 




19° 


Acetonitrile 


71 X 10-^ 




20.5° 


Nitrobenzene 


Less than 2 


X io-'» 


20° 


Carbon tetrachloride 


** 




20,5° 


Carbon bisulphide 


(t 




20.5° 


Toluol 






20° 


Pentane 


" 




19-5° 


Ethyl benzoate 


*' 




19° 


Ethylene dibromide 


it 




19° 


Ether 


** 




20.5° 


Pinene 


*' 




23° 



Copper Replacement Experiments 

The method of procedure in these experiments was as 
follows. The saturated solution of a copper salt in one of 
these solvents was placed in test tubes and in each tube was 



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I04 Charles BaUtwin Gates 

also put a small piece of carefully cleaned chemically pure 
metal, usually in the form of foil. The cleaning was accom- 
plished by scouring with emery paper and then scraping 
bright and smooth with a steel tool. The test tubes were 
allowed to stand for several days and observed from time to 
time. Some of the experiments were conducted in oil-baths, 
heated to 75® C or over, and while results were generally 
hastened in this manner, they were practically the same as 
those obtained at room temperatiu-e. Most of the experi- 
ments were run for several days; but often copper deposition 
took place noticeably within ten minutes of the time metal 
and solution were brought together. The conductance of the 
solutions was determined at about 20® C. Data as to con- 
ductance, temperature and time will be foimd in Table 12. 
The detailed observations made in connection with each 
experiment follow. 

Oleic Acid as Solvent 

Copper cinnamate. Lead and bismuth were coppered. 

Copper acetoacetic ester. Very dark green solution. 
Lead, zinc, bismuth and cobalt were coppered.* The solution 
containing the mercury lightened in color a very little. 

Copper palmitate. Green solution. Lead, bismuth and 
tin were coppered. The solutions containing lead and tin 
became dark yellow. 

Copper abietate. Green solution. Zinc, lead and bis- 
muth were coppered. The solutions containing zinc, lead and 
tin became yellow, bismuth and cobalt slightly yellow. 

Copper margarate. Light green solution. Lead and zinc 
were coppered. The solution containing cobalt became 
darker, lead yellowish-green and tin yellow. 

Copper anisate. Lead, zinc, tin and magnesium were 
coppered. On heating these solutions, they changed from a 
clear, dark green to a clear, light brown. On further heat- 
ing, they became opaque and metallic copper separated out. 
In general, all oleic acid solutions behaved in a similar manner. 

Copper phthalate. Lead, zinc, bismuth and magnesium 
were coppered. 



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Replacement of the Metals in Non-Aqueous Liquids 105 

Copper camphorate. Lead, bismuth and zinc were 
coppered. 

Copper latirate. Bright green solution. Zinc, lead and 
bismuth were coppered. The solution containing cobalt 
became greenish-yellow, lead a trifle yellow, and mercury, 
zinc and tin olive green. 

Copper capronate. Green solution. Zinc, lead and bis- 
muth were coppered. The solution containing zinc became 
lighter, lead yellow, tin a little deeper green and cobalt a very 
little deeper green. 

Copi>er isovalerianate. Light green solution, as only a 
very little of the salt could be dissolved. Zinc, lead and 
bismuth were coppered. The solution containing cobalt 
became a more pronounced green, zinc olive green, lead light 
yellow and magnesium greenish-yellow. Both cobalt and 
magnesium had a loosely adhering coat of brownish-black 
material. 

Benzaldehyde as Solvent 

Copper camphorate. Green solution. Cobalt, iron, zinc, 
lead, bismuth and tin were coppered. The solution con- 
taining cobalt became dark brown, silver darker green, mer- 
cury a trifle more yellow, aluminum light green and solid, 
bismuth light green, antimony more olive green, tm straw 
yellow, nickel solid. Magnesium was entirely disintegrated. 

Copper phthalate. Light green solution. Cobalt, bis- 
muth and lead were coppered. The solutions containing 
mercury, lead, zinc, bismuth, antimony, tin, magnesium and 
nickel became yellow, cobalt yellowish-brown, iron brownish- 
black. The iron was coated with a soft black substance. 

Copper cinnamate. Green solution. Cobalt, zinc, 
magnesium, lead, bismuth, tin and antimony were coppered. 
The solution containing nickel became slightly yellowish, 
cobalt light brown, mercury light green, lead yellowish-green, 
aluminum and magnesium olive green, bismuth browji, anti- 
mony light greenish-yellow, tin straw yellow, and cobalt, 
mercmy and zinc solid. A duplicate was nm in the case of 



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io6 Charles Baldwin Gates 

antimony for eleven days, at 75® C. The metal was again 
coppered. 

Copper abietate. Green solution. Cobalt, iron, zinc, 
lead, bismuth, tin and magnesium were coppered. The solu- 
tion containing iron became slightly yellowish, lead still more 
yellow, zinc dark yellow, cobalt reddish-brown, and bismuth, 
tin and magnesium light yellow. 

Copper margarate. Green solution. Cobalt, iron, lead, 
tin, aluminum, bismuth, magnesium and antimony were 
coppered. The solution containing nickel became slightly 
more yellow, cobalt and iron red, mercury yellowish-green, 
and zinc, lead, aluminum, bismuth, tin and magnesium yellow. 
A duplicate was successfully rtm in the case of antimony for 
eleven days at 75® C. 

Copper anisate. Green solution. Aluminum, cobalt, 
zinc, iron, lead, bismuth, tin and magnesium were coppered. 
Magnesium was almost entirely replaced by copper. The 
solution containing nickel became slightly more yellow, 
silver and mercury a lighter green, cobalt purplish-black, iron 
brownish-red, and zinc, lead, bismuth, tin and magnesium 
yellow. 

Copper palmitate. Green solution. Cobalt, zinc, iron, 
lead, aluminum, bismuth, tin and magnesium were coppered. 
The solution containing tin became slightly more yellow, 
cobalt and iron red, mercury greenish-yellow, and zinc, lead, 
bismuth, and magnesium yellow. Magnesium was almost 
entirely replaced by copper. 

Copper isovalerianate. Light green solution. Cobalt, 
lead, bismuth and nickel were coppered. The solution con- 
taining iron became reddish-brown, nickel greenish-yellow, 
bismuth and tin light yellow, and cobalt, zinc, lead, antimony 
and magnesium yellow. Zinc was covered with a soft black 
deposit and iron with a similar gray one. Magnesium was 
completely disintegrated and a yellowish-white solid left. A 
successjul duplicate was run in the case of nickel for eleven 
days at 75° C. 

Copper acetoacetic ester. Deep blue-green solution. 



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Replacement of the Metals in Non-Aqueous Liquids 107 

Cobalt, zinc, lead, bismuth, tin and magnesium were coppered. 
The solution containing cobalt became a deep red, zinc red- 
dish-brown, iron deep green, magnesium brown, and lead, 
tin, nickel and antimony olive green, and mercury solid. The 
lead and zinc tubes showed a gray precipitate and bismuth 
a white one. 

Carbon Tetrachloride as Solvent 

Copper margarate. Iron was coppered. The solution 
was a clear green as long as the temperature was 50® C or 
over. Below 50® C, the liquid separated into two layers — a 
clear colorless lower layer of piu-e solvent and a cloudy, light 
green upper layer, containing the salt. 

Copper palmitate. No replacement. Two layers; the 
blue salt all came to the top. 

Copper acetoacetic ester. Zinc, lead, tin, magnesium, 
iron and silver were coppered. In the solutions containing 
cobalt, silver, mercury, lead, aluminum, bismuth, antimony, 
tin, magnesium and nickel a whitish or greenish solid separated 
out. The solution containing iron became red, and zinc light 
brown. The silver was coated with a light gray deposit, be- 
neath which was a little red copper on a dark background. 

Copper capronate. Light blue solution. Zinc was 
coppered. The solution containing lead became greenish- 
yellow, and cobalt, mercury, zinc, aluminum and tin color- 
less. 

Carbon Bisulphide as Solvent 

Copper margarate. Nothing whatever happened. 

Copper abietate. Deep green solution. Lead was cop- 
pered in the first trial, but could not be duplicated in two 
later attempts — one of them continued for eleven days at 
75® C. The solution in all three attempts became greenish- 
yellow. 

Copper acetoacetic ester. Brownish-red solution. The 
metals were all coated with an iridescent tarnish. The color 
of the solutions and the brown deposit on the bottom of the 
tubes would seem to indicate a disintegration of the copper 
salt and the presence of free copper. 



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io8 Charles Baldwin Gates 

Copper laurate. No replacement. Every solution, ex- 
cept the one containing antimony, had a blue solid substance 
separated out and floating on the top. The laurate itself is 
deep green. 

Copper palmitate. Light green solution. No replace- 
ment. Silver, bismuth and lead were tarnished. The solu- 
tion containing zinc was a trifle lighter. 

Nitrobenzene as Solvent 

Copper acetoacetic ester. Lead and alumintmi were cop- 
pered. 

Copper palmitate. Only a very little of the salt would 
dissolve, even when heated. The solution containing the 
lead became slightly more yellow. 

Copper anisate. Green solution. Lead and zinc were 
coppered. The solution containing cobalt became blue. The 
silver looked as though it had been oxidized. 

Pyridine as Solvent 

Copper cinnamate. Lead and zinc were coppered. The 
salt appeared to form an addition product with the pyridine. 

Copper anisate. Green solution. Silver, lead, bismuth 
and magnesium were coppered. The piece of silver was en- 
tirely disintegrated. 

Copper phthalate. Light blue solution. The solution 
containing zinc became straw yellow, mercury and cobalt 
dark green, lead and silver light green, and aluminum, bismuth 
and antimony bluish-green. Silver was tarnished and zinc 
corroded. 

Copper palmitate. Deep blue solution. Aluminum was 
coppered. The solution containing mercury became some 
lighter, silver green, lead lighter, aluminum brownish-yellow, 
bismuth deeper blue, magnesium yellow, and cobalt, iron and 
tin indigo blue. The lead, tin and nickel tubes contained a 
brown deposit, aluminum gray, and magnesium brownish- 
gray. There was a gray deposit on the silver. Magnesium 
was partly disintegrated. 



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Replacement of the Metals in Non-Aqueous Liquids 109 

Copper acetoacetic ester. Deep green solution. Zinc 
and lead were coppered. All solutions became opaque. 
The solution containing zinc showed a yellow precipitate, lead 
a light yellow, nickel a grayish-brown, and mercury and bis- 
muth a brown. There was a grayish-yellow deposit on the 
silver. 

Ethyl Benzoate as Solvent 

Copper cinnamate. Blue-green solution. Cobalt, zinc, 
lead and magnesium were coppered. The solution containing 
cobalt became blue, and lead and magnesium colorless. 

Copper abietate. Deep green solution. Zinc, lead and 
magnesium were coppered. The solution containing zinc 
became yellow, nickel slightly more yellow, and lead and 
magnesium brownish-yellow. 

Copper palmitate. Deep green solution. Zinc, lead, 
bismuth, tin and magnesium were coppered. The solution 
containing mercury became a trifle lighter, cobalt indigo blue, 
zinc olive green, bismuth lighter, and lead and magnesium 
colorless. The bismuth tube contained a blue precipitate. 

Copper acetoacetic ester. Deep green solution. Cobalt, 
zinc, lead and magnesium were coppered. The solution con- 
taining iron became much darker, lead light yellow, zinc 
olive green, magnesium yellowish-green, mercury and cobalt 
light green, silver and tin light blue, bismuth and antimony 
a trifle lighter. A light blue precipitate formed in the tubes 
containing merciuy, cobalt, silver, tin, zinc, bismuth, anti- 
mony and magnesium. 

Toluol as Solvent 

Copper abietate. Green solution. The solution con- 
taining lead became slightly yellowish and the metal tarnished. 

Copper margarate. Green solution. No replacement. 
The solution containing cobalt became slightly yellow, and 
and iron yellowish-green. 

Copper acetoacetic ester. Deep green solution. Zinc 
was coppered. The solution containing lead became slightly 
yellow, nickel brown, and antimony grayish-yellow. 



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I lo Charles Baldwin Gates 

Copper palmitate. No replacement. The solution con- 
taining lead became more green. Zinc was corroded. 

A my I Alcohol as Solvent 

Copper abietate. Green solution. Lead and aluminum 
were coppered. A successful duplicate was run in the case 
of the aluminum for fifteen days at 75° C, but the metal was 
coppered only on an edge that protruded from the solution. 
This was no doubt due to the solubility of copper in the 
alcohol. A yellowish-green precipitate was formed. The 
other metals gave the following results: cobalt, magnesium 
and nickel gave yellowish solutions; lead and aluminum 
yellowish-brown solutions and precipitates; cobalt, nickel, 
magnesium, antimony and bismuth tubes contained brown, 
needle-shaped crystals, which were translucent and non- 
malleable. 

Copper palmitate. Bluish-green solution. Silver was 
coppered and this was later duplicated. The solution con- 
taining zinc became slightly yellowish and magnesium yellow- 
ish-green, iron more blue — with a light colored precipitate, 
lead greenish-yellow — with a light colored precipitate. Bis- 
muth was covered with an iridescent tarnish. There was a 
brownish deposit in the solutions containing magnesium, 
nickel, tin, antimony, aluminum, zinc, silver and cobalt. 

Copper capronate. Green solution. Aluminum and lead 
were coppered. In a duplicate run in the case of aluminum 
for fifteen days at 75° C, the metal was coppered as before 
and a black precipitate formed. The solution containing 
magnesium became very light blue, lead greenish-yellow, 
cobalt, mercury, zinc, bismuth, tin and aluminum dark 
brown, and nickel, antimony, iron and silver yellowish-brown. 
Bismuth showed an iridescent tarnish. There was a gray 
deposit on the silver and magnesium. 

Copper acetoacetic ester. Green solution. Aluminum 
and silver were coppered — ^the latter also in a duplicate. 
The solution containing aluminum became dark greenish- 
yellow, lead yellowish-green, antimony greenish-yellow. The 



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Replacement of the Metals in N on- Aqueous Liquids 1 1 1 

mercury and zinc tubes contained a dark brown precipitate, 
cobalt, iron, bismuth, magnesium and nickel a green, lead a 
white, and antimony a brown. Bismuth had an iridescent 
tarnish and there was a grayish-black deposit in the solution 
containing magnesium. 

Ethyl Alcohol as Solvent 

Copper acetoacetic ester. Clear dark green solution. 
Zinc, lead and aluminum were coppered. The solution con- 
taining zinc became yellow, cobalt and bismuth lighter green — 
also a green precipitate, silver and nickel light yellow — a 
brown precipitate, mercury light green — a green precipitate, 
aluminum light brown, antimony greenish-yellow — a dark 
green precipitate, tin colorless — a white precipitate — a gray 
coating on the metal, magnesium yellowish-green — a dirty 
white coating on the metal, lead grayish-yellow and a pre- 
cipitate of the same color. 

Pinene as Solvent 

Copper palmitate. Green solution. Cobalt was cop- 
pered. The solution containing antimony became a trifle 
lighter, mercury yellow, magnesium, tin and cobalt pale 
green, lead and zinc brownish-yellow — with yellow precip- 
itates, iron yellowish-brown — the metal was corroded. The 
silver was tarnished and the magnesium looked brassy. Zinc 
and lead had a black deposit on the metal, and bismuth a 
gray. 

Copper abietate. Very light green solution. Zinc was 
coppered. The solution containing iron became a little 
lighter, and the silver and bismuth yellow. 

Copper acetoacetic ester. Deep green solution. Noth- 
ing whatever happened. 

Acetonitrile as Solvent 

Copper acetoacetic ester. Light green solution. No re- 
placement. The solution containing cobalt became more 



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112 Charles Baldwin Gates 

yellow, zinc and lead still more yellow, nickel more yellow 
still, silver, mercury, aluminum and tin greenish-yellow, iron 
and antimony yellowish-green, bismuth yellowish-green — a 
precipitate of same color, magnesium almost colorless — a 
gray precipitate — ^metal completely dissolved, nickel a yel- 
lowish-gray precipitate and aluminum a yellowish-brown. 

Copper anisate. Very light green solution. No replace- 
ment. The solution containing cobalt became brownish- 
yellow, iron and antimony yellow, and merciuy, zinc, lead, 
aluminum, tin, magnesium and nickel colorless; zinc, alumi- 
num and magnesium a white precipitate, antimony a yellow 
and bismuth a light colored one. Aluminum and magnesium 
were both corroded. 

Copper capronate. Green solution. No replacement. 
The solution containing tin became a deeper green, cobalt, 
mercury and aluminum Ught yellow, nickel and zinc greenish- 
yellow, antimony deep yellow, magnesium light blue, lead 
colorless and an iridescent tarnish formed on the metal. Bis- 
muth showed a similar tarnish. Aluminum and magnesium 
were corroded. 

Ether as Solvent 

Copper abietate. Very light green solution. No replace- 
ment. The solution containing mercury became a little more 
yellow. 

Copper acetoacetic ester. Light green solution. No re- 
placement. The solution containing mercury became a 
deeper green, aluminum yellow, antimony greenish-yellow, 
and cobalt, zinc, tin and magnesium slightly yellowish. 

Pentane as Solvent 

Copper capronate. Light green solution. No replace- 
ment. The solution containing lead became light yellow, 
mercury and zinc colorless. 

Copper acetoacetic ester. Nothing whatever happened. 

Acetaldehyde as Solvent 
Copper cinnamate. Zinc, iron, aluminum and lead were 
coppered. 



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Replacement of the Metals in N on- Aqueous Liquids 113 

Copper acetoacetic ester. Light blue-green solution. 
Zinc and iron were coppered. The solution containing zinc 
became a little yellow, iron deeper yellow, cobalt slightly 
more blue — ^metal corroded, aluminum colorless — a rough 
black deposit on the metal, bismuth a light grayish-white 
precipitate. Magnesium was corroded. 

Copper- palmitate. Light blue solution. Cobalt, zinc 
and iron were coppered. The solution containing cobalt be- 
came dark brown, iron light brown, zinc light yellow, lead 
colorless, magnesium almost colorless, and silver, mercury, 
tin and nickel sUghtly lighter. The lead and bismuth tubes 
contained a gray deposit. 

Acetone as Solvent 

Copper abietate. Light green solution. No replace- 
ment. The solution containing magnesium became slightly 
yellowish, and mercury, antimony and aluminum slightly 
turbid. 

Copper acetoacetic ester. Deep green solution. Mag- 
nesium was coppered — under a grayish-black deposit. The 
solution containing magnesium became greenish-blue, cobalt 
and bismuth slightly yellowish, silver, mercury, iron, lead and 
nickel cloudy. Cobalt, lead, bismuth and antimony were 
tarnished. Aluminum had a black coating. There was a 
brown deposit on the antimony and cobalt tubes. This was 
dissolved in nitric acid to a green solution, evaporated to dry- 
ness and the nitrate decomposed by heat. Brown copper 
oxide was left. 

Copper capronate. Light blue solution. No replace- 
ment. The solution containing antimony became greenish- 
blue, zinc, lead and magnesium lighter, iron slightly yellowish, 
aliuninum a light colored precipitate. Lead had a grayish- 
yellow coating and bismuth a yellowish tarnish. 

Ethylene Dibromide as Solvent 

Copper palmitate. Deep blue solution. Zinc and lead 
were copf)ered. The solution containing nickel became 



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114 Charles Baldwin Gates 

bluish-green, zinc colorless — a yellow precipitate, lead yellow — 
a whitish precipitate. The solution containing silver con- 
tained a grayish deposit, iron a dark gray, aluminum a black. 
Cobalt had a yellow deposit on the metal, and antimony and 
magnesium each a yellowish-brown coating. The solution 
containing antimony and magnesium became dark yellow in 
both cases and a dark brown precipitate formed on the tubes 
at the top of the liquids. The metal bismuth was darkened. 

Copper acetoacetic ester. Deep green solution. Zinc 
was coppered. The solution containing nickel became blue- 
green, silver and bismuth lightened a little, cobalt brownish- 
black, zinc yellow, lead yellow-brown — a precipitate of the 
same color and a black deposit, aluminum dirty green — a 
precipitate of the same color and a gray deposit, antimony 
dark red and there was a thick, dark brown, gummy mass 
on the metal and tube. The magnesium tube showed a dirty 
brown precipitate and solution, and a dark deposit. The 
silver tube contained a brownish-yellow deposit and iron a 
gray one. 

Copper anisate. Deep blue solution. Zinc and lead were 
coppered. The solution containing zinc became colorless, 
cobalt yellow, bismuth green, antimony light green, sUver 
lighter — a yellowish-brown deposit, mercury yellow — a thick, 
brown paste on the tube, iron red — a blackish-brown deposit, 
lead colorless — a white precipitate, aluminum very light 
yellow — a grayish-black deposit, tin yellow — a thick, brown 
substance on the metal, which was very soft, magnesium dirty 
greenish-yellow — a gray deposit, nickel yellow — a soft yellow 
deposit. 

Three solutions in contact with metallic mercury were 
observed for twenty-two months, to see if color changes could 
be noticed, (i) Copper acetoacetic ester in amyl alcohol. 
The dark green solution became grass-green and a precipitate 
of the same color separated out. (2) Copper acetoacetic 
ester in acetonitrile. The green solution became brown and a 
slight green precipitate formed. (3) Copper phthalate in 
pyridine. The blue solution became light green. As blank 



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Replacement of the Metals in N on- Aqueous Liquids 115 

solutions without mercury showed none of these changes, it 
would appear that some reaction had taken place in each case. 

There now follows a series of experiments in which the 
time of exposure was much longer and the temperature higher. 
They were all conducted in sealed tubes. The solvents 
were specially prepared as follows: (i) Amyl alcohol was 
dried over copper sulphate and twice fractionated. The 
fraction distilling between 130° and 131° C was used. Its 
conductance was 18 X lo"**. (2) Ethyl benzoate was twice 
distilled. B. P. was 213° C and conductance was less than 
2 X lo"* at 17.6® C. (3) Pyridine was distilled from calcitmi 
chloride at 115° C, after long standing. Its conductance was 
25 X io~* at 17.6® C. (4) Carbon tetrachloride was twice 
distilled. B. p. was 77° C. Its conductance was less than 
2 X lo"'* at iq"* C. 

The data of Tables 3-1 1 show that higher tempera- 
ture and longer duration of time simply influence the 
quantitative side of the experiments. The brassy appearance 
observed in some cases was interesting and indicates the for- 
mation of copper alloys. This effect was observed with all 
the metals used except magnesium and mercury, the first 
of which was usually heavily copp)ered, while the mercury 
would dissolve the copper. 

All replacement results secured with copper salts in 
solution have been collected in Table 12. All the metals 
were used in all the exf)eriments, with the exception of 
cadmium, which was tried in only nine cases of the sixty-nine. 
Where metallic copp)er was thrown out, it is indicated in the 
table by a cross (X). A good many experiments showed no 
copf)er, but evidences of chemical action were plain — such 
as a change in color of the solution or the formation of a pre- 
cipitate. These cases are marked in the table with a circle 
(O). The most plausible explanation of these ''indicated'* 
replacements is that the solvent or solution or both have 
slight solvent prof)erties toward copper or the other metal 
present. This was actually found to be the case in a number 
of instances. When mercury was used, any replaced copper 



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ii6 



Charles Baldwin Gates 



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Replacement of the Metals in N on- Aqueous Liquids 117 



Table 4 

Copper Abietate in Amyl Alcohol 

Conductance — 30 X lo-* Grass-green solution 



MeUl Time 1 Temp. 



Cd 

Mg 

Pb 

Zn 

Fe 

Ni 

Sb 

Co 

6i 

Sn 

Hg 

Al 

Ag 

Zn 

Fe 

Ni 

Sb 

Co 

6i 

Sn 

Hg 

Al 

Ag 



' 20 days 

j 20 days 

' 20 days 

I 20 days 

20 days 

20 days 

20 days 

! 20 days 

I 20 days 

20 days 

20 days 

20 days 

20 days 

25 days 

25 days 

25 days 

25 days 

25 days 

25 days 

25 days 

25 days 

25 days 

25 days 



20' 
20^ 
20^ 
20^ 
20^ 
20^ 
20' 

20^ 
20' 
20^ 
20^ 
20^ 
75^ 
75^ 
75' 
75' 
75' 
75' 
75' 
75' 
75' 
75' 



. Solution change 


Metal change 


Yellow 


Coppered 


Yellow 


Coppered 


Color unchanged — cloudy 


Coppered 


Color slightly yellowish 


Darkened 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Unchanged 


Dark yellow — ppt. same 


Darkened 


Dark yellow — ppt. same 


Brassy 


Dark yellow — ppt. same 


Brassy 


Dark yellow — ppt. same 


Brassy 


Tube broke 


Brassy 


Tube broke 


Brassy 


Dark yellow — ppt. same 


Brassy 


Dark yellow — ppt. same 




Dark yellow — ppt. same 


Brassy 


Dark yellow — ppt. same 


Brassy 



After 25 days at 75^ C, a blank solution became dark yellow and a pre- 
dpitate of the same color separate out. 

After 15 hours at 95** C, silver was very yellow, suggesting a copper 
alloy. Zinc became brassy. 

Copper in amyl alcohol gave a slightly greenish-yellow solution. This be- 
came yellow and a precipitate of the same color separated after 25 days at 75 ^'C. 



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ii8 



Charles Baldwin Gates 



Table 5 

Copper Palmitate in Amyl Alcohol 

Conductance — 73 X lo-*. Light blue solution — later light yellow 



Metal Time 



Mg 
Zn 

Cd 
Pb 
Ag 
Hg 
Sb 
Ni 
Al 
Bi 
Fe 
Co 
Sn 
Ag 25 
Hg 25 
Sb 25 
Ni 25 
Al 25 
Bi 25 
Fe 25 
Co 25 
Sn 25 



Temp. 



days 

days 

days 

days 

days ' 

days 

days 

days 

days ( 

days i 

days i 

days 

days 

days 

days 

days 

days I 

days 

days 

days 

days 

davs I 



20 
2o- 
20' 
20^ 
20^ 

20' 
20' 

20^ 
20^ 
20' 
20^ 
20' 
20^ 

75^ 



75° 


C 


75° 


Ci 


75° 


cl 


75° 


c 


75° 


c 


75° 


c 


75° 


c 



Soludon change 

Unchanged 
Unchanged 
Colorless — white ppt. 
Colorless — white ppt. 
Unchanged 
Unchanged 
Unchanged 
Unchanged 
Unchanged 
Unchanged 
Unchanged 
Unchanged 
Unchanged 
Yellow — ppt. same 
Yellow — ppt. same 
Yellow — ppt. same 
Yellow — ppt. same 
Yellow — ppt. same 
Yellow — ppt. same 
Yellow — ppt. same 
Yellow — ppt. same 
Yellow — ppt. same 



Metal change 

Grayish-black 

Brassy 

Coppered and black 

Coppered and black 

Brassy 

Unchanged 
Unchanged 
Unchanged 
Unchanged 
Unchanged 
Unchanged 
Unchanged 
Brassy 

Brassy 
Brassy 
Brassy 
Brassy 
Brassy 
Brassy 
Brassv 



After 25 days at 75° C, a b'ank solution became colorless and a brownish- 
yellow precipitate formed. After 15 hours more at 95° C, the solution was 
yellow and the precipitate the same as before. 

After 15 hours at 95° C, the brassy appearance disappeared from the 
nickel and antimony. Silver became very yellow. 



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Reptacement of the Metals in Non-Aqueous Liquids 119 



Table 6 

Copper Acetoacetic Ester in Ethyl Benzoate 

Conductance less than 2 X lo-** Deep green-blue solution 



Metal 


Time 


Temp. 


Solution change 


Metal change 


Mg 


12 days 


20<^C 


Little greener — ppt. 


Coppered 


Cd 


12 days 


20® C Little greener — ppt. 


Coppered 


Pb 


12 days 


20^ C 1 Light green — ppt. 


Coppered 


Zn 


12 days 


20<^C 


Darker than Pb — ppt. 


Coppered 


Fe 


12 days 


20<^C 


Color unchanged — ppt 


^ Blackened a little 


Sn 


12 days 


20^ C 


Color unchanged — ppt 


Unchanged 


Ni 


12 days 


20^ C 


Color unchanged — ppt 


* Unchanged 


Sb 


12 days 


20<^C 


Color unchanged — ppt 


* Unchanged 


Ag 


12 days 


20<^C 


Color unchanged — ppt 


* Unchanged 


Al 


12 days 


20<^C 


Color unchanged — ppt 


Unchanged 


Co 


12 days 


20° C 


Color unchanged — ppt 


* Unchanged 


Hg 


12 days 


20*^ C 


Color unchanged — ppt 




Bi 


12 days 


20<^C 


Color unchanged — ppt 


* Unchanged 


Fe 


25 days 


75° C 


Blue salt separated 


Unchanged 


Sn 


25 days 


75° C Blue salt separated 


Unchanged 


Ni 


25 days 


75** C Blue salt separated 


Unchanged 


Sb 


25 days 


75^ C Blue salt separated 


Unchanged 


Ag 


25 days 


75^ C Blue salt separated 


Unchanged 


Hg 


25 days 


75*" C Blue salt separated 




Bi 


25 days 


75^ C 1 Blue salt separated 


Much darkened 


Al 


25 days 1 75° C ! Olive green 


1 Unchanged 


Co J 25 days 1 75° C 1 Olive green 


1 Coppered slightly 



* One or more large, deep blue crystals separated out. 

In every case there was a light blue precipitate. After 25 days at 75° C, 
from a blank solution there separated a blue solid. After 15 hours at 95° C, 
aluminum became slightly brassy. 

Copper in ethyl benzoate gave a deep greenish-blue solution. After 25 
days at 75** C, a precipitate formed on the tube and metal, which looked like 
freshly deposited copper. At the same time the solution became light green. 



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I20 



Charles Baldwin Gates 



Table 7 

Copper PaL itate in Ethyl Benzoate 

Conductance less than 2 X io~** Greenish-blue solution 



Metal 


Time Temp. 


Solution change 


1 Metal change 


Pb 


12 days 20** C 


Color unchanged — white ppt. 


; Coppered 


Zn 


12 days: 20** C 


Slightly greener 


j Coppered 


Cd 


12 days I 20** C 


Light green — white jelly 


1 Coppered 


Mg 


12 days 20® C 


Colorless 


1 Coppered 


Sn 


12 days 20** C 


Slightly yellow 


Coppered 


Co 


12 days 20*^ C 


Purplish-blue 


Unchanged 


Al 


12 days 20*^ C 


Unchanged 


1 Unchanged 


Ag 


12 days 20® C 


Unchanged 


' Unchanged 


Fe 


12 days 20° C 


Unchanged 


Unchanged 


Hg 


12 days 20° C 


Unchanged 


1 


Ni 


12 days 1 20° C 


Unchanged 


1 Unchanged 


Sb 


12 days 20° C 


Unchanged 


1 Unchanged 


Bi 


12 days 20° C 


Almost colorless — white 
gelatinous ppt. 


Unchanged 


Co 


25 days! 75° C 


Deep purple 


! Coppered 


All 


25 days 75*" C 


Unchanged 


j Unchanged 


others 






1 



After 15 hours at 95** C, there were no further changes. 



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Replacement of ike Metals in Non-Aqueous Liquids 121 



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122 



Charles Baldwin Gates 



Table 9 

Copper Abietate in Ethyl Benzoate 

Conductance less than 2 X icr** Very dark green solution 



Metol 


Time 


Temp. 


Solution change 


Metal change 


Cd 


7 days 


20*^ C 


Color unchanged — ppt. 


Coppered 


Pb 


7 days 


20<^C 


Colorless, yellow-green ppt. 


Coppered 


Mg 


7 days 20° C 


Colorless, yellow-green ppt. 


Coppered 


Zn 


7 days 20° C 


Yellow-brown 


Coppered 


Ni 


7 days ! 20® C 


Unchanged 


Unchanged 


Ag 


7 days ; 20° C 


Unchanged 


Unchanged 


Sn 


7 days 20*^ C 


Unchanged 


Unchanged 


Fe 


7 days 20** C 


Unchanged 


Unchanged 


Bi 


7 days 20° C 


Unchanged 


Unchanged 


Last 
five 


25 days 75° C 


Unchanged 


Unchanged 




After 15 h< 


3urs at < 


^5** C, silver was brassy. 





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Replacement of the Metals in N on- Aqueous Liquids 123 



Table 10 

Copper Cinnamate in Pyridine 

Conductance — 117 X lo"* Deep blue solution 



MeUl 


Time 


Temp. 


Solution change 


Metal change 


Pb 


6 days 


20° C 


Light blue — blue ppt. 


Brassy 


Ag 


6 days 


20° C 


Light green — b ue ppt. 


Unchanged 


Bi 


6 days 


20 °C 


Light blue — blue ppt. 


Unchanged 


Al 


6 days 


20° C 


Light blue — blue ppt. 


Unchanged 


Fe 


6 days 


20° C 


Light blue — blue ppt. 


Unchanged 


Mg 


6 days 


20° C 


Light green — blue ppt. 


Unchanged 


Sn 


6 days , 20° C 


Light green — blue ppt. 


Unchanged 


Hg 


6 days 1 20° C 


Light green — blue ppt. 


Unchanged 


Ni 


6 days \ 20° C 


Green — blue ppt. 


Unchanged 


Zn 


6 days 20° C 


Green — blue ppt. 


Unchanged 


Cd 


6 days 20° C 


Green — blue ppt. 


Unchanged 


Sb 


6 days 1 20° C 


Green — blue ppt. 


Unchanged 


Co 


6 days \ 20° C 


Brown — blue ppt. 


Unchanged 


Zn 


25 days 75° C 


Very light yellow 


Coppered 


Ag 


25 days j 75° C 


Tube broke 


Unchanged 


Sn 


25 days 75° C 


Tube broke 


Unchanged 


Al 


25 days 75° C 


Very light green — blue ppt. 


Unchanged 


Ni 


25 days ' 75° C 


Greenish-yellow — blue ppt. 


Unchanged 


Bi 


25 days 75° C 


Light green — blue ppt. 


^ Unchanged 


Sb 


25 days 1 75° C 


Light green — blue ppt. 


Unchanged 


Mg 


25 days 1 75° C 


Yellow — blue ppt. 


Unchanged 


Fe 


25 days i 75° C 


Green — blue ppt. 


Unchanged 


Hg 


25 days 1 75° C 


Green — blue ppt. 


Unchanged 


Cd 


25 days 75° C 


Green — blue ppt. 


Unchanged 


Co 


25 days 


75° C 


Brown 


Unchanged 



Immediately on sealing, the blank solution and also those containing 
silver and magnesium turned yellowish-green; mercury, nickel, lead, tin became 
greenish-blue; cobalt became dark lavender. 

After 15 hours at 95** C, cobalt was slightly brassy. 

Copper in pyridine gave an olive green solution and a blue salt crystal- 
lized out. After 25 days at 75** C, the solution became yellow and a brownish- 
yellow precipitate settled out on the sides of the tube. Copper itself became 
blackish-brown. 



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124 



Charles Baldwin Gates 



Table ii 
Copper Palmitate in Pyridine 



( 


Conductance— 46 X 


IO-* Blue-green solution 


Metal 


Time 
4 days 


Temp. 


Solution change 


Metal change 


Pb 


20*'C 


Greener 


Darkened 


Zn 


4 days 


20° C 


Greener 


Unchanged 


Hg 


4 days 


20*'C 


Greener 


Unchanged 


Mg 


4 days 


20^ C 


Blue. Green ppt. 


Unchanged 


Ni 


4 days 


20*'C 


Bluer 


Unchanged 


Al 


4 days 


20° C 


Bluer 


Unchanged 


Sn 


4 days 


20*'C 


Deep blue 


Unchanged 


Ag 


4 days 


20° C 


Unchanged 


Unchanged 


Cd 


4 days 


20*'C 


Unchanged 


Unchanged 


Bi 


4 days 


20° C 


Unchanged 


Unchanged 


Fe 


4 days 


20° C 


Unchanged 


Unchanged 


Sb 


4 days 


20*'C 


Unchanged 


Unchanged 


Co 


4 days 


20° C 


Unchanged 


Unchanged 


Pb 


25 days 


75" C 


Greenish-yellow 


Coppered slightly 


Zn 


25 days 


75" C 


Tube broke 


Brassy 


Mg 25 davs 


75° C 


Tube broke 


Unchanged 


Sn 


25 days 


75" C 


Tube brobe 


Unchanged 


Hg 


25 days 


75" C 


Green 


Unchanged 


Cd 


25 days 


75" C 


Green 


Unchanged 


Ag 


25 days 


75" c 


Unchanged 


Unchanged 


Ni 


25 days 


75" C 


Unchanged 


Unchanged 


Also 


Bi, Fe, 


Al. Sb, Co 


Unchanged 


Unchanged 



After 15 hours at 95° C, the solution containing cadmium became dark 
brown and the metal was brassy in places. 

was at once amalgamated, and analysis of the mercury, in 
representative cases, proved this. In order to be sure that 
''indicated" results were really effects of the metals intro- 
duced, blanks were invariably nm. In 20.2 percent of all of 
the solutions indicated in this table, metallic copper was 
thrown out, while 27 percent more showed indirect evidence 
of replacement. 

The number of cases where actual replacement occurred, 
as compared with the number of cases where no replacement 
resulted, varied when the same salt was dissolved in diflFerent 
solvents. The number also varied in the case of the same 



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Replacement of the Metals in Non-Aqueous Liquids 125 



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Replacement of the Metals in N on- Aqueous Liquids 127 





PD 


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g g g 
g g g 

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128 



Charles Baldwin Gates 





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Replacement of the Metals in Non-Aqueous Liquids i?9 

solvent when different salts were dissolved in it. And again 
the number of cases in which action occurred varied when the 
same metal was used to replace copper in different solutions. 
For the purpose of comparing the various solvents, as to the 
ratio of the actual number of replacements to non-replace- 
ments, Table 13 was compiled. The various salts are similarly 
compared in Table 14 and the various metals in Table 15. 
This comparison can only be approximate, since the salts 
were not all used in the same number of experiments, nor 
were the solvents. The ratios do indicate roughly which 
combinations of salt and solvent might be expected to give 
the largest percentage of instances of copper replacement. 
Table 15 is more significant, since all the metals but cadmium 
were given an equal opportunity to replace copper. 

Table 13 
Copper Replacements Secured in the Various Solvents 



Solvent 


Actual re- 
placements 
Percent 

257 


Actual and 

indicated 

replacements 

Percent 


Experiments 
performed 


Oleic acid 


34 8 


132 


Benzaldehyde 


52.7 


80.5 


108 


Pyridine 


16.6 


53-5 


62 


Carbon bisulphide 


0.0 


3-3 


60 


Ethyl benzoate 


42 -5 


61.5 


52 


Amyl alcohol 


20. 1 


75 


50 


Carbon tetrachloride 


16.6 


27.1 


49 


Toluol 


2.1 


16.6 


48 


Acetaldehyde 


25 


52.8 


36 


Ethylene dibromide 


13 9 


91.6 


36 


Nitrobenzene 


II . 1 


16.6 


36 


Pinene 


5-5 


36.1 


36 


Acetone 


2.8 


30.5 


36 


Aceton'trile 


0.0 


89.0 


36 


Ether 


0.0 


33-3 


24 


Pentane 


0.0 


12.5 


24 


Ethyl alcohol 


25.0 


91.8 


12 



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^30 



Charles Baldwin Gates 



Table 14 
Copper Replacements Secured with the Various Salts 



Copper salt 



Actual re- 
placements 
Percent 



Actnal and 

indicated 

replacements 

Percent 



Experiments 
performed 



Acetoacetic ester 

Palmitate 

Abietate 

Anisate 

Capronate 

Cinnamate 

Margarate 

Phthalate 

Camphorate 

Isovalerianate 

Laurate 



16 


7 


19 


5 


15 


8 


27 


8 


8 


3 


33 


3 


18 


4 


19 


5 


37 


5 


29 


2 


12 


5 



49 o 
45.8 

34-3 
62.5 
57 o 
40.0 
30.0 
61.3 
58.3 
58.3 
25.0 



I 



204 
144 
108 
72 
72 
60 
60 
36 
24 
24 
24 



Table 15 
Copper Replacements Secured with the Various Metals 







Actual replace- 




MeUl 


ments 
Percent 




Cd 


77.8 




Pb 


55 




Zn 


49-3 




Bi 


29.0 




Mg 


23.2 




Co 


21.8 




Sn 


17 4 




Fe 


H-5 




Al 


H-5 




Ag 


5-8 




Sb 


29 




Ni 


15 




Hg 


0.0 



Actual and indi- 


1 


cated replace- 


Experiments 


ments 


performed 


Perc 


wt 

8 


! 


77 


9 


73 


3 


69 


71 





69 


53 


6 


69 


50 


8 


1 69 


55 


I 


69 


46 


5 


69 


39 


I 


69 


34 


8 


1 69 


29 





69 


31 


9 


1 69 


30 


5 


69 


42 





69 



Comparison of Replacement Series of Metals in Non- 
Aqueous Liquids with Other Series 

An interesting comparison, from the electrochemical 
standpoint, is given in Table 16. All the metals used in the 



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Replacement of the Metals in Non-Aqueous Liquids 131 

preceding experiments are arranged in the first column ac- 
cording to the actual percentage of cases in which they re- 
placed copper. In the second column they are rearranged 
according to their percentage of actual and indicated re- 
placement. With three minor changes, this column re- 
mains the same as the first. The third column gives Neu- 
mann's electrochemical series, together with the diflference 
of potential between the metals and aqueous solutions of 
their salts. * The last column gives a series of metals as deter- 
mined by their single potentials in normal potassitmi cyanide 
solution.' 

Table 16 

Comparison of Various Series of the Metals 



Actual replace- 1 
ments 
Percent 



Cd 
Pb 
Zn 
Bi 
Mg 
Co 
Sn 
Fe 
Al 
Ag 
Sb 
Ni 
(Hg) 



77.8 
550 

49 3 
29.0 
23.2 
21.8 
17 4 
14 5 
14-5 
58 
2.9 

15 
0.0 



Actual and 


indicated 


replacements 


Percent 


Cd 


77.8 


Pb 


73-3 


Zn 


71.0 


Co 


55 I 


Bi 


53-6 


Mg 


50.8 


Sn 


465 


Hg 


42.0 


Fe 


39 I 


Al 


34-8 


Sb 


31 9 


Ni 


30 5 


Ag 


29.0 



Neumann's electro- 1 „„ B-nxr .<..^.. 
chemical series N/IKCN series 



Mg 

Al 

Mn 
I Zn 

Cd 
I Fe 
I Co 
! Ni 
I Pb 

I Sb 

Sn 

' Cu 

— . — I Ag 

— — , Pd 
; - : Pt 

— — I Au 

It must be remembered that cadmium was used in only 
about 13 percent of the total number of experiments; still in 

* Zeit. phys. Chem., 14, 229 (1894). 

' These results are the average of the findings of a class in Applied Elec- 
trochemistry at this University in 1907. 



+ I.23I 


Al 


+ 1.066 


-f I.0I5 


Zn 


+0.992 


+0.824 


Mg 


+0.935 


+0.503 


Cu 


+0.800 


+0.174 


Cd 


+0.691 


+0.087 


Sn 


+0.505 


—0.015 


Ag 


+0.351 


— 0.020 


Ni 


+0.270 


-0.095 


Pb 


+0.147 


— <^-3i5 


Fe 


— 0.006 


— 376 


Bi 


— 0.020 


—0.085 


Pt 


— 0.220 


--0.515 


C 


-0.456 


—0.980 




— 


—0.974 




— 


—1.066 




— 


— I . 140 




— 


—1-356 




— 



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13^ Charles Baldwin Gates 

these it gave as good results, or better, than did lead and 
zinc. Mercury falls at the bottom of the first column, because 
of its amalgamating properties. Its position in the second 
column is more probably its proper place. The only other 
differences are the shifting up of cobalt in the second column 
and the shifting down of silver. The reason for this is un- 
known. 

It is very evident from a comparison of the last three 
columns that the replacing power of the metals is not a fixed 
property of the metals themselves, but is largely dependent 
on the chemical nature of the solution in which the replace- 
ment occurs. The three series do not show even approxi- 
mately the same sequence of metals, in the maiority of in- 
stances. While there seems to be some connection between 
the electrical potentials of the metals and their basicity or 
replacing power in aqueous solutions, this does not appear in 
non-conducting solutions. Replacements occur, but these 
evidently cannot be ascribed to *' electrolytic dissociation," 
for the solutions are insulators. 

Effect of Small Amounts of Atmospheric Moisture in Re- 
placement Experiments 

Thinking that possibly some of these reactions might be 
due to moisture absorbed by the solutions from the air, over 
one hundred duplicates were run in sealed tubes. In these 
cases, the same results were always obtained as in the open 
tubes and therefore no further precautions were taken in this 
direction, except in the cases where solvents were known to 
be hygroscopic. All the copper salts and most of the solvents 
showed no such tendency. This confirms results on the 
effect of small amounts of water as previously found by other 
investigators. * 

Metal Replacement in Fused Salts 

Sammis* found that fused copper oleate and palmitate 
will both copper-plate lead instantaneously. The tempera- 

* J. L. Sammis: Jour. Phys. Chem., lo, 608 (1906); J. H. Mathews: Ibid., 
9, 663 (1905). 

* Sammis: Loc. cit., p. 612. 



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Replacement of the Metals in N on- Aqueous Liquids 133 

tures at which these salts melt preclude all possibility that 
replacement is due to the presence of moisture. In order to 
investigate such reactions farther, it was first determined 
whether the copper salts available could be fused without 
decomposition, by gradually heating them in an oil-bath. 

Copper acetoacetic ester became brown at 170*^ C and 
an odor resembling that of some of the higher esters was 
detected. This was probably acetoacetic ester, which boils 
at 181*^ C. On higher heating, the salt decomposed entirely, 
leaving copper and some copper oxide. Copper cinnamate 
became green at 160° C and decomposed at 250° C. The 
phthalate showed a similar change at 200° and broke up at 
280°. The abietate, capronate, anisate and isovalerianate 
decomposed respectively at 190°, 160°, 255° and 350°. Cop- 
per camphorate turned from light blue to green at 175°. 
This color change was completely reversible, depending on 
the temperature. The salt decomposed at 250°. Copper palmi- 
tate was entirely fused to a dark green, oily liquid at 200°. 
This was also the case with the stearate and margarate at 
240® and 255° respectively. The last three salts were used 
in the following tests. Pieces of metal were scraped clean, 
held in the molten salt from one to three minutes, taken out, 
the adhering mass of solidified salt removed mechanically 
or by solution, and the metal surface examined for copper. 
The results are given in Table 17. 

In all three salts, lead, zinc, tin and bismuth gave espec- 
ially good results, a heavy coating of copper depositing im- 
mediately. The usually strongly basic magnesium and 
sodium were surprisingly inactive, behaving about like nickel 
and cobalt. The inaction of aluminum and iron is also 
perplexing, unless it is assumed that their surface was pro- 
tected by a film of oxide. There is, however, no experi- 
mental evidence whatever upon which to base such an assump- 
tion. These results are important from the fact that the 
chemical reactions are as vigorous and instantaneous as similar 
replacements in aqueous solutions; and yet they take place 
in liquids that are completely anhydrous and non-conducting. 



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134 



Charles Baldwin Gates 



Table 17 
Copper Replacement in Fused Salts 



AtUl 


Copper paltnitmte, 220° 


Copper stearate, 250° 


Copper margarate, 
26o*» 


Pb 


Coppered 


Coppered 


Coppered 


Zn 


Coppered 


Coppered 


Coppered 


Sn 


Coppered 


Coppered 


Coppered 


Bi 


Coppered 


Coppered 


Coppered 


Cd 


Coppered 


Coppered 


Coppered 


Sb 


Coppered 


Coppered 


Coppered 


Hg 


Coppered* 


Coppered slightly* 


Coppered* 


Co 


Coppered 


Coppered slightly 


Not coppered 


Ni 


Coppered slightly 


Not coppered 


Not coppered 


Mg 


Coppered slightly 


Not coppered 


Not coppered 


Na 


Not coppered 


Coppered 




Al 


Not coppered 


Not coppered 


Not coppered 


Ag 


Not coppered 


Not coppered 


Not coppered 


Pt 


Not coppered 


Not coppered 


Not coppered 


Fe 


Not coppered 


Not coppered 


Not coppered 



The results do not agree very closely with what would be ex- 
pected from the position of these metals in the ordinary 
electrochemical series. In order to see what agreement there 
might be with that series, if fused salts that do conduct were 
used, the following experiments were carried out. 

Metal Replacement in Conduotlngr Fused Salts 

The action of metals upon solutions of silver nitrate has 
been carefully studied by Senderens.* Upon fiised silver 
nitrate but little has been done. The salt is easily melted 
at about 218*^ C without decomposition. 

Calcium reacted with the fused salt with evolution of 



* Mercury caused the molten mass to become brownish-black and spots 
of copper were seen floating on the surface of the metal. The mercury was 
removed, washed thoroughly with amyl alcohol and carbon tetrachloride until 
it was perfectly clean and white. It was then volatilized from a white porcelain 
surface and left a grayish-black spot, very thin and shiny. This was dissolved 
in nitric acid and gave a copper test with potassium ferrocyanide. A blank 
test left a p)erfectly clean porcelain surface. 

* Bull. Soc. chim. Paris, [3] 15, 208, 691 (1896); 17, 271 (1897); Comptes 
rendus, 104, 504 (1887). 



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Replacement of the Metals in Non-Aqueous Liquids 135 

light, and metallic silver was thrown out. Magnesium 
showed apparent decomposition around the metal and nitrogen 
peroxide was given oflF on continued heating. The magnesium 
entirely disintegrated and white metallic silver was formed. 
The fused mass was deliquescent when cold, indicating the 
presence of magnesium nitrate. This reaction took place 
below the melting point of magnesimn. 

Cadmitun and lead both gave vigorous reactions and 
nitrogen peroxide was liberated, because the temperature was 
above that of the decomposition point of the nitrates of these 
metals. Both precipitated metallic silver. The reaction 
of zinc was suflSciently exothermic to keep the silver nitrate 
melted and oxides of nitrogen were liberated. The zinc 
strip was disintegrated and silver precipitated. Tin melted 
in the fused silver salt and a coating of black stannous oxide 
formed over the bright metal, but the change was rather 
slower than the similar reaction in aqueous solution. Cobalt 
was covered with a dark gray tarnish, which gave a test for 
silver. 

Gold, aluminum, iron and silicon gave no results. Cop- 
per darkened a little in the nitrate, but this dark gray, metaUic 
stain gave no test for silver; nor was any copper found in the 
silver nitrate afterward. 

The effect of introducing metals into a fused mixtiu-e of 
silver nitrate and potassium nitrate was then tried. Copper, 
magnesium, iron, aluminum, zinc and cobalt gave the same 
results as in fused silver nitrate alone. The action of the 
zinc was much less vigorous than before. The salt arotmd 
the cobalt took on a pecuUar lavender color, but this dis- 
appeared with rise of temperature. 

Very little was done with fused mercuric chloride, as it 
was already known that many of the metals will reduce it to 
mercurous chloride, and even to mercury, when heated. 
Copper was tried and was mirrored with mercury at once. 
Gold remained unchanged. Silver was coated heavily and 
much silver was found in the fused salt afterward. This 



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136 Charles Baldwin Gates 

result was unexpected, as silver is generally more electro- 
negative than mercury in aqueous solutions. 

Fused silver chloride (460° C) was next tried. Copper, 
tin, iron, aluminum, nickel, cobalt, bismuth, magnesium, 
zinc, calcium and lead decomposed the salt and either free 
silver was thrown out or an alloy was formed. Gold, platinum 
and silicon produced no effect. The case of the aluminum 
was interesting because it gave no reaction imtil melted. 
Suspecting that this passivity might be due to an oxide film, 
the metal was scratched beneath the fused silver chloride 
with a glass rod. Vigorous reaction immediately resulted 
and dense white fumes of aluminum chloride were copiously 
evolved. In the case of the iron, the cold fusion mass was 
reddish-brown and in the case of cobalt bright green. The 
product resulting from the action of the zinc was strongly 
hygroscopic. As soon as the silver chloride fused, calcium 
reacted with it with strong evolution of light. 

The results when silver chloride was fused with sodium 
chloride were practically the same as when the silver salt was 
used. 

In fused zinc chloride (262° C), magnesium threw out 
metallic zinc. Copper, aluminum, and lead did nothing. 
The lead melted and could be alloyed with copper beneath 
the fused chloride, as one would naturally expect. 

Fused copper chloride decomposes rapidly, yielding 
chlorine and cuprous chloride. According to Moissan, some 
cupric oxide is also formed. The fused mass was dark brown, 
due to anhydrous cupric chloride. Iron, aluminum (on 
scratching), magnesium (explosively), and calcium, all re- 
acted with the fused mass with increasing violence. Gold, 
silver, silicon and nickel produced no action. 

Fused sodium chloride gave no reaction with either 
silicon or magnesium. 

Fused calcium chloride (7io°-8o6°) gave no results with 
copper, graphite, silver, nickel, cobalt, iron, aluminum and 
antimony. The last two metals melted and oxidized. Potas- 
sium and sodium reacted violently. Magnesium melted. 



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Replacement of the Metals in N on- Aqueous Liquids 137 

and the fused calcium chloride seemed to boil all around the 
liquid metal. This was accomplished by a continual crackling 
soimd and these tiny explosions were often attended with 
flashes of fire. Evidently some of the freed calcium was 
reaching the siuface and burning. Silicon gave results 
similar to those of magnesium, but these were even more 
energetic. It is known that alkaline chlorides, at high tem- 
peratures, react with silicon to form silicon tetrachloride.* 
And when the tetrachloride is passed over hot silicon, a 
hexachloride (Si^Clg) is formed; the vapor of this substance 
will burn when heated in air.^ The presence of a little of 
this vapor may accoimt for some of the phenomena observed. 
However, as exactly similar results were obtained with mag- 
nesium, where there could be no silicon chloride, the indica- 
tions are that it is metallic calcium which is liberated and 
bums. After cooling, the fused mass would not all dissolve 
in boiUng water, but hydrochloric acid would dissolve it with 
effervescence. This would show that some calcium oxide 
had probably been formed, and some of this was converted into 
carbonate during the boiling in water. Much of the liberated 
calcium doubtless alloyed with the silicon.' This probable 
alloy reacted with water very slowly (more rapidly if warm), 
indicating the presence of calcium. 

The results of this series of experiments are almost 
completely in accord with what would be expected as to the 
relative basicity of the metals concerned, judging from their 
action in aqueous solutions. But whereas in water solutions 
all more electropositive metals displace all less positive, in 
non-aqueous fused salts this is not always the case. 

Solution of the Precipitated Copper by the Solvents Used 

The power of an acid to conduct the electric current and 
its ability to exchange its hydrogen for a metal have been 



* Baudrimont: Jour. Pharm. Chem., [4] 40, 161 (1871). 

' Troost and Hautefeuille : Ann. Chim. Phys., [5] 7, 463 (1876); Comptes 
rendus, 73. 443 (187 1). 

*Wohler: Liebig's Ann., 125, 255 (1863); 127, 257 (1863); Moissan: 
Bull. Soc. chim. Paris, [3] 21, 865 (1899). 



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138 Charles Baldwin Gates 

thought to be associated usually with the presence of aqueous 
solutions. Indeed the presence of water has been assumed 
as a necessary condition for both phenomena. The elec- 
trolytic dissociation theory has accounted for both by postula- 
ting the existence of ions, and has aflSrmed that an acid that 
could not fiunish ions to carry a current, could not dissolve 
a metal. An insulating acid like oleic should show no dis- 
solving power whatever, to accord with the theory. There- 
fore it might be assumed that when oleic acid was used as a 
solvent in the foregoing experiments, replaced copper would 
be entirely safe from re-solution, since the acid had not the 
slightest conductivity. However, it was discovered acci- 
dentally that many of the metals do dissolve in pure oleic 
acid to a considerable extent. While the action is slow in 
most cases, in some instances it is as vigorous as that of 
aqueous hydrochloric acid solutions on zinc. 

In all cases where oleic acid was used as the solvent, 
replacements of copper were very frequent. It was also 
noticed that there were many cases where chemical action 
seemed to be taking place and yet no coating of metallic copper 
was visible. For instance, the solution would lose its green 
color wholly or in part, or a light colored precipitate would 
settle out, or the solution would solidify, or the metal would 
tarnish or disintegrate. This suggested the explanation that 
the solvent might be capable of dissolving metaUic copper as 
fast as it was thrown out and direct evidence of replacement 
would be destroyed or weakened by this secondary reaction. 
This led to a series of experiments to ascertain the solubility 
of copper and other metals in some of the solvents used. 

Solubility of Copper in Oleic, Palmitic and Stearic Acids 

Clean pieces of copper were placed in two samples of oleic 
acid, obtained respectively from Kahlbaum and Bausch & 
Lomb. Another piece was put in benzaldehyde. All three 
solutions soon became deep green in color at room tem- 
peratures. In the case of the oleic acids, hydrogen was 
visibly evolved. It was thought that this solvent action of 



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Repldcement of the Metals in Non-Aqueous Liquids 139 

the acid might be due to small amotmts of inorganic acids, 
but none were found. Both samples of oleic acid were tested 
with anhydrous copper sulphate for water. Their con- 
ductance was less than 2 X lo"*®. Samples of each were 
shaken up with distilled water and the filtered water was tested 
for hydrochloric, sulphuric and nitric acids. As a farther check, 
oleic acid was well shaken with a weak potassium hydrate 
solution. White potassium oleate precipitated out. Any 
mineral acid, present in traces, would be neutralized by this 
treatment. Yet some of the imsaponified acid, which rose to 
the surface on standing, dissolved copper as well as ever. 
It is therefore decided that when no replacement is observed 
in oleic acid solutions, this is not conclusive, because of the 
solubility of the metal replaced. 

Stearic and palmitic acids (Schuchardt) were melted on 
carefully cleaned copper foil and kept fused for half a minute. 
On cooling, they were both green. They were subjected to 
the same process for removing traces of mineral acids as was 
the oleic acid, and still both became green on copper foil. 
Cottonseed oil, which is essentially glyceryl oleate, would not 
dissolve copper in the least. 

A piece of clean zinc was placed in some of Kahlbaum's 
oleic acid. On warming, after a short period of induction, 
hydrogen was more vigorously evolved than in the case of 
copper. The solution was allowed to stand over night so 
that any traces of strong acids might be removed. But on 
warming again, the action was just as vigorous as at first. 

A quantitative examination of the solubility of copper in 
oleic acid was then undertaken and the first experiment ex- 
tended over two years. Most of the time the solution was 
kept at room temperatures, though occasionally it was heated 
as high as 75° C The results were as follows: 



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I40 



Charles Baldwin Gates 



Table i8 
Solution of Copper in Oleic Acid 



Weight of 
copper 1 
Gram | 


Date 


O . 4020 
0.3940 , 
0.3526 
0.3024 , 
0.2814 ' 
0.2145 


5/ 9/1907 
5/20/1907 
6/ 7/1907 
6/16/1908 
11/ 2/1908 
5/20/1909 



I Percent loss Time elapsed 



1 99 
12.29 

24 77 
30.00 
46.64 



II davs 
28 
402 

53S 
737 



The amoirnt of oleic acid with which the experiment 
started was 3 cc, but this became slightly less each time, as 
the metal was removed for weighing. On the last date, the 
solution had become as viscous as glycerin. It was very 
dark green and perfectly opaque (in an ordinary' test tube). 
The tube was kept tightly corked during the whole time. 
About two-thirds of the the available oleic acid was taken 
up by the metal and the green liquid was a saturated solution 
of copper oleate in the remaining third. The whole solution 
became a buttery solid on cooling below 50° C. 

Preparation of Pure Oleic Acid 

This curious behavior of oleic acid toward copper raised 
the question of how it would act toward other metals. In 
order to be surer of its purity, a quantity of oleic acid was 
prepared in the laboratory. High grade cottonseed oil was 
saponified with potassium hydrate and the oleic acid was 
then throwTi out of solution with tartaric acid. It was nearly 
colorless and was a solid at room temperature. The other 
acids possibly present were palmitic, stearic and linoleic.^ 
The melting points of these are: palmitic 62°, stearic 71°- 
71.5°, linoleic under 18°, and oleic 14°^ 

The purity of the cottonseed oil used was tested by 
cooling. It began thickening at — 5° and was like glycerin 
and opaque at — 10°. Palmitin solidifies at 58^-66°, stearin 

* Leach: "Food Inspection and Analysis," p. 418. 
'^ Lewkowitsch: "Oils, Fats and Waxes," p. 24. 



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Replacement of the Metals in N on- Aqueous Liquids 141 

at 55^-72^, and olein at — 6°. The amount of palmitin and 
stearin in the oil must therefore have been very small. 

The mixture of oleic acid with these small amounts of 
other acids was distilled from a double necked distilling flask 
imder a pressure of 10 mm and at a temperature of 2io°-22o°. 
This boiling point agrees very closely with the results of 
Krafft and Nordlinger on pure oleic acid.* The distillate 
was cooled with running water. It solidified into a pure 
white mass. At room temperature, this was put on a suction 
filter and an oil removed which was very slightly yellowish 
in color. The very small amount of white soHd left on the 
filter had a melting point of 60°, which agrees with that of 
palmitic acid. 

The oleic acid thus prepared showed the following con- 
stants: Slightly acid toward litmus. Slightly yellow, when 
in large quantity. Conductivity less than 2 X lo"***. Melt- 
ing point 13.5° C. (Gottlieb gives 14°.) Specific gravity 
was 0.8953 at 14^ C. (Chevreul gives 0.898 at 14°.) 
Solubility of Metals in Oleic Add 

A number of metals were cleaned and introduced into this 
pure oleic acid. Sodium, potassium and calcium immediately 
evolved hydrogen at room temperature and at a rate sufficient 
to enable it to be exploded in the test tube. Other metals 
were heated to 100° in the acid and, arranged in the order in 
which they were most vigorously attacked, they are copper, 
zinc, lead and cadmium. Silver and magnesium acted very 
slowly; that is, a few small bubbles of hydrogen were seen 
on the surface of the metal only after five minutes of heating 
at 100°. Aluminum, nickel, cobalt, antimony, iron, bismuth, 
tin, mercury and platinum were apparently unaffected. 

It was repeatedly found that a test tube containing 
copper and oleic acid gradually lost weight, which was too 
much to be accounted for by the slight evaporation of the 
acid itself. In a week, a tube containing only oleic acid and 
weighing 3.5234 grams lost no appreciable weight; whereas 
one containing oleic acid and copper and weighing 3.7040 

* Ber. chem. Ges. Berlin, 22, 819 (1889). 



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142 Charles Baldwin Gates 

grams lost 0.0027 gram during the same time. In this 3.7040 
grams there were 0.91 16 gram of acid, or 0.0032 gram of re- 
placeable hydrogen. The loss in weight is explained by the 
partial liberation and escape of the replaceable hydrogen. 
The reaction is probably expressed by the equation, 
Cu + 2C^H3,COOH = (Ci7H„C00),Cu + H,. 

Two series of experiments were imdertaken to study 
further the quantitative side of this solvent action of oleic 
acid toward metals. The first is summarized in the following 
table. In each case i cc of acid was used, but the weights 
and exposed surface areas of the metals diflfered, so the re- 
sults are not to be rigidly used for piuposes of comparison. 
In a general way, however, they show the relative afiinities 
of the metals for the acid. The metals were in contact with 
the acid for 120 hours at room temperature and then 10 hours 
more at 90^-100°. The copper solution became perceptibly 
greenish in twenty minutes (23° C). During the same time, 
the surfaces of the zinc, lead, cadmium and bismuth became 
dulled; tin, iron, magnesium and silver remained bright; 
and a white solid separated out in the case of the mercury. 

Table 19 
Solution of Metals in Oleic Acid 



Metal 



Wt. before Wt. after Loss in ^^"J^LVoi" ^^ Condition of solution 



in grams in grams 



Pb i 0.2402 0.21 12 



Hg 



11.7984 11.7792 



0.0290 Grayish-white Yellow. White ppt. 

coating 
0.0192 — Grayish-white ppt. 

Cd . 0.2705 0.2539 0.0166 Grayish-white Yellow. White ppt. 

j coating 

Zn ! 0.1920 o. 1785 0.0135 Grayish- white Solid. Light yellow. 

j I coating 

Bi I 1.4032 1. 392 1 o.oiiii — 

Sn 0.2155 0.2075 0.0080 Tarnished 
Cu I 0.1305 I 0.1277 0.0028 Bright I Deep green 

Mg I 0.0317 0.0294 0.0023 W'hite coating Yellow 
Fe ! 0.0741 0.0734 0.0007 i Bright Reddish-brown 

Ag 0.0769' 0.0768 — Bright I Yellow-brown 

Blank oleic add — light yellow (slight oxidation). 



Yellow. White ppt. 



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Replacement of the Metals in N on- Aqueous Liquids 143 

The experiments were repeated with a much longer 
time of exposure, especially at the higher temperature, and a 
much larger number of nietals was used, including some of 
the more uncommon ones. Again, care must be taken in 
making any comparisons other than the most general. Half 
a cubic centimeter of oleic acid was used in each case. The 
duration of the experiment was 290 hours, during 60 of which 
the temperature was between 90° and 100° C. Then the 
metals were taken from the solution, washed successively in 
amyl alcohol, ethyl alcohol and ether and weighed. 



Table 20 
Solution of Metals in Oleic Acid 



Metal 


Wt. before 


Wt. after 

•^ ,. 


Loss in 


Solution 


MeUl 




in grams 


m grams 
0.4635 


gram 






Pb 


0.5227 


0.0592 


a,d 




Na 


0.0874 


0.0425 


0.0449 


a,d 


m 


Tl 


2 . 2942 


2.2518 


0.0424 


f 




Ca 


0. 1066 


0.0732 


0.0334 


a,d 


m 


Cd 


0.4976 


0.4683 


0.0293 


a,d 




Mn 


O.917I 


0.8895 


0.0276 


a,d 




Zn 


0.1967 


0.1727 


0.0240 


a,d 




Cu 


0.0885 


0.0728 


0.0157 


g 




Sn 


0.1248 


0.1114 


0.0134 


c 




Mg 


0.0236 


0.0132 


0.0104 


b.c, 


k 


Fe 


0.0719 


0.0622 


0.0097 


b^h 




Bi 


0.9300 


. 9209 


0.0091 


b,d 




Hg 


1.4795 


1.4720 


0.0075 


c 




In 


0.0620 


0.0581 


0.0039 


d 




As 


0.2930 


. 2898 


0.0032 


c 




W (powder) 


0.2018 


0.2003 


o.ooi4(?) 


c 




Te 


0.2126 


0.2112 


0.0014 


d 




Sb 


1.0648 


I .0641 


0.0007 


d 




Ni 


0.0627 


0.0624 


o.ooo3(?) 


d 




S 


0.5178 


0.4843 


0.0335 


i 


n 


Ir 


0.0590 


0.0590 


— 


c 




Au 


0. i860 


0.1859 


— 


c 




Pt 


0.0563 


. 0562 


— 


c 




Pd 


0.0369 


0.0368 


— 


c 




Ag 


0.0759 


0.0758 


— 


c 




Cr 


O.I24I 


. I 240 


— 


c 




Mo 


0.2722 


0.2722 


— 


d 





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144 



Charles Baldwin Gates 



Table 20 — (Continued) 



MeUl 


Wt. before 
in grams 


Wt. after- 
in grams 


Loss in 
gram 


' Solution 

1 


Met 


Se 
Al 
Co 
K 


0. 1299 
0.0697 
0.2909 
0. 1480 


1 301 
0.0697 
0.2908 


— 


\ a, d 


m 


B 

Graphite 

Si 


0105 
. 0709 

O.IOOI 


07 1 1 
0. lOOI 


— 


1 c 
c 
c 


I 


P 


2051 


— 


-- 


i 






a — Solution became solid, when cold. 

6- -Solution thickened, when cold. 

c — Solution color was same as the blank oleic acid. 

d — Solution color became darker (light brown). 

^-—Solution color became quite brown. 

/ — Solution color became reddish -brown. 

g — Solution color became deep green. Also opaque. 

h — Solution became dark brown and opaque. 

i — Solution became brown-black and opaque. 

j — Solution became almost black and partly solidified. 

k —Coated with a white film. 

i — Small pieces of boron were ust»d and some of them could not be 
recovered. Probably no loss in weight. 

m — V'irtual'y all dissolved. A few small pieces remained, but could 
not he weighed. 

n- A rhombic crystal at first, but soon crumbled to powder. Some of 
the loss in weight was due to the slight solubility of sulphur in amyl alcohol and 
ether. 

o — Still part of the yellow phosphorus left, but it could not be separated 
and weighed. 

Solubility of Tin-Zino Alloys in Oleic Acid 

The solubility of a series of tin-zinc alloys, furnished by 
Mr. Alcan Hirsch, was similarly tested in oleic acid. The 
pieces used were practically all of the same surface area, so 
that the results are fairly comparable. The time of ex- 
posure and the temperatures were the same as before. Half a 
cubic centimeter of oleic acid w^as used in each case and the 
tubes were occasionally shaken. Hydrogen was evolved 
from the first. All the solutions became solid, on cooling to 
room temperature, toward the end of the experiment. With 



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Replacement of the Metals in N on- Aqueous Liquids 145 

the exception of the 30 percent tin alloy, the color became a 
little darker than that of the pure oleic acid, which was run 
as a blank. Examined with a lens, all the alloys appeared 
corroded, mainly in vertical streaks. 

Table 21 
Solution of Zinc-Tin Alloys in Oleic Add 



Metal 
Percent 



Wt. before in 
gram 



Zn 

Zn (95)- 
Zn (90)- 
Zn (85)- 
Zn (80)- 
Zn (70)- 
Zn (60)- 
Zn (28)- 



(100) I 
-Sn ( 5) 
-Sn (10) 
-Sn (15) 
-Sn (20) 
-Sn (30) 
-Sn (40) 
-Sn (72) , 
Sn (100) 



1967 

2354 
1717 
0959 
2757 
1852 
0.2364 
0.2188 
o. 1248 



Wt. after in 
gram 



Loss in gram 



o. 1727 
o. 1784 
0.1257 
0.0521 
o. 2299 
o. 1462 

0.1957 

o. 1806 
o. 1114 



0.0240 

0.0570 

o . 0460 

0.0438 
0.0458 
o . 0390 
o . 0407 
0.0382 
0.0134 



Each alloy dissolved considerably more than either pure 
zinc or tin. The ability of each metal to resist solution — its 
chemical inertia, so to speak — is lessened by combining it 
with the other. Solubility increases with the percentage 
of zinc and this is to be expected, since pure zinc is more 
soluble in oleic acid than pure tin. 

CONCLUSION 

(i) From non-aqueous, non-conducting solutions it is 
possible to throw out metallic copper by means of lead, zinc, 
cadmium, tin, bismuth, antimony, mercury, silver, iron, 
nickel, cobalt, aluminum, magnesium, sodium, potassium 
and calcium. Platinum and gold alone gave no results. 
Other experiments performed show that there is every indica- 
tion that other metals can be similarly replaced. 

(2) Copper may be precipitated from fused organic 
salts by many of the common metals. Similar replacement 
may be effected in any fused salt, without the presence of 
moisture. Such reactions are often as vigorous and in- 
stantaneous as in aqueous solutions. 



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146 Charles Baldwin Gates 

(3) A series of the metals arranged according to their 
relative basicity in non-aqueous solutions does not coincide 
with the electrochemical series. It is evident that such a 
series is dependent not alone on the relative affinities of the 
metals, but also upon the mutual relationship of the metals, 
the acid radicals and the solvents present in any given com- 
bination. The influence of the solyent is always a deter- 
mining factor in the ability of any metal to throw another out 
of solution. 

(4) The fact that so very many chemical replacements 
have been effected in liquids that are insulators is a certain 
indication that the apparent connection seen in aqueous 
solutions between such reactions and the electrical potentials 
of the metals is not a imiversal relationship. The chemical 
and electrochemical series alike are dependent on other 
factors than the metals themselves. 

(5) Many metals are appreciably dissolved by oleic acid, 
an insulating medium, with concomitant evolution of hy- 
drogen. Stearic and palmitic acids evidently act similarly. 

This work was suggested by Professor Louis Kahlenberg 
and carried out imder his direction. The author desires to 
take this opportimity to express his obligation to Professor 
Kahlenberg for the suggestion and guidance that have been 
given him throughout the prosecution of this research. 

Laboratory of Physical Chemistry ^ 
University of Wisconsin, 
July, igio 



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AN EXACT ELECTROLYTIC METHOD FOR DETER- 
MINING METALS. 



BY W. L. PERDUE AND G. A. HULETT 

The electric current is our most effective means for ob- 
taining metals from their compounds and the fact that metals 
may be separated from their solutions and each other at 
ordinary temj>eratures by this agent is the reason that so 
much attention has been given to electroanalysis. From a 
quantitative standpoint it is essential that the metal be de- 
posited in a pure state and with a surface such that it may 
be readily freed from the electrolyte and brought into a 
condition to weigh without loss or oxidation. 

The purity of the metallic deposit is affected by the 
presence of other metals in the solution. An electrolytic 
deposit undoubtedly contains all the metals which are in the 
electrolyte, but the relative amounts vary widely as they de- 
pend upon the decomposition potential of each ion upon the 
particular metallic surface presented to it and upon their 
concentration at this surface. The solubility and affinity 
relations of the metals for each other are also factors in de- 
termining the makeup of the deposit. It is possible how- 
ever to make many excellent separations, especially where the 
decomposition potential of one metal is below that of hydro- 
gen and the other above, ^ so that the hydrogen ion may act 
as a "safety valve." Or where it is possible to hold the volt- 
age below the decomposition voltages of the metals which are 
not wanted in the deposit.^ 

Aside from the metallic impurities in electrolytic de- 
posits there is the inclusion of the electrolyte in the deposi- 
ted metal to be considered. There is very little information 
on this point and hardly any that is reliable. Considerable 
attention has been paid to the purity of the silver deposited 
in the silver coulometer. Analyses of these deposits for 

* Bancroft: International Congress, 4, 703 (1904.) 
' Sand: Joixr. Chem. Soc., 91, 373 (1907.) 



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148 W. L. Perdue and G, A, Hulett 

total silver have been made by Rayleigh and Sedgwick* 
and later by Richards, Collins, and Heimrod.^ The results 
however were not concordant, so the authors finally resorted 
to the method of reheating the deposited silver in the dish 
in which it was determined and observing any change in weight. 
This method has been employed in all investigations on the 
silver coulometer, but the results have been contradictory 
and were not capable of interpretation as there was no in- 
formation as to the nature of the impurity. A new method was 
devised by Hulett and Duschak' in 1908. The silver was de- 
tached from the platinum dish, brought into a vacuum where 
it could be heated to the melting point and the gases evolved 
were examined as to their nature and amount. A continuation 
of this work, which will soon be published, is giving good 
quantitative results and indicates that these inclusions are 
not of the same composition as the electrolyte and are large 
enough to be taken into account in accurate work. That all 
metals deposited in the solid state contain inclusions can 
hardly be questioned. 

Even with a satisfactory method for determining the 
nature and amount of these inclusions it is still desirable to 
avoid them entirely. If the metal is deposited in the liquid 
state this is accomplished or if it is deposited in mercury 
and forms an amalgam there are no inclusions. The surface 
of a mercury or amalgam cathode is always a good one so 
that greater variations of current density and conditions in 
the electrolyte may be employed, also the metal is more 
easily and completely removed from the electrolyte with a 
mercury cathode. Mercury has been used as cathode for a 
long time in electro-analysis,* but not with the idea of avoid- 
ing inclusions. It has always been a difficult matter to get 
the amalgam into a weighable condition without a loss or 

' Phil. Trans., 175, 411. 
2 Proc. Am. Acad., 35, 123. 
' Trans. Am. Electrochem. Soc, 12, 255. 

* W. Gibbs: Am. Chem. Jour., 13, 571; Luckow: Zcil. anal. Chem., 26, 
113; Vortmann: Ber. chem. Ges. Berlin, 24, 2749. 



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Exact Electrolytic Method for Determining Metals 149 

oxidation of the metal deposited in it. The method de- 
scribed by Prof. E. F. Smith* is a great improvement on 
previous ones and is convenient for analytical pruposes, 
but washing the amalgam with water and other liquids which 
contain dissolved oxygen is bound to occasion some solution 
of mercury and the metal, also the necessary agitation of the 
amalgam causes some of it to divide into very fine globules 
which are easily washed away and escape detection.* 

The fact that mercury does not wet its container, but 
allows a film of liquid to get beneath the merciuy, is the 
chief source of difficulty encoimtered in removing the elec- 
trolyte and drying the amalgam, so our first attention was 
given to this point. Mercury does not ordinarily wet plat- 
inum but it is possible to amalgamate the inside of a crucible 
or cup so that mercury wets it completely and then the elec- 
trolyte never gets beneath the mercury. With this advan- 
tage only the upper surface of the amalgam need be consid- 
ered in removmg the electrolyte after the metal has been 
deposited. The electrolyte may of course be removed by 
displacement with water and the amalgam washed with 
water without any loss of mercury or metal by solution or 
oxidation provided we keep the amalgam cathode during this 
process. Furthermore, in the absence of a film of liquid 
between the amalgam and its container, this amalgam need 
not be disturbed or agitated so there is no tendency to form 
little globules which may be lost. The water is finally re- 
moved with a pipette and the drop or two of water which re- 
mains on the amalgam is allowed to evaporate in a vacuum 
desiccator over calcium chloride. One may readily observe 
the disappearance of the last trace of water and the dish 
and amalgam are ready to weigh in a few minutes. From 
the standpoint of accurate weighing, metallic surfaces are 
exceedingly well defined since there are no troublesome 
moisture films to contend against. Our desiccator contains 

* Electro-Analysis, p. 58. 

*H. J. Sand: Trans. Chem. Soc, 91, 373 (1907); also T. Slater Price: 
Trans. Faraday Soc., 3, 94-7 (1907). 



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ISO W. L. Perdue and G, A, Huleti 

a dish of mercury which maintains a vapor of mercury in the 
desiccator and so prevents a possible loss of mercury by 
evaporation. This vacuum method of drying mercury and 
amalgams will not do when they are in glass vessels or con- 
tainers which they do not wet as the film of liquid beneath 
the mercury or amalgam evaporates irregularly and explo- 
sively, throwing mercury out of the container in a quite un- 
controllable manner but when the mercury wets the container 
perfectly there is no trouble on this score. 

We have made many blank experiments to test all these 
points. After a determination has been made and the weight 
of the crucible with the amalgam known, we have returned 
the exhausted electrolyte to the amalgam and turned on the 
cturent. After repeating all the manipulations the crucible 
and amalgam have been reweighed, this gives the errors of 
the method. 

Weight of the cup and amalgam Weight after the blank 



101.4909 I 101.4908 

109.6732 109.6733 

132.3499 132 3498 

98.0254 , 98 0254 

These are typical trials and as we are determining two 
to three grams of cadmium in each case it is seen that the 
errors are less than i part in 20,000. The vacuum correction 
is easily applied, and we are therefore in a position to deter- 
mine the mass of metal in a given solution in a satisfactory 
manner and to know that nothing but the metal has been 
weighed. 

The solubility of platinum in mercury is very small, 
so that crucibles which have been amalgamated and used 
for this purpose may be readily cleaned with acids at any 
time. The loss of platinum is small and the crucibles are 
not injured. Our method of amalgamating the inside of a 
crucible is to plate it electrolytically from a mercury cyanide 
solution; when washed out and rinsed with mercury it should 



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Exact Electrolytic Method for Determining Metals 151 

show a continuous film of mercury to within a centimeter 
of the top. It is very difficult to amalgamate some crucibles 
satisfactorily by this method but Mr. J. S. Laird of this 
laboratory has foimd that this may be readily done in all cases 
by filling the crucible with mercury to the desired height and 
then heating it nearly to the boiling point of mercury. After 
plating with mercury the crucible is washed with water, filled 
with the necessary amoimt of mercury and dried in the vacuum 
desiccator. 

Fig. I shows the arrangement we employ in carrying 
out a determination. The fimnel (/) has a wide stem (7 mm), 




Fig. I 

while the rim fits nicely into the cup and thus prevents any 
loss of the electrolyte. The anode is a flat spiral made from 
platinum wire with the stem fused into a glass tube which is 
held by the clamp (a) and is independent of the funnel. The 
arrangement is such that the funnel may be raised clear of 
the cup without disturbing the anode. Towards the end of 
the electrolysis the current is increased to insure the com- 
plete removal of the metal. This is favored by the stirring 
of the electrolyte due to the increased generation of gas. 
The spraying thoroughly washes down the funnel and sides 



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152 



W. L, Perdue and G. A. HuleU 



of the cup so that it is seldom necessary to wash these through 
the top of the funnel. 

After the metal has been completely deposited, the fun- 
nel is raised clear of the cup an'd the electrolyte removed 
with a large pipette while water is simultaneously run in. 
The stem of the pipette is drawn down to a thin tube and 
cut off at a convenient length while a rubber tube is attached 
to the upper end so that the pipette may be conveniently 
handled. A reservoir of distilled water is provided with an 
outlet tube, nozzle, and pinchcock so that water may be 
run into the cup at any desired rate and thus the electrolyte 
is displaced with distilled water without interrupting the 
current, and when the ammeter shows ** zero '* reading the dis- 
placement is complete and the amalgam throughly washed, but 
the amalgam is still cathode by lo or 12 volts and under 
these conditions there can be no loss of mercury or metal by 
oxidation or solution. Since the amalgam is not disturbed 
or agitated there is no tendency to form fine globules. The 
water is now removed with the pipette, the anode raised, 
and after attention has been given to the outside of the cru- 
cible it is put into the vacuum desiccator and is ready for 
weighing in a short time. 

Analysis of Cadmium Sulphate. — CdS0^.8/3H20 is an 
exceptionally well defined and stable salt which may be ob- 
tained in a high state of purity as will be shown in the fol- 
lowing article. We have determined the percent of cad- 
mium in this salt with the apparatus and methods just de- 
scribed and offer a few of the preliminary determinations to 
give an idea of the possibilities of the method: 



Mass CdSO^.VaHjO 

1 8.2375 

2 , 9 2857 

3 6.5312 



MassCd 

3.6076 
4.0668 
2 . 8609 



Percent Cd 



43 795 
43 • 798 
43.804 



A detailed study of the properties and composition of 
this compound will be given in the following article. 



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Exact Electrolytic Method for Determining Metals 153 

Cadmium is one of the most soluble of the metals in mer- 
cury (5.6 percent), but some metals have only a very small 
solubility and in such cases a solid amalgam soon forms and 
floats on the surface of the merciuy cathode. The metal 
soon grows up and away from the mercury and may include 
some of the electrolyte. By agitating the mercury during the 
deposition of the metal this difficulty is overcome, for any 
motion of the mercury not only prevented the ** treeing'' 
of the metal but kept the amalgam covered with a film of 
mercury which prevents inclusions. We have accomplished 
this result by rotating the cathode crucible during the 
electrolysis. 

The accompanying sketch is self-explanatory. The cup 
and shaft were turned from solid brass while the shaft 
works in a bronze socket which is fitted into a lead base. 
The platinum cathode cup or crucible fits exactly into the 




Fig. 2 

brass cup and must rotate without vibration. The platinum 
spiral which serves as anode is fused into a little funnel and 
so arranged that the spiral is only a few millimeters from 
the mercury cathode when the crucible is at rest and at the 



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154 ^' L' Perdue and G. A. HuleU 

same time the sides of the fimnel nearly touched the top rim 
of the crucible. The funnel is conveniently held by an in- 
verted funnel (the two are held together by a rubber band) 
and electrical connections are made as indicated in the cut. 
Rotating the cup not only keeps any solid amalgam covered 
with mercury but causes the mercury surface to assume the 
form of a parabola which gives a large surface for a small 
amotmt of mercury. The electrolyte may be small in vol- 
ume and the conditions are such as to allow a large current 
density and rapid deposition of the metal. 

A few comparative determinations were made by de- 
termining the copper in equal portions of a copper sulphate 
solution and zinc in a zinc sulphate solution: 



Weight of zinc 



0.4700 
o . 4699 
0.4702 



Weight of copper 

0.4793 
0.4791 
0.4794 



A determination, weighings and all, took about 50 min- 
utes and the average error seems to be about i in 4,000, 
and while zinc is fairly soluble in mercury (2.2 percent), 
copper has a solubility of only i part in 100,000.^ Of course 
this method of rotating the cathode crucible offers many 
chances for accidental errors and cannot be compared in 
accuracy with the method previously described, but it has 
some advantages and is useful where great accuracy is not 
the main object. 

Princeton i ^ n ivers ity , 
November, igio 

* Gouy: Jour. Phys., 4, 320. 



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CADMIUM SULPHATE AND THE ATOMIC WEIGHT OF 

CADMIUM 



BY W. L. PERDUE AND G. A. HULETT 

The most generally used analytical method of deter- 
mining the equivalent weight of a metal is to determine 
the ratio of the metallic haloid to the silver haloid which is 
obtained from it. This method is not particularly direct 
but has been foimd to be the most satisfactory from an ex- 
perimental standpoint and this is due, in a large measure, to 
the refinements in method introduced by Richards and his 
collaborators. 

The estimation of a metal by electrolysis is one of the 
simplest and most direct methods for determining the ratio 
of a metal to its acid radical, haloid or to oxygen, but com- 
paratively few such determinations have been made and not 
much weight has been given to those which have been made 
in this way. It would seem that the trouble has been due 
to the difficulties encoimtered in removing the metal com- 
pletely from the solution in a sufficiently pure state and in 
obtaining it in a weighable condition without oxidation, loss or 
inclusions. In the preceding paper we have shown that it is 
possible to avoid these difficulties and the results obtained with 
cadmium sulphate were so concordant that it seemed worth 
while to make a more extensive study of this salt and the 
electroljrtic method of determining its percent of cadmium. 

Cadmium Sulphate 

CdS0^.8/3HjO is readily obtained in large clear crystals 
and it does not seem to be isomorphous with any other salts,* 
so that recrystallization offers an exceptional opportunity 
for bringing this substance to a high state of purity. 

Ferrous and cupric sulphates seem to be isodimorphous 
with the crystallized CdS0^.8/3HjO,' but only very small 

* Rammelsberg: Pogg. Ann., 115, 579; Kopp: Ber. chem. Ges. Berlin, 
12, 911; Retgers: Zeit. phys. Chem., 16, 590. 
' Retgers: Loc. cit. 



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156 W. L. Perdue andG. A. Hulett 

amounts of these substances are taken up by the CdSO^ 
crystals even when they are present in considerable concen- 
tration, but the method of purification we have used eliminated 
these metals. 

Kahlbaum's cadmium sulphate was dissolved to about a 
lo percent solution and H^S was added until the precipitate 
was clear yellow. The solution was digested on the water 
bath with this precipitate until all the other heavy metals 
had been displaced and the precipitate was in a good condi- 
tion to filter. The clear solution was now treated with H,S 
until most of the cadmium was precipitated. The cadmium 
sulphide obtained in this way was thoroughly washed and 
treated with redistilled nitric acid until the sulphide was 
changed to sulphate and nitrate. A slight excess of sulphuric 
acid was now added and the liquid evaporated and heated 
until fumes of sulphuric acid appeared. The whole was now 
cooled and the cadmium sulphate drained to free it from the 
excess of sulphuric acid and then it was heated in a covered 
platinum dish in a specially constructed furnace until all 
the excess of sulphuric acid had been driven off. The cad- 
mium sulphate obtained in this way was dissolved, filtered and 
repeatedly recrystallized. A saturated solution of cadmium sul- 
phate has a density of 1.61 and is very viscous so that it 
was found best to start with a rather shallow solution i cm 
deep in the crystallizing dish and then the crystals formed 
on the bottom of the dish in a very satisfactory manner. 
The dishes were covered with filter paper and then placed 
in a constant temperature room so that the evaporation 
would be slow and uniform. These conditions gave us the 
maximum number of clear crystals but in every crop there 
were some cloudy ones which showed inclusions of mother 
liquor. The difference between the clear and cloudy crys- 
tals was very striking, the clear crystals were ** water" clear 
in all parts and the microscope did not reveal a suggestion of 
inclusion. Only these clear crystals were taken for further 
recrystallizations and finally conductivity water and Jena 
glass or platinum dishes were used. The crystals were re- 



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Cadmium Sulphate and the A tomic Weight of Cadmium 157 

moved from the dish with ivory forceps and wiped with sheet 
rubber (the rubber dam used by dentists). This was done 
because it was found that filter paper left the crystals slightly 
etched. This we think is due to the phenomenon of ab- 
sorption. The filter paper coming into contact with the 
mother liquor on the face of the crystal, absorbs some of the 
dissolved cadmium sulphate and forms an undersaturated 
solution which attacks the crystals. With sheet rubber 
this action is a minimum and the faces of the crystals were 
left in a perfect condition. These crystals were perfectly 
stable in the dry air of our special balance room; a test ex- 
tending over 14 days showed no change in weight. 

Cadmium sulphate was described by Stromeyer^ in 1822, 
who gave it the formula CdS04.4H20, and it has been the 
subject of extensive investigations since that time; but only 
recently' has the composition of these crystals been definitelj'^ 
settled. The trouble has been in determining the percent 
of water by glowing the crystals. Not until a loss of sulphate 
was detected, when the salt crystals were heated above a 
red heat, were the proper precautions taken and then more 
concordant results were obtained. 

We find that CdSO,.8/3HjO loses its water at a red heat 
and some SO, and then the CdO volatilizes. This difficulty 
was obviated by heating the crystals in an atmosphere which 
contained a little SOg and then we found that all the water could 
be driven off and the CdSO^ remained perfectly stable up to at 
least 700°. Under these conditions the determination of 
the percentage of water in these crystals gave concordant 
results. 

The determination of the percent of water of crystalliza- 
tion was carried out as follows : 5 to 7 grams of the crystals were 
placed in a tall narrow platinum crucible (15 mm by 65 mm). 
This crucible was furnished with a tight-fitting cover but a 

* Schweiggers* Jour., 22, 368. 

' FoUenius: Wied. Ann., 65, 348; Worobieff: Zeit. phys. Chcm., 23, 557; 
Mylius and Funk: Ber. chem. Ges. Berlin, 30, 825; Kohnstamm and Cohen: 
Wied. Ann., 65, 348. 



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158 



W. L. Perdue and G. A. HtUeU 



special perforated cover was used when the crucible was 
heated and through this perforation extended the small 
porcelain tube which delivered the air with a little SO,. The 
crucible was heated in an electric fimiace and was inside a 
quartz test tube which was also covered. The temperature 
was imder excellent control and was measured with a thermo- 
couple. The arrangement is sufficiently indicated in Fig. 
I. The air which was passed over the crystals, while they 




Fig. I 



were being heated, was filtered and dried and then passed 
through fuming sulphuric acid which gave the necessary 
SO, concentration so that there was no loss of SO, or CdO 
from the crystals. A series of experiments gave the tem- 
perature and time needed to remove the water of crystal- 
lization so that there was no change in weight when heated 
to a higher temperature. The range used was from 600^ 
to 700°. After these conditions were worked out we under- 
took a determination of the water of crystallization in the 
purest crystals with the following results : 



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Cadmium Sulphate and the A tomic Weight of Cadmium 159 

Table I 
Percentage of H^O in CdSO^.S/sH^O 



No. 


Mass CdS04.8/3H,0 


Mass CdS04 


Mass H,0 


I 


6.32863 


5.14303 


I . 1856 


2 


6.72493 


5 


46507 




25986 


3 


6.87537 


5 


58677 




2886 


4 


5 65027 


4 


59205 




05822 


5 


6.81125 


5 


53568 




27557 


6 


7 34977 


5 


97274 




37703 


7 


7 74837 


6 


29717 




3572 


8 


7.8843 


6 


40718 




47713 


9 


6.6100 


5 


37196 




2480 



Percent H,0 



18.734 
18.734 
18.742 
18.729 
18.727 

18.736 
18.727 

18.734 
18.730 

18.733 



In the above table the percent of water amounts to 
18.733, which is the arithmetical mean of nine determina- 
tions, the probable error of the mean is ±0.001, while the 
probable error of a single experiment is ±0.0045. The re- 
sults seem to be entirely satisfactory, since we foimd that after 
the water had been expelled at say 670°, no further loss of 
weight was observed on heating to 700°. 

The vacuum corrections used in the above table were 
calculated from the density of CdSO^.S/aHjO and the den- 
sity of the anhydrous CdSO^. The determination of the 
density of CdSO^.S/aH^O was carried out as follows: The 
crystals were weighed in a small platinum crucible suspended 
by platinum wires (o . i mim) first in air and then in toluene. 
The toluene was dried and distilled and its density deter- 
mined at 25° and 23 . 7° with a Sprengle-Ostwald pycnometer. 
Two determinations gave 3.0900 and 3.0902 as the density 
{U/Y at 24°). 

The density of the dehydrated crystals was obtained 
by heating the crystalline salt to constant weight, ob- 
taining the weight of the dehydrated salt, and then placing 
it in a vacuum desiccator over calcium chloride where it 
remained in a vacuum of less than i .0 mm for several hours. 
The vacuum desiccator was provided with a separatory funnel 



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i6o W. L. Perdue and G. A. Hulett 

so arranged that it was possible to allow the toluene to drop 
slowly onto the salt while it was still in vactw; thus assurmg a 
complete penetration by the toluene into all the interstices of 
the salt and eliminatmg any error due to included air. The 
crucible and contents were now removed and weighed in 
toluene. The density of the dehydrated salt was found to be 
4.691 at 24°. The salt maintained the general contour of 
the crystals and did not fall into an amorphous powder but 
was quite hard. This greatly facilitates the ease of handling. 

All weighings were made in a special balance room 
where the temperature was very constant, and where the 
moisture content of the air was under control. The weight 
of one cc of air in this room was i . 1 8 mg and the variations 
from day to day were negligible. The weighings were made 
by the Borda method of substitution : the set of weights used 
being very carefully calibrated, using a loo-gram certified 
standard whose density was 8.391; standard certified i and 
10 gram weights were used as checks on the calibration at 
the proper places. 

The specific volumes of both salts and weights are as 
follows : 



CdSO,.8/3H,0 


D2, -- 3 0901 


sp. vol. 


= 0.3236 


CdSO, (anhyd) 


I>24 = 4 691 


sp. vol. 


= 0.2132 


Weights 


D =8.39 


sp. vol. 


= 0. II90 



Thus each gram of the crystals displaced o . 2064 cc more 
than the weights. The correction was 0.2046 X 1.18 = 
4-0.242 mg per gram. For the anhydrous salt the corre- 
sponding correction was +0. 123. 

Determinations were next made of the metallic content 
of both crystalline and anhydrous cadmium sulphate. The 
percentage of cadmium in both of these substances was de- 
termined by the method and apparatus described in the 
previous article. A slight modification was made in that 
the crucible and mercury were put into a glass cup which 
was provided with a split cover as indicated in Fig. 2. The 
object of this cup was to make sure that there was no loss 
of electrolyte. After each determination the cup was rinsed 



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Cadmium Sulphate and the A tomic Weight of Cadmium 1 6 1 

out and the washings tested for cadmium but none was ever 
found. We took particular pains to convince ourselves that all 
the cadmium was deposited in the mercury. 




Fig. 2 

The weighed crystals of CdSO^.S/sHjO were placed di- 
rectly on the mercury in the platinum crucible, then con- 
ductivity water was carefully added so as to cause as little 
solution of the sulphate as possible. A drop or two of sul- 
phimc acid was added to aid in the conduction of the ciurent 
and then the ciurent was regulated so that there was no 
generation of gas at the cathode. The cadmium was thus 
deposited as fast as solution took place and the crystals 
melted away without cadmium appearing in the upper part 
of the electrolyte. When the cadmium was practically 
all deposited the current density was increased and the genera- 
tion of the gas at both anode and cathode thoroughly stirred 
the electrolyte, rinsed down the sides of the crucible and at 
the same time the last trace of the cadmium was rapidly de- 
posited. The electrolyte was removed as described in the 
preceding article (p. 152) and it was of cotu-se examined for cad- 
mium by the ferrocyanide method, but no trace of the metal 



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1 62 



W. L. Perdue and G. A, HuleU 



was discovered in the exhausted electrolyte or any of the 
washings. 

Table II 
Percent of cadmium in CdSO^ . 8/3H3O 



No. 



I 
2 
3 
4 
5 
6 

7 



clS04.8/3H,0 ; 


MaMCd 


Percent Cd 


90902 i 


3 46335 


43 790 


07468 1 


3 


97434 


! 43 796 


32787 ' 


3 


20936 


1 43 796 


48847 


2 


84186 


43 799 


1 1684 1 


2 


24157 


43 808 


02954 


3 


51755 


43 807 


08743 


2 


22827 


43 799 



43 799 



The determination of the amount of cadmium in the an- 
hydrous sulphate was carried out in the manner alluded to 
under CdS0^.8/3H,0. The precaution was taken of thor- 
oughly washing out the crucible in which the salt had been 
glowed and adding the washings to the electrolyte. The re- 
mainder of the process was carried out exactly as that of the 
crystallized sulphate. 

Table III 
Percent of Cadmium in CdSO^ 



No. 

I 

2 
3 
5 
7 
8 

9 



Mass CdSO^ 
5 14303 


5 


46507 


5 


58677 


5 


53568 


6 


29717 


6 


40718 


5 


37196 



Massed 



2.77196 

2 94566 
3.01076 
2.98276 

3 39295 
345255 
2 89457 



Perc^t Cd 


53 


897 


53 


898 


53 


891 


53 


883 


53 


880 


53 


•887 


53 


883 



^t; 53-888 



The vacuum correction for cadmium dissolved in mer- 
cury was readily obtained from the density of cadmium amal- 



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Cadmium Sulphate and the A tomic Weight of Cadmium 1 63 

gams. Hulett and DeLury* found that the density of these amal- 
gams was a linear function of the percent of cadmium, and at 
24° could be expressed as follows: D24 = 13 5364 — 
0.0609 X />. From this it was easily foimd that a gram 
of cadmium dissolved in mercury displaced 0.107 cc of air 
and as a gram of brass weights displace 0.119 cc, the 
vacuum correction for each gram of cadmium dissolved in 
merciuy was — 0.014. 

In the crystals we foimd 43.799 percent of cadmium 
as the arithmetical mean of seven determinations, and the 
probable error of this mean was ±0.0016. The percent of 
water by difference was 18.733 (see above). The 191 1 
atomic weights give cadmium 112.40, sulphur 32.07, hydro- 
gen 1 .008. This gives the molecular weight of CdS04.8/3HjO 
as 256.51 and its percentage composition as follows: 

Cd =43819 

SO, = . . . . 
8/3H,0 = 18.729 

These percentages are decidedly different from those 
fotmd above. If, however, we take the atomic weight of 
cadmium as 112.30 the calculated percent is: 

Cd =43.797 

SO, = . . . 
8/3H,0 = 18.736 

which is in excellent agreement with our results. 

If now we take 1 1 2 . 30 as the atomic weight of cadmium 
then the anhydrous CdSO, would contain 53.895 of cadmium, 
while we found in the above table 53. 888 ± 0.0013. This 
difference is much greater than our experimental error. If 
the water had not all been expelled by heating the crystals 
the anhydride still contained water and the percent of cadmium 
would therefore have been low. Now the loss in weight 
of the crystals calculated as water was 18.733, the theoretical 
calculation being 18.736, which indicated a slight retention 



* Jour. Am. Chem. Soc, 30, 1805. 



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i64 W. L. Perdue and G. A. HuleU 

of water by the anhydride but not sufficient to measurably 
affect its percent of cadmium. If the crystals had lost a 
slight amotmt of SO,.CdO in spite of the presence of SO, 
in the air, then the observed loss would not all be water, 
but some of it would be SO,.CdO and a correspondingly 
greater amoimt of water would then be left in the anhydride. 
The data which we had obtained gave us the possibility of 
testing this point by a simple calculation: In the experi- 
ments in Table III the crystals were weighed, glowed, and 
the percent of cadmium in the residual anhydride was deter- 
mined. From this data we can also calculate the percent 
of cadmium in the original crystals and it gives 43. 793 ± 
0.00 1 instead of the 43.799 percent foimd in the imglowed 
crystals (Table II). This shows a loss of 0.006 percent 
of cadmium or o . 01 1 percent of CdSO^ lost by glowing the crys- 
tals so that the total loss, 18. 733 percent, was therefore com- 
posed of 18.722 percent of water and o.oii percent of CdSO^, 
consequently 100 grams of the crystals lost 18.722 grams of 
water and o.oii grams of CdSO^, while the remaining 81 .267 
grams of anhydride retained 0.014 gram of water (18.736- 
18.722) or 0.0172 percent of water. Now CdSO^ which 
contains 0.0172 percent of water would show 53.888 percent 
of cadmium if the atomic weight of cadmium is taken as 1 1 2 . 30 
We actually obtained in our results (Table III) 53.888 per- 
cent of cadmium in the anhydride. 

In our endeavor to get pure anhydrous CdSO^ we at- 
tempted to heat this substance to its melting point but as the 
SO,, used to prevent decomposition, is measurably dissociated, 
long before the melting point of the salt is reached, it is therefore 
no longer effective in preventing measurable decomposition 
of the CdSO^. From the constancy of the results and agree- 
ment with the calculated value (Table II) it seemed quite 
certain that all of the water had been expelled by heating to 
700° but it is evidently a case of small compensating errors 
and shows how constant such errors may be. 

The CdS0^.8/3H30 crystals used gave evidence of being 



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Cadmium Sulphate and the Atomic Weight of Cadmium 165 

very pure and free from all inclusions. The anal3rsis of this 
substance points to 1 12 . 30 as the atomic weight of cadmium, 
a value so much lower than the accepted 112.40 that it 
seems desirable to check this result by determining the percent 
of cadmitmi in simpler substances such as the oxide and 
chloride. 

Princeton University ^ 
November, igio 



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STUDIES IN THE ELECTRCX^HEMISTRY OF THE PRO- 
TEINS. IV. THE DISSOCIATION IN SOLUTIONS 
OF THE GLOBULINATES OF THE ALKALINE 
EARTHS 



BY T. BRAII^FORD ROBERTSON 

(From the Rudolf Spreckels Physiological Laboratory of the 
University of California) 

L Introduction 

Not only the ** basic'* casemates of the alkalies, but also 
the ** basic** caseinates of the alkaline earths obey, in solu- 
tion, the Ostwald dilution-law for the dissociation of a binary 
electrolyte.* From this and from other evidence pointing 
in the same direction, I have concluded that the molecule 
of a caseinate dissociates into two protein ions, in one of 
which the metal ion is bound up in a non-dissociable form. 

The results of W. B. Hardy' have shown that the serum 
globulinate of sodium obeys, in solution, Ostwald*s dilution 
law. The following data are obtained from Hardy's deter- 
minations of /£ (the "apparent** molecular conductivity of 
the globulinate, cf . Pt. I of these studies) by multiplying each 
value of fi by the corresponding concentration. 

Table I 
Temperature i8° 



m = Equivalent molecular concen- 
tration of NaOH neutralized to x = Conductivity of the solution in 

phenolphthalein by serum i reciprocal ohms per cc X lo* 
globulin X lo* 

3125 1044 

1563 I 627 

782 353 

391 189 

98 54 



* T. Brailsford Robertson: Part II of these studies, Journal of Physical 
Chemistry. 

^ W. B. Hardy: Jour. Physiol., 33, 251 (1905)- 



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Studies in the Electrochemistry of the Proteins 167 

The proportion of alkali to globulin in each solution was 
18 X I o""* equivalents per gram. Such solutions are neutral 
to phenolphthalein, accordingly m, the equivalent molecular 
concentrations of alkali neutralized by the globulin is, in these 
solutions, equal to the total concentration of sodium. 

In previous commxmications* I have shown that the 
Ostwald dilution-law for a binary electrolyte may be written 

^ _ 1.037 X 10-' , 1.075 X 10-* ^a . 

-Vi + v^ G{Vi + v^y 

where m is the equivalent-molecular concentration of the 
electrolyte, x its conductivity in reciprocal ohms per cc, G 
its dissociation-constant and v^ and v^ are the ionic velocities 
in cm per sec. per potential gradient of i volt per cm. 

In applying equation i to solutions of salts of proteins 
we have no guarantee that w, the equivalent-molecular 
concentration of salt, is the same as m, the equivalent-molec- 
ular concentration of the alkali neutralized in its formation. 
But if not one, but p equivalent gram-molecules of globulinate 
are produced by the neutralization of one equivalent gram- 
molecule of NaOH then we may write equation i in the form 

_ 1.037 X 10-' 1.0 75 X 10- * 

W = z i r— X "1 j^T- j rj- X (2; 

p{v, + V,) pG(v^ + v,y 

in which m is now identical with the equivalent-molecular 
concentration of the alkali neutralized in the formation of 
the globulinate.' 

Applying equation (2) to Hardy's results, enumerated 

I 0'^7 ^ IO~' 

in Table I and computing the constants ' , . r— and 

^'?J, — r— TT from all of the observations by the method of 

pG(v^ + v^y -^ ^ 

least squares we obtain 

m = 17.65 X + 0.0115 X lo* jc^ 
Inserting, in this equation, the observed values of x, we 

* T. Brailsford Robertson: Jour. Phys. Chem., 11, 542 (1907); 12, 473 
(1908). 

* Of. number II of these studies, Ibid., 14, 601 (19 10). 



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i68 T. BraOsford Robertson 

can compute the "theoretical" values of m, that is, the 
equivalent concentration of NaOH neutralized by the globulin 
which should, provided the sodium globtdinate dissociates 
into two ions, correspond to the observed conductivities. In 
the following table the observed and calculated values of m 
are compared: 

Table II 



M X 10^ observed { m X lo^ calcuUted 



3125 3095 

1563 ] 1559 

782 767 

391 I 375 

98 99 

It is evident that the correspondence between the experi- 
mental results and those which are indicated by the Ostwald 
dilution-law for a binary electroljrte is very close. It ap- 
peared to be of importance to ascertain whether the alkaline- 
earth salts of globtdin, like those of casein, also obey the 
dilution-law for a binary electrol)rte. Accordingly the fol- 
lowing experiments were imdertaken 

11. Experimental 

(*) The preparation of the globtUin. 

The globulin employed by Hardy in the experiments 
cited above was the "insoluble** globulin oi ox-serum* pre- 
pared by precipitation from dilute serum through the cautious 
addition of acetic acid. I have employed the same globulin, 
precipitated, however, by passing a stream of CO, through 
the diluted serum, as recommended by Quinan. The follow- 
ing was the complete procedure. 

Three liters of ox-serum were diluted with ten times their 
volume of distilled water and CO, was bubbled through the 
mixture for about half an hour. The globulin which was 
thus precipitated was allowed to settle in tall glass cylinders, 
the supernatant fluid being syphoned off after settling. The 

* Cf. Quinan: Univ. of California Publ. Pathol., i, i (1903). 



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Studies in the Electrochemistry of the Proteins 169 

precipitate was then washed with about 60 liters of distilled 
water, in two washings. 

The globulin was then dissolved in a minimal quantity 
of N/io KOH. This precipitate, after settling and the 
decantation of the supernatant fluid, was washed in 60 liters 
of distilled water in 6 successive washings, the precipitate, 
after each agitation with distilled water, being allowed to 
settle for 24 hours in the presence of toluol, after which the 
supernatant fluid was drawn off and the globulin suspended 
in a fresh quantum of distilled water. The thick suspension 
of globulin which was thus obtained after the final washing 
was kept, in the presence of toluol, in a stoppered bottle and 
used in this form, since globulin, if washed with alcohol and 
ether and dried, is redissolved only with diflSculty. The 
suspension was, of coiu-se, always well shaken before with- 
drawing a sample. 

Twenty-five cc samples of this suspension were placed in 
small and accurately weighed beakers: the fluid was then 
evaporated to dryness on a water bath and the residue was 
dried at 70® over H,SO^ xmtil its weight became constant. 
Three determinations yielded the following results: 



Dctermiiiations ^""« globnlin in 100 cc of 

A^«^^Auiiu«v«vu9 .suspension 



1 1.49 

2 I 1-47 

3 1 148 



1 Average, 1.48 

In all, about 14 grams of globulin were obtained. 

(ii) Experimental results. 

The experimental procedure was the same as that de- 
scribed in previous communications.^ Since Hardy's ex- 
periments were conducted upon sodium globulinate and at 
18** and all my determinations were made at 30°, for purposes 



Part I of these studies, Jour. Phys. Chem., 14, 528 (1910). 



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I70 T. Brails ford Robertson 

of comparison, I have not only measured the conductivities 
of solutions of the globulinates of calcium, barium and 
strontium, but also those of solutions of the globulinate of 
potassium. 

According to Hardy bases dissolve globulin in molecular, 
not equivalent-molecular proportions, about lo X lo"* 
equivalents of an alkali and 20 X lo"* equivalents of an 
alkaline earth being required to dissolve i gram of globulin. 
The latter solutions are neutral to phenolphthalein, the 
former to litmus; but if i gram 6f globulin be dissolved in 
20 X io~* equivalents of an alkali then the resultant solu- 
tion is also neutral to phenolphthalein. That is to say, 
globulin combines with bases in equivalent molecular pro- 
portions to form solutions neutral to phenolphthalein, but in 
molecular proportions when the base is combined with the 
maximum quantity of globulin which it can hold in solution. 

The solutions employed in the following experiments 
(except the solutions of strontium globulinate) were all 
prepared in the following manner. To 100 cc of the globulin- 
suspension (containing 1.48 grams of globulin) were added 
29.6 cc of a himdredth-normal solution of the base and the 
resultant solution was diluted to 200 cc. One himdred cc 
of this solution was then diluted to 200, one himdred of the 
new solution to 200 and so on. The solutions of strontium 
globulinate were made up by adding to 25 cc of the sus- 
pension 7.4 cc of himdredth-normal Sr(OH)j, diluting to 200 
cc and then proceeding as described above. 

All of these solutions were practically neutral to phenol- 
phthalein, one-tenth of a cc of N/io KOH sufficing to render 
100 cc of the most concentrated solutions alkaline to this 
indicator. 

The resistance-capacity of the conductivity-vessel em- 
ployed was 0.1949. The conductivity of the distilled water 
(4.0 X 10"*) has been subtracted from each of the observed 
conductivities. The following were the results obtained 
(temperature 30*^) : 



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Studies in the Electrochemistry of the Proteins 171 



Table III 
Potassium globulinate 



m ^ equivalent-moleciilar concen- 
tratioo of KOH neatralized . 
by globnlin X 10^ 



X = condnctiTity in reciprocal 
ohms per cc X 10^ 



296 






116 


148 






64 


74 






33 


37 






18 


18 


1 

Table IV 
Calcium globulinate 


9 



fH =z: equivalent-molecular concen- 
tration of Ca(OH), neutralized 
by globulin X i<^ 



296 

148 
74 
37 
18 



X = conductivity in reciprocal 
ohms per cc X ic^ 



45 
26 

15 
9 
4 



Table V 
Barium globulinate 



fH = equivalent-molecular concen- 
tration of Ba(OH), neutralized 
by globulin X 10* • 



X = conductivity in reciprocal 
ohms per cc X 10^ 



296 

148 

74 
37 
18 


i 
Table VI 


49 

27 

16 

9 

4 




Strontium globulinate 





m = equivalent-molecular concen- 
tration of Sr(OH)2 neutralized 
by globulin X 10* 



74 
37 
18 



X = conductivity in reciprocal 
ohms per cc X 10* 



17 
9 

5 



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172 T. Brailsford Robertson 

III. Theoretieal 

Applying equation 2 to the results enumerated in Table 

III and computing the constants ''^^^ ^ 'T^ and ]f]^ ^ '^ 

from all the observations by the method of least squares we 
obtain: 

m = 19.62 X + 0.0519 X io*a;' 

inserting in this equation the observed values of x and com- 
paring the corresponding ''theoretical" values of m we ob- 
tain: 

Table VII 

Potassium globulinate 



Iff X 10^ obterved mX i<^ calculated 



296 I 297 

148 ! 147 

74 ' 70 

37 I 37 

18 I 18 

Applying equation 2 in the same way to the results 
enumerated in Table IV* we obtain : 

m = 43.25 X + 0.502 + lo* x^. 

The observed values of m and those calculated from this 
formula are compared in the following table: 



Table VIII 
Calcium globulinate 

w X 10* observed ' w X 10* calculated 


=^-:zr 


296 296 

148 1 146 

74 76 

37 43 

18 18 



* Only the ist, 2nd, 3rd and 5th determinations in Table IV were em- 
ployed in the computation of the constants, the 4th being obviously somewhat 
in error. 



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Studies in the Electrochemistry of the Proteitis 173 

Applying equation 2 to all of the results enumerated in 
Table V we obtain : 

m = 42.61 X + 0.369 X lo* x^ 

The observed values of m and those calculated from this 
formula are compared in the following table. 





Tab 


UE IX 








Barium globulinate 






Iff X 10^ observed 


Iff 


X 10^ calculated 




296 






297 




148 






142 




74 






78 




37 






41 • 




18 






18 





Applying equation 2 to the results enumerated in Table 
VI we obtain: 

m = 32.85 X + 0.628 + lo* x^ 
whence 

Table X 
Strontium globulinate 



m X 10^ observed f« X 10* calculated 



74 74 

37 36 

18 ' .19 

It is evident that the Ostwald dilution-law for a binary 
electrolyte holds good for the globulinates of the alkaline 
earths as well as for the globulinates of the alkalies; that the 
dependence of the conductivity of solutions of the globulinates 
of the alkaline earths upon their concentration, like that of 
the conductivity of solutions of the caseinates of the alkaline 
earths, is such as would be anticipated if they dissociated 
into two ions. 

If we compute, from the values of the constants in equa- 



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1 74 T, Brails ford Robertson 

tion 2, the values of p{v^ + v^ for these globulinates we 
obtain. 

For potassium globulinate piy^^ + ^j) "■ 529 X lo* 

For calcium globulinate ^(r, -I- 1^,) 24.4 X lo* 

For barium globulioate p{v^ + v,) 24.3 X lo* 

For strontium globulinate p(v^ + ^2) 28 . 5 X lo* 

The relation between the values of p{v^ + i;,) for the 
globulinates of the aUcaUes and of the alkaline earths is very- 
similar to that which subsists between the corresponding 
values for the caseinates* and at once suggests the ratio 
I : 2. 

The above values of p{v^ -h v^ for the globulinates of 
the alkaline earths are 50 percent less than the velocities of 
the metal ions themselves. As in the similar case of the 
caseinates, the only feasible explanation of this is that the 
globulinates dissociate into two complex protein ions and p is 
twice as great for the globulinates of the alkalies as for the 
globulinates of the alkaline earths.' 

Since, at neutrality to phenolphthalein globulin neu- 
tralizes bases in equivalent molecular proportions, the mole- 
cule of calcium globulinate must, at this hydroxyl concen- 
tration, be twice as heavy as that of potassium globulinate. 
Hence representing the mode of dissociation of potassium 
globulinate (neutral to phenolphthalein) by the various 
schematic formulae : 

I. 2. 3. 

KX++ + X(OH); K,X++++ + X(OH);' K,X++++++ + X(0H)7 

according to the number of — COOH groups concerned in the 
neutralization of bases, then the calcium globulinate (like 
calcium caseinate) must be represented by the corresponding 
schematic formulae : 



* Cf. Part II of these studies. Journal of Physical Chemistry. 

' The full discussion of this interpretation will be found in Part liof these 
studies, referred to above. I refrain from unnecessary reiteration of the argu- 
ment. 



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Studies in the Electrochemistry of the Proteins 175 

X. 2. 

x+ x(OH);, ^x++ x(OHr 



C< [ +J "; Ca,C II + 

\X+ X 



(OH);^ ^x++ x(OH); 

3. . 

^X+++ X(OHr 

Caa^lll +111 ". 

^X+++ X(OH);' 

Assuming that schematic formulae (2) represent the true 
state of affairs, as they do in the case of the caseinates, we can 
at once understand why bases dissolve globulin in molecular 
and not equivalent molecular proportions. Evidently the 
molecule KHX++++ + X(OH);' can exist in solution, but 

the molecule: 

Ca = X++ X(OH): 

11+11 
H, = X++ X(OH); 

splits off H,XX(OH)^ which is the insoluble free globulin 
and two residual halves, derived from molecules which have 
decomposed in this manner, xmite to yield the calcium globu- 
linate, represented in schematic formulae (2), which is neu- 
tral to phenolphthalein : 

The same assumption obviously accounts for the fact 
that the combining capacity of globulin for the alkalies at 
neutrality to phenolphthalein is twice as great as it is when 
the alkali in solution its maximum capacity of globulin. 

Assuming that the value of p for the globulinates of the 
alkaline earths is i , while for those of the alkalies it is 2 (corre- 
sponding with any of the above pairs of schematic formulae), 
then the values of v^ + 1;, at 30® for the above globulinates 
would be : 

For potassium globulinate 26.5 X io~* 

For calcium globulinate 24.4 X io~* 

For barium globulinate 24.3 X lo"* 

For strontium globulinate 28.5 X lo"* 

Hardy has shown, by direct observation* that the specific 
velocity, per volt per cm potential gradient, of the globulin 

» W. B. Hardy: Loc. cit. 



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176 T, Brails ford Robertson 

ion at 18^ lies between 10 X lo"* and 20 X lo"* cm sec. 
Increasing these values by 2.7 percent per degree centigrade 
rise in temperature (which, according to the same observer, 
is the temperature coeflScient of the conductivity of globu- 
linates) at 30^ they become, respectively 13 X lo"* and 
26 X lo"*. The above results, therefore, point to the lower 
value as being, more probably, the correct one. 

Calculating, on the assumption that /t> - 2, the vfdues 
of G, the dissociation constant for these globulinates at 30^ we 
obtain : 



Salt G 

Potassium globulinate o .01470 

Calcium globulinate 0.00360 

Barium globulinate o . 00493 

Strontitmi globulinate o . 002 1 1 

As in the case of the caseinates, the dissociation-constants 
of the globulinates of the alkaline earths are considerably 
smaller than those of the globulinates of the alkalies — ^this 
is not improbably connected with the greater size of the 
molecules of the protein salts of the alkaline earths. 

Conclusions 

(i) The serum-globulinates of the alkalies, in solutions 
neutral to phenolphthalein (i gram globulin = 20 X 10-* 
equivalents of base), obey Ostwald's dilution-law for a binary 
electrolyte. 

(2) The serum-globulinates of the alkaline earths, in 
solutions neutral to phenolphthalein, also obey Ostwald's 
dilution-law for a binary electrolyte. 

(3) The value of piv^ -f v^) where p is the number of 
equivalent gram-molecules of globulinate which is formed by 
one equivalent gram-molecule of base, and i/j and r, are ionic 
velocities of the globulinate ions, in cm sec. per potential 
gradient of i volt per cm, is twice as great for the globulinates 



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Studies in the Electrochemistry of the Proteins 177 

of the alkalies as it is for the globulinates of the alkaline 
earths. 

(4) It is concluded that at neutrality to phenolphthalein 
the globulinates of the alkalies and alkaline earths dissociate 
into two protein ions, each possessed of twice as many valencies 
as there are molecules of base bound up in one molecule of 
globulinate. 

(5) On the basis of this conclusion the values of v^ + v^ 
(stun of the ionic migration-velocities, or molecular con- 
ductivity at infinite dilution) and those of the dissociation- 
constant are computed for the various globulinates at 30®. 

(6) It is probable that at neutrality to phenolphthalein 
each molecule of globulinate contains two atoms of base, 
the globulinate of an alkaline earth containing two molecules 
of globulin linked together, and that the molecule so formed 
dissociate, in solution, into two quadrivalent protein ions, 
in one of which the metal is boimd up in a non-dissociable 
form. When an alkali is combined with the greatest amoimt 
of globulin which it can hold in solution, the globulin neu- 
tralizes only half the amoimt of the alkali which it will neu- 
tralize at neutrality to phenolphthalein. In such solutions, 
therefore, the molecule of globulinate probably contains only 
one atom of base. 



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STUDIES IN THE ELECTROCHEMISTRY OF THE 
PROTEINS. V. THE ELECTROCHEMICAL EQUIV- 
ALENT OF CASEIN AND ITS RELATION TO 
THE COMBINING— AND— MOLECULAR- 
WEIGHTS OF CASEIN 



BY T. BRAILSFORD ROBERTSON 

(From the Rudolf Spreckels Physiological Laboratory of the Uni- 
versity of California) 

\. Introduction 

If a direct current of about i milliampere be passed 
through a solution of potassium caseinate, which is neutral 
to litmus, gas is observed to be evolved at both electrodes, 
but a firm white spongy precipitate is deposited upon the 
anode, the cellular texture of which is attributable to entan- 
gled bubbles of gas, presumably oxygen. 

A quantity of this precipitate was collected in the course 
of the experiments described below. The anode consisted 
of a spiral of platinum wire some 9 cm long. This wire, 
when coated with the precipitate, was well washed in a stream 
of distilled water, and the precipitate was then scraped off 
into 99.8 percent alcohol. The precipitate, although firmly 
adhering to the wire, could readily be separated from it 
by merely passing the wire through the jaws of a pair of 
forceps held moderately firmly in the hand. The precipi- 
tate which was thus collected under alcohol was washed 
with alcohol and ether and dried at 30^ over HjSO^ for 48 
hours. 

The precipitate proved to be uncombined (base-free) 
casein. In fact so nearly was it devoid of mineral content 
as to practically realize that elusive ideal, the ** ash-free 
protein," for one gram of the precipitate yielded less than 2 
milligrams of ash. Yet this casein, in every way in which 
it was tested, proved to be perfectly normal. One gram of 
the substance, dissolved in 100 cc. of N/io KOH, increased 



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Studies in the Electrochemistry of the Proteins 179 

the refractive index of the solvent by 0.00155 ±0.00010/ 
while one gram, dissolved in 25 cc. of N/io KOH and titra- 
ted to neutrality to phenolphthalein with N/io HCl, neutral- 
ized 8.3 ccof N/io KOH.' 

The possibility was thus indicated of estimating the 
electrochemical equivalent of casein. Accordingly, the fol- 
lowing experiments were imdertaken : 

II. Experimental 

The casein which was employed in these experiments 
was prepared from Eimer & Amend C. P. Casein '*nach 
Hammersten," fmther purified by methods described in 
Part I of these studies.' 

The caseinate solutions were placed in a U-tube of about 
30 cc capacity, 25 cc of solution being employed in each ex- 
periment. The anode consisted of a spiral of platinum 
wire about o . 5 mm thick and 9 cm long, the diameter of the 
spiral being about 1.2 cm and the "pitch** about 45®. The 
cathode simply consisted of a platinum wire dipped in the 
fluid in the outer arm of the U-tube. The U-tube was pro- 
vided at the bottom with a 3- way stop-cock, which could 
either be tixmed so as to provide fluid communication between 
the two arms of the tube, or else so as to permit the contents 
of the anodal limb to escape into a receptacle. In this way 
it was possible to investigate separately, if desired, the con- 
tents of each arm of the U-tube. It was foimd that after 
electrolysis the fluid in the anodal arm, in which the deposi- 



^ Addition of i percent casein changes the refractive indices of aqueous 
solvents by 0.00152. T. Brailsford Robertson: Jour. Phys. Chem., 13, 469 

(>909). 

' One gram of casein neutralizes about 8.0 cc of N/io alkali to phenol- 
phthalein. Soldner, Landw. Versuchsstat., 35, 351 (1888), quoted after Van 
Slyke and Hart: Am. Chem. Jour., 33, 461 (1905); Courant: Arch. f. d. ges. 
Physiol., I, 109 (1891): L. de Jager: Nederl. Tijdscher. v. Geneesk, 2, 253 (1897); 
quoted from Jahresber. f. Thierchem., 27, 276 (1897): H. Timpe: Arch. f. 
Hyg., 18, I (1893); quoted after Raudnitz: Ergeb. d. Physiol., 2, i, 193 (1903): 
Laqueur and Sackur: Beitr. z. chem. Physiol, u. Path., 3, 193 (1902); Van 
Slyke and Hart: Am. Chem. Jour., 33, 461 (1905). 

■ T. Brailsford Robertson: Jour. Phys. Chem., 14, 528 (1910). 



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i8o T. Brails ford Robertson 

tion of casein occurred, was practically unaltered in reaction 
although its casein content was much diminished. In the 
cathodal arm, not only did the casein content diminish, but 
the alkalinity of the fluid was markedly increased. 

The current was led from the terminals of the University 
iio-volt circuit through a i6 c. p. lamp, a milliamperemeter, 
a silver titration-voltameter containing 30 cc of N/ioo AgNO,, 
and through the solution of caseinate. 

The silver was determined by titration with N/ioo am- 
monium thiocyanate in the presence of a constant excess 
of nitric add, a constant quantity (= 5 cc of a saturated 
solution) of ferric alum being employed as indicator. 

The amount of casein which had been precipitated by 
the current was estimated by determining the refractive 
indices of the original and of the electrolyzed solutions at 
the same temperature; the difference between the refractive 
indices divided by 0.00152 yields the decrease in the per- 
cerUage of casein contained in the solution consequent upon 
electrolysis.* The quantity of solution employed was always 
25 cc. Hence the decrease in the percentageHX>ntent of 
casein, divided by 4, was the amotmt of casein precipitated 
by the current. 

The experiments were all conducted at 30®. 

Varying amotmts of casein were dissolved in 100 cc each 
of KOH solutions of varying concentration so that the pro- 
portion of base to casein = 50 X lo"* equivalents per gram 
(neutral to litmus)' or 80 X io~* equivalents per gram (neu- 
tral to phenolphthalein) or 100 X lo"* equivalents per gram. 

In estimating the current employed, the electrochemical 
equivalent of silver, in grams per coulomb, is taken as 
o.ooiiiS.' 

It was foimd that solutions containing a higher propor- 
tion of base yielded an apparently lower electrochemical 



' T. Brailsford Robertson: Jour. Phys, Chem., 13, 469 (1909). 
* Cf. references in the introduction; also T. Brailsford Robertson: Ibid., 
14, 528 (1910). 

'Guihe: Bull. Bureau of Standards 1905, i, 3. p. 362. 



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Studies in the Electrochemistry of the Proteins i8i 



M K> M M 

"13 "13 "13 *t3 



Oo Oo 04 Oo 




xxxx 

M M M M 

nil 

££££ 
g.E.g.g. 

ssss 

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vO Cn Ca 1^ 

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S S P P 

B P S B 

C/l (A (A C/l 



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s 

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i82 r. Brails ford Robertson 

equivalent for the casein. This was speedily traced to reso- 
lution of the casein from the electrode after precipitation. 
The anode, after having been coated with casein by the ac- 
tion of a current of i milliampere passing through a 3 per- 
cent solution of casein, neutral to litmus, was washed in 
water, alcohol and ether, dried and weighed. It was then 
immersed in a solution of casein (3 percent), neutral to lit- 
mus, for 2 hours, then withdrawn and washed, dried and 
weighed as before. It was foxmd to have lost 11 milligrams 
in weight. Similar experiments were conducted in which 
the solutions in which the coated wire was immersed were 
neutral to phenolphthalein and alkaline to phenolphthalein. 
The foregoing were the results obtained. 

Hence doubling the rate of deposition makes very little, 
if any, diflference to the rate of resolution of the casein, but 
increasing alkalinity of the solution in which the deposition 
occurs increases the rate of resolution very markedly.* 

Assuming the rate of resolution to be constant since the 
contents of the anodic arm are inappreciably altered in re- 
action in the electrolysis, it is possible to calculate from the 
above data for each of the solutions and periods employed 
the loss due to resolution. In the column headed "loss due 
to resolution" in the accompanying tables these quantities 
are given; on adding them to the amoimts of casein lost from 
the solution, from which the ** apparent" values of the elec- 
trochemical equivalent are estimated, one obtains the ** cor- 
rected" values. 

The possible error in the refractometer reading is i' of 
the angle of total reflection; this corresponds to an error of 
o.oooio in the refractive index, that is, to an error of 0.07 



* If the anode be much less than 9 cm in length there is a tendency, after 
prolonged electrolysis, to what may be termed "flocculent deposition," or pre- 
cipitation of the casein within the body of the fluid in the anodal arm and not 
upon the wire. Under these conditions resolution is apparently more rapid 
and even if the flocculent deposit be filtered off from the anodal fluid before 
the alkaline cathodal fluid is mixed with it, the values of the electro-chem- 
ical equivalent which are obtained arc low. No such phenomenon was observed 
when the anode was of sufficient length. 



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Studies in the Electrochemistry of the Proteins 183 






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1 84 



r. Brailsford Robertson 




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Studies in the Electrochemistry of the Proteins 185 

in the estimated decrease in the percentage of casein due to 
electrolysis of the solution, and to an error of 0.0175 ^ the 
estimate of the amoimt of casein deposited by the ciurent. 
The possible error in each estimate of the electrochemical 
equivalent, arising from this source, is indicated in the tabu- 
lated results. 

III. Theopetieal 

(/) The Valency of Casein Ions, — ^These average values 
are obviously, within the experimental error, identical. Now 
in solutions containing 50 X lo"* equivalents of base per 
gram the combining capacity of casein is 50 X lo"* equiv- 
alents per gram, in solutions containing 80 X io~* equiva- 
lents per gram it is 80 X io~* equivalents per gram and in 
solutions containing 100 X io~* equivalents per gram it is be- 
tween 99 and 10' X lo"* equivalents per gram.* In the 
solutions investigated therefore, the combining weight of 
casein varies 100 percent yet the electrochemical equivalent 
remains the same. 

This fact is probably to be interpreted as follows: I 
have elsewhere shown* that the caseinates of the bases dis- 
sociate into two protein ions, in one of which, the cation, 
the base is bound in a non-dissociable form. On electro- 
lysing a solution of potassium caseinate, therefore, the anion, 
free from potassium, would migrate to the anode. There it 
may be presumed to react with water, liberating oxygen 
and free casein which combines with the excess of base until 
the proportion of base to casein in the film in immediate 
contact with the anode falls to that which obtains at "satura- 
tion" of the base with casein. Any additional casein, thus 
migrating into the film in contact with the anode, must be 
precipitated as uncombined casein. The cations, con- 
taining the potassium, migrate to the cathode and there re- 
act with water, liberating KOH, casein and hydrogen, the 
casein reacting with the excess of KOH to again form potas- 

^ References in Introduction. Also T. Brailsford Robertson: Jour. 
Phys. Chem., 14, 528 (19 10). 

' T. Brailsford Robertson: Ibid., 14, 601 (19 10). 



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1 86 T. Brails ford Robertson 

sium caseinate and to again participate in carrying the cur- 
rent in each direction. 

Hence the electrochemical equivalent which is actually 
meastu-ed must in solutions of all reactions be that of casein 
at **satiu:ation" of the base with the protein. 

Rejecting the data obtained in the solutions alkaline 
to phenolphthalein, on accoimt of the possible error arising 
from hydrolyisis, the average of all the determinations yields 
the value 0.0242 ±0.0019 for the electrochemical equiva- 
lent of casein. Multiplying this by the Faraday constant, 
96530, we obtain the weight of casein in grams which trans- 
ports one atomic charge. This is 2336 ± 183. 

Now at "sattu-ation*' of a base by casein the proportion 
of base to casein is 11.4 X io~' equivalents per gram.* 
Corresponding, if, at this reaction, casein combines with only 
one molecule of base, with a molecular weight of 8772. The 
sum of the valencies of the casein anions must therefore be, 

on this assumption, — ^ . ^ = 3.8 ± 0.3 or, in round 
^ 2336 ± 183 ^ o ^ 

numbers, 4. 

If we assume that at ** saturation ** of the base with casein 
two, three or four, etc., molecules of base are bound up in 
one molecule of caseinate the molecular weight of the casein 
would be, three, or four, etc., times 8772 and the sum of the 
valencies of the casein anions would be a corresi>onding 
multiple of 4. I have elsewhere shown' from the depression 
of the freezing point of water which results from the solution 
of caseinates therein and from conductivity data that the 
sum of the valencies of the casein anions or cations in 
solutions neutral to phenolphthalein must be 4. Hence the 
data obtained from very different lines of inquiry yield con- 
cordant results. 

(//) The Relationship of the Salts which are Formed at 
Saturation of a Base with Casein, to Those which are Formed 

* T. Brailsford Robertson: Jour. Phys. Chem., i^ 469 (1909); 14, 538 
(1910). 

*T. Brailsford Robertson: Ibid., 14, 601 (19 10). 



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Studies in the Electrochemistry of the Proteins 187 

at Neutrality to Litmus and to Phenolphthalein, — Since, at 
neutrality to phenolphthalein the molecule of caseinate 
contains 2 atoms of base, the average molecular weight 
of the salts contained in the solution must be 2500, for at this 
reaction 80 X io~* equivalents of base are bound by one 
gram of casein. 

This would appear to indicate the mixture of a mol. 
wt. about 2200 with a small proportion of a molecular weight 
of about 4400. In other words, of: 

K2X++++ -f X(OH);' 

with a small proportion of : 

KHX++ X(OH); 

II + II 

KHX++ X(OH); 

^ In solutions neutral to litmus the salts of casein must 
possess an average molecular weight which is a multiple of 
2000, Since at this reaction 50 X io~* equivalents of base 
are bound by one gram of casein. Assuming that at this 
reaction, also, two atoms of base are bound by one molecule 
of casein these figures indicate an admixture of: 

KHX++ X(OH); 

II- + II 
KHX++ X(OH); 

with a small proportion of 

KjX++++ + X(OH);'. 

At "saturation" of the base potassium with casein we must 

have: 

KHX++ X(OH); 

II II 

H,X X(OH)„ 

II + II 

H^X X(OH)„ 

II II 

H,X++ X(OH); 

While the corresponding calcium salt would be : 



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1 88 T. Brails ford Robertson 



Or: 



HPC++ 


x(OH); 


II 


II 


H^ 


X(OH). 


II . 


II 


HpC 


X(OH). 


II 


II 


/HX 

C< II + 


X(OH). 


II 


X(OH). 


It 


II 


H,X 


X(OH). 


II 


II 


H,X 


X(OH), 


II 


II 


HPC++ 


X(OH): 


CaX++ 


x(OH); 


II 


II 


H,X 


X(OH). 


II 


II 


H,X 


X(OH). 


II 


II 


H^ 


X(OH)» 


II + 


II 


H,X 


X(OH), 


II 


II 


H,X 


X(OH). 


II 


II 


H,X 


X(OH). 


II 


II • 


H,X++ 


x(OH); 



In theyanalogous cases aflForded by the globulinates 
this latter salt is not stable, and hence bases dissolve globulin 
in molecular and not equivalent-molecular proportions al- 
though at neutrality to phenolphthalein they are bound by 
the globulin in equivalent-molecular pro|>ortions. * 

It appeared of importance to ascertain whether the 
same is true for the caseinates or whether, on the contrary, 
the calcium salt of casein which is depicted above is stable. 

It is impossible, so far as I have been able to ascertain, 



* W. B. Hardy: Jour. Physiol., 33i 251 (1905); T. Brailsford Robertson: 
Jour. Phys. Chem., 15, 170 (191 1). 



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Studies in the Electrochemistry of the Proteins 189 

to determine by any direct method the equivalence between 
casein and the alkaline earths at " saturation " of the alka- 
line earth with the protein. One cannot proceed by simply 
stirring excess of casein in the solution of alkaline earth be- 
cause, after the attainment of neutrality to litmus, the rate 
of solution is so slow that the attainment of " satiuration " 
of the base would be a matter of years.* 

Nor can one proceed as in the determination of the ** satura- 
tion" equivalence between the alkalies and casein, by dis- 
solving the casein in excess of base, neutralizing the base 
with HCl until some casein is precipitated and then deter- 
mining the proportion of casein which is held in solution by 
the unneutralized proportion of the base' because the casein- 
ates of the alkaline earths are precipitated by the correspond- 
ing chlorides. For example: 

Four grams of casein were dissolved in 100 cc of 0.048 N 
Ca(OH)j and then 40 cc of N/io HCl were cautiously delivered 
into the solution by means of a pipette of which the open- 
ing was held below the surface of the fluid, the mixture being 
rapidly and continuously stirred meanwhile. The total 
volume was then made up to 200 cc and the mixture filtered 
through soft filter paper. A similar mixture was made up 
(the "solvent") containing, however, no casein. The re- 
fractive indices of the "solvent" and of the "solution" 
were determined: 

Refractive index of solution i . 33216 
Refractive index of solvent i .33201 



Difference o . 000 1 5 

Corresponding to the presence, in the solution, of o.i per- 
cent of casein.* The 0.008 equivalents of imneutralized 
Ca(OH)„ therefore held in solution, under these conditions, 
only 0.2 gram casein, although, in the absence of CaCl,, 



* T. Brailsford Robertson: Jour. Phys. Chem., 14, 377 (1910). 

• T. Brailsford Robertson: Ibid., 13, 469 (1909)- 



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I90 T. Brails ford Robertson 

0.0008 equivalent of Ca(OH), will readily dissolve i gram 
of casein, rendering the solution neutral to phenolphthalein. 

In order to determine the equivalence between calcium 
and casein at "saturation*' of the base with casein, there- 
fore, an indirect method had to be devised. 

I have elsewhere shown that* when casein (concentra- 
tion C percent) is dissolved in solutions of the hydroxides 
of the alkalies of varying alkalinity (equivalent-molecular 
concentration of base = 6,) the depression in the conduc- 
tivity of the solution which is brought about by the addi- 
tion of the casein (= X) is connected with its concentration 
and with the concentration of the base by the formula: 

>l X io» = ab^ — ^b^—rc 

Where a, ^ and y are constants such that when ^ = o the 
value of b^ is that which would be just suflScient to hold the 
concentration c of casein in solution ( = , for the alkalies, 
II .4 X lo"' equivalents per gram). 

I therefore proceeded to ascertain whether the same law 
holds good for solutions of casein in Ca(OH)j of varying con- 
centration. 

In 400 cc of 0.024 N Ca(OH), were dissolved 12 grams 
of casein, thus making a 3 percent solution neutral to phenol- 
phthalein. To 50 cc |>ortions of this solution were added 
o, 2, 4, 6, 8 or 12 cc of 0.048 N Ca(OH)j and each mixture 
was diluted to a total volume of 100 cc. The percentage of 
casein in each of the solutions was therefore 1.5, Exactly 
similar solutions were made up (** solvents'*) containing, 
however, no casein. The conductivities of these solutions 
were measured in a vessel of resistance capacity 0.1949, 
at 30° C. The technique employed was the same as that de- 
scribed in Part I of these '* studies."* The difference be- 
tween the conductivity, in reciprocal ohms, of the solvent 
and that of the solution is ^, the depression in conductivity 
due to the presence of the casein. 

' T. Brailsford Robertson: Jour. Phys. Chem., 14, 528 (1910). 



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Studies in the Electrochemistry of the Proteins 191 

The following were the results obtained : 
Table IV 



I ^^. 



A — ^^.,;«..i^.,f .^^i^^ ' ;ri = the con- ! ;r=:thecon 
^,=: equivalent molec- i— ^vitv in I H;;7Hvitv in 



ular concentration of 

Ca(OH), in solvent 

Xio* 



120.0 
129.6 
139.2 
148.8 

158.4 
177.6 



ductivity in I ductivity in ! ; v io« = r ^ — ^^ 
reciprocal ohms I reciprocal ohms ] '^ . v*i ^J 
of the solvent 
X 10* 



263 
286 
305 
325 
345 



of the solution 
Xio* 

17. 1 



X 10^ 



382.2 



19 
23 
27 
32 



41.8 



246.3 
266.9 
281.8 

297 5 
312.6 

340.4 



Applying the above equation to these results and com- 
puting the constants from the first, fourth and sixth deter- 
minations^ we obtain : 

^ X 10* = 30830 b\ — 488000 bl — 53.4 

Inserting in this equation the above values of 6, and compu- 
ting the corresponding "theoreticar* values of, we obtain: 



Table V 



Jl X 10^ Experimental 



246 3 
266.9 
281.8 

297 5 
312.6 

340.4 



A X 10* Theoretical 

246 -3 
264.2 
281. 1 
297 5 
312.5 
340.4 



It is evident that the relation holds good, also, for solu- 
tions of casein in solutions of the hydroxides of the alkaline 
earths. Computing, from the numerical values of the con- 
stants, the value of ft^ when >l = o we obtain : 

6, =0.031585 ±0.029803. 

* These results do not lend themselves to determination of the constants 
by Gausse's method of solution by least squares, since the normal equations are 
very nearly identical, the factors differing only by magnitudes commensurate 
with the experimental error. 



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192 T. Brails ford Robertson 

Taking the smaller value* 

ftj - 0.001782, 

dividing this by 1.5, the percentage of casein, we find X ^ o 
when the equivalence between the casein and the calcium 
hydroxide is: i gram — 11. 9 X lo"* equivalents, a value so 
near to that (i i . 4 X lo*) obtained for the alkalies that 
they may be regarded as being, within the experimental 
error, identical. 

Hence it appears that the bases dissolve casein in equiv- 
aletU-molecular not molecular proportions, or in other words» 
that the calcium salt of casein which corresponds to the 
potassium salt at "saturation " of the base by casein is stable 
and does not break down into a molecule of salt and a mole- 
cule of imcombined protein as the corresponding salt of glob- 
ulin does. 

(Ill) The Two Possible Types of Salts of the Proteins 
with Alkaline-earth Bases. — We have seen that the caseinate 
of calcium at satiuration of the base with casein may be 
represented by either of the schematic formulae (i): 





HjX 


x(OH); 




II 


II 




HpC 


X(OH), 




II 


II 




HjX 


X(OH). 




II 


II 




.HX 

C< II 


X(OH). 




+ II 

X(OH), 




II 


II 




H,X 


X(OH), 




II 


II 




H,X 


X(OH), 




II 


II 




H,X 


x(OH); 


or (2) 







* The larger value probably merely indicates that the effect of small 
amounts of added casein upon the conductivity of a very alkaline solution is 
negligible. Cf. T. Brailsford Robertson: Jour. Phys. Chem., 14, 528 (1910). 



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Studies in the Electrochemistry of the Proteins 193 

CaX++ X(OH)' 



II 
H,X 


X(OH)» 

jl 


X(OH)„ 


II 


II 


H^ 


X(OH), 


II + 


II 


H,X 


X(OH), 


II 


II 


HPC 


X(OH)„ 


II 


II 


h;!c 


X(OH), 


II 


It 


HjX++ 


x(OH); 



It would appear probable that the stability and solu- 
bilit}" of a molecule of the second tjT^e would be very different 
from those of a molecule of the first type. It is possible 
that the difference between the behavior of the caseinates 
and of the globulinates of the alkaline earths at " sattu-ation " 
of the base with protein is due to the formation of a salt of 
the first type by casein and of a salt of the second tjT^e by 
globulin, the latter splitting across the middle, setting free a 
molecule of soluble calcium globulinate. 

The possibility may also be indicated that the differ- 
ence in physical behavior between^ the caseinate and the 
paracaseinaie of calcium produced from the caseinate through 
the agency of rennet may be due to a transformation of 
salts of the first type into salts of the second type, since 
paracasein, freed from its combination with calcium, differs 
in no respect from casein.* 

(JV) The Relationship between the Combining Capaci- 
ties of Casein and the Amino-add Content of the Casein Mole- 
cule, — ^We have seen that at neutrahty to phenolphthalein 
and to litmus the caseinates in solution may be considered 
to be mixtures of two salts in forming which the molecular 
weight of the casein is, respectively, about 2200 and 4400, 
while at ** saturation" of the base with casein the molecular 



Van Slyke and Hart: Am. Chem. Jour., 33, 461 (1905). 



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194 T, Brailsford Robertson 

weight of the combined casein is probably about 8800. It 
remains to be considered what relation these "theoretical" 
molecular weights bear to the actual minimum weight of the 
casein molecule, as indicated by its amino-acid content. 

The amino acids which admit of most precise determina- 
tion are glutamic acid and tyrosin. According to Abderhalden 
and Rona* the percentage of glutamic acid in casein derived 
from cow's milk is ii.o, indicating a minimum molecular 
weight, for casein, of 1336, which, multiplied by 3, yields 
4008. 

The percentage of tyrosin in casein derived from cow's 
milk is, according to the same authors, 4.5, indicating a min- 
imum molecular weight, for casein, of 4022. 

From the percentage of sulphur and phosphorus in casein 
we similarly deduce a minimum molecular weight approx- 
imating to 4000. 

The minimum molecular weight of casein, as indicated 
by the above data, therefore agrees excellently witk the 
molecular weights of casein, deduced from electrochemical 
data, when in solutions neutral to litmus (4400) or "satura- 
ted" with casein (8800) but it is almost twice the weight 
which we have deduced from electrochemical data for the 
greater proportion of the casein salts in solutions neutral to 
phenolphthalein, on the assumption that in such solutions 
one molecule of casein binds two molecules of base. 

Since the depression of the freezing-point of water, which 
is observed in solutions of caseinates of the alkalies which 
are neutral to phenolphthalein, is exactly equal to that of 
a solution of the same molecular plus ionic concentration of 
the neutralized base, each molecule of the neutralized base 
must, at least, give rise to one ion of caseinate. If, there- 
fore, we assume the true molecular weight of casein, in these 
solutions, to be 4400, we must assume that four molecules 
of base are bound in one molecule of the caseinate and that 
each molecule of caseinate gives rise, in solution, to four 

* E. Abderhalden and P. Rona: Zeit. physiol. Chem., 41, 278 (1904). 



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Studies in the Electrochemistry of the Proteins 195 

ions. Yet these solutions obey Ostwald's dilution law for a 
binary electrolyte. 

Without endeavoring to definitely reconcile this dis- 
crepancy the tentative suggestions may be advanced that 
the greater part of the caseinate, in solutions neutral to 
phenolphthalein, dissociates into two positive and two nega- 
tive ions.* Assuming the possibility of free interaction be- 
tween all of these ions such a system would behave like a 
mixture of two salts in constant proportions and would obey 
Ostwald's dilution law for a binary electrolyte. 

Conelusions 

(i) If a direct current of about i milliampere be passed 
through a solution of potassium caseinate (neutral to Htmus 
or to phenolphthalein), gas is observed to be evolved at 
both electrodes, but a firm white spongy precipitate is de- 
posited upon the anode, the cellular texture of which is at- 
tributable to entangled bubbles of gas, presumably oxygen. 
This deposit is identical with base-free casein. 

(2) The electrochemical equivalent of casein, whether 
in solutions containing 50 X io~*, 80 X lo"' or 100 X lO"* 
equivalents of base per gram of casein is 0.0242 ±0.0019 
grams per coulomb. 

(3) It is concluded that the casein anion migrates to 
the anode where it reacts with water, liberating oxygen 
and free casein, which combines with the excess of base in 
the film siUTOunding the anode until the proportion of base 
to casein in this film falls to that which obtains at "satura- 
tion" of the base with casein. Any additional casein thus 
migrating into the film is precipitated upon the anode in the 
form of free, uncombined casein. 

(4) The weight of casein, in grams, which transports 
one atomic charge is thus 2336 ±183. 

(5) It is concluded that the sum of the valencies of the 

^ Analogous types of dissociation are encountered in solution of many 
complex salts, for example K^Fe(CN),. Cf. Jones and Bassett: Am. Chem. 
Jour., 34, 313 (1905). 



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196 T. Brailsford Robertson 

casein anions, in solutions of base "saturated" with casein, 
is 4 or a multiple of 4. 

(6) Solutions of casein in solutions of Ca(OH), of vary- 
ing concentration obey the law 

A X io» = a6i — ^6J — T-c. 

where i is the depression in the conductivity of the solution 
of Ca(OH), which is brought about by the introduction of 
the casein, b^ is the equivalent-molecular concentration of 
Ca(OH), in which the casein is dissolved, c is the percentage 
of casein introduced and a, p and j- are constants, such that 
when ^ = o the proportion of Ca(OH) , to casein is 1 1 . 9 X lo"* 
equivalents per gram. 

(7) It is inferred that the alkahes and alkaline earths 
dissolve casein in equivalent molecular proportions. 

(8) The probable modes of formation and dissociation 
of the various casein salts are discussed in the light of these 
data. 



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NEW BOOKS 

Radiation, light and Illumination. A Series of Lectures delivered at 
Union College, By Charles Proteus Steinmetz. Compiled and edi'ed by Joseph 
LeRoy Hayden. i6 X 24 cm; pp. xii 4- jo^. New York: McGraw-Hill Book 
Company, 1909. Price: $3.00 net. — The lectures which compose the work are: 
nature and different forms of radiation; relation of bodies to radiation; physio- 
logical effects of radiation; chemical and physical effects of radiation; temperature 
radiation; luminescence; flames as illuminants; arc lamps and arc lighting; 
measurement of light and radiation; light flux and distribution; light intensity 
and illumination; physiological problems of illuminating engineering. It is 
a pleasure to come across a book like this. The author knows his subject, in 
fact has made his subject, and one cannot read ten consecutive pages without 
perceiving the difference between first-hand knowledge and the second-hand 
knowledge which is all that many of us have on any subject. The book is 
written primarily for electrical engineers interested in problems of illumination; 
but most of it is of direct interest to chemists and certainly a great deal of it 
should appeal to physicists, while the consumer would be benefited by glancing 
over the last two lectures. 

There is only one point on which the author has gone astray. It would 
have been a great deal better to have pointed out that chemical action is pro- 
duced only by those ra3rs which are absorbed and not to have laid much stress 
on the chemical action being some kind of a resonance effect, p. 62. As it is 
the author has an unnecessarily bad time with silver salts and with ozone, p. 95. 

The effect of different sources of light on the apparent color of bodies is 
brought out very clearly on p. 35. 

"As the eye perceives only the resultant of radiation, very different com- 
binations of radiation may give the same impression to the eye, but when blotting 
out certain radiations, as red and green, in the mercury lamp, those different 
combinations of radiation may not give the same resultant any more, that is, 
become of different colors, and inversely, different colors, which differ only by 
such component radiations as are blotted out by an illuminant, become equal 
in this illuminant. For instance a mixture of red and blue, as a diluted potassium 
permanganate solution, appears violet in daylight. In the mercmy light it 
appears blue, as the red is blotted out, and in the light of the incandescent lamp 
it appears red, as the blue is blotted out. 

"I show you here, in the light of an incandescent lamp, two pieces of black 
velvet. I turn off the incandescent lamp and turn on the mercury lamp, and 
you see the one piece is blue and the other black. Now I show you two pieces 
of brownish black cloth in the mercury light. Changing to the incandescent 
lamp you see that the one is a bright crimson, and the other still practically 
black. In both cases the color deficient in the illuminant appeared as black. 

"This tube of copper chloride crystals appears green in the incandescent 
lamp. In the mercury light it is a dirty white. The excess color, green, is 
blotted out. These crystals of didymium nitrate, which are a faint light pink 
in daylight, are dark pink in the incandescent light. In the mercury light they 



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198 New Books 

are blue: the color is a mixture of red and blue, and the one is blotted out in the 
mercury light and the other in the incandescent light. These two tubes, one 
containing a concentrated solution of manganese chloride, the other a solution 
of didymium nitrate, are both a dark pink in the incandescent light. In the 
mercury light the first becomes a very faint pink, the second becomes grass- 
green. 

"These tubes, one containing a solution of didymium nitrate, the other 
a diluted solution of nickel sulphate, appear both light green in the mercury 
Ught. In the incandescent lamp the former is dark pink, the latter dark green. 
(Didymium, which formerly was considered as an element, has been resolved 
into two elements, praseodymium, which gives green salts, and neodymium» 
which gives pink salts. It is interesting to see that this separation is carried 
out photometrically by the light: the mercury lamp showing only the green 
color of the praseodymium, the incandescent lamp the pink color of neodymium.) 

" I have here a number of tubes which seen in the light of the incandescent 
lamp contain red solutions of nearly the same shade. Changing to the mercury 
lamp you see that they exhibit almost any color. As the red disappeared in 
the merctu'y lamp the other component colors, which did not show in 
the incandescent lamp as they were very much less in intensity than the red, 
now predominate: potassium permanganate solution turns blue, carmine blue; 
potassium bichromate greenish brown; coralline (an aniline dye), ojive-green; 
etc., etc. 

"Again a number of tubes which in the mercury light appear of the same or 
nearly the same blue color, turn to a very different color when seen in the incan- 
descent lamp, due to the appearance of red and green, which were not seen with 
the mercury light. 

"A solution of rhodamine, however, which looks a dull red in the light of 
the incandescent lamp turns a glowing crimson in the mercury lamp, due to its 
red fluorescence. This diluted solution of rhodamine and methyl green (aniline 
dyes), which is gray in the light of the incandescent lamp, turns brownish red 
in the mercury lamp, the green is blotted out while the rhodamine shows its 
red fluorescence. Thus, you see, the already very difficult problem of judging 
the subjective colors of bodies under different illuminants is still greatly increased 
by phenomena as fluorescence. 

"To conclude then: we have to distinguish between colorless and colored 
bodies, between opaque colors and transparent colors, between color, as referred 
to the visible range of radiation only, or to the total range, including ultra-red 
and ultra-violet, and especially we have tp realize the distinction between objec- 
tive or actual color, and between subjective or apparent color, when deaUng 
with problems of illuminating engineering." 

The bearing of Fechner's law of sensation on photography is discussed on 
p. 40. 

"The result of this law of sensation is that the physiological effect is not 
proportional to the physical effect, as exerted for instance, on the photographic 
plate. The range of intensities permissible on the same photographic plate, 
therefore, is far more restricted. A variation of illumination within the field 
of vision of i to 1000, as between the ground and sky, would not be seriously felt 
by the eye, that is, not give a very great difference in the sensation. On the photo- 



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graphic plate, the brighter portions would show 1000 times more effect than the 
darker portions and thus give halation while the latter are still under-exposed. 
A photographic plate, therefore, requires much smaller variations of intensity 
in the field of vision than permissible to the eye. In the same manner the varia- 
tions of intensity of the voice used in speaking are far beyond the range of 
impression which the phonograph cylinder can record, and while speaking into 
the phonograph a more uniform intensity of the voice is required to produce 
the record, otherwise the lower portions of the speech are not recorded, while 
at the louder portions the recording point jumps and the voice breaks in the 
reproduction." 

The physiological effects of ultra-violet light are more serious than most 
of us realize, p. 50. 

"Excessive intensity, such as produced at a short-circuiting arc, is harmful 
to the eye. The human organism has by evolution, by natiural selection, de- 
veloped a protective mechanism against the entrance of radiation of excessive 
power into the eye: at high intensity of illumination the pupil of the eye contracts 
and thus reduces the amount of light admitted, and a sudden exposure to ex- 
cessive radiation causes the eyelids to close. The protective mechanism is 
automatic; it is, however, responsive mainly to long waves of radiation, to the 
red and yellow light, but not to the short waves of green, blue and violet light. 
The reason for this is apparently that all sources of excessive radiation which are 
found in nature, the sun and the fire, are rich in red and yellow rays, but fre- 
quently poor in rays of short wave length, and therefore, a response to short 
wave lengths alone would not be sufficient for protection as they might be absent 
in many intense radiations, while a response to long waves would be sufficient 
since these are always plentiful in the intense radiations found in nature. 

"It is only of late years that illuminants, as the mercury lamp, which are 
deficient in the long waves, have been produced, and for these the protective 
action of the eye, by contracting the pupil, fails. This absence or reduction of 
the contraction of the pupil of the eye in the light of the mercury. lamp is noticed 
when passing from a room well illuminated by incandescent lamps to one equally 
well illuminated by merciuy lamps and inversely. When changing from the 
incandescent light to the mercury light, the illimiination given by the latter 
at first appears dull and inferior as the pupil is still contracted, but gradually 
gains in intensity as the pupil opens; and inversely, coming from the mercury 
light to the incandescent Hght, the latter first appears as a big glare of light, 
the pupil still being open, but gradually dulls down by the contraction of the 
pupil. 

"This absence of the automatic protective action of the eye against light 
deficient in long waves i? very important, as it means that exposure to excessive 
intensity of illumination by mercury light may be harmful, due to the power 
of the light, against which the eye fails to protect, while the same or even greater 
power or radiation in yellow light would be harmless, as the eye will protect 
itself against it. The merciu*y Ught, therefore, is the safest illuminant, when 
of that moderate intensity required for good illumination, but becomes harm- 
ful when of excessive intensity, as when closely looking at the lamp for con- 
siderable time, when operating at excessive current. The possibility of a harm- 
ful effect is noticed by the light appearing as glaring. This phenomenon explains 



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the contradictory statements occasionally regarding the physiological effect 
of such illuminants. 

"Up to and including the green light, no specific effects, that is, effects be- 
sides those due to the power of radiation, seem yet to exist. They begin, however, 
at the wave length of blue light. 

''I show you here a fairly intense blue- violet light, that is, light containing 
only blue and violet radiation. It is derived from a vertical mercury lamp, 
which is surrounded by two concentric glass cylinders welded together at the 
bottom. The space between the cylinders is filled with a fairly concentrated 
solution of potassium permanganate (strong copper nitrate solution or a cupric- 
ammon salt solution, though not quite so good may be used) which is opaque 
to all but the blue and violet radiations. As you see, the light has a very weird 
and uncanny effect, is extremely irritating: you can see by it as the intensity 
of illumination is fairly high, but you cannot distinguish everything, and espe- 
cially the lamp is indefinite and hazy: you see by it, but when you look at it, 
it disappears, and thus your eye is constantly trying to look at it and still never 
succeeds, which produces an irritating restlessness. It can well be believed 
that long exposure to such illumination would result in insanity. The cause 
of this weird effect — which is difficult to describe — is that the sensitive spot 
on the retina, that is, the point on which we focus the image of the object which 
we desire to see,*or the fova is blue-blind, that is, does not see the blue or violet 
light. Thus we see the lamp and other objects indistinctly on the outer range 
of the retina, but what we try to see distinctly disappears when focused on the 
blue-blind spot. This spot, therefore, is often called the "yellow spot," as we 
see yellow on it — due to the absence of the vision of blue at this particular 
place of the retina. 

"To produce this effect requires the merciuy lamp; most other illuminants 
do not have sufficient blue and violet rays to give considerable illumination of 
this color and even if they do, no screen which passes blue and violet is suffi- 
ciently opaque to the long waves not to pass enough of them to spoil the effect, 
if the illuminant is rich in such long waves. The mercury lamp, however, is 
deficient in these, and thus it is necessary only to blind off the green and yellow 
rays in order to get the blue and violet light. 

" I show you here a mercury lamp enclosed by a screen consisting of a solu- 
tion of naphthol green (an aniUne dye) which transmits only the green light. 
As you see, in the green the above described effect does not exist, but the vision 
is clear, distinct, and restful. 

"Beyond the vio!et the radiation is no longer visible to the ejre as light. 
There is, however, a faint perception of ultra-violet light in the eye, not as a 
distinct light, but rather as an indistinct, uncomfortable feeling, some form of 
dull pain, possibly resulting from fluorescence effects caused by the ultra- 
violet radiation- inside of the eye. With some practice the presence of ultra- 
violet radiation thus can be noticed by the eye and such light avoided. In 
the ultra-violet, and possibly to a very slight extent in the violet and even in 
the blue, a specific harmful effect appears, which probably is of chemical nature, 
a destruction by chemical dissociation. The effect increases in severity the 
further we reach into the ultra-violet, and probably becomes a maximum in 
the range from one to two octaves beyond the violet. These very short ultra- 



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violet rays are extremely destructive to the eye: exposure even to a moderate 
intensity of them for a very few minutes produces a severe and painful inflamma- 
tion, the after-effects of which last for years, and long exposures would probably 
result in blindness. The chronic effects of this inflammation are similar to the 
effect observed in blue light: inability or difficulty in fixing objects on the sensi- 
tive spot, so that without impairment of the vision on the rest of the retina 
clear distinction is impaired and reading becomes difficult or impossible, especially 
in artificial illumination. It appears as if the sensitive spot or the focusing 
mechanism of the eye were over-irritated and when used, for instance in reading, 
becomes very rapidly fatigued and the vision begins to blur. If further irrita- 
tion by ultra-violet light or by attempting to read, etc., is avoided, gradually 
the rapidity of fatigue decreases, the vision remains distinct for a longer and 
longer time before it begins to blur and ultimately becomes normal again. 

"The inflammation of the eye produced by ultra-violet light appears to be 
different from that caused by exposure to high-power radiation of no specific 
effect, as the light of a short circuit of a high-power electric system, or an ex- 
plosion, etc. 

"The main differences are: 

"i. The effect of high-power radiation (power bum) appears immediately 
after exposure, while that 'of ultra-violet radiation (ultra-violet burn) appears 
from 6 to 18 hours after exposure. 

'*2. The external symptoms of inflammation : redness of the eyes and the face, 
swelling, copious tears, etc., are pronounced in the power burn, but very moderate 
or even entirely absent in the ultra-violet burn. 

"3. Complete recovery from a power bum even in severe cases usually 
occurs within a few days, leaving no after-affects, while recovery from an ultra- 
violet bum is extremely slow, taking months or years, and some after-effects, 
as abnormal sensitivity to radiation of short wave lengths, may be practically 
permanent. 

"The general phenomena of a severe power burn are: 

"Temporary blindness immediately after exposure, severe pains in the eyes 
and the face, redness of eyes and face, swelling, copious tears, etc. These effects 
increase for a few hours and then decrease, yielding readily to proper treatment; 
application of ice, cold boric acid solution, etc., and complete recovery occurs 
within a few days. In chronic cases, as excessive work under artificial illumina- 
tion, the symptoms appear gradually, but recovery, if no structural changes in 
the eyes have occurred, is rapid and complete by proper treatment and discon- 
tinuance of work under artificial illumination. 

"Most artificial light is given by temperature radiation (incandescent lamp, 
gas and kerosene flame), and therefore its radiation consists of a very small 
percentage only of visible light (usually less than i j>ercent) while most of its 
energy is in the ultra-red and invisible, and for the same amount of visible radia- 
tion or light the total radiated power thus is many times greater than with day- 
light. Regarding chronic "power bum," artificial light, therefore, is much 
more harmful than daylight, that is, much more energy enters the eye under 
incandescent illumination than under more powerful daylight illumination. 

"In a severe ultra-violet burn no immediate symptoms are noticeable, ex- 
cept that the light may appear uncomfortable while looking at it. The onset 



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of the symptoms is from 6 to 18 hours later, that is, usually during the night 
following the exposure, by severe deep-seated pains in the eyes; the external 
appearance of inflammation is moderate or absent, .he vision is not impaired, 
but distinction made difficult by the inability to focus the eye on any object. 
The pains in the eyes and headache yield very slowly ; for weeks and even months 
any attempt of the patient to use the eyes for reading, or otherwise sharply 
distinguishing objects, lead to blurring of the vision; the letters of the print seem 
to run around and the eye cannot hold on to them, and severe headache and deep- 
seated pains in the eyes follow such attempt. Gradually these effects become 
less; after some months reading for a moderate length of tim^ during dayHght 
is possible, but when continued too long, or in poor light, as in artificial illumina- 
tion, leads to blurring of the vision and head- or eye-ache. Practically complete 
recovery occurs only after some years, and even then some care is necessary, 
as any very severe and extended strain on the eyes temporarily brings back the 
symptoms. Especially is this the case when looking at a light of short waw 
length, as the mercury arc; that is, there remains an abnormal sensitivity of 
the eye to light of short wave lengths, even such light which to the normal eye 
is perfectly harmless, as the mercury lamp. 

*'In chronic cases of ultra-violet bum, which may occur when working on 
unprotected arcs, and especially spark discharges (as in wireless telegraphy), 
the first symptoms are: occasional headaches, located back of the eyes, thai i«, 
pains which may be characterized either as headache or as deep-feated eyc- 
achc. These recur with increasing frequency and severity. At the same 
time the blurring of the vision begins to be noticeable and the patient finds 
it more and more difficult to keep the eye focused for any length of time on 
objects, as the print when reading. These symptoms increase in severity until 
the patient is ob'iged to give up the occupation which exptised him to ultra- 
violet light, and then gradual recovery occurs, as described above, if the damage 
has not progressed too far. 

"In mild cases recovery from power burns may occur in a few hours and 
complete recovery from mild ultra-violet burns in a few weeks.** 

Stcinraetz agrees with Woodrufi" that the black color of negroes is essentially 
a result of protective pigmentation, p. 59. 

'*The penetration of the radiation of the sunlight into the human body 
is very gradually reduced by acclimatization, which leads to the formation of 
a protective layer or pigment, more or less opaque to the light. Such accli- 
matization may be permanent or temporary. Permanent acclimatization has 
been evolved during ages by those races which developed in tropical regions, 
as the negroes. They are protected by a black pigment under the skin, and 
thereby can stand intensities of solar radiation which would be fatal to white 
men. A temporary acclimatization results from intermittent exposure to 
sunlight for gradually increasing periods: tanning, and enables the protected 
to stand without harmful effects exposure to sunlight which would produce 
severe sunburn in the unprotected. This acquired protection mostly wears 
off in a few weeks, but Fome traces remain even after years. 

"A slight protection by pigmentation also exists in white men, and its 
<IifTcrcnccs lead to the observed great difTcrcnccs in sensitivity t<> solar radiation: 



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blondes, who usually have very light pigmentation, are more susceptible to 
sunburn and sunstroke than the more highly pigmented brunette people. 

"In sunburn we probably have two separate effects superimposed one 
upon the other: that due to the energy of the solar radiation and the specific 
effect of high frequencies, which to a small extent are contained in the sunlight. 
The two effects are probably somewhat different, and the high-frequency effect 
tends more to cause inflammation of the tissue, while the energy effect tends 
toward > the production of pigmentation (tanning) and the symptoms of sun- 
burn thus vary with the different proportions of energy radiation and of high- 
frequency radiation as depending on altitude, humidity of the air, the season, 
etc." 

The paragraphs on the question of heat luminescence in the Welsbach mantle, 
p. 91, are of great interest. 

"A body, which gives at any frequency a greater intensity of radiation 
than a black body of the same temperature is called luminescent, that is said 
to possess 'heat luminescence.' Characteristic of heat luminescence, thus is 
an excess of the intensity of radiation over that of a black body of- the same 
temperature for some frequency or range of frequencies, and the color of lumi- 
nescence is that of the radiation frequencies by which the luminescent body 
exceeds the black body. 

"It is not certain whether such heat luminescence exists. The high effi- 
ciency of light production of the Welsbach mantle, of the lime light, the mag- 
nesium flame, the Ncrnst lamp, etc., arc frequently attributed to heat lumi- 
nescence. 

"The rare oxides of the Welsbach mantle, immersed in the bunsen flame, 
give an intensity of visible radiation higher than that of the black body, as a 
graphite rod, immersed in the same flame, and if we assume that these oxides 
are at the same temperature as the flame in which they are immersed, their light 
must be heat luminescence arid not colored radiation, and the latter cannot 
exceed that of a black body. It is possible, however, that these oxides are at 
a higher temperature than the flame surrounding them, and as the radiation 
intensity of a black body rapidly rises with the temperature, the light radiation 
of the rare oxides, while greater than that of the flame temperature may still 
be less than that of a black body of the same temperature which the oxides have, 
and their radiation, thus, colored temperature radiation and not luminescence. 
Very porous materials, as platinum sponge, absorb considerable quantities of 
gases, and by bringing them in close contact with each other in their interior 
cause chemical reaction between them, where such can occur, and thus heat and 
a temperature rise above surrounding space. Thus platinum sponge, or fine 
platinum wire immersed in a mixture of air and alcohol vapor at ordinary tem- 
perature, becomes incandescent by absorbing alcohol vapor and air and cans ng 
them to combine. The oxides of the Welsbach mantle, as produced by the de- 
flagration of their nitrates, are in a very porous state and thus it is quite likely 
that in the bunsen flame they absorb gas and air and cause them to combine 
at a fa more rapid rate than in the flame, and thereby rise above the flame 
temperature. An argument in .'avor of this hypothesis is that these oxides, 
when immCTScd in the bunsen flame in close contact with a good heat conductor, 
as platinum, and thereby kept from rising above the flame temperature, do 



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204 New Books 

not show this high luminosity. I have here a small fairly closely womid plat- 
inum spiral filled with these oxides. Immersing it in the bunsen flame you see 
the oxides and the platinum wire surrounding them glow with the same yellow 
light, but see none of the greenish luminosity exhibited by the oxide when free 
in the flame, except at a few points at which the oxide projects beyond and is 
not cooled by the platinum spiral. The absence of a high selective luminosity 
of these oxides, when heated electrically in a vacuum or in an inactive gas, 
also point this way. The gradual decay of the luminosity shown by such radia- 
tors may be due to their becoming less porous, by sintering this would account 
for the very rapid decay of the light of the lime cylinder in the hydro-oxygen 
flame, and the very small decay of the more refractive oxides in the Welsbach 
mantle — but it also may be the general characteristic of luminescence, as we 
have found in the discussion of fluorescence and phosphorescence. 

" In favor of heat luminescence as the cause of very high efficiency of these 
radiators is, however, the similarity of the conditions under which it occurs, 
with those we find in fluorescence and phosphorescence. Just as neither calcium 
sulphide nor zinc silicate nor calcium carbonate are fluorescent or phosphorescent, 
when chemically pure, but the fluorescence and phosphorescence are due to the 
presence of a very small quantity of impurities, as manganese, so the pure oxides, 
thoria, erbia, ceria, do not give very high luminosity in the bunsen flame, but 
the high luminosity is shown by thoria when containing a very small percentage 
of other oxides." 

The relative merits of some different forms of arc conduction are discussed 

on p. 122. 

"Essentially, however, the efficiency of light production by the arc is a 
characteristic of the material of the arc stream, and thus substances which give 
a large part of their radiation as spectrum lines in the visible range — as calcium 
— give a very efficient arc, while those substances which radiate most of their 
energy as lines in the invisible, ultra-violet or ultra-red — as carbon— give a very 
inefficient arc. The problem of efficient light production by the arc therefore 
consists in selecting such materials which give most of their radiation in the 
visible range. 

"CarboUj which is most generally used for arc terminals, is one of the most 
inefficient materials: the carbon arc gives very little light, and that of a dis- 
agreeable violet color; it is practically non-luminous, and the light given by 
the carbon arc lamp is essentially incandescent light, temperature radiation 
of the incandescent tip of the positive carbon. The fairly high efficiency of 
the carbon arc lamp is due to the very high temperature of the black body radia- 
tor, which gives the light. 

*'The materials, which give the highest efficiencies of light by their spectrum 
in the arc stream are mercury, calcium, and titanium. As mercury vapor 
is very poisonous, the mercury arc has to be enclosed air-tight, and has been 
developed as a vacuum arc, enclosed by a glass or quartz tube. Its color is 
bluish green. Calcium gives an orange-yellow light of a very high efficiency, 
and is used in most of the so-called 'flame-carbon arcs,' or 'flame arcs.* Ti- 
tanium gives a white light of extremely high efficiency. It is used in the so- 



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called ' liuninous arc/ as the magnetite arc in direct current circuits, the titanium- 
carbide arc in alternating current circuits." 

The question of efficiency comes up on p. 126. 

"As, by electro-luminescence, electric energy is converted more directly 
into radiation, without heat as intermediary form of energy, no theoretical 
limit can be seen to the possible efficiency of light production by the arc, and 
in the mercury, calcium and titanium arcs, efficiencies have been reached far 
beyond those possible with temperature radiation. Thus, specific consump- 
tions of 0.25 watt per mean spherical candle power are quite common with power- 
ful titantitmi or caldimi arcs, and even much better values have been observed. 
It is therefore in this direction that a rapid advance in the efficiency of light 
production appears most probable. At present, the main disadvantage of light 
production by the arc is the necessity of an operating mechanism, an arc lamp, 
which requires some attention, and thereby makes the arc a less convenient 
illuminant than, for instance, the incandescent lamp, and especially the limita- 
tion in the unit of light : the efficiency of the arc decreases with decrease of power 
consumption and, while the arc b very efficient in units of hundreds or thousands 
of candle power, its efficiency is much lower in smaller imits, and very small 
units cannot be produced at all. Thus, for instance, while a 500 watt flame 
arc may give 10 times as much light as a 500 watt carbon arc, to produce by a 
flame arc the amount of light as given by a 500 watt carbon arc requires very 
much more than one tenth the tx)wer. So far no way can be seen of maintaining the 
efficiency of the arc down to such small units of light as represented by the 16- 
or 20-candle power incandescent lamp." 

The following paragraph, p. 174, shows that Steinmetz is not a believer 
in the photometer. 

"Light is used for seeing things by, that is distinguishing objects and dif- 
ferences between objects. Regarding this feature, the distinction of objects 
given by them, different colored lights can be compared, and a green light can 
be made equal to a red light in illuminating value. 

" It thus means that any two lights, regardless of their color, have the same 
intensity if, at the same distance from them, objects can be seen with the same 
distinctiveness, as, for instance, print read with equal ease. The only method, 
therefore, which permits comparing and measuring lights of widely different 
color is the method of 'reading distances,' as used in the so-called luminome'ter. 
It after all is the theoretically correct method of comparison, as it compares 
the lights by that property for which they are used. Curiously enough, the 
luminometer, although it has the reputation of being crude and unscientific, 
thus is the only correct light-measuring instrument, and the photometer correct 
only in so far as it agrees with the luminometer, but, where luminometer and 
photometer disagree, the photometer is wrong, as it gives a comparison which 
is different from the one shown by the light in actual use for illumination. 

"The relation between luminometer and photometer for measuring light 
intensity, therefore, is in a way similar to the relation between spark gap and 
voltmeter when testing the disruptive strength of electrical apparatus: while 
the voltmeter is frequently used, the exact measure of the disruptive strength 
is the spark gap and not the voltmeter, and, where the spark gap and volt- 
meter disagree, the voltmeter must be corrected by the spark gap. In the 



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same manner the luminometer measures the quality desired — the illuminating 
value of the light — but the photometer may be used as far as it agrees with 
the luminometer." 

The development of the American city Ughting system is given on p. 274. 

"In the early days of using arc lamps for American city lighting, lighting 
towers were frequently used, and such tower lighting has still survived in some 
cities. One or a number of arc lamps are installed on a high tower and were 
supposed from there, like artificial suns, to spread their light over an entire 
city district. 

"This method of city lighting was found unsatisfactory, as it did not give 
enough light. It is unsatisfactory, however, not in principle, but becau^ it 
was too ambitious a scheme. If, in street illumination, we double the distance 
between the lamps, each unit must have four times the light flux to get the same 
minimum density, as the distance is doubled, and the flux density decreases 
with the square of the distance. At twice the distance between the lamps, each 
lamp thus must have four times the hght flux, and each mile of street thus re- 
quires twice the power. Reducing the distance between lamps to half reduces 
the power to one-half with the same minimum illumination. In street lighting 
it is therefore of advantage to use as many units of illuminants as possible, and 
bring them together as close as possible, and correspondingly lower their intensity, 
up to the point where the increasing cost of taking care of the larger numbers 
of units and increasing cost of poles and connections compensates for the de- 
creasing cost of energy. There is a minimum which probably is fairly near our 
present practice. 

"When, however, you come to square and exposition lighting, you find 
that the distance between the illuminants has no effect on the efficiency. Let 
us assume that we double the distances between the lamps which light up 
a large area. Then each lamp requires four times the light flux to get the same 
minimum flux density between the lamps, but at twice the distance between 
the lamps each lamp illuminates four times the area, and the total power per 
square mile of lighting a large area, like an exposition, thus is independent of 
the number of lamps used, and, whether you place them close together or far 
apart, you require the same total flux of light, and if you keep the same propor- 
tions of height from the ground and distance between lamps, you also get the 
same variation between maximum and minimum intensity. But, supposing 
the lamps to be placed further apart, the maximum or minimum points also 
are further apart, and you get a more satisfactory illumination by having a less 
rapid intensity variation. That points to a conclusion that, for exposition 
lighting, the most efficient way would be to use a relative moderate number 
of high-power sources of light on high- towers at distances from each other of 
the same magnitude as the height of the towers. We would get a greater uni- 
formity and better physiological effect by having the illumination further apart, 
and they would require the same total light flux, and therefore the same power, 
as if you bring the lamps close to the ground, and place them very close to each 
other. The tower lighting therefore is the ideal form for lighting a large area. 
When the arc was first introduced, it was so much superior to any other illuminant 
known before, that people vastly overrated it. They thought that they could 
light the whole city by it, and in trying to do so these towers would have been 



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the proper way, but very soon it was found that even with the efficiency of the 
arc, to light not only the streets, but the whole area of the city, would require 
an entirely impracticable amount of light flux. It thus was too ambitious a 
scheme for city lighting, but it should be done in exposition work. City illumina- 
tion thus has come down from this first ambition to light the whole city to an 
attempt to light only the streets. For the latter purpose, however, lighting 
towers are inefficient, since much of the light flux is wasted on those places which 
we no longer attempt to light ; in exposition lighting, however, the most effective 
general illumination would be given by white arcs on high towers, leaving the 
concentrated or decorative illumination to the incandescent lamp and flame 
arc, of yellow c6lor." 

Most of us believe that diffused lighting is an ideal, though expensive method 
for interiors; but Steinmetz is by no means dogmatic on this point, p. 279. 

''Furthermore, the relations between directed and diffused light have in 
the illuminating engineering practice been obscured to some extent by the re- 
lation between high and low intrinsic brilhancy and between direct and indirect 
lighting. Thus, to eliminate the objectionable feature of high intrinsic brilliancy 
of he illuminant, direct lighting by light sources of high brilliancy, which was 
largely directed lighting, has been replaced by indirect lighting, by reflection 
from ceilings, etc., which is diffused lighting. Where such change has resulted 
in a great improvement of the illumination, it frequently has been attributed 
to the change from direct to diffused lighting, while in reality the improvement 
may have been due to the elimination of high brilliancy light sources from the 
field of vision, and engineers thereby led to the mistaken conclusion that 
perfectly diffused lighting is the preferable form. Again, in other instances such 
a change from direct to indirect lifting has not resulted in the expected im- 
provement, but the indirect lighting has been found physiologically unsatisfactory^ 
and the conclusion drawn that the elimination of high brilliancy from the field 
of vision has not been beneficial, while in reality the dissatisfaction with the in- 
direct light was due to the excess of diffused light and absence of directed lights 
and this improper proportion between directed and diffused light more than 
lost the advantage gained by eliminating the light sources of high brilliancy 
from the field of vision. In this case the proper arrangement would have been 
to reduce the brilliancy of the light sources, by diffusing or diffracting globes, 
to a sufficiently low value, but leave them in such a position as to give the neces- 
sary directed Ught. 

"Thus, in illuminating engineering, as in other sciences, it is very easy to 
draw erroneous conclusions from experience by attributing the results to a wrong 
cause. Any changes in the arrangement usually involves other changes: as in the 
above instance, the change from high to low brilliancy commonly causes a change 
from directed to diffused light ; by attributing the results to the wrong cause, 
serious mistakes thus may be made in basing further work on the results." 

The reviewer would have been glad to have quoted twice as many pages 
from this extremely interesting book; but it would probably be just as difficult 
to stop then as now. Wilder D. Bancroft 

La Chimie de U Mati^re vivante. By Jacques Duclaux. (Nouvelle Col- 
lection scierUifique . Directeur: Entile Borel.) 12 X 18 cm; pp. 281. Paris: 
Filix Alcan^ ipio. Price: paper ^ j.^o francs. — The headings of the chapters 



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are: the law of chemistry; chemical synthesis; notions of symmetry; the function 
of chlorophyll; the diastases; alcoholic fermentation; organized matter; catalysis; 
chemical equilibrium: chemical infinitesimals; life and death. 

The unsuccessful attemps of Cotton to produce optically active substances 
by the action of circularly polarized light, p. 53, bring up the whole question. 
"We have been forced to assume the existence in nature of asymmetric forces. 
What are they? In the vegetable kingdom, all the compounds are formed orig- 
inally from carbon dioxide and water, both symmetrical substances, under the 
influence of light which is a symmetrical force. The only place where asymmetry 
can come from is the seed The whole vegetable is only a developed seed and 
it is quite conceivable that the asymmetrical forces existing in the seed, in 
consequence of the presence of optically active substances, might cause asym- 
metry during germination or development when they act on carbon dioxide, 
light and water. That leaves us face to face with the question why the seed 
should be as3mimetric. This is as much of a puzzle as the question whether 
the hen or the ^^'g came first." 

From the author's calculation, p. 71, as to the utilization of the sun's rays 
by growing crops, he concludes that less than one percent efficiency is obtained. 
If we could get one hundred percent efficiency we could raise one hundred and 
fifty pounds of potatoes per square foot, p. 74, which would be intensive farming 
with a vengeance. While one percent efficiency seems low, we must remember, 
p. 77, that "in one thousand liters of air there is only one-third of a liter of carbon 
dioxide and perhaps twenty liters of water vapor. A plant which has to nourish 
itself on this mixture is in much the same state as the traveler, who should try 
to drink the water dissolved in the wind of the Sahara." 

We usually call a substance a catalytic agent when it can convert a rela- 
tively large amount of one substance into another without any appreciable 
change in its concentration taking place. The author points out. p. 84, that 
we must be careful in applying such a test because we have a reaction according 
to the law of definite proportions between carbon tetra-iodide and hydrogen 
in which one gram of hydrogen converts five hundred and twenty grams of 
carbon tetra-iodide into hexa-iodo ethane. 

On p. 92, we learn that "although our nourishment seems complicated, 
it is really quite simple since we have only to deal with three classes of food: 
the carbohydrates (starch, sugar); nitrogenous substances (casein of milk, 
albuminoids of legumes or of meat) and fats (vegetable oils, animal fats). 
There are special diastases for each one of these groups. The first, as we have 
just seen, has amylase and its two acids: the second has pepsine, secreted by 
the mucous membrane of the stomach, and also the different diastases of the 
pancreas, among which is trypsine. The third group has lipase. 

"All these digestive diastases have one character in common. Under normal 
conditions their action is one of splitting and they simplify the molecule of the 
substance on which they act, decomposing them into others which are simpler 
and more soluble. Glucose is more simple than maltose and dextrine more 
simple than starch. The peptones, formed by the action of pepsine on nitrog- 
enous foods, have simpler molecules than the foods from which they are formed. 
Glycerine and the fatty acids are also simpler than the fats from which they are 
formed by the action of lipase on the fats or oils." 



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New Books 209 

At first sight it seems as though it ought to be easy to crush the cells of 
yeast so as to obtain the zymase; but the author points out, p. 114, that it is 
rea ly a very difficult matter because the cells are less than 0.0 1 mm in diameter 
and are as elastic as small rubber balls. 

The author is in the Pasteur Institute and naturally is anxious to uphold 
Pasteur's dictum that living matter is essential to fermentation. In the case 
of Buchner's zymase, p. 1 15, it is admitted that there are no cells and that "alco- 
holic fermentation can take place in the absence of any living organism, in the 
sense in which we usually use (he phrase.'* 

The author gets around the difficulty by considering zymase, p. 120, as 
living matter. "The external membrane of a cell is necessary for the continued 
existence of the cell, for, if it were not there, the slightest agitation would cause 
the contents of the cell to mix with the surrounding liquid. It is not however 
a necessary condition of life, at least for a short time. It encloses and protects 
the cell but does not constitute it. Buchner's process of extraction is really 
one of skinning the cell. It takes from the cell its individuality and its defence 
against the outside world ; but not its life, and that is why we find the properties 
of yeast in the juice which has been pressed out. A fiask full of this juice is 
a rudimentary cell. When left to itself, this cell dies like an ordinary cell, 
i. e., it loses its diastasic properties. It loses them less rapidly if one adds sugar, 
because sugar is a food for it even in its mutilated state. It still breathes because 
it gives off carbonic acid spontaneously. Possibly it assimilates because one 
only finds eighty-five grams of sugar in the form of alcohol and carbonic acid 
for every hundred grams of sugar supplied. The other fifteen grams have 
disappeared without leaving a trace, as though they had combined with some- 
thing. Of course those properties which depend on the structiu-e and form of 
the cell or on the presence of the nucleus are completely destroyed. One 
would not expect to see such a giant cell reproduce itself. But, no matter how 
savage the treatment to which the yeast is subjected during the extraction of 
th; juice, there is nothing in the rapid extraction which would cause a chemical 
change in the protoplasm of the cell, since the only substances with which it 
comes in contact are sand and tripoli, both completely inert substances. We 
thought that we were realizing life without a cell and all tha^ we have done 
was to change several millions of resisting cells into a single one which is much 
larger and more delicate. Zymase has not yet been separated from living matter; 
it is still to be discovered.*' 

To the reviewer the p eceding paragraph seems like a case of special 
pleading; but the author's point of view is certainly an interesting one. The 
author's idea that starch is an amorphous crystal, p. 134, is also a novel one. 

"The structiure of the starch molecule enables us to account for its properties 
fairly readily. We understand, for instance, why starch cannot be obtained 
in crystals; its molecule is too complex just as we had been led to suppose. 
We have already seen that a molecule containing six atoms can only form crystals 
which are almost comp!etely lacking in symmetry. Molecules containing six 
hundred atoms will form entirely unsymmetrical crystals with irregular piling. 
This does not mean that the substances are completely isotropic like glass (that 
i», having the same properties in every direction) : but merely that the exterior 
form may be anything. In fact, when we look into the matter more closely, 



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2IO New Books 

we find it necessary to modify what I said at first. It is not absolutely accurate 
to say that organized substances do not oystallize. Many of them do, but 
in the amorphous system. 

"This sounds like a joke and calls for an explanation. Crystals are not 
characterized solely by their external form, by their faces and by the constant 
angles which the faces make. They are also characterized by their optical 
properties and especially by the phenomena to be noted when the crystals are 
examined in polarized light. The crystals, so-called, are not the only substances 
which show these phenomena. Under certain conditions, certain liquids give 
the same results. This has caused people to broaden the definition of a crystal 
considerably and to make it depend much more on the optical properties than 
on the external form. In addition to the crystalline systems of the mineralogists, 
we also recognize the amorphous system for all substances which have these 
properties without having a constant geometrical form. Many of the organized 
substances, and especially starch, belong in this category for it yields under 
polarized light results which are very much like those obtained with crystals." 

On p. 145, the author calls attention to the act that when colloidal solu- 
tions are evaporated to dryness, the solid residue becomes absolutely insoluble. 
"I am forced to insist on the word 'absolutely* because many chemists have 
the bad habit of calling substances insoluble when they are not readily soluble: 
calcium carbonate, for instance, of which a liter of water dissolves three centi- 
grams; barium sulphate or silver chloride which dissolve to the extent of two 
milligrams in a liter of water. The word ' insoluble ' should be kept for colloidal 
substances which usually dissolve to less than one one -thousandth of a milli- 
gram per liter of water. The difference may not appear large if one considers 
the amount of substance per liter of water; but it becomes more noticeable if 
one considers that 500 liters of water would dissolve one gram of silver chloride 
while it would take at least one million liters to dissolve one gram of a colloid. 

"This gives us a very simple reason why certain organisms are composed 
of colloids; insolubility is an absolute essential for existence. We cannot con- 
ceive of fishes whose bodies are soluble in water. It is still more difficult to 
conceive of such a thing in the case of microbes, because their bodies are so very 
small that they would dissolve * nstantaneously in water if they were soluble to any 
extent. The outer membrane of the microbe must resist water indefinitely and 
to do that it must be absolutely insoluble, for microbes are often in contact with 
enormous masses of water. In one experiment of Trenkmann's sixteen hundred 
of the tuberculosis bacilli were kept alive in one centimeter of water although 
this means that a gram of microbes (dry weight) was suspended in an ocean of 
en million liters of water and that the contact surface was ten square meters. 

"This necessary insolubility does not by itself prove that the membranes 
must be colloidal, for the body of a microbe would resist the action of water if 
the microbe were wrapped in gold-leaf which is not a colloid at all. Even if 
we ignore the fact that the skin of the microbe must be permeable to water 
and to certain salts, a condition not fulfilled by gold-leaf, we must remember 
that the membrane is formed by the microbe. In every case in which an absolutely 
insoluble substance is formed by a chemical reaction which does not take place 
too slowly (and that is not the case here), the molecules of the compound unite 
to form micellae and the compound assumes the colloidal form regardless whether 



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New Books 211 

it remains suspended or whether it appears at once as an amorphous solid. There- 
fore the membrane, being insoluble and being formed by the microbe, must be 
a colloid." 

On pp. 250-252, we find some suggestive paragraphs — "In a chapter de- 
voted to life and death, a place should be reserved for the intermediate state 
known as sickness. Death is the final upsetting of all the functions and sick- 
ness is a temporary disturbance of them, in other words a chemical or physico- 
chemical change in some of the functions. It is therefore chemistry which 
must fight against sickness. This is now being done and the number of remedies 
increases day by day. Unfortunately progress is made blindly and as the result 
of luck. If medicine is ever to become a science, we must study and recognize 
a disease before trying to cure it. We must know the way in which all the 
organs act, in other words we must know the diastases which are secreted, the 
equilibria which are maintained, and the reason for everything that happens. 
The study of these matters is simplified very much by the fact that most of the 
functions continue after death even when the organ has been removed from 
the body. This enables us to .make a preliminary classification into independent 
groups. Since each disturbance can be defined and measured by its disap- 
pearance or decrease, or by an abnormal increase in some of the functions, it 
will be relatively easy then to find a remedy. 

"To show that all this is possible, I will cite a case where the physiologists 
have already done half the work. For digestion to take place in the stomach, 
there must be a diastase present, pepsin, and there must also be a certain amount 
of free hydrochloric acid. This can be shown by a purely chemical experiment 
in a test-tube; when there is no acid, the pepsin is inactive. Since dyspepsia 
is due to an insufficient digestion in the stomach, it seemed plausible to attribute 
this to a lack of hydrochloric acid. Once this was recogni^d, it was a very 
simple matter to help things along by increasing the amount of hydrochloric 
acid artificially, in other words by taking a few drops of acid with each meal. 
This is a very good instance of the method which ought to be followed in all 
cases, through it must be remembered that we have found a palliative and not 
a remedy. A real cure will not be effected until the mucous membrane of the 
stomach has recovered the power to secrete sufficient quantities of hydrochloric 
acid. 

"All the functions can be submitted to an examination like that made on 
the effect of gastric juice on digestion. No matter what the disturbance, chem- 
istry can find a specific remedy as soon as the examination is finished. The 
examination must be based in the study of the diastases, the catalyses, and 
the chemical equilibria of which we have recognized the importance in the pre- 
ceding chapters. Above all it must be based on the study of the colloidal 
substances which form the greater part of our tissues. This study has been 
begun along several lines; but, unfortunately, by empirical methods so that it 
is difficult to interpret the results that have been obtained. We have tried to 
go too fast and to draw conclusions applicable in medicine and physiology 
before knowing the exact nature of colloids. It was a bad way to do and 
the result of it is that the word 'colloid* is conside-ed by many merely as a 
■serviceable one to use when putting out new pharmaceutical products. We 



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212 New Books 

must start in again practically from the beginning, making continuous use of 
physical chemistry, as that seems to be our only chance of success." 

Wilder D, Bancroft 

La Stability de la Vie. 6iude htergiHque de revolution des Espkces. By 
FHix Le Dantec. (Bibliothique Scieniifiqtte Internationale.) ij X 22 cm; 
pp. xti + 300, Paris: Filix Alcan, 1910. Price: bound, 6 francs. — ^The book 
is divided into four parts: biology and physics; the language of energetics; 
continuous phenomena; vital energy. There is a good deal in the book, to 
which most people will take exception; and the author is rather given to quib- 
bling, as in the paragraphs on the degradation of energy, page 46. For all that, 
there are many paragraphs which are of great interest. 

On page 11 the author says: ''I believe that life has its place among the 
other natural phenomena, and that biology is only a subdivision of physics. 
I therefore believe that, in biology as in physics, there are fundamental principles 
from which can be deduced consequences which are easy to predict. I believe 
that we may have deductive biology just as much as thermodynamics or mathe- 
matical optics. I also believe that this deductive biology will some day play 
as important a part in the natural sciences as does mathematical physics in 
physics. We can then make experiments which will mean something, instead 
of so-called experiments having no aim and no justification, made by investi- 
gators unfamiliar with scientific method. We shall then be able to say in re- 
gard to certain alleged observations that they are either inacctu-ate or have 
not been interpreted properly. If there is no such deductive biology there is 
no natiural science. I claim that there is a deductive biology and that many 
of its principles are known." 

On page 14, we find the following paragraph: " My views on the inheritance 
of acquired characters have not yet been confirmed by any ftu'ther experimental 
investigation. I hope to show, without introducing any hypothesis, that 
such a verification is absolutely unnecessary and that the known biological 
facts permit us to establish d priori and without possibility of error, a law with- 
out which evolution would be a meaningless word." 

The fundamental principle of the book is summed up as follows on page 20: 

1. A living substance is in a state of stable equilibrium. 

2. When a living substance undergoes pathological changes which do not 
cause death, it either returns to the former stable state, in which case there 
is no specific variation; or it undergoes a specific variation in which case it passes 
into a more stable state than the one it has left. 

This is true enough as the author intends it ; but it is not happily expressed,, 
and it is not very helpful because it does not show the direction of the change. 
What the author really means is that a system changes so as to become better 
adapted to the new conditions. It is of course more stable under those condi- 
tions because it no longer tends to change; but the use of the word " stable "^ 
is misleading. Unless one knows in what way the system is to change, no use 
can be made of the author's generalization, it the author had made consistent 
use of the Theorem of Le Chatelier, page 25, he would have placed his deductive 
biology on a much firmer foundation. Wilder D. Bancroft 



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TEMPERATURE MEASUREMENTS IN AN EXPERI- 
MENTAL CARBORUNDUM FURNACE 



BY H. W. GII.I.ETT 

The following is an account of work done on an experi- 
mental carborundum furnace, with special reference to the 
temperatures attained, the methods of measuring those tem- 
peratures, and the calibration of the pyrometers used. 

The power available in the preliminary experiments 
was from the A. C. lighting circuit, giving up to 200 amperes 
at no volts and regulated by a brine rheostat; in the final 
experiments, that from a G. E. motor generator, consisting 
of a Form K, Type i, 60 cycle, 2200 volt, 40 ampere, 150 H. P. 
induction motor with starting compensator; the motor being 
directly coupled to a Form A, Class 6, 2000 ampere, 35 volt, 
27.4 cycles, 75 H. P. double current generator from which 
D. C. can be drawn direct, and A. C. through a form B-i, 
Type GO, 150 H. P. oil transformer. The generator is 
separately excited by a Form H, Class 2, 125 volt, 26 ampere 
D. C. generator. By adjustment of the transformer ratios 
and the field and exciter rheostats any voltage from o to 200 
may be obtained by steps of about one volt. The voltage 
was measured on a Thomson double scale voltmeter and the 
current either on a 500 ampere Weston instrument, or a 2100 
ampere Leeds and Northrup mercury ammeter, the latter 
being set up permanently in series with the fiunace. The 
mercury ammeter is very satisfactory for student use in a 
university laboratory for such work as the preparation of 
aluminum, where an accidental short-circuit through the 
bath, in student hands, may overload and ruin an ordinar}'^ 
ammeter. 

For the temperature measurements, there were avail- 
able: thermocouples; Wanner, Morse and Thwing pyrometers; 
a Lummer-Brodhun spectrophotometer with rotating sector 
disk; Weston, and Leeds and Northrup potentiometers; tubes 



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214 H' W^. Gill^^i 

of carbon, graphite and carborundum composition, etc. 
These will be described later. 

The electrodes were of carbon, from the National Car- 
bon Co., or Acheson graphite, and varied in size from a diam- 
eter of I Vie'' in the preliminary nms to 2" X 4^^ in the final 
ones. The square or rectangular electrodes were held in 
specially designed watercooled electrode holders of Tobin 
bronze, consisting of a plate 8'' X 4^^ X ''f^" upon which was 
a box 4^^ X 4^^ X 2" high, with *// walls, the box contain- 
ing two tubes of V/ bore, one reaching almost to the bot- 
tom of the box and one just passing through the top, to 
carry the cooling water. Holes were drilled in the projecting 
parts of the base plates, and by bolting two of these plates 
around an electrode, we can offer 16 sq. in. of cooling surface 
on two sides of the electrode. These holders were very 
eflBcient. We have run under such an overload that the 
electrodes would be red hot within an inch of the holder, 
and with a full stream of cooling water, the electrode between 
the two parts of the holder would not be too hot to handle. 
The holders insured very good electrode contacts.* 

The furnaces were built up of Queen's Run firebrick, 
loosely laid together. The walls were in all cases 4^^ thick, 
the width of a brick. The furnaces varied in size from about 
12'' to 20'' long, 12'' wide and 12'' high, inside dimensions, 
taking 15 to 25 kw in the preliminary runs, to 2-]" long and 
the cross-section dimensions shown in Fig. i, taking up to 
50 kw and using about 150 pounds of charge, in the final 
runs. 

The small circles in Fig. i represent gas pipe supports 
running underneath three layers of the brick. Using this 
form instead of a rectangular one, we do away with the waste 
space in the comers and hence have much less unchanged 
charge at the end of the run. The Niagara furnaces as now 
built are of an approximately circular cross-section, the curved 



* These holders may be obtained from Champaign Bros., Ithaca, N. Y., 
at a cost of less than $20.00 for a complete set of four pieces. 



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Temperature Measurements in Carborundum Furnace 215 

side walls being made in movable sections of firebrick set in 
iron frames.* In the old rectangular furnaces there was 
considerable unchanged charge, which was worked up into 
the next charge ^^' p* ^^ In the present form of fiunaces 
almost no unchanged charge is obtained, and what little 
there is is used in the silicon furnaces instead of being worked 
up into other carborundum charges. H. N. Potter' has 
also used it in the manufacture of silicon monoxide. 




Fig. I. — Cross-section of furnace. 

The electrodes in the furnace shown in Fig. i were of 
carbon, 2'' X 4^^ (made up of two 2" X 2") and projected 
through the furnace walls 5V2", this distance being sufficient 
to prevent slagging of the brick walls. Between these was 
built a core 2" wide, 4" high and 16'^ long, consisting of gran- 
ular (crushed) carbon from the National Carbon Co. This 
carbon all passed a sieve of 3 meshes to the inch, 55 percent 
remained on a 6-mesh sieve, 54 percent on a 12-mesh, and 
only I percent passed the 12-mesh. 

The raw materials for the charge were white sand or 
crushed quartz, obtained through the kindness of Mr. F. J. 
Tone, of the Carborundum Co., analyzing 99.4 percent Si02, 
0.4 percent residue from HF treatment, 0.2 percent loss on 
ignition; coke analyzing 83 percent fixed carbon, 10 percent 



* These figures refer to the bibliography at the end of this paper. 



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2i6 H. W. GiUeU 

ash, 3 percent moisture, and 4 percent volatile; sawdust ana- 
lyzing 38 percent carbon; and commercial salt. 
The normal charge was as follows : 



Parts by weight 



53.5 

40.0 

5.0 

1-5 



Sand 

Coke, ground to pass a 14-mesh sieve 



Sawdust 
NaCl 



The equation SiO, + 3C = 2CO + SiC requires 36 
parts carbon for each molecular equivalent, 60.4 parts SiOj. 
The charge given above figures to the ratio of 39.6 parts of 
total carbon for each 60.4 parts SiOj, or an excess of 10 
percent carbon above the theoretical. 

We were led to the use of this charge by a series of runs 
made in the preliminary work. We were using a small cubical 
furnace, a foot on a side, inside dimensions, with a granular 
carbon core 6^ long and iVic'^ diameter. At that time we 
were limited to the low power supply on which about 100 
volts could be obtained across the electrodes at the start. 
Using only the theoretical amount of carbon, ground to 14 
mesh, it was foimd that the runs went smoothly up to a cer- 
tain point, usually about 20 minutes after starting, when the 
power used was about 4 kw. The voltage, which up to this 
point had been falling gradually, would suddenly rise, and 
the current would fall almost to zero. As we could not in- 
crease the voltage enough to force more current through the 
resistor, the run had to stop. On dismantling the furnaces, 
siloxicon was foimd, but no carborundum whatever except in the 
core itself. The carbon grains of the core, however, were cov- 
ered with a yellowish green crystalline coating whose hardness 
and microscopic appearance showed it to be carborundum. 
Compare FitzGerald.* We had practically formed "Silun- 
dum'* in the core, the electrical resistance of which was so 
high that the current could no longer flow. Had we been 
able to raise the voltage suflSciently to force enough ciurent 



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Temperature Measurements in Carborundum Furnace 217 

through to give a high enough temperature to decompose 
this SiC into Si and graphite, the run would have gone on, 
but at the expense of more power. 

We explained this formation of SiC in the core on the 
hypothesis that the first reaction in the charge was SiO, + 
2C = 2CO + Si, the second, xSiO^ + i^Si + 2€ = vCO + 
Si^CyO,, where Si^C^O, represents the oxycarbides known 
as siloxicon. The next reaction is either the decomposition 
of the siloxicon into SiC and CO, or else Si^C^O, + mC = 
^SiC + nCO. The silicon from the first reaction in the outer 
reacting zone of the furnace passes in past the siloxicon in 
the next zone nearer the core, and since the carbon particles 
have become coated with a siloxicon coating through which 
the silicon vapor will not penetrate easily and since the Si 
necessary for the second reaction has already reached that 
point and been absorbed, there is nothing to stay the progress 
of the silicon vapor until it reaches the core itself. There it 
finds carbon at a temperature suitable for the direct reaction, 
Si + C = SiC, and hence we form carborundum in our core. 

A series of runs was made to test this point. Runs 27, 
28 and 29 were made with the theoretical amoimt of 14-mesh 
carbon only, and the silundizing of the core occiured in just 
20 minutes, in all three. Run 30 had a thin layer of sand 
right aroimd the core, and the theoretical charge outside 
this. This should hasten the first reaction and provide 
free silicon vapor right at the core for the direct formation 
of SiC. In this run the voltage fell for three minutes and 
then rose. In 10 minutes the current had dropped to zero. 
The sand was found to be fused, blackened, and the core 
silimdized. In run 31 we used a charge with almost twice 
the theoretical amount of carbon. This nm went on without 
a hitch and was continued for lY^ hours; 210 grams of SiC 
contaminated with carbon was obtained, for an expenditure 
of 8 kwh. The core was perfectly clean at the end of the 
run. 

Then runs with 20 percent and 10 percent excess carbon 
were tried, running ly^ hours, using respectively 9 and 8.3 



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2i8 H. W. Gillett 

kwh. Both went smoothly, the [first giving 310 grams 
SiC and the second 375 grams. The cores were perfectly 
clean at the end of the run. 

This showed conclusively the beneficial effects of an ex- 
cess of carbon, and also showed that better yields were ob- 
tained with the lower amounts of carbon, as long as we had 
enough present to prevent the formation of SiC within the 
core. 

Now if the carbon be present in such large particles 
that they do not enter entirely into the reaction, but become 
covered with a coating of siloxicon too thick for the silicon 
vapor to penetrate, the silicon will pass through to the core. 
Hence the necessity for the excess of carbon. The theoretical 
amount of carbon should suffice if the particles are tiny 
enough. However, if the particles are too small, they will be 
blown away from the places where they are needed, by the 
escaping CO. Thus even a large excess of carbon, in large- 
sized grains, should not be sufficient to prevent the silimdizing 
of the core. To test this, another run was made with the 
theoretical amoimt of carbon only, but ground to 32 mesh, 
over half of it passing a 40-mesh sieve. This run went on 
smoothly in the main, but after about 25 minutes the voltage 
rose to 100, showing that some SiC was forming in the core; 
the ciurent, however, did not fall off so rapidly as in the 
runs with the theoretical amount of 14 mesh. Soon the 
voltage fell again and the current rose, showing that we 
were reading the decomposition temperature of carborundum 
within the core. After i y^ hours the run was stopped. The 
core showed a little SiC on the exterior grains at the points 
nearest the electrodes, and the rest of the granules showed 
distinct graphitization, which is not the case where the carbon 
core is simply heated to the temperatures attained under 
these conditions, but only when some carbide former is pres- 
ent. 300 grams SiC were obtained for 9 kwh showing a 
lower yield of SiC in grams per kwh than in the runs with 20 
percent and 10 percent excess of 14-mesh coke, because of 
the extra power used up on account of the silundization. This 



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Temperature Measurements in Carborundum Furnace 219 

run was just on the ragged edge between success and failure, 
and showed that the coke would have to be even finer than 
32 or 40 mesh if we are to use only the theoretical amoimt. 

As a further check on the size of the grains of coke, we 
made a run with 10 percent excess carbon, the coke being 
grotmd to 12 to 14 mesh, all passing the 14-mesh being 
discarded, whereas in the previous rtm with 10 percent ex- 
cess we used 14 mesh, a large proportion of which would 
pass a finer sieve. In this run the voltage rose and the cur- 
rent dropped oflf to zero in 16 minutes. No SiC was obtained 
in the charge, and the core was found to be silimdized. 

Thereafter we always used 10 percent excess of 14-mesh 
coke, as given in the composition of the ** normal*' charge, 
and never had any trouble from formation of SiC in the core. 

Stansfield ^^' p- ^^^ says that the charge in the carbo- 
nmdum furnace is practically the theoretical, and the 
data of Richards' for coke with the ordinary carbon con- 
tent, are slightly below the theoretical. However, Mr. 
Tone, of the Carborundum Co., told the writer that they 
now use a slight excess of carbon. Some of the Niagara 
charge was secured and an analysis made, which shows a 
proportion of 38.9 parts C for each 60.4 parts SiO, — or an 
excess of 8 percent above the theoretical. The fineness was 
about the same as our normal charge, i, e,, 14 mesh. By 
sieving out the larger particles of sawdust and then getting 
an idea of the relations of sawdust to coke by determinations 
of the total carbon, volatile and loss on ignition, it was foimd 
that the proportion of sawdust in our charge was about the 
same as that used at Niagara. Hence the composition of 
oiu* charge is fully justified. 

Since this work was done and the above written, Tone^ 
has stated that the charge used at Niagara is 35 . i coke, 
54.4 sand, 7 sawdust and 3.5 salt, which is an excess of car- 
bon. This figures, taking the same values for carbon con- 
tent of coke and sawdust as in our materials, to 40.2 parts C 
per 60.4 parts SiOj, against the 39.6 parts we have used, a 
close agreement. 



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220 H. W. GUleH 

In order to study the reactions in, and the behavior of, 
the carborundum furnace, it is necessary to have some means 
of determining the temperature at diflFerent points in the fur- 
nace, since the reactions that take place, and the range 
through which they will occur, are functions of the tempera- 
ture attained, and of the form of the temperature gradient 
throughout the furnace. 

The temperatures reached are far above the range of 
any known thermocouple; hence we are limited to the use 
of optical or radiation pyrometers, or to indirect methods. 
FitzGerald' has used the change in density of carbon to 
show the temperature to which it has been raised. This 
can, however, only, give an approximation to the true value, 
inasmuch as it can only show the maximum temperattwe 
reached. Since there may be, indeed must be, a time factor 
involved in the transformation of ordinary carbon to denser 
forms, it will not show temporary fluctuations. Moreover, 
it does not give the results till the run is over, and it must be 
based at some time or other on actual temperature measure- 
ments, which brings us back to the original problem. 

Confining ourselves, then, to optical and radiation in- 
struments, we need, in order to use these instruments, some 
substance which will be raised to the temperature of the 
furnace at the point where we wish to measure that tempera- 
ture, and a method of sighting on this substance. This means 
a plug of some refractory material at the end of a tube. 

Since we are above the melting points of such refrac- 
tories as alumina or magnesia, we are practically confined to 
three materials, carbon, graphite and carborundum itself. 
The choice of these is determined by their refractory quaU- 
ties, their heat conductivity, and their porosity or permea- 
bility to gases and furnace fumes. 

The question of fumes is a vital one, since in the carborun- 
dum furnace, as in most resistance furnaces, even if made 
up with only a charge of coke or crushed carbon, fumes are 
evolved, which, if not removed, obscure the pyrometer read- 
ings to such an extent that no results at all can be obtained. 



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Temperature Measurements in Carborundum Furnace 221 

Burgess' says that the fume problem is one of the most 
embarrassing phenomena we have to deal with in optical 
pyrometery. Potter and Tucker^" have used a current of 
hydrogen or other inert gas to sweep out the fumes. In the 
tubes used in our work we have used air, for practical reasons, 
inasmuch as the fumes formed as readily in an atmosphere 
of nitrogen as in air or oxygen, and the troubles from oxida- 
tion were not very great, particularly when using carborun- 
dum tubes. 

Two forms of tubes have been used in this work, first 
one of carbon, graphite or carborundum, i V/ O.D., i'^ I.D., 
and 12'^to iS'^ long, according to the size of the furnace, bear- 
ing a tightly fitted graphite plug at one end. Near the 
closed end a hole was bored to take a carbon tube Vj'^ O.D., 
y/ I.D., and about 12" long, fitted in at right angles, thus 
making an elbow tube. A glass tube was then fitted into the 
small carbon tube and all joints between tubes, or plug and 
tube, luted with a paste made of fine carbonmdum powder 
(3 F)i waterglass and water, using as httle waterglass as was 
consistent with getting an adherent paste. This paste was 
also of great value in minimizing oxidation and disintegra- 
tion of the surface of tubes and electrodes. 

Gentle suction from a Chapman pump was then applied 
through a rubber tube slipped over the glass tube, thus sweep- 
ing out the fumes. Attempts to blow out the fumes by a 
blast of air, hydrogen or nitrogen instead of pulling them 
out by suction, showed that suction was by far the more 
efficient, and that it should be applied as near the hot end 
as possible. 

This form of tube was quite efficient up to 1800° C, but 
it had several disadvantages. It is hard to make a mechanical 
joint that will withstand 2000° C without leaking. More- 
over, the fumes condense in the cooler parts of the small tube, 
and if not removed, will choke it up entirely. 

After an hour or so frequent poking was necessary to 
keep the small tube open, and this poking often broke the 



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222 H. W. Gilleti 

tube or joint. Hence a second tube was devised, consisting 
of two tubes, one inside the other, as shown in Fig. 2. 




-grophite <- SiC-^ 

Fig. 2. — ^Tcmperature Tube. 

The outer tube was 2'// O.D., i »// I.D., and 12'' to 18^ 
long and was closed at one end by a very carefully ground 
and fitted graphite plug Vi«'' thick. The inner tube was 
I V/ O.D., i" I.D., and 12'' to iS'^ long, and was placed close 
up against the plug, a notch being cut in the inner end to 
allow the air to pass freely. A carbon tube Vj'^ O. D., V/ 
I.D., and i" to 4^^ long was inserted between the two tubes, 
cutting them out enough to admit it. A glass tube was then 
fitted into the small carbon tube and joined by a rubber tube 
to the suction pump. The joint between the outer and inner 
tubes was packed with fibrous asbestos and the whole made 
air-tight by painting with the carborundum-waterglass paste. 
This tube was highly satisfactory, as by its use the fume 
difficulties at the temperatures reached were reduced from 
the most troublesome factor to the least troublesome. 

This tube, if properly made, will go up to 2300® without 
fumes, by the aid of gentle suction. Above that, or in that 
neighborhood, with very rapid heating, even this tube will 
show some fume part of the time. Directing a blast of air 
into the open mouth of the tube will help considerably. For 
temperatures above 2300° it is best to make the glass tube 
longer than shown in the figure, so as to prevent melting the 
rubber tube. 

The oxidation of the graphite plug in the current of air 
is very much less than one would expect. In runs of 4 to 6 
hours, where 2500° or 2600° was reached, and the temperature 
was above 2300® for a considerable part of the time, it was 
rare that a plug burned through. By making the plug 



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Temperature Measurements in Carborundum Furnace 223 

thicker, or by only using the suction during intermittent 
temperature readings, its life may be prolonged still further. 

One difficulty still remains. At temperatures from well 
below 2000° up, crystals of SiC form inside the tube, and un- 
less constantly poked out with a stout carbon or graphite 
rod, will gradually contract the bore of the inner tube near 
the plug. This must be especially watched in using a radia- 
tion pyrometer where the angular opening is such as to re- 
quire the full field of the plug. 

This formation of SiC crystals is interesting, since it 
must come either from direct sublimation of SiC, by the com- 
bination of Si vapor with the carbon in the walls of the tube, 
or by the direct union of Si vapor with the carbon vapor from 
the decomposition of SiC. Since the crystals formed in as 
great abundance in tubes made of carborundum, without 
much free carbon, we incline to the last view. 

In connection with this it is worthy of note that the al- 
most black carborundum usually obtained is only colored in 
that way when at some hotter portion of the furnace we have 
reached the decomposition point of SiC into graphite. In 
several runs made in the preliminary part of this work where 
the power available was low, we made carborundum without 
reaching its decomposition temperature at any point, as shown 
by the absence of graphite. In every such case the carborun- 
dum was of a greenish golden color. We understand that at 
Niagara whenever they find a portion of the carborundum 
free from this black color, on tearing down the furnace, these 
lighter colored crystals are separated and kept for special 
work, such as making dentist's wheels. If they would be 
content with a smaller yield of carborundum, this light colored 
product could be obtained at will by regulating the tempera- 
ture so as not to exceed the decomposition point. Moissan 
(".p. 353) has made practically pure SiC, which is colorless. 
Acheson*' says the black color is due to opaque crystals of 
free graphitic carbon. 

Let us come back to the question of fumes for a moment, 
and consider their probable composition. They might con- 



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H. W, Gillett 

sist of Si and C vapor, of minute particles of charge carried 
off by the CO, of NaCl vapor, or of the vapor of compounds 
present in the ash of the coke, or formed from this ash, or of 
disintegrated particles from the tube itself. The last cause 
is certainly present, as there is always some disintegration 
of the walls of the tube, which is especially noticeable both 
on the outside and inside, where the tube goes through the 
firebrick walls, just at the junction of charge and outside air. 
The electrodes also disintegrate at this point, the CO from the 
furnace bimiing to COj, which again reduces to CO in con- 
tact with the hot carbon. 

However, the portion of the fumes which condenses in 
the space between the outer and inner tubes, and in the glass 
and rubber tubes, is a white powder which collects into a 
mossy sort of structure. Analysis of this shows it to be 
very slightly attacked by acids other than HF, and to con- 
tain almost nothing but SiO, and CaO. In one of the first 
preliminary runs a carbon tube was placed . transversely 
through the furnace and became filled with fumes. It was 
closed by carbon plugs at each end and allowed to cool undis- 
turbed. Quite a few needle-like crystals were foimd in the 
tube, some of them being i . 5 cm long. They were appar- 
ently hexagonal and showed peculiar etching figures when 
treated with HF. Microchemical analysis showed them to 
contain SiO, and CaO with traces of Na, Fe, and Mg. They 
may perhaps be calcium metasilicate, CaSiO,, as described by 
Allen, White and Wright '^ 

The material for the temperature tubes may be graph- 
ite, carbon, or a carborundum composition. The last is the 
most satisfactory for use in the carborundum furnace. We 
were led to the use of this material by the desire to have a 
substance which, when heated, would have as nearly as pos- 
sible the same temperature gradient as that of the charge. 
Since in the zone nearest the core we have the carborundum 
decomposing to graphite, the only way to get a tube which 
would consist of graphite in the graphite zone and carborun- 
dum in the carborundum zone, and to have the graphite zone 



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Temperature Measurements in Carborundum Furnace 225 

in the tube follow that in the charge as it increased, was to 
start with carborundum, which would automatically decom- 
pose, just as the charge does. How nearly the temperature 
gradients really agree will be discussed later. 

With this idea in view, we requested the National Carbon 
Co. to make up for us tubes containing as much carborundum 
as possible. They took up the problem, and furnished us 
with tubes of various sizes which proved to be very satisfac- 
tory. Though these tubes were made at our suggestion and 
on our order, the makers refused to tell us their composition. 
Analysis shows, however, that the finished tubes contain 
from 70 percent to 80 percent of fairly finely ground SiC, the 
remainder being mainly carbon, either put in as such or de- 
rived from the binder. 

A few rough determinations of some of the physical 
properties of the carborundum tubes were made. They are 
naturally very hard to work and destructive to tools. They 
can be sawed, with the use of some elbow grease, it is true, 
with a saw practically devoid of teeth, the particles of SiC 
torn torn off acting as the abrasive, and giving us a sort of 
band saw. A rapidly rotating carborundum wheel was of 
great value in working the tubes. 

A rough determination of the apparent density (not the 
true density for the air-free material) gave 2.22 for the SiC 
tube, against i . 53 for the ordinary carbon tube. 

Some crushing and transverse tests were made to com- 
pare them with carbon tubes, which are tabulated in Table 
I. The testing machine was a 50,000-lb. Riehl^ belonging 
to the Sibley College of Mechanical Engineering of Cornell 
University : 



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226 



Material 



Carbon 



Carborundum 



H. W. GUleU 

Table I 
Crushing Strength 



Average 

O.D. 

inches 



Average 

I.D. 
inches 



Average 



Broke at 



I 52 
1.56 
1.56 
1-53 



I 



I 
I 

1-53 



50 

54 



1 .00 

1 .00 

1 .01 
0.99 



0.89 
0.88 
0.90 



0.49 
1.48 
I 49 
1.54 



1.53 
I 52 
1-53 



7200 
5100 
6100 
6800 



Strength 
lbs. per 
sq. in. 

6700 
4225 
5490' 
6360 



Aver., 5770 



5400 
5050 
6700 



4720 
4020 
5520 



Aver., 4770 



Formula S 



n/^W-d,^)' 



Material 


Average 

O.D. 

inches 

1.56 
I 52 


Average 

I.D. 
inches 

1.02 
0.88 


Test 
length 
inches 

16.0 
16.0 


Broke at 
pounds 


Strength 
lU. per 
sq. in. 


Carbon 
Carborundum 


160 
280 


2890 
2910 


i< 


1.52 


0.89 


16.0 


220 


2100 




Formula 


-».,' 


P/r, 







Only one transverse test was made on carbon, as at that 
time there was only the one tube of the required length in 
stock. The carborundum shows up slightly less well in these 
tests, but the strength of both materials is of the same order 
of magnitude. 

A test was then made to determine the relative permea- 
bility of the two tubes to gases at room temperature. The 
tubes were closed at one end by a solid rubber stopper and at 

^ Cracked lengthwise at 3000 lbs. 



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Temperature Measurements in Carborundum Furnace 227 

the other with a rubber stopper bearing a glass tube which 
was connected through a manometer to a motor-driven 
Geryk oil pump. All joints and connections were carefully 
shellaced. The dimensions of the tubes are given in Table 

II: 

Table II 



Material 



Carbon 
Carborundum 



Average 

O.D. 

inches 



1.55 
I 52 



A-age ,SfL 



inches 



1 .02 
0.895 



of wall 
inches 



0.53 
0.625 



Height 

of un- 

shellaced 

portion 



5.30 
6.25 



Vacuum 
obtained 
cm Hg. 



19.0 

8.5 



After an hour's pumping the carbon tube showed a 
vacuum of 19 cm of mercury, or y^ atm.; further pumping 
did not increase the vacuum. Under similar conditions the 
carbonmdum tube showed 8.5 cm, or y^ atm. 

On cutting off the pump, neither tube would maintain 
the vacuum even momentarily, though the leakage back 
through the carbonmdum tube was the slower. This easily 
explains why the fumes pass from the furnace into the tubes, 
and shows that, though both are very permeable, the carbo- 
rundum is the less so. 

In resistance to oxidation and durability the carborun- 
dum tubes were distinctly superior to the carbon tubes. Of 
course a tube which has been raised to graphitization tem- 
peratures cannot be used again, since the temperature gradient 
through it the second time will not be the same as that of 
the furnace till the furnace has reached the same condition 
in the second run that it was in at the end of the first. How- 
ever, by making the tubes longer than is necessary at first, 
the graphitized portion can be cut off and the shortened 
tube used again. The second shipment of carbonmdum 
tubes was not quite as dense as the first, and they were not so 
desirable, though their dimensions were more accurate than 
those ordered than the first lot, which were about 0.9'' I.D. 
instead of i.o''. Even these, however, were vastly superior 
to the carbon tubes. 



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228 H. W. Gillett 

In using this form of tube in the actual measurement 
of furnace temperatures, we have several factors to consider. 
We have (i) the temperature gradient through the tube and 
its relation to that through the charge, (2) the uniformity 
of heating of the plug, (3) the difference in temperature be- 
tween the outer and inner surfaces of the plug, (4) the effect 
of the current of air through the tube, and (5) the deviation 
from "black body radiation'' of the plug. Let us take these 
up in order. 

To measure the temperature of any part of the furnace 
by our tube, we must be certain that the difference in tem- 
perature gradient between the furnace is small, in order that 
too high or too low heat conduction through the tube may not 
cause the heat to be drained away from, or piled up at, the 
plug. If we cannot attain this exactly, we must come as 
near to it as possible. This is important when we are using 
simply the plug in the end of the tube, but when we use a 
movable plug to measure the temperature at different points 
through the tube, it is of prime importance. From a theo- 
retical point of view, the carborundum tubes should be the 
best in this respect. 

To test this out, a run was made on three tubes, a carbon, 
a graphite and a carborundum. A furnace was built of the 
dimensions given in Fig. I, and filled with 150 lbs. of the 
normal charge. The tubes were all of the dimensions given 
for Fig. 2, and 12^^ long, and were like that figure save that 
the glass tube was luted directly into the space between the 
two tubes, no small carbon tube being used. The plugs were 
placed against the core, which was 4" high, thus extending 
'//' above and below the plug. The core was built with 
great care as to uniformity of cross section, by carefully 
leveling the charge to the level of the bottom of the electrodes, 
placing parallel sheet iron strips across past each side of the 
electrodes, filling in to the top of the strips with charge, then 
filling the trough thus made with the granular carbon core 
and leveling the top, removing the iron strips, and filling in 
the rest of the charge. The tubes extended through the 



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Temperature Measurements in Carborundum Furnace 229 

wall about i'^ into the open air. They were spaced equally 
along the 16'^ core, i. e., with their middle points 4^^ from the 
middle point of the adjacent tubes, or from the junction of 
core and electrode. Previous runs had shown that the cool- 
ing effect of the electrodes did not extend 4!^ into the core. 
The graphite tube (B, Table III) was placed in the middle, 
the carbon (A) on one side and the carborundum (C) on the 
other. 

Midway between the graphite and carborundum tubes, 
and exactly 3^^ from the nearer surface of the plug (3 '/,«'' 
from the core) was placed the junction of a Pt, Pt 10 percent 
Rh thermocouple, in a porcelain protection tube, the end of 
which has been ground off to a thickness of 0.4 mm, to avoid 
as much as possible the heating lag of the couple due to the 
porcelain wall. Graphite plugs, '/i/ thick, and of such size 
as to slip easily in the tubes, were mounted on small graphite 
rods, and the rods graduated to read the distance of the 
nearer surface of the movable plug from the nearer surface 
of the stationary plug at the end of the tube. By setting 
these movable plugs 3'' from the stationary ones and sighting 
on them with the Wanner pyrometer, we get a means of 
reading the temperature at that point in each tube, which 
may be compared with the temperature shown by the thermo- 
couple at the same distance from the core, which may be 
taken as the true temperature of the furnace at that point. 
The thermocouple had been checked against one certified 
by the Bureau of Standards, read on a potentiometer, and the 
Wanner pyrometer had been checked against this thermo- 
couple by means of an experimental "black body" in a plat- 
inum furnace as well as checked by a spectrophotometer on 
the basis of Wien*s law, as will be explained later. « 

By adjustment of transformer switches and the field 
rheostat of the generator, the power was varied so as to con- 
trol the temperature as desired. 

Tables III, IV, and V give the log of this run. The 
data of Table V are plotted in Fig. 1 1 . 



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230 



H. W. GilleU 




O C Q Q »0 Q O O O 
M ^ r>. On "^ •-• 



O O O O »o »o 
00 On W »O00 On 
fO f*5 -^ ^ -^ -^ 



On' 



o 



B 



^&) 
at" 

-s 5 
8-2 

B* 
i2 



If 



Mi 

a 

S 



CO 



I 



1 1 



> ►-• lo ►^ vO I r^o5 ►^ "^00 O 



«•§. 



& 



<l 



to 



I I 



lO »0 »0 Q »0 
lO fO t^ On ^ 

O M i-i iM C4 



O O O 
On »0 r^ 

^ Th "^ to »o 



O »o O 



O O O O «o 

Q Q M M M 



lO O »o O »o O 
•I fO »o t^ w »o 
Th Th Th Th to to 



I 



O O 



lo O »o to to 

00 r^ to I Q I ^ 

r^ r^ r^ I o I On 

M M 1-4 M IM 



«|. 



& 



o ^ 
to O 



I^^S" 



to O O 
00 r^ Th 
r^ r^ r^ 



8 I 



O 

ON 



IH 1-4 M M M 



a 

s 



^ 

ui 



a 

< 



o 



o 

O Q O 

to O "^ 

O ^ rO 



to O »o 
00 r^ to 
r^ r^ t^ 



to 

8 I 



I 



to 

CO 



f^vO NO On <^ 
vO to to W O 



O O ►^ 00 
sO to 






to 



O O O O O 
lO to to to "^ 



O O I to ^ ^nO Hh 
to ^ I fO O O 00 On 



O O 



85 I 



r^oo I O O 



to 00 

On 00 



S 



r^wvo Ooo n ioOnO too •OQ totoO O 
f^totoo ^ ^ ^ fOf0^to«oO O ^ ^j ^ 

t^ r^ i>.00 0000000000000000 OnOnOnOnOn 



s 



s. 



a 



5 •" X 
^ fe 5" 



;i! 



4^ V U V 2 



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Temperature Measurements in Carborundum Furnace 231 
Table IV 



Time ' Volts ' Amps. K. W. 



' ^^^P; ' Temp. 
I y^ back 



9:35 


•• 


9:50 


80 


9:52 


100 


9:55 


80 


10:00 


90 


10:03 


83 


10:07 


72 


10:15 


67 


10:20 


70 


10:25 


71 


10:30 


69 



station- 
ary plug ' 



170 
200 
225 
300 
320 

310 
300 
290 
290 
290 



13.6 
20.0 
18.0 
27.0 
26.6 
22.3 
20. 1 
20.3 
20.6 
20.0 



2000 ! 1580 



Temp. 
Sic 
tube (C) 
station- 
ary plug 



Temp. 

Sic 
tube (C) 
y^ back 



2CXX) 



2080 
2120 
2160 
2200 
2220 
2220 
2220 
2220 



1515 



1660 



Table V 



Temps, in graphite tube ( B ) 



Time 



9:35 
10:07 



At 
plug 



2000 



back ' back 



18851 1730 



Temps, in SiC tube (C) 



At 



V/' 



1 27/ 



back I plug , back back back 'back I back I back 



1580 2000' 



18601 



1 1 670 



2220 2100 I 2005 1 1930 1 830; 1 7551 1660 



1515 



There was graphite on the end of the SiC tube at the end 
of the run. This showed that we were slightly above the 
decomposition temperature. The highest temperature 
reached was 2220°, plus the correction for drop through the 
plug, to be determined later. The carbon tube was badly 
corroded at the end of the run, the graphite somewhat less 
so, while the carborundum tube was but slightly attacked, 
being in very good shape at the end of the run. The glass 
tube extending into the graphite tube had fused together, 
those in the other two tubes had not softened. 



* The rubber tube on the graphite tube was melting. The glass tube was 
softening. No more readings taken in this tube. 

* At the end of the run the part of the graphite tube extending outside 
the furnace was at 935® when sighted on with the Wanner. The SiC tube had 
not begun to glow outside the furnace. 



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232 



H. IV. Gillett 



Table VI shows the deviations of the temperatures in 
the three tubes at the three-inch point from that of the thermo- 
couple, after the thermocouple lag due to rapid heating had 
been overcome : 

Table VI 



Temp, by thermo- 
couple 



mo 
1 1 70 
1380 
1390 
1420 
1450 
1485 
1495 
Average 
deviation 



Carbon 

o 

+ 5 
+ 35 
+ 40 

+ 35 
+ 20 
+ 40 

+ 55 

+ 30 



Deviations in degrees C 
Graphite 



+ 80 

+ 75 
+ 60 

+ 65 
+ 50 
+ 40 
+ 65 

+ 75 

+ 65 



Sic 



o 
— 10 
— 10 
— 10 

— 5 
— 10 

— 5 
-hio 



At this particular rate of heating there is no noticeable 
error in the readings of the carbon tube up to 1200°, but 
thereafter the error becomes serious. The agreement in 
the case of the SiC tube is uniformly good, holding for a 
range of 400° and for 50 minutes. It is plain that the graphite 
tube gives much too flat a gradient, compared with that 
through the furnace, and temperatures measured in that 
tube by the movable plug give readings above the true fur- 
nace temperature. This is shown not only by the data, but 
also from the foot-notes, as the outer end of the graphite tube 
was at all times much hotter than the outside of the charge. 
The carbon tube was better, but even that gives too high 
readings, while the caborundum tube gives correct readings 
within the limits of error in setting the Wanner pyrometer. 

The second point, the uniformity of heating of the plug 
over the field of view, varying from V/ to i" diameter in the 
tubes used, may be dismissed with a few words. If we use a 
very small core and place the tube so that, say, only the 
lower part of the plug touches the core, that part would begin 



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Temperature Measurements in Carborundum Furnace 233 

to glow first, but even in such extreme cases the field becomes 
practically uniform above 1 200° when explored by the Wanner 
or Morse pyrometers. Using a core large enough to give a 
uniform source of heat as large as, or larger, than the plug, 
no trouble from this source was noted at any temperature. 

The third point, the difference in temperature between 
the outer and inner surfaces of the plug, requires a little more 
attention, since what we wish to measure is the temperature 
clear at the end of the plug, and what is read is the tempera- 
ture at the nearer surface. Measurements were made to de- 
termine this factor, using ^/^^ graphite plugs in SiC tubes. 
The charge was of the normal composition. The method used 
was to insert a second tube in the furnace, the reading on the 
plug in which will show if we are holding the temperature 
constant, then with the temperature remaining constant, to 
insert, one at a time, ^// plugs ground with true surfaces, so 
that four plugs would stack up the just V/, and read the 
temperatures of their exposed surfaces by the Wanner. 

It was found by inserting a solid plug ^/^^ thick that the 
contacts were so good that, within the limits in reading, the 
solid plug gave the same results as foiu* ^/^^ plugs. The plugs 
were jammed in tightly and held in place by a small graphite 
rod. The results follow : 

Table VII 



Temp, visible 

surface 

original 

plug 


Temp, visible 

surface added 

plug V/^ 

back 


1350° ' 


1326° 


1550 
1665 


1524 
1645 


1730 


1712 


2050 1 


2035 


2150 


2136 


2160 1 


2149 



y/' back 



1305 
1508 
1615 
1694 
2020 
2121 
2136 



Correction for 
V plug 



+35° 

+31 

+30 

+27 

+22 

+20 

+17 



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234 ^. W. GUleti 

From 1800® up to 2500® a correction of +20° added to 
the temperature read on the visible surface, will give values 
close enough to the true temperatiu-e at the back of the 
plug. 

These readings were taken with the furnace at a con- 
stant temperature; i. e., practically at a stationary state. 
With very rapid rates of heating the drop will be somewhat 
greater. With large furnaces, and hence a flatter gradient, 
it will be rather less. However, the chief use we had made 
of this correction is in determining the temperatiu-e of forma- 
tion and decomposition of SiC. These were determined in 
fiunaces of the same size as the one used in this determina- 
tion, and with the furnace at almost a stationary state, so 
the conditions are quite comparable. 

Now we come to the effect of the current of air. Al- 
though we only use as gentle suction as will avail to carry off 
the fumes, it is obvious that there must be some cooling ef- 
fect due to it. Whether it will be of such magnitude as to 
affect the readings appreciably, is another question. This 
was tested at several temperatures, sometimes in the regular 
furnace when conditions were favorable, as in cooling down 
from higher temperatures, when the suction could occasion- 
ally be left off for a few minutes without the formation of 
fumes; and sometimes in special furnaces packed with crushed 
SiC, which evolves less fume than the normal charge. For 
instance, at 960° and at 1190° in the later form of the tube 
and at 1740° in the elbow form, no change that could be de- 
tected by the optical pyrometer was noted whether the suc- 
tion was on or off. In the run at 1190° a thermocouple in a 
porcelain tube was inserted into the tube against the plug to 
aid in holding the furnace at a constant temperature. The 
thermocouple readings are lower than the plug temperatures 
owing to the temperattu-e drop through the 2 mm of porce- 
lain between plug and couple. Readings were taken at 3- 
minute intervals : 



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Temperature Measurements in Carborundum Furnace 235 

Table VIII 
Rising Temperatures 



Temp, by thermocouple 


Temp, by Wanner 


Suction 


1 147 
1 149 
"53 


1 184 
1187 
1 189 


off 
on 
off 



"53 
1152 
1 148 
1 146 
"45 



Falling/Temperature 

1187 
1 184 
1181 
"77 
"74 



off 
off 
on 
off 
off 



In the later type of tube we once got conditions so that 
no fumes were evolved for a few minutes at 2000°. No 
difference could be detected whether the suction was on or 
off. Again, at 2200°, the fumes were once slight and when 
the suction was off lay quietly in the lower part of the tube. 
Sighting on the upper part of the plug, and turning the suc- 
tion on full, no change in temperatiu-e could be observed. 
In the double tube a good deal of the cooling effect of the 
incoming air, which cools the inner tube and is itself heated 
before passing by the plug, must be counteracted by the air 
that has passed the plug, cooling off on its outward passage 
and giving up its heat to the outside of the inner tube, which 
thus is heated almost enough to compensate for the heating 
it itself exerts on the incoming air. The air heated by pass- 
ing through a foot or more of tube at a slow rate would not 
be expected to cool the plug very much, and though in theory 
there must be some cooling, it is not detectable by optical 
pyrometers, and hence is negligible. At any rate, we cannot 
get on without the current of air. 

We now come to the last point, the deviation of the 
radiation of the plug from true "black body" radiation. 

All bodies heated to the same actual temperatiu-e do 
not emit the same amount of radiation. For instance, if we 



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236 H. W, Gillett 

look at a glowing carbon strip and a smooth platinum strip, 
both heated to the same temperature, the carbon appears 
to be much the hotter. If we sight an optical or radiation 
pyrometer on the surface of a bath of molten copper, the 
temperature read will be much lower than the true tempera- 
tiu-e of the bath". This is due to the fact that the cop- 
per and platinum both have high reflecting power, and con- 
sequently low emissive power, since for an opaque body the 
sum of the reflecting and emissive powers is unity**. In 
i860 Kirchhoff" brought out the idea of a theoretical 
"black body,'* which is one with |>erfect emissive power and 
zero reflecting power. Synonymous with this, and better 
and more expressive, though less used, is the term "complete 
radiator" <*^» ">. 

If a substance, say platinum, that does not give com- 
plete radiation is made into a hollow sphere, this sphere imi- 
formly heated and the radiation observed through a small 
opening, this radiation will be exactly the same as that of a 
true black body, no matter how far the surface radiation may 
be from complete, because the radiation reflected back by 
any portion of the surface is just great enough to make up 
for the amoimt that is not radiated directly from that por- 
tion of the surface, because of its lack of perfect surface radia- 
tion. In other words, a hot body in the open air rarely 
approximates complete radiation, since almost everything 
reflects some radiation, and does not absorb all that falls 
upon it. Only a body that would absorb 100 percent of the 
radiation falling on it will emit 100 percent of the radiation 
that it is entitled to, barring reflecting power, at that tem- 
perature. On the other hand, in a imiformly heated enclos- 
ure, it is quite an indifferent matter what the hot body is 
composed of, or what its surface is. 

However, if we have a reflecting material, i, e., not a 
complete radiator, in an enclosure, as a sphere or tube, which 
is not uniformly heated, then in this case the reflection does 
not make up for the lack of complete radiation, for the radia- 
tion that is reflected by the surface under consideration 



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Temperature Measurements in Carborundum Furnace 237 

comes from a region of higher or lower temperature than this 
surface. This is not negUgible, since the intensity of the red 
rays emitted by a body at 1300° C is about 130 times, and at 
2000° C more than 2100 times as great as at 1000° C ^^®' p^') 

Hence in determining the ** blackness" of any body we 
have two distinct factors to consider; first the approach to 
complete surface radiation, which means an approach to 
zero reflecting power, and second, the approach to a condition 
of uniform heating throughout the enclosiu-e containing the 
body. If either factor is 100 percent, if either the surface 
radiation is complete, or if the enclosure temperature is ex- 
actly uniform, changes in the other factor will have no effect. 

Most fortunately, lampblack or matt-surfaced carbon 
or graphite, gives, even in the open, the nearest approach 
to complete, or black body surface radiation, of any sub- 
stance known ^'®* p- ^o) (19. p- 177)20 Hence we have only a few per- 
cents or probably a few tenths of a percent of deviation from 
complete radiation to make up by having a uniformly heated 
enclosure in our temperature tube. Moreover, carbon does 
not show selective radiation or absorption (20. p. 327) 21^ hence 
as good an approach to black body radiation shown for a 
single wave-length, say in the red, as used in the optical 
pyrometers, should hold for the total radiation, visible and 
invisible, as used in the radiation pyrometers. 

We have stated above that carbon approaches complete 
radiation; the next question is, is this true not only for low 
red heats, but also for the highest temperatures? Will it 
become more of a reflector, and a poorer black body with ris- 
ing tem|>erature? The radiation emitted of course increases 
with the temperature, but our problem is, will the ratio of 
the emissive and reflecting power vary with changes of tem- 
I>erature? No measurements of this appear to have been 
made on carbon, but for platinum, where we would expect a 
change, if any occiu-s in any material, data are available. 
Waidner and Burgess, in a paper i^^p-^f) published in 
March, 1905, plot the deviation from black body radiation of 
platinum against the true temperatures as a straight line. 



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238 //. W, GtUett 

Now it is stated earlier in this same paper, that Wien's 
law holds for bodies which deviate from black body radia- 
tion, but with different values of the constants. We shall 
deal with this law a little later, but we will anticipate for a 
moment. In this paper by Waidner and Biu-gess, it is shown 
that the Wien law may be expressed as follows : log I = K, -h 

K,;?, where I is the intensity of light of a definite wave 

length, T the absolute teraperatin-e, and K^, K, constants. 
Then for the same intensity we may express it 

log I = c\ + C, g 

where B is the "black body*' temperatiu-e of a body not a 
complete radiator, and C^ C„ the corresponding constants. 
B is the absolute temperatiu-e to which a true black body 
would have to be raised to give equal photometric bright- 
ness. B is always less than T and Cj and C, always less than 
K, and K,. 

Equating the values for the same intensity, we get 

K, + K,^ =Cj + C,g.or^ = '^^ * + K,B' 

or a linear relation between w and . If this relation, which 

follows from Waidner and Burgesses own statements, be true, 
then it is an algebraic impossibility to have a linear relation 
between T — B and T, which is what they are plotting in 
their curve. This impossibility might be straightened out 
if we assume that the constants Kj, Kj, Cj, Cj, are not abso- 
lutely constant. This will be referred to later. But Waid- 
ner and Btugess do not dodge the question in this way, for 
when Lucas" showed that there is a linear relation be- 
tween Y and — , they accepted his results'* and backed 

them up by data of their own. Still later ^'^^ p '^^ they 
give a curve for the radiation from platinum showing a curved 
line relation between T — B and T, which when transformed 



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Temperature Measurements in Carborundum Furnace 239 

into the values of = and ^ shows a straight line relation be- 

tween these two quantities. They do not, however, comment 
on or explain the reason for the discrepancy between this 
curve and their earlier curve, evidently thinking that their 
acceptance of Lucas's results had tacitly corrected their 
first erroneous curve. The two different forms of the same 
curve published by the same people without any explanation 
puzzled us for some time, however. 

Lucas's results, and the later ones of Waidner and Bur- 
gess, then, show that polished platinum is just so far and no 
farther from a complete radiator at one temperatiu-e as at 
another, and while the results of Lummer, and Pringsheim 
(a6) (27)^ which will be referred to later, throw a shadow 
of doubt on this, we may say at least that even for platinum, 
with its great deviation from the condition of a complete 
radiator, there is no definite proof of any appreciable change 
in ** blackness" for wave-lengths in the visible spectrum. 
For other wave lengths, see Coblentz". Hence for carbon, 
which deviates so little anyway, we are pretty safe in assum- 
ing no great increase in this deviation. Waidner and Biu*- 
gess point out^**'^*^^ that this constant deviation need 
only hold in case the substance undergoes no chemical change 
during the range of temperature used. It will probably be 
safer to except also changes of state, such as metal passing 
through an inversion point, or from the solid to the liquid 
state <"• P ^' ^> ^^' P- ^5) (^. p. u)^ On the other hand, see curve, 
Waidner and Burgess ^^s. p. 186) 

Since our graphite plug, if graphitized at a high enough 
temperature, will not change through our temperature range, 
this need not worry us. Thus we know that the emissive 
power of our plug will not grow worse with rising tempera- 
tures; on the other hand, the fraction of a percent it lacks 
of complete surface radiation will be more and more made up 
as oiu- tube becomes more uniformly heated through the flat- 
tening of the temperature gradient right at the plug with 
higher temperatiu-es. 



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240 H. W. GiUeU 

Hence we expect that the deviation of our tube from 
trUe black body radiation will be very small at the worst. 

One precaution is necessary; polished graphite has con- 
siderable reflecting power. In an unpublished observation 
by Mr. V. Skillman, of this laboratory, a layer of graphite 
powder was placed over half of the bottom of a very smooth, 
polished graphite crucible and the whole heated to about 
1750° in an Arsem vacuum furnace. The polished graphite 
read much lower than the powder, when sighted on with the 
Wanner pyrometer, although Arsem'® states that all 
bodies heated in the vacuum furnace show black body radia- 
tion. Hence care was taken to make all plugs with a dis- 
tinctly matt surface. Oxidation of the surface of the plug 
during use will tend to increase the ''blackness*' through 
pittting ^'^ P *°\ When we deal with total radiation instead 
of monochromatic radiation, the "blackness** of bodies 
that are not complete radiators increases with the tempera- 
ture ^"' p* '''\ hence we are running under still more favorable 
conditions in this case, with rising temperature. 

The uniformity of heating may be tested qualitatively 
up to 1750° C by holding a piece of smooth platinum against 
the plug at the end of the tube. If the tube is uniformly 
heated, the platinum will give off black body radiation, and 
be invisible against the carbon. The degree of visibility 
will show something of the error present through lack of 
uniform heating, i. e., it will tend to show how much of those 
few tenths of a percent the graphite plug lacks of being a 
complete radiator, we are making up. At 1100°, in oiu* sec- 
ond form of tube, the platinum is quite visible, but at 1500° 
one has to know just where it is to find it against the plug, 
and above 1600° it is lost entirely. Lampen'* has at- 
tempted to determine whether a hot plug showed deviation 
from a black body, by placing a bare thermocouple near it, 
or one in a i mm thick fireclay protection tube, directly 
against it, and reading the temperatiu-e of the plug by the 
Wanner pyrometer. This was compared with the thermo- 



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Temperature Measurements in Carborundum Furnace 241 

couple reading, and was always higher, sometimes by 20- 
25° C. 

Now unless the thermocouple is actually in contact 
with the plug, it will read low (see Table VIII, where we 
have a difference of 40® for 2 mm of porcelain). Now if 
the plug shows deviation from black body radiation, it will 
also read lower than the true temperatiu'e, since no body 
at the same photometric brightness as the black body can 
have a higher temperatin-e. Hence, if both the methods 
of reading may give us low results, an approximate agreement 
between them tells us little or nothing as to the true tem- 
perature of the plug. 

However, we can really test the "total blackness" of 
our plug, that is, the effect of both the factors that affect it, 
combined, by the application of Wien*s law, and to this we 
will now turn oiu* attention. 

In 1896 Wien" took up the problem of the distribu- 
tion of energy in the spectrum of a black body. He found 
that the energy for a given wave length was expressed by 

I = CiA-«e-^^*r, 

where I is the energy, or intensity of light corresponding to 
wave length A, T the absolute temperature of the black body, 
e the base of the Napierian system of logarithms, c„ c, and n 

constants ^*9. p. 183) (aa. p. 204) 

For a black body, n is 5<*7.p.7i7) fhis formula was 
checked by several observers and found to hold for the visi- 
ble spectrum, but deviations were found for longer wave 
lengths. Planck, however, deduced a similar expression from 
purely thermodynamic principles. This holds for all wave 
lengths and is 

When this is expanded in a power series, we get an expression 
the first term of which is the Wien equation given above, 
and further terms of which are negligible for wave-lengths 
in the visible spectrum". Waidner says ^'** ^ 5'\ "For the 



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242 H. W. GUleU 

wave-lengths of the visible spectrum, Wien's equation 
represents the results of experiment with every required de- 
gree of precision, since for values of T not exceeding 3000, 
Wien's and Planck's equations differ by less than i percent. 
The former may, therefore, within the visible spectrum, be 
used for extrapolation to the highest attainable temperatures 
(4000® C or more)." 

Now consider the Wien equation. Taking the natural 
logarithm of each side we get 



putting 
we get 



log I = log q — n log k— ^Xogcj^. 
log ^i — ^ 1^ A = Kj and y log e = K„ 



I 



logI = K,-K,^. 

Waidner and Biu-gess ^"' ^ "**^ err in giving this without 
the minus sign before the second constant, which would 
show the intensity of the light to decrease with rising tem- 
I>erature, which is absurd. 

Now we know that the intensity of light varies as the 
square of the distance, so if for any two intensities I^ and I,, 
at temperatures T^ and Tp we have the distances x^ and re,, 
we get 

li ^/ c^X-^(^<'*l^'^i' 
Taking logarithms again, we have : 

log lo — log li = 2 log x^ — 2 log Xj = ^' log e{^^ ■" t )• 
Then let 

and we get 

log x^— eg ^, = C (^ — ^ j. 

But if we measiu-e the temperature of the hot body at some 



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Temperature Measurements in Carborundum Furnace 243 

temperature Tj by any convenient means, we have a meas- 
urable X, corresponding to it, and knowing C, the only un- 
known factors left are x^ and T^ . 
We may write the above as 



log Xo = (log x^ + ^J—Q ^ 



Here C and the expression in parenthesis are constants, and 
we may write 

logxo = R— C Y» 

which is a linear relation between log x^ and ^ . When we 

have a means of measiu-ing x^, we know T^, and on this is 
based a method for the calibration of optical pyrometers, 
of which we shall shortly make use. 

Wien's law applies to bodies which are not complete 
radiators as well as to the black body, Cj, Cj and n varying 
with the nature of the substance ^"' ^^'^^ Since all of 
these save c^ cancel out in the equation as we shall apply it, 
we are concerned only with that, and so will consider its 
constancy and value. 

Lummer and Pringsheim" say that c, has a progres- 
sive variation such that the curves plotted between log I 

or log x and ^ are convex to the ^ axis. In the data given 

in the literature we often find that the values for c^ for what 
is intended to be a black body, are considerably greater at 
the lower temperatures than the mean value for all tempera- 
tures. It is quite possible, though no one seems to have 
|K)inted it out, that this is due to the greater deviation from a 
condition of uniform heating right around the hot body in 
the ordinary electrically heated "black body" at the lower 
temperatures. In this connection, see Day and Sosman ^^^ p- '°*^ 
At all events, in those experiments in which the workers 
consider that they attain most nearly to black body condi- 
tions, and especially at the higher temperatures, the values 
for c, become more and more constant, and the value usually 



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244 H. W. GilleU 

taken, c, = 14500 for a complete radiator, is perhaps the 
means of all reliable determinations. Nutting*^ gives c, 
as 14500 ± 300, which seems to be about the proper limits 
to set. Inasmuch, however, as the value for c, given by 
bodies that are not complete radiators is higher than that 
given by the black body, we incline strongly toward the 
lower value of c, for a complete radiator. Moreover, Hol- 
bom and Valentiner'* in the most recent careful work on 
the value of c,, give, as the result of some 140 very careful 
and closely agreeing determinations, the value 14200 ± i 
percent. Their temperatures to 1600® C were based on the 
nitrogen thermometer. This leads them to the figure 1789® 
C for the melting point of platinum. The difference in the 
values used for c, largely accounts for the failure of the figure 
1753° obtained by Waidner and Burgess" to check with 
this figure, and Waidner" says that on account of the un- 
certainty in the value of c, further work must be done on the 
determination of this constant. It is to be hoped that Day 
and Sosman, at the Geophysical laboratory, will take up this 
problem, since their nitrogen thermometer has undoubtedly 
been brought to the highest state of perfection yet attained, 
and an extension of their very careful methods to this ques- 
tion would do much to clear away the uncertainties now at- 
tending the measurement of temperatures above 1600® C. 

We shall refer again to the value of c^ 

Many references on the subject of black body radiation, 
Wien's law, and the value of c^ have been consulted, and 
will be found in the bibliography^ **• ^*\ Chwolson, in 
Vol. 2, Part I, and Vol. 3, Part i, of his Traits de Physique, 
gives a good summary of the whole subject, and a copious 
bibliography. 

Now since C in the equation, 

log x^ = R — C i 

depends on Cj and X, and gives the slope of the log x^, =^ 
curve, this slope will give us a means of testing the deviation 



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Temperature Measurements in Carborundum Furnace 245 

from black body radiation of our tube, because for bodies 
that are not complete radiators, c, is greater than 14500, or 
14200, whichever is the true value. A slope which figiu*es 
back to a large value, say 15000, would show considerable 
deviation, while one close to 14200 would show that we are 
getting practically black body radiation. 

In order to determine this deviation by the application 
of Wien's law to our problem, we must have some means of 

I X ^ 

measuring the ratio f, or -2 • 

The spectrophotometer is such a means. 
This instrument** in the form used in this work 
(Fig. 3), consists of two collimator slits, A and B, and two 

rnJB 



TlN VW g) rg3 



D E F G 

Fig. 3. — Diagram of Spectrophotometer. 

lenses, C and D, which transmit light from two sources through 
a Lummer-Brodhim comparison cube, made of two totally 
reflecting prisms with such a figure etched or ground upon 
their faces as to give a quadruple field by which the intensity 
of the two lights may be matched. Both Fleming ^^ p ^s?) ^nd 
Lummer and Brodhun*^ give drawings of the field. 

This field is now viewed through a series of direct vision 
prisms F, and a lens G. A small telescope eyepiece, which 
may be removed at will, fits in at I, back of a cross-hair. The 
system of prisms, lens and eyepiece may be swung over a 
graduated scale, so as to allow setting for any desired wave 
length, and may be clamped in position. Thus we use prac- 
tically monochromatic light. If then, we set the instrument 
to use red light (0.66/1), and place two sources of light of 
the same intensity before A and B, at equal distances from 



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246 H. W. Gillett 

the slits, with the slit width of A and B the same, the dis- 
tance of A and B from E the same, and of the absorption of 
light through both collimator systems is the same, the fields 
will be equally illuminated. Or, if one light source is of 
greater intensity than the other, it may be put at such a dis- 
tance from its slit that the fields again match. Meastuing 
the distances from light sources to slits gives us x^ and x, 
for our formula. 

The spectrophotometer used in this work was loaned 
by the Department of Physics, and was the instrument used 
by Prof. E. L. Nichols in his work on Theories of the Color 
of the Sky**, with the single difference that the Nicol prism 
shown in his diagram was not used. 

Theoretically, there are two ways in which the instru- 
ment might be used: knowing the temperature of one light 
source, we may vary its distance from the instrument, and 
also vary the distance of the other light, or with a source 
of light that cannot be moved, as a large electric fiunace, 
we may vary the distance from that source, of the whole 
system, instrument and other Hght source. Or with a Hght 
source of constant intensity at a constant distance from the 
instrument, we may vary the distance of the whole system 
from the unknown source. Then knowing the distance and 
temperature of the source whose temperature is thereafter 
to be sought, for any one temperature or for any range of 
temperature, we can figure the value for unknown higher 
temperatures from the distances corresponding to them. 

In a way, the first method would be the easier, since we 
may bring our known sources nearer if we get to distances 
from the unknown source which are inconveniently great. 
The second method requires either a very long room or a means 
of cutting down the intensity in a known ratio. 

We started by trying the first method, but the results 
were ragged and not satisfactory. To find out why, we 
compared tungsten lamps, the required voltages of which 
for equal intensities had been determined by substitution 
at the same distance from one collimator slit, against another 



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Temperature Measurements in Carborundum Furnace 247 

lamp run at a constant voltage at a constant distance from 
the other collimator slit. Then we placed the two lamps 
that were of equal intensity, as shown by substitution in 
this way, at equal distances from the two slits, and the slits 
were set at exactly the same opening (determined by cali- 
brating the graduated drums of the sHts by a microscope 
with micrometer eyepiece), all conditions such as slit dis- 
tances from the cube, etc., being rigidly the same. The 
fields, however, did not match, which meant that absorption 
of Ught through the two colHmator systems was not the 
same, and, though a long series of trials was made, we could 
not hit upon any ratio of slit widths that would compensate 
for this so that the light sources could be interchanged. The 
Physics Department reports the same diflBculty with an ex- 
pensive spectrophotometer recently made for them imder 
the direction of the German Reichsanstalt. 

Hence we were forced to fall back on the second method; 
keeping the tungsten lamp used as constant comparison 
source at a constant distance from the instrument. The in- 
strument was moimted on a portable stand and the lamp 
mounted on a rigid bracket attached to the stand. The posi- 
tion of the lamp relative to the slit was thus kept constant. 
The width of both slits was kept constant (with one iminten- 
tional exception to be noted later), the position of the tungsten 
lamp (a 25 watt rosette type) on its axis was kept constant, 
the distance from slits to cube was constant; in fact the 
whole system was kept rigidly the same. Pieces of uniform 
ground glass were placed before each slit, as otherwise an 
image of the lamp was formed, and care taken to keep these 
glasses, the lamp, and cube clean. It would not matter 
whether the two ground glasses were the same or not, since 
the method we use makes the absorption in each collimator 
system immaterial as long as it is the same throughout 
the series of measurements. 

The correct positions of the comparison cube so as to 
give the same portion of the spectrum from each source was 
regulated by testing the instrument with sodium flames be- 



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248 



H. W. GilleU 



fore each slit, using the eyepiece, which is removed when 
we make the fields. If the cube is set correctly, and the 
collimator tubes are at right angles, the sodium flames will 
coincide. When this condition has been obtained, the cube 
is clamped in that position. 

The point at which to set the prism system was deter- 
mined by calibrating the scale over which that system plays 
by means of the Na, Li, and Tl flames. 



Table IX 



Flame 



Tl 

Na 
Li 



0.535 
0.589 
0.671 



Scale reading 

350 
3 675 
3 925 



Plotting this, we get 3.90 on the scale equal to 0.665 ± 
0.005 since the scale divisions were so small that the accuracy 
of setting was not over two-tenths of a small division. The 
pointer was set at 3 . 90 as closely as possible and kept clamped 
at that point without once disturbing it, throughout the 
whole series of measurements. Thus X is kept constant. 
Whether X is 0.655, 0.665 or 0.675 does not affect the ac- 
curacy of our pyrometer calibrations made from the log x, 

y= curve, an iota, but it does affect the value for c, deduced from 

that slope. Since C, the slope of the curve, equals -, log e, 

we get, since log e = 0.4343, the following table, assuming 
different values of A and of c^ : 







Table X 
Value of ( 

>l = 0.660 

4854 
4770 
4687 


'^ 








X = 0.065 

4818 

4734 
4646 


X = 0.670 


^2 = 
C2 = 
C, = 


14800 
14500 
14200 


4797 
4700 
4602 



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Temperature MeasuremetUs in Carborundum Furnace 249 

We shall come back to this in the discussion of our ex- 
perimental results. 

The constancy of the wave-lengths we are using, then, 
•is assured, but there are several other variables about this 
type of spectrophotometer that we must look to. The slits 
move in the collimator tubes and care must be taken to have 
them exactly perpendicular. The whole instrument must 
be set up in a straight line with the axis of the temperature 
tube, which may be attained by sighting across the instru- 
ment, by noting the shadow cast on the instrument by the 
projecting part of the slit holder, and by the use of a trans- 
lucent screen in front of the slit, by aid of which the instru- 
ment may be so set that the sUt is in the center of the light 
spot. 

Let us now consider for a moment the comparison light. 
This was a 25 watt tungsten lamp rated at 112 volts. It 
was aged at 1 10 volts for 24 hours, and in use was run at 92 
volts. Even carbon lamps aged in this way and then run 
below their rated voltage remain very constant ^'^ ^' ^°^ 
and the tungsten lamp is even better in this respect, since 
Ives and WoodhuU ^••^ found that after two months daily 
running for 4 to 7 hours, a timgsten lamp had changed in 
the voltage required to give 16 c. p., less than two-tenths of 
one i>ercent. 

This assures the constancy of our light source, if kept 
rigorously at the same voltage. This was taken care of by 
using an adjustable Riihstrat resistance and a Weston stand- 
ard portable A. C. and D. C. voltmeter with temperature 
adjustment, external resistance being put in series with the 
voltmeter by a resistance box so as to bring the reading for 
the desired voltage on the most sensitive portion of the scale. 
A. C. was used simply because the spectrophotometric work 
was done at night, and the University D. C. went off at 10 
p. M., while the A. C. was on till midnight. As the lighting 
load is not heavy at night, and does not fluctuate greatly, the 
voltage stayed quite constant, and only slight adjustment 
of the rheostat was needed. 



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250 H. W. GiUett 

A second lamp was calibrated, so that the voltage at 
which to run it gave exactly the same intensity by substitu- 
tion as the standard, was known, and was kept in reserve 
against accident to the standard. 

The log jc, Y curve was taken with the spectrophotom- 
eter on an experimental black body consisting of a graphite 
plug inside a carbon tube heated in a platinum woimd tube 
furnace. This black body was made up with the same rela- 
tive dimensions, with graphite diaphragms placed at pro- 
portional distances, and in every way as much as possible 
like the ones pictured in references 19, 22 and 25 in the bibli- 
ography. The true temperature of the black body was read 
by a Pt-Pt 10 percent Rh thermocouple and single pivot 
galvanometer with zero adjustment. Two such couples were 
calibrated in a platinum woimd fiunace to 1470® against a 
standard couple whose cold junction was kept in melting ice. 
This couple belongs to the Physics Department and has been 
calibrated by the Bureau of Standards, so that all our tem- 
perature measurements finally rest on this. The tempera- 
ture of the standard couple was read on a Leeds and Northrup 
potentiometer. Our two couples were absolutely identical 
and the deviations from the Bureau of Standards couple 
were small. A calibration curve was plotted by which all 
readings were corrected. One of these couples was used 
throughout the work and the other kept as a secondary 
standard and the working couple periodically checked against 
it. The following data (Table XI) and the corresponding 
points on the lower curve I in Fig. 5 were obtained in the 
nms on this black body. The distances were measured with 
a Keuflfel and Esser tape. Sufl5ce it to say here that the 
radiation is shown to be black body radiation within the 
small limit of error in reading the thermocouple and spectro- 
photometer. 

It is also of interest to note that the temperatures read 
by the Wanner pyrometer, which is calibrated to read " black 
body temperatures," ^'^'P'^'^ check the temperature as given 



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Temperature Measurements in Carborundum t^urnace 251 



by the thermocouple within the limits of error in set- 
ting the pyrometer, as shown in Table XII. This checks 
the Wanner calibration, as well as our assumption that we 
are getting practically black body radiation. This Wanner 
pyrometer had been checked against another which was 
certified to as correct within 1° at 1000°, 1200°, and 1400°, 
by the Reichsanstalt, throughout the range over which both 
were sensitive, and found to agree within the limits of set- 
ting: 

Table XI — Wien's Law Curve — Spectrophotometer on Black 

Body in Platinum-wound Furnace 

Run of Dec. 5. 



OistAocc 


Temp, degrees 




I 


X in inches 


abs. by thermo- 
couple 

1628 


1 Logx 

1 


1 ^ . 10-* 


53-2 


1.726 


614 


59 


1662 


1. 771 


602 


61.5 


1668 


1.789 


600 


56.0 


1643 


1.748 


609 


54-2 


1633 


1.740 


612 


47 


1613 


1.672 


620 


42.5 


1581 


1.628 


632 


38.4 


1562 


1584 


640 


35-3 


1527 


I 548 


655 


31 9 


1497 


1.504 


667 


28.1 


1478 


1-447 


677 


243 


1445 


1.386 


692 


20.2 


1395 


I 305 


717 




Run of 


Dec. 6. 




24.4 


1425 


1.387 


699 


27.2 


1450 


1-435 


690 


30.1 


1475 


1.478 


678 


33 2 


1498 


1. 521 


667 


39 I 


1531 


1-592 


653 


43 


1559 


1.663 


641 


47.8 


1585 


1.679 


631 


53 


1609 


1.724 


622 


60.1 


1653 


1.779 


605 


657 


1667 1 


1. 818 


600 


70.4 


1683 


1.848 


594 


80.0 


1715 


1.903 


583 



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^52 //. W. GUleti 

With the slit width used (1.80 on the drum) the field 
was so faint at first that accurate settings could not be made 
below 1122° C (1395° Abs.). A wider slit would have meant 
inconvenient distances at very high temperatures. For 
fear of injuring the platinum wound furnace the highest 
point taken was 1442® C (1715° Abs.). 

Day and Sosman ^^ p '*^^ have shown that the thermo- 
couple temperature scale, as usually given by extrapolation 
above the copper point, leads to low results at the higher 
temperatures as compared with the nitrogen thermometer, and 
Waidner^'^'P ^^ gives a correction table. 

The results here given have not been corrected, since the 
Bureau of Standards calibration of the standard couple may 
have been made on the basis of their 1546° determination 
of the melting point of Pd, which is in fair accord with the 
results of Day and Sosman. If the corrections were applied, 
they would change the slope of the curve but slightly, and 
what change would be made would be in the direction of a 
lower value for the slope, and hence a lower value for c, of 
the Wien equation, and would tend to show an even more 
complete approach to black body radiation from our tem- 
perature tube. 

Table XII — Temperatures of Black Body in Platinum Fur- 
nace 

By thermocouple By Wanner 

1165° 1167^ 



1200 
1238 
1280 
1321 
1324 
1345 
1370 



1205 
1236 
1276 

1323 
1318 

1341 
1367 



1375 1378 

1430 I 1427 

The thermocouple was in a porcelain protection tube 
which was inserted into a hole bored in the graphite plug. 



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Temperature Measurements in Carborundum Furnace 253 

The position of plug and couple could be varied by several 
centimeters inside the furnace without changing the reading 
of the couple, hence the results are not open to the criticism 
we made on Lampen^s. 

One run was made with the bare couple inserted in a 
tiny hole in the plug. Agreement of couple and Wanner 
was good up to about 1200°, when carbide was formed in 
the couple, and the readings became erroneous and the couple 
brittle. The couple was .cut off back of the crystallized 
position, fused together in the oxyhydrogen blast, the re- 
sistance of couple and leads again adjusted to the proper 
value, the couple annealed at white heat by an electric ciurent 
and the couple again calibrated against the secondary stand- 
ard, when it gave the same readings as before. 

It is worthy of note that in this run the platinum was at 
no time visible against the graphite, showing that we had prac- 
tically a uniformly heated enclosure. 

The data on the platinum furnace are necessary to give 
the distance corresponding to known temperatures with the 
spectrophotometer, and also give information on the slope 
of the Wien's law curve and the value of Cj. The next step 
is to get a similar curve for the regular temperature tube. 
Comparison of the two slopes will show the deviation from 
black body radiation of our tube. 

In the work with the regular tube, the crux is really 
to determine the true temperature of the surface of the plug. 
(Compare abstract of report of work of Reichsanstalt for 
1908 ^'®\ First we tried inserting a porcelain pyrometer 
tube 2 mm thick between the two tubes shown in Fig. 2, 
cutting in the plug to receive the end of the tube, a recess of 
such depth that the junction of the couple was just at the 
level of the surface of the plug. With this arrangement 
the Wanner read from 50° to 150° higher than the couple, 
the diflference decreasing as the temperature rose. Now the 
'* black body*' temperature shown by the Wanner cannot be 
higher than the actual temperature, since that would mean 
that the body was giving more than black body radiation, an 



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254 



//. W. Gilleti 



impossibility; hence the trouble is due to the slow heat con- 
ductivity of porcelain, with consequently too great a drop 
in temperature through the porcelain. 

The next attempt was made by grinding down the end 
of the porcelain tube to a thickness of 0.4 mm. This was 
then placed tightly against the plug, in a depression 0.4 
mm deep, and the thermo junction made very small, to allow 
close contact with the porcelain, and thus prevent lag. This 
gave somewhat better results than before, but the readings 
of the couple were still too low. 

Though these Berlin porcelain tubes do not soften ap- 
preciably throughout at 1600°, they showed a fusion of the 
glaze at between 1200*^ and 1400®, so that the jimction be- 
came embedded in the glaze, and the tube had to be broken 
to get the couple out. This was remedied by putting a tiny 
pinch of pure A1,0, in the porcelain tube before inserting 
the couple, so as to get a dust of A1,0, over the inner surface 
of the tube, and keep the junction from actual contact with 
the glaze. 

An attempt was next made to determine the tempera- 
ture of the back of the plug by inserting it in a bath of cop- 
per, as shown in Fig. 4, and taking the temperature of the 
copper with a thermocouple. 



thermocouple tube 




Toture tube 



Fig. 4. — Copper Bath for Black Body Radiation. 

The crucible was turned out of Acheson graphite and 
fitted with the usual inner tube, as shown. Outside the cru- 
cible the usual outer tube was fitted on. The crucible was 
placed in a resistance furnace for crucibles with a granular 



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Temperature Measurements in Carborundum Furnace 255 

carbon core, after the style of the furnace recommended 
by Fitz Gerald^* and Tucker,^' and heated. It was neces- 
sary to place the core as shown by the dotted square in 
Fig. 4, as otherwise the crucible itself formed too great a part 
of the resistor, and its walls got hotter than the contents, giving 
us a tube having a temperature gradient with a hump in it. 

By heating slowly and stirring the copper we can get 
the temperature of the inside surface of the plug, and by 
using plugs of known thickness and proceeding as was done 
in the work on the temperature drop through the plug in 
the regular tube, we can extrapolate back and find the tem- 
perature drop through the plug from copper to open air. 
This was done, and for temperatures of 1083® and 1133® it 
was found that the extrapolated temperatures of the back of 
the plug, determined by the Wanner, and the true tempera- 
tiu'e as shown by the thermocouple, checked within less than 
five degrees, or as close as the Wanner could be read. This 
shows that we have practically black body conditions in this 
tube. But we have more ideal conditions as to uniformity 
of heating of the cavity right aroimd the plug, and the tem- 
perature gradient right at the plug is not so steep. Besides 
this, we have the uncertainty of an extrapolation. Hence 
the results are not conclusive for the regular tube. 

We got 1083® for the melting point of pure electrolytic 
copper, against the usual value of 1084® — and that of Day 
and Sosman, 1082.6®,*' thus checking our thermocouple 
calibration nicely. The cold junction of the thermocouple, 
with this arrangement, was near the furnace, and to keep it 
and the leads and galvanometer at uniform temperature, the 
couple and leads were threaded through a condenser bearing 
a thermometer. Cooling water was then run through the 
condenser at such a rate as to keep the thermometer in con- 
tact with the cold jimction inside, and one at the galvanom- 
eter, at the same temperature, which could then be used in 
correcting the thermocouple back to the cold junction tem- 
perature used in calibration. 

In using the crucible with the inserted tube it is neces- 



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256 



H. W. GiUett 



sary to pour out the copper while still molten, since if it soUd- 
ifies, the crucible splits in two, because the expansion before 
melting in the next heat is so great, and because free motion 
is prevented by the projecting tube. 

The next step was to try a platinum plug in the end of 
a porcelain tube inserted between the outer and inner tubes 
of the regular temperature tube, instead of one of solid por- 
celain. A porcelain tube open at both ends was tightly fitted 
with a little platinum cup made of foil o. 2 mm thick, so shaped 
as to give a flat platinum diaphragm at the end of the tube. 
The tube was so inserted that the platinum rested tightly 
against the plug, and the thermojunction was then pressed 
tightly against the platinum. Save for the drop in tempera- 
ture through 0.2 mm. of platinum, which should be negUgi- 
ble, we thus measure the actual temperature of the surface 
of the plug. 

It was recognized that the platinum cup, being in con- 
tact with the graphite, would form carbide; and since the 
platinum cup could not be fitted in gas tight, it was expected 
that the reducing atmosphere present would injure the couple, 
hence it was planned to use a new platinum cup for each run, 
and to check the thermocouple after each run. 

The first run went beautifully, the following data being 
obtained on the relation between temperatures as read by 
the Wanner, and by the thermocouple. 

Table XII — Regular Temperature Tube 



Temperature by thermocouple 



Temperature by Wanner 



963° 


959 


982 


986 


996 


996 


1000 


1005 


107 1 


1073 


1 198 


1 198 


1285 


1284 


1306 


1304 


1397 


1396 


1435 


1441 


1473 


1472 


I5I0 1 


1516 



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Temperature Measurements in Carborundum Furnace 257 

Since the Wanner reads black body temperatures, and 
the couple, disregarding the drop through the platinum, 
the true temperatures, we see that the deviation from black 
body radiation is entirely negligible. 

A few points were taken with the spectrophotometer 
on this run, the data for which are given at the beginning of 
Table XIV, under "Run of Dec. 28,'' and are plotted on the 
upper curve (II) in Fig. 5. It will be noted that the slope 
of this line and that of curve (I), the lower portion of which 
is plotted from data taken on the black body in the platinum- 
wound furnace, is exactly the same, but that this line lies 
above the others. On hunting for the cause of this, it was 
found that, most unfortunately, the drum that regulates 
the sHt width of the slit receiving radiation from the tem- 
perature tube, being rather loose in its bearings, had moved 
in moving the instrument. On checking up the settings of 
the slits, as was done before each run, and continually during 
the run, it was found that the drum had been set back, after 
its displacement, to 2 . 800 instead of i . 800. That is, two 
and eight-tenths revolutions of the drum had been made 
instead of one and eight-tenths. This will not affect the 

slope of the log %, ^ curve at all, but only the intercept, hence 

the agreement between the slopes of the two curves really 
shows as well that our tube is actually giving black body 
radiation, as it would if the points lay on the first curve, 
though it is not quite so pretty a proof. 

After this run the thermocouple was checked in freezing 
copper, and gave 1083®. Hence it has not been affected 
by carbide formation, and our results are trustworthy. The 
platinum cup was crystalline and brittle, showing carbide 
formation. This, however, had not extended clear through 
the cup, the inner surface, next the junction, being smooth 
and uncrystallized. 

We then attempted to dupHcate this run, and get points 
for our ciUT'e with the proper opening of the spectrophotom- 
eter slit, but in three trials we were unable to finish a run 
without carbide formation in the couple and consequent 



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258 



H. W.GiUett 



invalidation of the readings. With this we stopped the work 
on the question of deviation from black body radiation, and 
began to compare the temperatures shown by matching the 
spectrophotometer field when set at the proper distance from 
the hot body to give some definite temperature, taken from 

the extrapolated log x, ^ curve, with the readings of the 

Wanner pyrometer, up to 2600® C. We shall deal further 
with these data under the discussion of the p3a-ometer, but 
since the spectrophotometer readings and those of the pyr- 
ometer agreed satisfactorily over the entire range, they show 
that, if we assume the correctness of our extrapolation, the 
pyrometer calibration was correct; or if we assume the pyr- 
ometer correct, it checks our Wien's law curve over the range 
from 1200® to 2600®, as being the continuation of the one 
obtained on a black body in the platinum fiunace, when the 
temperatures were measured by a thermocouple over the 
range 11 20® to 1450®. Since compensating errors would 
hardly balance things up through this range, it is likely that 
both assumptions are correct. 

Table XIV — Data for Ix)g x, ^ Curve, Regular Temperature 

Tube 
Run of Dec. 28 



X inches 


Tabs. 
1370 


logjr 


iATlO-' 


32.5 


1.512 


730 


32 


5 


1378 


1. 512 


729 


37 


3 


1387 


I 572 


719 


191 





1789' 


2.281 


539 


19 


2 


1268 


1.284 


789 


19 


7 


1276 


I 295 


784 


29 


6 


1343 


1-471 


745 


39 


3 


1384 


1.5" 


722 


55 


5 


148 1 


1-744 


675 


148 


5 


1708 


2.172 


585 



* First four readings made with Wanner alone. The rest by thermo- 
couple in platinum tipped porcelain tube and checked by Wanner readings. 
See Table XIII. 

Spectrophotometer slit at 2.800. Plotted on upper curve (II). Fig. V. 



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Temperature Measurements in Carborundum Furnace 259 

Table XIV— (Continued) 
Run of Jan. 2 



X inches 


T abs. ! 

i 


logx 


f^ 10-* 


39? 


1565 


1.600 


639 


26.8 


1443 


1.428 


693 


35-9 


1503 


1-555 


665 


47.2 


1573 


1.674 


636 


67.2 


1663 


1.827 


601 


90.3 


1743 1 


1.956 


574 


218.0 


2053' 1 


2.337 


487 



Rim of Jan. 



29.0 
36.2 
45.7 
59.7 
60.4 
80.2 

155.5 
184.0 
218.0 



306.6 
319.6 
319.6 
397 6 
397 6 



226.5 

497 5 
586.0 
344 o 
206.0 



H54 
1503 
1565 
1640 

1675 
1714 

1945 
2001 
2053 » 

Run of Jan. 

2183 

22l8» 

2200 

2306* 

_?333__ 

Run of Jan. 

2030 

2498> 

2581 

2290 

2083 



3^ 
1 .462 

1.559 
1 .660 
1.776 
1. 781 
1.904 
2.192 
2.265 
2 •_337 
8^ 



688 
665 

639 
610 

597 
584 
514 
500 
487 



2.486 
2.505 
2.505 
2.599 
2:599_ 

ri2 



458 
450 

455 
434 
429 



2 

2 
2 


.355 
.697 
.768 


493 
400 

387 


2 
2 


.537 
.314 


437 
480 



Run of Jan. 



7cx).o 
795 o 
795 o 



2673 
2778 
2788' 



11^ 

^8^ 
2.900 
2.900 



374 
361 
359 



Spectrophotometer slit at i .800. 
Temperature read by Wanner. 

« Temperatures measured by Wanner with dark giass K = 2586. 
» Temperatures read by Wanner with dark glass K = 205 unless other- 
wise noted. 

Instances measured with aid of rotating section or disk, K <-* 25. 






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f6o 


H. W. GiUeU 


\ 






Table XV 








Log X, ^ curve 




Spectrophotometer set 






I - - 


at proper distance to 


Temp, read by 


Logjr 


^ X 10— • from 


give, from extra- 


Wanner 


polated curve 




1-435 


Wanner readings 


1200*^0 


1209^ C 


675 


1300 


1300 


1. 718 


636 


1400 


1402 


1. 812 


597 


1500 


1507 


1.966 


562 


1600 


1615 


2.147 


530 


1700 


1705 


2 . 240 


506 


1800 


1800 


2.345 


482 


1900 


1900 


2.447 


460 


2000 


2005 


2.540 


439 


2100 


2100 1 


2.625 


421 


2200 


2200 ' 


2.705 


405 


2300 


2300 


2.777 


389 


2400 


2410 


2.850 


372 



The slope of both curves in Fig. 5 is 4600 ± 30. Com- 
paring this with Table IX, we see that it indicates that either 
for ^ = o. 665 at which we tried to set the spectrophotometer, 
or for X = 0.670 which we might have had, owing to the 
difficulty of setting the instrument exactly, the value for 
the constant c, of the Wien equation must be nearer 14200 
than the usually accepted value of 14500. This checks with 
the Holbom and Valentiner figure of 14200 ± i f>ercent. 

Owing to the difficulty of mantaining the regular furnace 
at a constant temperature throughout the reading of both 
spectrophotometer and Wanner, and on account of the im- 
possibility of accurately determining X with this spectro- 
photometer, and the many variables affecting this form of 
the instrument, our results are not to be taken as conclusive 
on the value of c^. However, since it is certain that the more 
perfect the black body the lower the value of c„ our results 
have led us to adopt the Holbom and Valentiner figure of 
14200 in all calculations based on Wien's law throughout 
this paper. 



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Temperature Measurements in Carborundum Furnace 261 

Though our work carmot attain to the dignity of a new 
determination of Cj, yet it proves conclusively the point we 
wished to establish, that the temperature tube gives prac- 
tically black body radiation, so that no correction for devia- 



aoo 




Fig. 5. — Wien's Law Curve. Crosses denote temperatures read by Wanner 
pyrometer. Circles denote temperature read by thermocouple. 

tion is necessary. Were we on the other side of 14500, say 
at 14800, we should fear deviation from the condition of a 
complete radiation, but at 14200 we are certainly gettmg 
negligible deviation from black body radiation for pyrom- 



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262 H, W. GiUeU 

eters like the Wanner, which use red light. It will be shown 
later that the same is true for total radiation pyrometers. 

To sum up the factors aiBfecting temperature measure- 
ments made in our double- walled carborundum tube, we 
have seen that the tube has such a temperature gradient in 
respect to the furnace gradient, as to give practically correct 
readings; that the plug imder normal conditions is imiformly 
heated; that the difference in temperature between the two 
surfaces of the plug may be approximately corrected for at 
any given temperature, and such corrections have been ob- 
tained; that the use of suction to sweep out the fumes intro- 
duces no measurable error; and that the deviation from 
black body radiation is negligible. Above all, the fume 
difficulties have been minimized. 

Having covered the question of the tube, let us now turn 
our attention to the pyrometers employed, and their calibra- 
tion from 1200° to 2600° or above. 

Three types of pyrometers were available for this work, 
the Wanner, the Morse, and the Thwing. 

The Wanner used throughout the work was a very good 
instrument of recent manufacture, belonging to the Depart- 
ment of Physics. For diagrams and descriptions of this in- 
strument see references 15, p. 72; 19, p. 229; 22, p. 226; 37, 
p. 462, in the bibliography. The Chemical Department owns 
a Wanner of earlier date, put out, in fact, before the necessity 
of keeping the current passing through the comparison lamp 
constant by means of a voltmeter or ammeter, was realized. 
This has a Reichsanstalt certificate showing it to be correct 
within 1° at 1000®, 1200°, and 1400°. When used above 
1600°, however, it does not give the same color of object and 
comparison fields, while the Physics instrument does not 
show this fault till well above 1800°. Throughout the 1000°- 
1400° range, the two instruments agree within 5®, or to the 
error of setting. 

In using either instrument the current was kept constant 
at the value found to give the proper "normal number" 
against the standard Hefner amy lace tate lamp, by means of 



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Temperature Measurements in Carborundum Furnace 263 



an ammeter or voltmeter, and adjustable resistance. Cf. 

reference 19, p. 229. The instrument was always used 

normal to the hot surface, to prevent errors due to polariza- 
tion < '9. p. 235), 

The Chemical Department Wanner is not provided with 
a dark glass for a higher temperature range; the other is. 
However, on plotting for the Physics instrument, scale read- 
ings against the temperatures from the calibration table, it 
is found that either with or without the dark glass the instru- 
ment is quite insensitive between 1750° .and 2100°. Fig. 6, 




1000* 1300* 2000' 2500' 

Fig. 6. — Calibration Curves. Wanner Pyrometer. 

Curve I, shows the curves for the instrument without any 
dark glass, and Curve III that with the dark glass supplied 
with the instrument. Since the formation temperature of 
carborundum, which we wish to determine, lies in this range, 
the Wanner as it stands, is not satisfactory. The use of the 
dark glass to cut down the intensity of light from the hot 
source, thus allowing reading of higher temperatures, depends 
on another application of Wien's law. If we insert a dark 
glass, an absorbing mirror, or a rotating sector disk in the 
path of the light from the hot body, we cut down the inten- 
sity in some certain ratio, which ratio is the coefficient of 
absorption of the absorbing medium used. 
Since 

I, V 
the ratio f is the coeflficient of absorption, K, and if T^ js 



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264 H' ^' GUlett 

the true temperature, then Tj is the apparent temperature 
when the absorbing medium is interposed. 
Then we have 

Hence if we once determine the coeflBcient of absorption, K, 
we can figure back to the true temperature corresponding 
to the Wanner reading obtained with it. Figuring from the 
Wanner tables, we find for the dark glass supplied with the 
Wanner (Fig. 6, Curve III) that K = 2586 if c, = 14200, or 
3000 if c, = 14500, for X = 0.656//. 

Then if we use a glass of the proper absorption power, 
lower than 2586, we should be able to obtain such a curve 
as II, Fig. 6, when the most accurate readings lie in the 1800°- 
2250° range we wish to use hereafter. 

The absorption factor of such a glass may be determined 

X ' 

by the spectrophotometer, since K = ° where x^ is the dis- 

tance corresponding to the true temperature T^, and x^ the 
distance corresponding to the apparent temperature T„ to 
the equivalent of which the radiation from the body at T^ 
is cut down by the interposition of the glass. K should of 
course be determined, using the same wave-length of light in 
the spectrophotometer as will be used in the pyrometer to 
which the glass is to be applied, since most glasses show some 
selective absorption. 

On attempting to determine K for the dark glass supplied 
with the Morse instrument so as to be able to use that glass 
with the Wanner, it was found that, in order to get a large 
enough x^ to allow accurate setting of the si>ectrophotoni- 
eter, x^ was too great for the length of the room. This 
same difficulty had to be overcome in working above 1700° 
in getting Fig. 5. Hence some absorbing medium, with a 
rather low and accurately known coefficient of absorption is 
needed, so that by its use we may cut down x^ to a reason- 
able figure. 



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Temperature Measurements in Carborundum t^urnace 265 

Waidner and Burgess" and Hyde'* have shown that 
the rotating sector disk may be used for this piupose, 
and that it has the advantage that K may be determined 
by measurement of the angle of the sector opening as well 
as by the spectrophotometer. For instance, one made with an 
opening of 14.4° gives K = 25, and the distances measured 
with it are just one-fifth of those measured without it. One 
15 inches in diameter was made up with this opening, from 
thin sheet metal, painted dull black. It was rotated by 
an 1800 R.P.M. motor. This speed was rapid enough to 
prevent flicker. By the spectrophotometer, two determina- 
tions of K gave 24.9 and 25.1. 

By sighting a spectrophotometer on a black body 
whose temperature was known, by thermocouple or otherwise 
at a couple of temperatures, and measuring the corresponding 
distances, and thereafter setting the instrument at a fixed 
distance from the body whose temperature is to be measured, 
it would be possible to calculate from Wien*s law the distances 
required for any other higher temperature. Then these dis- 
tances could be calculated over, so that we knew the opening 
of a sector disk which would have to be interposed, so as to 
make the distance at which the spectrophotometer was set, 
equivalent to any greater distance. An adjustable sector 
disk, such as is shown by Fleming ^^•p**^'^ could be used, 
and the temperatures corresponding to diflferent equivalent 
distances, i. e., to diflferent openings of the sector, could be 
placed on the scale over which the lever that governs the 
size of the sector opening, plays. Thus a laboratory having 
a spectrophotometer, but no optical pyrometer, could impro- 
vise a usable direct reading pyrometer for laboratory inves- 
tigations. 

Now having our rotating sector, we are in a position to 
get the absorption of our dark glass. Using the spectrophotom- 
eter, we got 204, 205, 200, 198. By taking readings with 
the Wanner with and without the glass, and using c, = 14200, 
we got 207, 208, 201. Hence we may take 205 as the value 
for this glass. It was impossible to make a determination 



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266 H. W. CUleU 

on the dark glass originally supplied with the Wanner, as it 
was too small to cover the spectrophotometer slit. 

Using this value of K for our dark glass, a table was 
made on the basis of Wien's law, which gives the values 
plotted on Curve II, of Fig. 6. Comparative readings on the 
Wanner with no glass and with this glass, or with this glass 
and with t^i-* origina one, taken at points where the curves 
overlap, agree v/ithin the limits of error in setting the instru- 
ment. Thus we have made the Wanner sensitive to about 
io° C over the range we wish to measure. 

The principle of the disappearing filament used in the 
Morse thermogage is described by Chwolson ^** ^- ^\ Waid- 
ner and Burgess ^''^ p- "«>, LeChatelier <'^p**'>, Ikl^ <37.p.^3) 
and Waidner ^*®' ^ ^^\ While the principle is properly stated, 
Waidner and Burgess say that Morse uses a large spiral 
filament which is hard to match, that the pyrometer de- 
mands too high a voltage (40-60), has no focussing device, 
needs red glasses before the eye and a dark glass before 
the filament, for high temperatures. Burgess ^'''P*^^ con- 
demns it for use above 1200°, though in the work at the 
Bureau of Standards imder his direction, as for instance that 
on the melting point of platinum,'* they continually use 
what they call the Holbom-Kurlbaum pyrometer. This is 
simply the German form of the Morse instrument; it is manu- 
factured under the Morse patent and can only be obtained 
in this country from the Morse Thermogage Co. Save for 
the use of absorbing mirrors instead of dark glass, and for a 
slightly more compact form, it differs in no essential form from 
the Morse instrument. Since Morse defeated Siemens and 
Halske, who were making the Holbom-Kurlbaum instru- 
ment, in the patent litigation in Germany (see Waidner and 
Burgess (22, insert slip p. 233) and Ikl^ (37, p. 463, footnote)) 
it only seems right to give him the credit that is his due, 
more particularly as each and every point criticized by Waid- 
ner and Burgess in earlier papers, and passed over in silence 
in later ones, has been attended to in the modem Morse in- 



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Temperature Measurements in Carborundum Furnace 267 

strument, and Waidner and Burgess must have been aware of 
the improvements. 

In the latest form it uses a 6-volt tungsten lamp with 
a simple W-shaped filament; the instrument is a telescope 
and may be focused for object and filament; both red and dark 
glasses are provided and when prof>erly calibrated, it may be 
used with good results up to 2500° C. By the use of a still 
thicker dark glasses the range might be extended to the 
highest attainable temperatures. 

In the earlier part of this work, a Morse instrument 
belonging to the Department of Physics was used, but its 
dark glass was not dark enough to allow us to go as high as 
we wished. Moreover, at about 1700®, according to the cali- 
bration of this instrument, a point was reached at which a 
considerable increase in current gave but little increase in 
brightness of the filament, thus making settings uncertain. 

The second instrument was made up with a specially 
thick dark glass, and loaned by Mr. Morse to Prof. Bancroft 
for this work. 

We procured a special Weston laboratory standard milli- 
ammeter for use with this pyrometer, having a 12-inch scale 
for 2000 milliamperes, thus allowing very delicate readings. 

We made a calibration curve for the Morse instrument, 
plotting milliamperes passing through the lamp against tem- 
perature of the hot body as shown by the spectrophotometer. 
Morse's calibration was seen at once to give too low readings 
if we took the brighter part of the filament, so we used the 
darker side, since the illustration on the calibration sheet 
showing the part of the filament to use, might be taken to 
mean either side of the filament, according to which way 
the lamp was faced. Using the darker side, we found Morse's 
calibration for the dark glass low by 30° at 1200°, the devia- 
tion growing less up to 1800°. From that point up the agree- 
ment was very close. The calibration thus obtained against 
the si>ectrophotometer was the one used in the measurement 
of the formation and decomposition temperatures of carbo- 
rundum recorded later in this paper. 



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268 



H. W.GiUeU 



On communicating our results to Mr. Morse, we found 
that the brighter side of the filament was the one that wbs 
supposed to be used. Then, using that part of the filament, 
we took the calibration of the instrument up to 1320° C on 
a black body in a platinum furnace, measuring tempera- 
tures by the thermocouple and then in the regular form of 
temperature tube in the regular carbonmdum furnace from 
that point up to 2500°, reading temperatures by the Wanner. 

Over the 900^-1200® range our figures for the instrument 
without either dark or red glasses, agreed well with those 
furnished by Morse, our values averaging about 5® higher. 
1200® is as high as readings can be made without the red 
glasses. With the red glasses, but no dark glass, the range 
is extended to over 1400®. Morse did not furnish a calibra- 
tion corresponding to this. 

With both red and dark glasses, using the bright side of 
the filament, we foimd Morse's calibration 120® low at 1130®, 
the deviation growing less at higher temperatures imtil at 
2475° his values were correct within the errors of observa- 
tion. The data are given in Table XVI and our calibration 
curve is given in Fig. 7 : 



2500" 


d 


^ 


2000* 


81 

t 

E 


7 


isooT 


. 


/ 




■ / 




1000* 


: / 


,x^^^ 




/ 


Milliamperes 



600 1000 1200 1400 1600 

Fig. 7. — Calibration Curves. Morse Pyrometer. 



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Temperature Measurements in Carborundum Furnace 269 



Tablb XVI — Morse Pyrometer 



MUli- 
amperes 


Degrees 
centigrade 
red glasses, 

no dark 
glass 


' Degrees centi- 
grade red and 
1 dark glasses 

! 


Degrees centi- 
grade Morse 
calibration 

red and 
dark glasses 


I I 
To T, 


900 


700 


i 

1 1 130 


lOIO 


0.000246 


1000 


910 


1 1360 


1320 


0.000233 


1 100 


1045 


I 1590 


1540 


0.000233 


1200 


1 130 


i 1760 


1740 


0.000221 


1300 


1 200 


1 1930 


1920 


0.000225 


1400 


1280 


1 2100 


2090 


0.000223 


1500 
1600 


1345 
1410 


\ 2240 
i 2385 


2250 
2388 


0.000220 
0.000218 


1700 




! 2475 


2470 





The last column gives ^ =r, where T^ is the absolute 

temperature of the hot body for a given current through the 
lamp without the dark glass, and Ti the temperature for the 
same current with it. We have already seen that where 
Wien's law strictly applies, the value is a constant. The reason 
it is not constant here is because, imlike the Wanner, which 
is a spectroscopic instrument, the red glasses used in the 
Morse are not wholly monochromatic, but admit a band of 
light. This can be readily seen by viewing the lithium and 
sodium flames through the red glasses, the sodium flame be- 
ing almost as bright as the lithium. 

Now we know that the wave-length corresponding to 
maximum light intensity, shifts, with rising temperature of 
the luminous source, towards the shorter wave-lengths. 
Waidner and Burgess ^"' p ~'^ plot ciurves showing this. 
Watson'* explains how the red is the first light to appear 
on heating a body, the yellow beginning to appear at about 
1000®, while at 1600® the light is practically white. This 
shift from the red to the violet end of the spectrum of the 
light emitted from a hot body was very noticeable on our 
regular temperature tubes at temperatures of 2500*^-2600° 
C, as the light emitted was distinctly greenish; so much so 
that people coming into the room, and seeing it reflected 



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^70 //. W. CiUeH 

from the walls opposite the tube, would conunent on its green 
color at once. 

Using the value 205 for the absorption coeflBcient of oiu- 

dark glass and substituting the observed values of = ^ 

in the Wien equation, 

logK = ^'log.(^'^-^-) 

we find that at 1130® our effective wave length is about 
0.65/x, while for 2475° it is about 059/1. This is checked by 
the fact that the impression the eye receives on looking into 
the eyepiece of the pyrometer at the highest temperatures 
is that of a distinctly yellowish color. This does not agree 
with the results obtained by Waidner and Burgess ^*5* ^* ''^^ 
where they found the position of the maximum of intensity 
as viewed through a red glass, to shift towards longer wave 
lengths over the range 1000^-1450®. Whether this is due to 
a difference in the nature of the red glasses used by them 
and by us, we cannot say, but it seems strange that they 
should find that the maximum of intensity viewed through a 
certain glass shifts in exactly the opposite direction from that 
in which the maximum of intensity is really shifting in the 
spectrum of the hot body. 

In order to find out how the values in the Morse calibra- 
tion table suppUed with the instrument were obtained, we 
took the matter up with Mr. Morse. After ageing his lamp 
for 24 hours at a voltage above the highest at which it will 
be used, he calibrates the instrument without dark or red 
glasses, using an electrically heated hot body, against another 
Morse pyrometer whose calibration is known. Then, read- 
ing the temperatures with the standard instrument, he takes 
three readings with the instrument to be calibrated, using 
the red and dark glasses. He then takes the current through 
the lamp, corresponding to each of these three readings and 
from his calibration curve without the dark or red glasses, 
finds the temperature there corresponding to those values of 
the current. Then he has three pairs of temperature read- 



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Temperature Measurements in Carborundum Furnace 271 

ings, each pair for the same current, with and without the 
glasses. He then plots temperatures with the glasses against 
those without, draws a straight line through the three points, 
and then takes from this straight line the temperatures with 
the glasses, corresponding to those without. He states that 
he always finds these three to lie on a straight line when 
plotted this way. 

Now this corresponds to the assumption that T^ = KT^, 
whereas according to the Wien equation, the relation is 

= :=- = K. The only way that Morse's assumption can 

be approximately true, is to have, by good luck, a red glass 
through which the eflfective wave-length shifts with the 
shifting of the maximum of intensity, just enough to com- 
pensate for the diflference in the two formulae. 

For temperatures from 1900° to 2500°, as Table XVI 
shows, this happy accident has occurred. Were this not the 

case, and we had X = o.65;x at 2475®, as at 1130®, = 7p 

would then equal 0.000246 as at 1130® and the pyrometer 
would indicate 2760°, on the basis of Morse's calibration, or 
300® too high. 

The set of readings taken by Morse in the calibration of 
the pyrometer lamp used in our instrument is given below: 

Table XVII 



No glasses 


With dark and red glasses 


I I 


op 


oc 


op oc 


To T, 


1561 
1628 
1686 


855 
892 

925 


! 
2122 1 1167 

2252 1237 
2374 • 1305 


0.000194 
0.000216 
0.000273 



The value of = =- which we have calculated from his 



J I 

T T 

figures shifts in the opposite direction from that in our set of 
readings. However, figuring the corresponding wave length 
of the effective Ught from the Wien equation for his values 



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21^ //. W, GUleti 

at 1 167®, we find X = 0.52/1, which is in the green, and we do 
not believe that at 1167® the displacement of the maximum 
of intensity will force green rays through a red glass. The 
difficulty of making accurate readings at the low intensity 
corresponding to 1167° with the dark glass, is great, and 
may accoimt for much of his error. 

Since the calibration provided by Morse without the 
dark or red glasses only goes up to 1220 milliamperes, or 1 140°, 
he has to extrapolate the current-temperature curve (which 
is a curve and not a straight line, see Fig. 7) before he can 
take the corresponding temperatures with the glasses that 
correspond to current values above 1220 milliamperes. Er- 
rors in this extrapolation may also have aided in compensa- 
ting for the error due to his assumption that the relation is 
To = KTj. It will be noted that the values for T^ and T, 
from Table XVI do not lie on a straight line. 

We therefore think that the Morse calibration for the 
instrument with the dark glass is based on an erroneous as- 
sumption, and that the almost complete compensatism for 
this error, which brings his values out so nearly correct at 
higher temperatures, may be traced to the shift in the effec- 
tive wave-length of light, due to lack of monochromatism in 
the red glasses. 

While a Morse pyrometer for high temperatures ought to 
be calibrated against a spectrophotometer, or at least a 
Wanner, in order to make certain that readings are giving 
actual as well as merely reproducible temperatures, one so 
calibrated is satisfactory for high temperature work, and has 
the very great advantage for work with experimental electric 
furnaces that it demands the smallest hot body of any high 
temperature pyrometer known, and hence large temperature 
tubes may be dispensed with. 

We think that the Morse instrument might be vastly im- 
proved by adding a collimator slit, and a prism between 
the eye and the lamp so that the field be illuminated by 
monochromatic light, as is the case with the Wanner. Wien*s 
law would then be strictly appHcable, and calibration of 



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Temperature Measurements in Carborundum Furnace 273 

the instrument for high ranges by the use of absorption 
glasses would not be complicated by the shift of the maximum 
of intensity and would rest on a sound theoretical basis. 
To avoid any danger of selective absorption in the dark glass, 
a rotating sector of small opening might be used, which would 
have the advantage of allowing a determination of the coeffi- 
cient of absorption by calculation from the angular opening 
as well as by direct determination. The rotating sector 
would hardly be practicable for a commercial instrument, 
since the vibration might jar the filament too much, though in 
the Ives colorimeter a rotating color mixer is used that runs 
with ahnost no vibration. (See note at end of bibliography.) 

For measurements at 1800^-2600®, radiation pyrom- 
eters of the F^ry or Thwing type, seemed very promising. 
With optical pyrometers like the Wanner or Morse, it is 
necessary to cut down the intensity so much by absorbing 
glasses that we vastly reduce the delicacy of our readings. 
With radiation pyrometers, the scale readings for a given 
temperature increment, increases with increasing tempera- 
tiu"e, i, e., the higher we go the more delicate our readings. 

A F^ry instrument was tried out by one of their sales- 
men in comparison with the Wanner and the Morse belong- 
ing to the Physics Department. All these were sighted on a 
graphite plug i'' in diameter at the end of a 12'' elbow form 
temperature tube. The following temperatures were read : 



Wanner 



1596° c 
2010 



Morse 

1605° ( 
1810 



F^ry 

1450° c 

1910 



The higher temperature was above the point where this 
Morse instrument was known to be inaccurate, hence the 
lack of agreement there is not surprising. That the F^ry 
gave low readings showed that the hot body was too small to 
cover the field entirely at that distance. It was figured that 
a 3" plug would not have been much too large. The F^ry 



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274 H, W, GiUett 

readings were consistent, and could be duplicated to a re- 
markable degree of exactness. 

The large size of the hot body needed, while not a vital 
fault in many industrial operations, throws the F6y out of 
consideration as a laboratory instrument, for to get a field 
3," in diameter in our form of temperature tube, the outer 
tube would have to be about 4*/,'' in diameter, and to get 
uniform heating of the plug, and to keep the volume occupied 
by the tube from being too large a percentage of the total 
furnace volume, we would have to enlarge our experimental 
furnaces to unwieldy sizes. 

While the F^ry could probably be modified to meet our 
special conditions, its price is prohibitive even without any 
special modifications. 

Hence we turned our attention to the Thwing pyrometer. 
Our conditions were rather unusual. We wished to use a 
small field, and yet to get a high degree of accuracy at tem- 
peratures far above the usual range for which high tempera- 
ture pyrometers are used. Dr. Thwing took up the problem 
and furnished several pyrometers, each of which was tested 
in turn, criticised and reported on. Using the facts thus dis- 
covered. Dr. Thwing would modify the pyrometer accord- 
ingly. 

The commercial form of the instrument consists of a i^ 
metal tube about 3' long, at one end of which may be in- 
serted diaphragms of various sizes. Near the other end is 
an aluminum cone about ^^ long, Vg'^ diam. at the larger 
end and ^f^" at the smaller, open at both ends. This serves 
the same purpose as the parabolic mirror in the F6y instru- 
ment; it acts as a sort of funnel, receiving the radiation from 
the hot body and concentrating it, by multiple reflection, on 
the hot junction of a tiny thermocouple placed behind the 
smaller end of the open cone. This couple is very thin, only 
about Viooo i^ch in thickness, to allow it to assume equilib- 
rium rapidly, and to insure a rapid return to zero reading on 
the galvanometer when the radiation is cut off. Its com- 
position being a trade secret with Dr. Thwing, we were told 



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Temperature Measurements in Carborundum Furnace 275 

only that the wires were nickel alloys. The nickel-nichrome 
couple is finding considerable use nowadays but whether 
chromium enters into the composition of either element of 
the couple we do not know. The e.m.f. produced by the 
heating of this couple from the total radiation falling on it 
from the hot body is read on a delicate portable galvanometer, 
corrected for temperature changes by an ingenious device. 

Since the intensity of radiation varies as the square of 
the distance from the hot body, and since the area of the spot 
of light admitted by the diaphragm also varies as the square 
of the distance, the pyrometer is independent of its distance 
from the hot body as long as the body is large enough so that 
at the farthest distance it completely fills the angle substi- 
tuted by the diaphragm. A diagram of the commercial in- 
strument is shown by Waidner ('^'P-sa) 

The commercial instrument needs slightly too large a 
hot body to be applicable to our work, in which we did not 
wish to use a hot body larger than 1" in diameter nor to put 
the pyrometer closer than iS'^ from the radiating source. 
To meet our conditions. Dr. Thwing used a Leeds and North- 
rup wall galvanometer, the sensibility and resistance of 
which could be varied by a device shown in Fig. 8. This also 



$Stdxeo5 




35-^ 




—60000 Ohms llOO"-k- 

Fig. 8. — Device for Constant Sensibility and Resistance, Thwing Pyrometer. 

allows us, by noting the deflections obtained when a Weston 
standard cell is connected across the galvanometer and ad- 
justing device, to make sure that the galvanometer has not 
changed from the conditions imder which it was calculated, 



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276 H, W. GilleU 

or if it has changed, to restore it to the original conditions by 
varying the resistances. 

The first couple was in the usual long i" tube, but showed 
grave faults in the matter of prompt return to zero, the 
couple having too great heat capacity. The next one was 
similarly moimted, but its return to zero was not good, and 
placing the hand on the tube just over the couple would heat 
the cold junction and give a large negative reading. Blow- 
ing on the tube at that point would cool the cold junction and 
increase the deflection by an amount corresponding to a few 
hundred of degrees increase in the temperature of our hot 
body. Hence it was necessary to insulate the couple from 
outside influences, and to this end it was placed in a large 
wooden box. To prevent heat reaching the cold junction by 
conduction along the metal tube, the diaphragms were of 
sheet aluminum held between steel rods fastened to the out- 
side of the wooden box. 

This solved the problem of insulating the couple from 
outside influences, but the steel rods were so flexible that every 
time the instrument was moved the relative positions of the 
diaphragms, and hence their effective size, was changed, and 
no concordant results could be obtained. 

Next the diaphragms were held by a stiff brass frame- 
work, which solved this last difficulty. The instrument in 
its present form consists of the usual tiny couple at the back 
of the aluminum cone, contained in a wooden box, of half-inch 
stuff, whose outside dimensions are iiV,'' X iiV,'' X 15 7/ 
long. The cone is 6" from the front wall of the box. A 7/ 
diaphragm is placed 20^^ from the box, and an iris diaphragm, 
arranged with projecting pins acting as stops so as to give two 
definite sized diaphragms (V/ and '/le'^) without any imcer- 
tainty of setting the pointer on a given mark, at sVa'^'away. 
In order to allow removing the instrument and replacing it 
in the same place, its three legs (of adjustable height) fit into 
depressions in three brass plates, each bearing sharp points 
on the bottom by which they are stuck in the wood of the 
table on which the instrument is placed. A dust-proof cap 



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Temperature Measurements in Carborundum Furnace 277 

fits over the opening in front of the cone when the instru- 
ment is not in use. 

The pyrometer is centered by noting the position of the 
spot of light on the diaphragms, and moving the box till they 
are in the center of the spot. Using the */j/ diaphragm, the 
instrument can be placed iS'^ to 20^^ from a hot body i'' in 
diameter without exceeding the limits of the field. With the 
V/ diaphragm, this distance from the hot body may be con- 
siderably increased. 

The instrument was calibrated against the spectrophotom- 
eter and the Wanner, since Dr. Thwing had no facilities for 
calibration at such high temperatures. The data are plotted 
in Fig. 9, showing scale deflections against temperatures. 



250(f 



200Cf 




l5CXf • 



_^ ' Scale reading 

'^^^^ 10 20 30 40 ^50 

Fig. 9. — Calibration Curves. Thwing Pyrometer. Curve I, with ^/^^ diaphragm. 
Curve II with V/ diaphragm. 

From Figs. 6, 7, and 9 the relative sensitiveness of the 
Wanner, Morse and Thwing instruments can be found for any 
temperature, since the Wanner may be set to about half a 
scale division, the Morse filament may be matched to about two 



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278 H. W. Gillett 

milliamperes, and the Thwing readings may be made to a 
fiftieth of a centimeter on the 50 cm scale, and may be re- 
produced to at least a tenth of a centimeter. At the highest 
temperatures the Thwing is the most sensitive of the three. 

Radiation pyrometers, like the F^ry and Thwing, should 
follow the Stefan-Boltzmann law, E=K (T* — T^') or 
E = oT^ when T^ = o. Here E is the energy of total radia- 
tion visible and invisible, T the absolute temperature of the 
hot body, T^ that of the pyrometer, and K and o, constants. 
(Waidner and Biu-gess^^ '»'^). When the radiation E falls 
on the **hot" junction of the tiny thermocouple of the 
Thwing instrument, it is transformed into heat, which pro- 
duces an e.m.f. in the couple. If, then, the e.m.f. tempera- 
tiu-e relation of the couple is a straight line fimction, and if 
the galvanometer has a straight line function between e.m.f. 
and scale deflections, then the relation between galvanometer 
deflections and the fourth power of the absolute temperature 
of the radiating source should be a straight line function. 
On plotting the data shown in Fig. 9 in this way, however, a 
slight curvatiu-e was found. 

In order to determine if this was due to deviation from 
black body radiation of the temperature tube, or to devia- 
tion from a straight line relation in the couple or galvanom- 
eter, we tried to determine the e.m.f. scale deflection ciu^e 
for the galvanometer, with its compensating device in series 
with it, using a Weston potentiometer. The contacts on the 
tenths of ohms dial had apparently become dirty, so that di- 
rect measiu-ement on the galvanometer as it stood, using only 
the tiny e.m.f. equivalent to that generated by the couple, 
was impossible. This e.m.f. is of the order of 0.00005 volts 
per scale division (one centimeter) of the galvanometer. 
100,000 ohms was put in series with the galvanometer and ad- 
justing device; then varying the e.m.f. by using the 1,000- 
15,000 ohm dial, so that slight differences in contact resis- 
tance due to dirt became negligible, it was found that the 
e.m.f. scale deflection curve was an exactly straight line. This 
indicated that the discrepancy was due to a deviation of the 



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Temperature Measurements in Carborundum Furnace 279 

e.m.f. temperature relation of the couple from a straight 
line. 

To test this, Dr. Thwing loaned us another couple, said 
to be a duplicate of the one in our pyrometer. The couple 
was connected to the galvanometer plus its compensating de- 
vice, the cold junction being kept in melting ice, and the 
"hot** junction in a beaker of water. Delicate Beckmann 
thermometers that could easily be read to Vj^ degree were 
fastened to the hot and cold junctions by rubber bands. 
The temperature of the hot junction was varied by changing 
the temperature of the water in the beaker. Readings were 
taken over the whole scale and a slight curvature found in 
the temperature-scale deflection curve. This gives us a cor- 
rection for the curvature of the temperatiu-e-e.m.f. rela- 
tion of the couple, plus any deviation in the e.m.f. scale de- 
flection ciu^e of the galvanometer, though from the results 
with the potentiometer it is doubtful if any such deviation 
exists. 

We found that the difference in temperature of the hot 
and cold jimctions to give a deflection of 50 scale divisions 
on the galvanometer was only 515^0, and to give 38 . 5 only 
about 4®. By reference to Fig. 9, it will be seen that with 
the larger diaphragm a temperature of 2500° C at the hot 
body only causes a rise in temperature of 5.15*^ at the hot 
junction of the couple, or of only 4*^ with the small diaphragm. 
This explains why in the metal tube form of the Thwing the 
couple was so very sensitive to outside influences. As a con- 
sequence of the information gained in working with the 
special instrument. Dr. Thwing is now putting out his com- 
mercial couple with a wooden cylinder lo'^ long and 3'' in 
diameter, about the couple. We tested out such a couple 
and found it to be perfectly protected by the wooden box. 
While most of his commercial instruments do not use so deli- 
cate a couple as this special one, yet the addition of the wooden 
cylinder must make the commercial instrument vastly more 
reliable. 

Correcting the scale deflection readings back to equal 



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28o 



H. W. GiUett 



temperature increments at the hot junction of the tiny couple, 
and plotting against the fourth power of the absolute tem- 
perature of the hot body, we get the ciu^es in Fig. lo, which 
are seen to be straight lines. 




Increments of temp, ot hot junction 
of couple. (Thwing, pyrometer) 



10 



20 



30 40 



30 



Fig. lo. — Stefan-Boltzmann Law Curve. 

The agreement between the Stefan-Boltzmann law used 
by the Thwing, and the Wien law used by the spectrophotom- 



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Temperature Measurements in Carborundum Furnace 281 

eter and the Wanner, is complete and shows that our tem- 
perature tube is giving sensibly complete radiation, not only 
for optical pyrometers using red light, but also for total 
radiation instruments. Waidner and Burgess (^p-*56) have 
found the Wien and Stefan-Boltzmann laws in accord at 3570*^ 
absolute, the temperatiu-e of the arc, and Lummer and Prings- 
heim" foimd them to agree at 2300*^ absolute. 

Now we have all three pyrometers calibrated to read 
over the 1700*^-2500° range we are interested in. It is more 
or less of a toss-up which pyrometer is the best for our pur- 
poses. The Wanner has been available longer than the other 
instruments, and through long use we have become accus- 
tomed to it, and place considerable reliance in it. It, how- 
ever, requires constant checking against the standard amyl 
acetate lamp, which is a nerve-racking job, owing to the in- 
constancy of the light due to flicker from the tiniest draught 
of air, or the breath of the observer. A black body in a 
platinum or nichrome furnace, with its tempeature read 
by a standard thermocouple is a much better means for 
checking the normal number of the Wanner. 

The Morse instrument has to be calibrated empirically, 
and there is always the danger of deterioration of the lamp. 
With a properly aged lamp this is slight and may always be 
checked by the black body as above. Though at present 
we rather prefer the Wanner to the Morse for this particular 
problem, oiu* attitude might be reversed had we used the 
Morse as much a§ the Wanner, particularly in view of the 
great advantages of the small field required by the Morse. 

The Thwing, in the special box form, is imwieldy if it 
has to be moved from one temperature tube to another. 
Its sensitiveness is the best of the three above 1800°, and for 
use with a single temperatiu-e tube, where it can be left in 
position throughout an entire run, it is ideal. There is no 
question of inaccuracy of watching a field due to fatigue of 
the eye, as in the other two. It is likely that for most of the 
further work on the carborundum furnace it is planned to 



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282 H. W. GUleU 

undertake in this laboratory, the Thwing will be the most 
satisfactory of the three. 

Any one of the three, then, properly calibrated, will 
serve to measure the temperatures in the carbonmdum fur- 
nace. 

Now, having studied the variables affecting the tem- 
perature tube, and calibrated our thermometers, we may pro- 
ceed with our original object, the measurement of the tem- 
perattu-es in the carborundum furnace. 

The values given in the literature for the formation 
and decomposition temperatures of crystallized carborundum 
and of siloxicon, vary greatly. Acheson" gives 3500®- 
4000*^ F as the range over which siloxicon is formed. Dim- 
lap'* gives 7000*^ F as the formation temperature of car- 
borundum, and 4500^-5000® F as the siloxicon range. 
Wright ^'' ^ *'^ gives the same figiues. Scott^ says that silox- 
icon goes over into carborundum at 3000*^ C. Kimz'' 
gives Moissan's figiwes" of 1200°- 1400® C as the tempera- 
ture at which SiC is formed in fused silicon (not in the regu- 
lar furnace) and 3400*^ C as the temperature of decomposition 
of SiC. Thompson '• speaks of the formation of SiC by 
melting Si in a graphite crucible at "ordinary heats." 
Pring,*® working at extremely low pressures, gives the forma- 
tion temperatures of SiC from Si and C as 1250^-1300® C and 
says the reaction goes on rapidly above 1400®. He finds that 
in practically a vacuum. Si containing 5 percent Fe and 0.7 
percent Al reacts with carbon at all temperattu-es above 1200®, 
the product being crystalline under the microscope and hence 
SiC and not siloxicon. Greenwood** finds that at pres- 
sures of 2 to 3 mm Hg, carbon reduces silica at 1460® C, form- 
ing either SiC or siloxicon. Pring and Fielding*' find that 
at very low pressiu-es carbon interacts with Si from the vapor 
of SiCl^ mixed with an excess of H,, to form SiC at 1700® C. 
With the addition of C^H, vapor the reaction goes at 1700- 
1850®. The Dictionary of Chemical and Metallurgical Ma- 
terial gives 2250® C as the decomposition point of SiC. 
Stansfield <5.p. 152) g^ys "The temperature of the carbo- 



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Temperature Measurements in Carborundum Furnace 283 

rundum furnace has never been measured, and has been sup- 
posed to be as high as 3000*^ C." Stansfield quotes Tucker 
and Lampen'* giving the dissociation temperature of SiC 
as 2220® C. He further says ^5* p. 56) *'Siloxicon has been 
said to turn into carborundum at 5000° F, or 2760*^ C, carbo- 
nmdum fire sand to crystallize into carbonmdum at 7000*^ F, 
or 3870® C, and carborundum to be infusible at the same 
temperatiu-e, while it is admitted that these substances are 
less refractory than carbon, whose boiling point is taken to be 
3700*^ C, or 6700*^ F. Recent experiments (those of Tucker 
and Lampen), however, place the formation temperature 
of carbide of silicon (siloxicon) at 1600*^ C, its crystallization 
at 1950® C and its decomposition into graphite and silicon 
vapor at 2220° C." 

This work by Tucker and Lampen has brought some 
order out of chaos, and gives the only figures we can put any 
sort of reliance in as showing the actual temperatures in the 
commercial furnace, using the commercial charge, and work- 
ing at atmospheric pressure. Lampen*' gives the follow- 
ing: formation of siloxicon about 1615*^ C; decomposition of 
siloxicon and formation of crystalline carborundum between 
1900® and 2000°; decomposition of SiC to graphite, 2220*^ 
to 2240®. 

Tucker and Lampen'* placed a graphite tube trans- 
versely through a carborundum furnace, determined the 
temperatiu-e gradient through the tube by means of a Wanner 
pyrometer sighted on a movable plug, much as we did in 
getting the gradient through the different kinds of tubes, 
then when the nm was over, cut down through the furnace 
and measiu-ed the width of the graphite, carborundum and 
siloxicon zones. They found 2218° and 2223*^ C for the 
temperatiu-e of the point in the tube at the same distance 
from the center of the furnace as that at which SiC was de- 
composed to graphite in the charge; and 1980® and 1920*^ 
for the temperatiu-e of the point corresponding to the forma- 
tion of SiC in the charge. They do not fix a figiu-e for the 
formation temperatiu-e of siloxicon, but from their curve it 
seems to be about 1600®. 






284 ^. ^' Giliett 

The chief criticism here is the tacit assumption that the 
temperature gradient through the graphite tube is the same as 
that through the furnace. Our determinations of the grad- 
ients in the carbon, graphite and carborundum tubes, and in 
the furnace itself, show that this is not the case. Through- 
out the graphite zone the tube and furnace gradients will be 
practically the same, hence we may exj>ect the value 2220° 
for the decomposition temperature to be about right. The 
temperature at the junction of the carborundum and siloxicon 
zones, however, may be expected to be really considerably 
lower than that shown in the graphite tube, owing to the 
higher heat conductivity of the graphite. Moreover, there 
is a discrepancy of 60*^ between their two determinations, 
1920*^ and 1980®. 

In our preliminary work, using the elbow form of tem- 
perature tube, made of carbon, not correcting for the differ- 
enqe in temperature between the two siuiaces of the plug, 
and reading temperatures with the Wanner without any 
glass, or with the thick dark glass supplied with the instru- 
ment, we get the following results : 

Run 50 Crystallized SiC at 1790^-1805° 

Run 52 Crystallized SiC at 1820°. Crystallized SiC formed 

iV/ away from the core, which only reached 

1950^ 
Run 54 Much siloxicon at 1625° and below — no SiC 
Run 55 Crystallized SiC i" away from the core which 

reached 1920° 
Run 56 Crystallized SiC at 1820° 
Run 57 Crystallized SiC below 1850°, formed i" from core, 

which reached 1910° 
Run 58 Crystallized SiC at 1825° to 1850° 
Run 59 Crystallized SiC at 1800° — much at 1825° — none 

at 1790° 
Run 60 Crystallized SiC at 1800 °-i825°— also below 1850** 

in another tube 

In these preliminary experiments we were limited as to 
power, and seldom reached the dcomposition temperature 
of SiC, so we had no data on that point. These readings 
are not accurate to more than 25°, and since no corrections 
were made, the total inaccuracy may be 50®, but they do 



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Temperature Measurements in Carborundum Furnace 285 

show that the 1950® figure for the formation of SiC given 
by Tucker, is too high. 

This seems reasonable, too, when we consider that in 
the commercial furnace they get, from the core out, first one 
to two inches of graphite, then ten to twelve inches of crys- 
talline SiC, then two to four inches of **fire sand'' or siloxicon, 
and then about two inches of unchanged charge. Tucker's 
figures — 2220*^ to 1950® — give only 270*^ for the range over 
which crystalline SiC is formed in the furnace, and this seems 
a small temperature drop for a whole foot. 

After we had evolved the fumeless tube, and calibrated 
the pyrometers, we made further measurements to settle 
this point on a furnace of the size and shape shown in Fig. i , 
filled with 150 lbs. of the normal charge. In this were placed, 
side by side, two carborundum tubes of the dimensions given 
below. Fig. 2, the center line of each being 2^^ from the mid- 
dle of the furnace, i. e., they were placed symmetrically, 
with their centers 4," apart. One of them had the back of 
its plug y/ from the core, and the other had it 1" from the 
core. The temperature was raised, at first fairly rapidly, 
and then less so, till at the end of the 2*/^ hoiu- run, the last 
50® took 20 minutes and the last 20*^ took ten minutes. We 
will call this Run A. The same thing was done in the same 
way in other ftunaces in Runs B and C, save that in B the 
tubes were respectively V/ and ^/^^ back from the core, 
and in C, respectively 2'// and 3". 

Table XVIII shows the results. The temperatures 
given are the highest temperatures reached in the respec- 
tive nms : 

Table XVIII 





Tube nearer the core 

1 


Run 


By 
Wanner 


By 
Morse 


Thwing 

1825 
2230 


Average 

1 

1822 
2233 
1548 


A 
B 
C 


1820 
2240 
1547 


1823 
2230 
1550 



Tube farther from the core 



Wanner Morse Thwing 



1790 I 1800 i 1800 
2190 I 2180 I 2180 
1526 I 1520 I 



Average 



1797 
2183 

1523 



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286 H. W. GiUett 

By reference to Table VII we see that at iSoo® the cor- 
rection for drop through the Vie'' P^^S ^ +25*^, at 2200® 
+ 17*^, and at 1550® +31*^. The rate of heating employed 
here was very comparable to that used in determining these 
corrections, so they apply without change. 

This gives us the following corrected values : 

Table XIX 



Rnn 


Nearer tube 


Farther tnbe 


A 
B 
C 


1847° 
2240 

1579 


1822° 

2210 

1554 



Now as to results. In Rim A we foimd crystalline SiC 
past the end of the nearer tube, and just to the farther one. 
There was a solid wall of SiC back of the nearer plug when 
it was pulled out, and there were many crystalline specks 
clinging to th^ back of the plug. 

In Rim B, the nearer tube had graphite on it ^f^" past 
the end, while the farther tube was about ^f^" outside the 
graphite zone. In Run C there was siloxicon y/ past the 
end of the nearer tube and about ^f^" past the ends of the farther, 
that is, even the farther one was a trifle above the formation 
temperature of siloxicon. 

These give us our final figures; decomposition point of 
SiC, 2220*^ ±20*^; formation of crystallized SiC, 1820 ±20^; 
formation of siloxicon, 1540*^ ±30®. The ±30*^ allotted to the 
siloxicon is greater than the ± 20*^ given to the others, because 
of the greater difficulty of telling just where the zone begins. 

This value for the graphite point is checked by the nm 
tabulated in Table IV, where the highest temperature reached 
was 2220*^ and where graphite had just begun to be formed. 
This agrees exactly with Tucker's figure. Our figures, how- 
ever, are 130® lower for the carbonmdum point, and 60® 
lower for the siloxicon point. 

Tucker used about 18 lbs. of charge against the 150 lbs. 
used in our furnace. His movable plug was ^f^" thick and its 
exact position during readings is not stated, so we cannot 



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Temperature Measurements in Carborundum Furnace 287 

tell whether or not there is any error due to disregard of tem- 
perature drop through the plug. Tucker's graphite tube 
was 1^ O.D. and V/ I.D. somewhat smaller than our tem- 
perature tube. If we assume, however, that conditions 
in his tube and furnace were comparable to those in our larger 
furnace and tube, we can get an approximate correction for 
the error introduced by his disregard of the diflference be- 
tween the temperature gradient of tube and furnace, by using 
the data obtained in our work on the gradients through 
graphite and carborundum tubes, Tables IV and V. 

Tucker has fortimately given us his actual readings. 
Changing his distances into inches, measured from the edge 
of the core, instead of centimeters measured from the center, 
so as to correspond with oiu-s, and averaging his figures for 
both sides of the furnace, we get the following: 

Table XX 



Material 






Distance from core 


</' 


V,'' 


1'' 


iV/' 


2// 


aV/' 


y' 


Our graphite tube 
Our SiC tube 
Tucker's graphite tube 
Our SiC tube 


2000'' 
2000 
2240 
2220 


2130'' 
2100 


1885° 
i860 
2060 
2005 


1980° 
1930 


1730° 
1630 
1900 
1830 


1810^ 

1755 


1580° 

I5I5 
1750 
1660 



These are plotted in Fig. 1 1 . 



2200' 



2000*1 



1800" 



1600" - 




Fig. II. — ^Tube Temperature Gradients. Circles denote graphite tubes. Crosses 
denote carbonmdum tubes. 



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288 //. W. GUleU 

Tucker found SiC on one side of the core at 1940*^ and at 
1900*^ on the other side. This core temperature was 20® 
higher than ours, but the conditions are at least roughly 
comparable. 

1940° in the graphite tube corresponds to 1870° in the 
SiC tube, or in the furnace, and 1900*^ corresponds to 1830®. 
Hence his lower figures, thus corrected, comes within the 
1820® ±20*^ indicated by our determinations. 

If we continued these curves down to the siloxicon point, 
given by Tucker as 1600° and by us 1540*^ ±30°, Tucker's 
corrected value would give about 1500® for siloxicon. How- 
ever, on reading his paper it will be noted that Tucker does 
not appear to base his 1600® value on the run in the fiunace 
with the movable plug method, but rather on the work of 
Lampen, who mixed sand and coke in a tiny graphite boat 
heated inside the tube resistor of a tube furnace, and de- 
termined the temperature by sighting on the graphite boat 
with a Wanner. In this way he finds about 1600*^ for the 
siloxicon point, 1900° and 2000° C for the SiC, and 2220® 
for the graphite point. Since these determinations differ by 
100® at the SiC formation temperature, it is plain that they 
cannot lay claim to any great degree of accuracy. 

Hence from our accumulated evidence and from the 
very fair agreement with Tucker's corrected results, we be- 
lieve the figures 1540° ±30° for the formation of siloxicon, 
1820® ±20° for that of crystallized SiC and 2220*^ ±20® 
for the decomposition of SiC, to be correct within the limits 
given. 

We have not attempted to fix a temperature for the 
formation of ** Amorphous SiC" which is often stated to occiu* 
between the zones of crystalline SiC and of siloxicon, since we 
consider that it is at least an open question whether any such 
substance exists, or at least, whether it is formed either in 
commercial or laboratory furnaces. Direct determination of 
the question by analysis of the zone next to the crystalline 
SiC is impossible with the product made in a laboratory 
scale furnace. The siloxicon grades oflF from a whitish gray on 



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Temperature Measurements in Carborundum Furnace 289 

the outside to a dark greenish gray inside. There is no line 
of demarcation nor any physical property by which ** amor- 
phous SiC" may be distinguished from siloxicon. As soon as 
we get beyond the point where the change in color of the 
siloxicon ceases to be continuous, microscopic examination 
shows the presence of crystalline SiC mixed with the amor- 
phous siloxicon. We asked Mr. Tone, of the Carbonmdum 
Co., if he could give us for analysis samples of "amorphous 
SiC* from the commercial furnaces, where the zones are 
wider. He said that if a zone of amorphous SiC does exist, 
he does not know where it begins or ends, and cannot separate 
it. 

Tone'* very properly sidesteps the whole matter by 
calling the zone extending from crystallized SiC out to im- 
changed charge, "carbonmdum fire-sand.*' Fitz Gerald*^ 
says that Schiitzenberger obtained amorphous SiC by heating 
SiC and carbon in a gas-fired fiunace provided with blast. 
The formation of regular carbonmdum in this way has been 
reported by Thompson.^* Schiitzenberger *s original arti- 
cle,** however, only says it was pulverulent. He gives no 
microscopic examination on which to base the belief that it 
was really amorphous. Moreover, Moissan got crystals by 
this method. Fitz Gerald says that outside the SiC zone is a 
small zone of grayish green " white stuflF" considered to be 
amorphous silicon carbide — outside this being unchanged 
charge. He does not use the term siloxicon, or oxy-carbide, 
at all in this paper. 

The statements of Mulhauser*' in 1893 that he ob- 
tained amorphous SiC have gone down through the litera- 
ture and form the chief basis of the belief in that material. 
He took the zone just outside the crystallized SiC, pulver- 
ized, floated, ignited, boiled with HCl, extracted with water, 
dried, and treated with HF and H^SO^. After ton,^ treatment 
with HF and H,SO, he fumed off the H^SO, extracted with 
water, dried and analyzed, obtaining 



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290 H. W, Gillett 

C 29.73 percent 

Si 65.42 

Fe,0, 4- A1,0, 5.09 

CaO 0.38 

MgO 0.21 



98.93 



He started with 100 parts of coke containing 90.24 
percent C, 100 parts sand containing 99.55 percent SiO, and 
25 parts NaCl. Now this is a large excess of carbon, in which 
case there does not seem much justification in figuring Fe 
and Ca, at least, to the oxides. Even taking his figures just 
as they stand, there is one percent that may be oxygen. 

The above was taken from his German article. In his 
paper in English he says he piuified and crystallized SiC by an 
HF treatment, and in the treatment of the "amorphous 
carbide of silicon," "as it was evident that it was an amor- 
phous form of SiC,'* a similar process of ptuification was 
used. 

Now it is well known, as Potter states,** that siloxicon 
is attacked by HF with elimination of Si and O, leaving a 
residue which after ignition approximates the formula SiC. 
Hence Mulhauser's method of analysis was exactly such as 
to prevent him from finding out that his amorphous ma- 
terial from the furnace really was siloxicon. In the English 
paper Mulhauser states that the zone just outside the "amor- 
phous carbonmdum" is unchanged charge. In the German 
article he analyzes the zone just outside the amorphous zone, 
and finds AlSijO^, though the formula staggers him a bit and 
he concedes that the question of the composition of this zone 
is open. 

The composition of siloxicon is given as varying from 
SijCjO to SiyCyO, and while most authorities say it is "about" 
SijC^O, almost all agree that its composition is very variable. 
It is seldom looked upon as a true chemical compound. 

To illustrate the loose way in which the terms "silox- 
icon" and "amorphous carborundum" are used, we quote 
from Tone,** "In any mixture of carbon and silica the 



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Temperature in Measurements Carborundum Furnace 291 

first products to be formed when the charge is heated to the 
temperature at which silica begins to reduce, are siHcon- 
oxygen-carbon compounds in which these elements may be 
combined in various and most complex proportions, the com- 
pounds being at the same time intimately associated with 
free carbon and free silica. T)rpical of these silico-carbides 
are siloxicon and amorphous carborundum.** Also the fol- 
lowing from Potter ^'•' p- ^K 

Specific Heat Determinations 



No. 


Substance 


Sp. heat 


Remarks 


30 
32 


SiC amor p. 
Siloxicon 


0.1894 
0.1911 


Average of 4 detns. made 
from siloxicon 



We admit that an amorphous material corresponding 
fairly well with the formula SiC may be obtained by long 
treatment of siloxicon with HF, and ignition, but we doubt 
very much if any such substance is obtained directly in the 
carbonmdum furnace. Our own idea of the matter is that 
the siloxicon zone consists of a complex series of solid solu- 
tions of Si, C, and O, the proportion of O being greater at the 
outside of the zone and lower at the inside, corresponding to 
the gradation of color from light to dark gray-green, though 
this is of course merely an h)rpothesis. At any rate, we feel 
justified in disregarding the so-called zone of amorphous car- 
borundum in our temperature determinations. 

During the course of this temperature work, a couple of 
observations were made which may be of enough interest to 
record. With the fimiace and core as given in Fig. i, using 
the normal charge, it was foimd very difiicult to get the tem- 
perattu-es above about 2400°. In some cases we have reached 
as high as 2675° C, read by the Wanner, but these higher tem- 
peratures were reached in a furnace packed tightly with 
crushed carbonmdum instead of the regular charge, using a 
core of small original cross section, and heating the furnace 
up at a rapid rate. In ordinary cases, 2400° was the high mark. 



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292 



H.W.GUleU 



This was not due to reaching the limit of power that the 
generator would supply, since the kw would increase, while 
the temperature fell. In one run where the furnace was 
taking about 32 kw and giving 2300°, the power rose to 35 
kw and over, while the temperature dropped slightly below 
2300°. 

The reason is not far to seek. As soon as we get above 
2220° the SiC that has been formed decomposes into graphite, 
which then forms part of the resistor. The cross section of 
our effective core is thus increasing at so great a rate that 
even with increased power the calories per unit of effective 
core surface are less than formerly, and the temperature 
drops promptly. This would not be the case if graphite hap- 
pened to have its regular heat conductivity without its elec- 
trical conductivity. Consider the data in Table XXI: 

Table XXI 



- 


- 





Time 


Volts 


Amps. 


8.10 


160 


25 


8.20 


150 


50 


8.30 


155^ 


50 


8.40 


155 


100 


8.50 


98 


250 


9.00 


90 


280 


9.10 


73 


325 


9.20 


67 


360 


9.30 


74^ 


450 j 


9.40 


93 


540 , 


950 


70 


590 


10.00 


70 


600 . 


10.05 


62^ 


550 


10. 10 


46^ 


400 


10.15 


30^ 


100 





A 


B 


C 


D 


V. 


Temp. 


Temp. 


Temp. 


Temp. 




at core 


2'' back 


2*//^ back 


4'' back 


.0 


20° 


20° 


20° 


20*» 


•5 
•7 


965 






30 


•5 


1190 






60 


•5 


1725 






80 


.2 


1990 






160 


•7 


2140 


1000 


850 


520 


. I 


2200 


1181 


1055 


940 


•3 


2280 


1410 


1190 


1080 


•4 


2300 


1665 


1380 


1250 


•3 


2330 


1830 


1430 


1350 


.0 


2360 


2080 


1830 


1520 


.1 


2330 


2120 


1830 


3 


•4 


2300 


2020 


1830 




.0 


2250 


1930 


1770 





4- 

7. 

7- 
15- 
24- 
25- 
23- 
24 
33- 
39- 
41 
42. 

34- 
18. 

3- 

In this run three temperature tubes were used. A, at the 
core; B, 2^^ back; and C, 2V/ back from the core. A thermo- 

* Power increased by means of field rheostat. 
' Power decreased by means of field rheostat. 

• Couple removed. 



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Temperature Measurements in Carborundum Furnace 293 

couple, D, in a porcelain tube with the end ground off to a 
thickness of 0.4 mm, was placed 4.^ away from the core. The 
temperatures given are not corrected for drop in tempera- 
tiu*e through the plug. 

In Fig. 12 we have plotted some of the data of Table 



250CC- 



aoooc 



isbcT 



lOOOC-' 




5o<^ I 2 3 4 

Fig. 12. — Furnace Temperature Gradients. 

XXI. Ciu^e I is the temperature gradient after the fur- 
nace has been running i hour, Curve II that after i y^, hours, 
and Curve III that corresponding to the highest temperatures 
reached. As will be seen from the table, we decreased the 
power just before the normal lowering that would have taken 
place, due to graphite formation, occurred, because we wished 
to keep the temperature at tube C from rising above 1850° 
(corrected), in order to get a determination of the formation 



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294 H. W, GiUett 

temperature of SiC. Hence the data do not illustrate our 
point as well as they might. However, the phenomenon of 
the lowering of temperature was a perfectly general one, 
and since we seldom had more than two temperature tubes in 
the furnace during the runs that went up to 2400°, and hence 
did not determine the gradient so completely as in this run, 
this case will serve. 

In passing we may remark that we found SiC past the 
end of tube C, about Vg'^, and siloxicon about V/ past the 
point where the thermocouple was placed, these observations 
being in complete accord with our other determinations 
of the formation temperatures of SiC and of siloxicon. 

Inspection of Fig. 1 2 will show that in any given form 
of carborundum furnace, at any given rate of heating, there 
is some maximum temperature above which we cannot go, be- 
cause the increase in core cross-section will overbalance the 
power supply. This maximum temperature is far below that 
which would be attained at the normal stationary state of 
the furnace for a given power input, if the graphite formed 
did not carry the current. 

For instance, if in Fig. 1 2 the effective core had remained 
only 2" thick as at the start, instead of 4'' thick at it was at 
the end of the run, instead of the gradient being in the form 
of Curve III, it would have been approximately that of 
Curve II, where we had just reached the temperature of 
graphite formation, but moved along to some position which 
we may represent diagrammatically by Curve IV. In the 
actual case our graphite zone is represented by the area OAB, 
the SiC area by ABCDK, and the siloxicon by KDEL. In 
the hypothetical case, our graphite zone would have spread 
out much farther and the graphite area would be PAJ, the 
SiC, AJGK, and the siloxicon, KGHEL. The gradient would 
probably not have exactly the form given, but the change 
would be in that general direction. Then our SiC zone would 
be considerably decreased. 

In other words, the most efficient carborundum furnace 
is the one in which the 400° between the formation and de- 



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Temperature Measurements in Carborundum Furnace 295 

composition temperatures of carborundum extends over as 
long a distance as possible, that is, where we have a flat tem- 
perature gradient. The steeper the gradient between 2220° 
and 1820°, the less efficient the furnace. The auto-increase 
of the core cross-section keeps the maximum temperature 
down, and tends to give a flatter gradient. Hence the suc- 
cess of the commercial furnace is largely due to the fact that 
SiC decomposes into a substance that carries the current and 
forms part of the resistor. 

To this same principle is due the fact that if we wish to 
get a large yield of siloxicon we must use multiple cores, ac- 
cording to Acheson's patent,*' since siloxicon decomposes, 
on heating, into carborundum which is practically a non- 
conductor of electricity, though a good conductor of heat. 
The carbonmdum plays no part in the siloxicon furnace 
analogous to that of the graphite in the carborundum furnace, 
hence in the former much more care has to be paid to keep- 
ing the core temperature down. 

Some data on the gradients through carbon and graphite 
electrodes was obtained in the preliminary work, and may 
be worth recording in view of the work now being done by 
Hering *'* •\ Hansen*', and ForsselP* on furnace and elec- 
trode design. 

Hering** gives the following diagram (Fig. 13) for 



Saibon 



Electrode distance 



Hot Cold 

Fig- 13- — Hering's Electrode Temperature Gradients. 

the theoretical heat gradients through carbon and graphite 
electrodes, and concludes from his theoretical considerations 
that carbon is the worst material for electrodes, on the basis 
of electrode losses, thus being inferior to graphite. He says, 



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296 H. W. GiUeU 

** Graphite, like iron and unlike carbon, tends to crowd the 
heat toward the hot end where it belongs." 

Our work on graphite and carbon tubes, not carrying 
current, shows that this is not the case, since at any given 
point in the tube, for equal temperatures at the hot ends, the 
graphite is the hotter. 

The data given in Tables XXII, XXIII, and XXIV, and 
plotted in Figs. 14, 15, and 16, show that it is not true for 
electrodes carrying ciurent, under our conditions. The 
data were taken in a small furnace where we were limited to 
the low power at first available, and to poor regulation. The 
furnace was 2^" long, i^" wide and 12^ high, inside dimen- 
sions, with fire-brick walls, and packed with the normal 
carborundum charge. The electrodes were cylindrical in 
shape and 2" in diameter. They had not been previously 
used. The core was of 6-12 mesh crushed carbon, 10* long 
X 2" diameter. Just at the junction of the core and elec- 
trode a carbon temperature tube of the elbow type was in- 
serted so the plug rested tightly against them both. The 
temperature of the plug was read by the Wanner pyrometer, 
no correction being introduced for temperature drop through 
the plug. 

Six inches back from this junction a hole was bored in 
the electrode to take a porcelain pyrometer tube and thermo- 
couple. At six and twelve inches back from this were bored 
other holes in which were inserted nitrogen filled thermom- 
eters, powdered graphite being packed in the waste space in 
the hole, so that the thermometer fitted closely. The elec- 
trodes rested in a 4^^ X 4^^, inside dimensions, firebrick trough, 
filled with siloxicon, the trough extending 2* past the outer 
thermometer. They were not water-cooled. 

The proper way to take these data would have been to 
use one carbon and one graphite electrode in the same run, 
and take readings on both. At that time, however, only one 
thermocouple was available, so we had to make runs using 
first graphite and then carbon electrodes. As the power 
could not be controlled so as to exactly duplicate conditions 



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Temperature Measurements in Carborundum Furnace 297 

in two consecutive nms they are but roughly comparable as 
to rate of heating and maximum temperattu-e reached. 



Table XXII 
Run 59. New Graphite Electrode 





i 




i "1 ' 

1 1 Electrode distances from hot end 




1 




1 
1 

I K.W. 


&^ 6^^ 


„// 


tV 


Time in 
minutes 


j Volts 1 Amps. 


Temperature read by 

L __ 


r 




i ' 
1 1 


1 

j Wanner 


Thermo- 
couple 

(20°) 


1 Thermom- 
1 eter 

20° 


1 

. Thermom- 

1 eter 

1 





1 ! 

icx) 25 


1 2.5 (20°) 


j 20» 


15 


100 52 


1 5-2 1 850 


150 


70 


1 40 


30 


1 98 97 


' 9-5 1 1005 


280 


135 


' 75 


45 


1 82 152 


1 12.3 1300 


470 


235 


140 


60 


1 73 180 


1 13. 1 1600 ! 600 


280 


180 


75 


] 67 


193 


12.9 1700 


700 


325 


225 


90 


62 


196 


12.2 1720 


810 


385 


270 


105 


60 


200 


12.0 1730 


850 


400 


295 


120 


' 58 


200 


II. 6 1740 


905 


435 


320 


135 


1 56 


195 


10.9 1790 


970 


460 


325 


150 


1 56 


190 


10.6 i860 


1020 


485 


340 


165 


54 1 200 


10.8 1865 


1070 


500 


345 


180 


54 1 190 


10.2 1 1865 1 mo 
Table XXIII 


5»5 


350 




Run 60. New Carbon Elec 


:trode 







100 


25 


2.5 


(23°) 


(23°) 


"-^30^ 


"l^o-- 


15 


90 


87 


7.8 


925 


60 


46 


44 


30 


70 


180 


12.6 


1550 


150 


100 


95 


45 


65 


190 


12.4 


1830 


320 


225 


210 


60 


64 


200 


12.8 


1905 


470 


275 


245 


75 


62 


195 


12. 1 


1905 


600 


290 


265 


90 


60 


200 


12.0 


1945 


700 


330 


275 


105 


58 


195 


11.5 


1970 


815 


370 


290 


120 


58 


195 


II 5 


2120 


950 


400 


282 


135 


57 


185 


10.5 2120 


1090 


435 


295 


150 


58 


195 


II. 5 1 2120 


H50 


450 


300 


165 


56 190 


10. I 1 2150 


1210 


470 


300 


180 


56 


190 


10. 1 


2180 1 


1270 


495 


300 



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igS 



H.W.GiUeU 









Table XXIV 










Run 61. New Carbon Electrode 








, Blectrode distances from the hot end 




Volts 




1 &' 6^' 12^' 


18'' 


Time in 
minutes 


Amps. 


K.W. Temperature read by 










1 Wanner 


Thermo- 
couple 

(24^) 


Thermom- 
eter 


Thermom- 
eter 


O 


100 


25 i 2.5 ' (24^) 


24" 


24° 


15 


72 


150 , 10.8 950 


125 i IOC 


90 


30 


68 


190 13.0 1350 


250 180 


175 


45 


66 


180 1 1. 9 1450 


280 225 


220 


60 


63 


185 


I I. 7 1 1520 


425 


295 


290 


75 


62 


185 


II 3 ; 1675 , 555 


310 


300 


90 


60 


190 


II. 4 1 1770 


640 


330 


315 


105 


60 


170 


10.2 , 1815 


755 360 


320 


120 


60 


182 


10.9 1820 


830 370 


325 


135 


59 


160 


9.4 1900 


970 395 


330 


150 


60 


160 


9.6 1 1950 


1075 , 405 


330 


165 


60 


160 


9.6 2000 


1 185 I 425 


330 


180 


60 


160 


9.6 2000 


1210 


430 


330 




6 12 18 

Fig. 14. — Electrode Temperature Gradients— Graphite, Run 59. 



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Temperature Measurrments in Carborundum Furnace 299 



200(f 



l50Cf 



lOOCf 



50(f 




12 18 

Fig. 15. — Electrode Temperature Gradients — Carbon, Run 60. 




6 12 (8 

Fig. 16. — Electrode Temperature Gradients — Carbon, Run 61. 



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300 H. W. GiUea 

Rim 6 1 on the carbon electrode is more comparable 
with 59 on the graphite than is 60, on accomit of more nearly 
equal rate of heating and final temperature. We do not 
insist on the absolute accuracy of the temperatiu-e readings, 
since there may have been some thermocouple lag and the 
thermometer may not have fitted tightly enough to give ex- 
actly the temperature of the points at which they were placed, 
but the temperattu-es cannot be enough out to obscure the 
results. 

These data show that for our conditions, all the factors, 
as C'R heating, thermal conductivity lengthwise, and loss of 
heat from the surface of the electrodes to the packing about 
them, being taken together, the two materials give tempera- 
tiu-e gradients that are surprisingly alike. The curves have 
been drawn diagrammatically through the observed points. 

If there is really any such difference in the gradients as 
Hering's diagram claims, it must be wholly within the first 
six inches, where we made no measiu-ements. This does not 
mean that at other terminal temperatures, with other fur- 
nace charges and electrode packing, and at other electrode 
current densities, the gradient will be the same as here given; 
but for oiu- conditions, the two materials show a marked 
similarity. This is checked by the fact that no difference 
in the shape of the football-shaped mass of carborundum 
and siloxicon that is found after a run, when the unchanged 
charge is scraped away, has so far been noted whether car- 
bon or graphite electrodes were used, indicating that the 
electrode losses of the two were not notably different. 

Fiuther work on this point by other observers in this 
laboratory is planned, since by using a tubular electrode 
with movable plug for temperature measurements, and by 
noting the rise in temperature of the water passed through 
the water-cooled electrode holders, the point should be easily 
settled. 

In view of the importance of the work being done on 
electrode losses and furnace design, it may not be out of 
place to emphasize that since it is easy to make tubes for tern- 



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Temperature Measurements in Carborundum Furnace 301 

perature observations that are free from fumes, it is perfectly 
possible to verify experimentally the different theories now 
in process of evolution. No such theories can be considered 
of much accoimt till they are experimentally verified. In 
such experimental work, too great care cannot be taken to 
have the gradients through furnace and temperature tube the 
same wherever the movable plug method is used. It is neces- 
sary to have them the same with a stationary plug, to be sure 
of the results, but for the movable plug it is vital if true re- 
sults are to be obtained. 

In the case we have dealt with, the formation tempera- 
ture of SiC, the error due to disregard of this point was 7 
percent at 1800°. Such an error might materially mislead 
an experimenter seeking the true laws of furnace and elec- 
trode design. 

Forssell*' in telling his theoretical assumptions, says 
that in a furnace containing SiO„ information may be obtained 
as to the temperature reached, by noting where graphite, 
crystalline SiC, and siloxicon are formed on the electrodes, 
and gives Tucker's values already cited, for these points. 
In view of this, the present revision of the value for the forma- 
tion temperatiu-e of carborundum should have a distinct bear- 
ing on the problem of electrode losses. 

Summary 

1. The composition of the charge for the carborundum 
furnace has been studied, and an excess of carbon foimd ad- 
visable. 

2. A form of tube for temperature measurement by 
optical and radiation pyrometers has been devised which 
minimizes fume troubles. 

3. The use of carborundum tubes for the measurement 
of temperatures in the carborundum furnace, has been intro- 
duced, and their mechanical properties studied briefly. 

4. The variables affecting the temperature tube have 
been studied; the cooling effect of the current of air used to 
suck out fumes, found to be negligible, and the corrections 



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302 H. W, GilleU 

for the temperatixre drop through the graphite plug deter- 
mined. 

5. The tube has been found to give practically black 
body radiation both for optical and radiation pyrometers. 

6. The Wanner pyrometer has been made more sensi- 
tive over the range desired. 

7. The calibration of the Morse thermogage has been 
examined. 

8. A special form of Thwing radiation pyrometer has 
been installed and improved. 

9. All three pyrometers have been calibrated against a 
spectrophotometer on the basis of Wien's law. 

10. Data have been obtained indicating the value 14200 
for the constant c, in Wien's law. 

11. The Wien and Stefan-Boltzmann laws have been 
found in agreement up to 2500® C. 

12. The temperature of formation of siloxicon has been 
determined as 1540° C ± 30®, that of carbonmdum as 1820° ± 
20°, and the decomposition temperature of carborundum to 
graphite, as 2220® ± 20®. 

13. The discrepancy between the figure ust given for 
the formation of carborundum and that previously obtained 
by Tucker has been f oimd to lie in the difference between the 
temperattu-e gradients of a graphite tube and of the car- 
borundum furnace. 

14. It has been shown that "amorphous carborundum" 
is probably not formed in the commercial furnace. 

15. We have discussed the influence of the formation of 
graphite around the core by the decomposition of carborun- 
dum, on the temperatiu*es attained in the fiunace. 

16. Some data have been given for the heat conduc- 
tivity of carbon and graphite electrodes. 

17. We have emphasized the necessity of having the 
same temperature gradient through a tube used for optical 
or radiation pyrometry, as through the fiunace. 

The writer's thank are due the Department of Phjrsics 
for the loan of instruments, to Mr. E. F. Morse for the loan of 



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Temperature Measurements in Carborundum Furnace 303 

a Morse pyrometer and for co-operation in the examination 
of its calibration, and to Dr. C. B. Thwing for his interest 
and aid in the improvement of the Thwing pyrometer. 
Thanks are also due Mr. J. C. Andrews for aid in taking cer- 
tain spectrophotometric measurements and to Messrs. E. E. 
Bragg, T. R. Briggs, E. Freudenheim, S. D. Hiltebrant and 
I/. R. Milford, with whom the preliminary observations were 
made. Above all, hearty thanks are due Prof. Bancroft, at 
whose suggestion and imder whose direction this work has been 
carried on, for continual kindly advice and encouragement. 



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Cornell University, 
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The chemical world owes thanks to the editor and the publisher for the 
appearance of this useful volume. Wilder D. Bancroft 

Die Methoden zur Herstellung koUoider Ldsungen anorganischer Stol!e. 
Ein Hand- und Hilfsbuch fur die Chemie und Industrie der KoUoide, By Tke 
Svedberg. 15 X 23 cm; pp. xii -\- 512. Dresden: Tkeodor Steinkopff, igog. 
Price: paper, 16 marks; bound, 18 marks. — The author distinguishes two methods 
of making colloidal solutions. In the condensation method so called, one 
starts from a true solution; in the dispersion method one starts from a pre- 
cipitated material and causes it to go into solution. Under condensation methods 
we have four subdivisions: reduction; oxidation; hydrolysis; and miscellaneous. 
Under the dispersion methods we have only two sub-divisions: mcchaniral 
and chemical; electrical. 
Typical instances of the reduction method are the preparation of colloidal 



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New Books 307 

gold by means of hydrogen, methyl alcohol, or hydroxylamine; Carey Lea's 
preparation of colloidal silver by means of ferrous sulphate, etc.; Billitzer's 
method of preparing colloidal gold, silver or mercury electrolytically. The 
most important instance of an oxidation method is the preparation of colloidal 
sulphur from hydrogen sulphide. The best known case of hydrolysis is the 
preparation of colloidal ferric hydroxide. Under miscellaneous methods we 
have the preparation of colloidal arsenious sulphide in solutions where the 
concentration of ions is kept low, and the preparation of colloidal silver bromide 
in presence of gelatine as a protecting colloid. 

Typical instances of mechanical or chemical disintegration are found in the 
peptonizing action of caustic soda on a silicic add gel or in the alternate action 
of alkaline and add solutions on chromium, platinum, iridium, etc. Under 
the electrical dispersion methods we have the original process of Bredig and 
the modification of it by Svedberg. 

Under each sub-division the author has given a very satisfactory bibliography 
and the book is an excellent one from every point of view. Wilder D. Bancroft 

The Relations between Chemical Constitution and Some Physical Proper- 
ties. By Samuel Smiles. 13 X 20 cm; pp. xiv + 5<9j. New York and 
London: Longmans, Green & Co., 1910, Price: $4,00. — In the preface the author 
says: "As indicated by tbe title, this volume does not exhaustively treat of 
the whole subject in question. For various reasons a few physical properties 
have been omited from consideration, the more important being Crystalline 
Form, Optical Rotatory Power, Electric Conductivity, and Heat of Combustion . . . 
Some other physical properties, for example. Solubility, Dielectric Constant 
and Magnetic Susceptibility have been omitted because the relations between 
them and constitution are not yet sufficiently elucidated to call for spedal treat- 
ment .... A book of this kind runs the risk of satisfying neither the physical 
chemist nor the structural chemist; but it is necessary to point out that it has 
been written from the stand-point of organic chemistry. This standpoint has 
been assumed both from necessity and from personal inclination, the former 
arising from the fact that by far the greater portion of research in this sub- 
ject has been focused on the compounds of carbon." 

The properties have been classified as mechanical, hermal, optical, and 
electrical. Under mechanical properties we find capillarity, viscosity, and 
volume relations. Under thermal properties we have specific heat, fusibiUty, 
and boiling point. The optical properties are sub-divided into: refractive and 
dispersive power; abrorption of light; fluorescence; and magnetic rotatory 
power. Anomalous electric absorpt on is the only electrical property discussed 
as such. 

The book seems to be worthy of the series. For personal reasons, the 
reviewer has been interested chiefly in the chapters on absorption of light, 
fluorescence, and anomalous electric absorption; and he confesses to having 
read these much more carefully than the others. These are probably not the 
chapters to which most people will turn first. If the others get as much out 
of the book as the reviewer did, the au hor will have no cause to complain. 

Wilder D. Bancroft 



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3o8 New Books 

The Organic Chemiitry of Nitrogen. By Nevil Vincent Sidgwick. 717 X 26 
cm; pp. X + 415. Clarendon Press: Oxford^ 1910. Price: 14 shillings net. — 
In the preface, the author says: ''It is becoming generally recognized that 
organic chemistry cannot be treated satisfactorily without reference to those 
questions of physical chemistry which it involves. To attempt a separation 
of the two is to refuse all the assistance which can be derived from what is really 
the quantitative side of chemistry. The various physical questions are, there- 
fore, discussed as they arise. A full treatment of the phenomena of tautomerism 
would have required too great an interruption of the main current of thought ; 
but I have tried to indicate the more important points in which they are illus- 
trated by the bodies under consideration. The dynamics of organic reactions 
is a field which, in spite of the increasing amount recently devoted to it, is still 
very largely unexplored; and yet it is of the utmost value for elucidating the 
mechanism of chemical change. I have therefore, made the references to in- 
vestigations of the velocity of reaction as complete as I could, and the methods 
of analysis adopted in each case have been described." 

The subject is treated under four heads: compounds with no nitrogen 
directly attached to carbon; bodies containing one nitrogen atom attached to 
carbon; compounds containing an open chain of two or more nitrogen atoms; 
ring compounds. As the reviewer has said so often, this is the land of a book 
which we want and the more we get of them the better. This particular one 
is a good specimen of the class and it is difficult to see how any chemist could 
glance through it without finding something of interest. 

On page 25, the author points out that even the determination of the con- 
centration of hydroxyl ions does not necessarily give us the true strength of a 
base. In an ammoniacal solution, for instance, we have the non-hydrated 
base NH,, the undissociated hydrated base NH^OH, and the dissociated hy- 
drated base NH^. In the ordinary methods for determining basicity we measure 
the concentration of the ions in a solution in which the total concentration of 
the base in all three forms is known, the existence of the first form, the non- 
hydrated base NH, (or R,N) being neglected. The value of the strength cal- 
culated from this is not the true strength but what may be called the apparent 
strength. 

"Hence the apparent strength of the base is smaller than the real strength, 
and the more so the greater the proportion of anhydrous amine present. When, 
therefore, the strength of an organic base (other than quaternary) is spoken of, 
what is meant is the product of two factors, the hydration constant and the 
dissociation constant. And until recently there was no method known for 
determining either of these two factors separately. The measurement of the 
ionization is no use, as the hydration factor comes in to the same extent at every 
dilution. The determination of the partition -coefficient between water and 
air or an organic solvent has been suggested; but this does not help us either. 
The concentration of the R,N in the other solvent is proportional to that of the 
R3N in water, and therefore, also to that of the R3NHOH: which leaves us where 
we were before. The problem has at length been solved by Moore. He points 
out that all methods of solution must fail, in which the observations are all 
made at the same temperature. If, however, we measure the partition-co- 
efficients and the degree of dissociation at different temperatures, and if we fur- 



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New Books 309 

ther make the assumption, which for small differences of temperature is justi- 
fiable, that the temperature coefficients of these two quantities are constant, 
we obtain a sufficient number of equations to solve the problems. In this way 
we can determine for any amine (for the method applies equally to all pseudo- 
adds and pseudo-bases, and to such bodies as carbonic acid and the lactones) 
the proportion present in the non-hydrated form, and the true dissociation- 
constant. So far, the necessary data have only been obtained for three sub- 
stances, piperidine (which does not concern us at present), ammonia, and tri- 
ethylamine. The results show that in an aqueous solution of ammonia at 20°, 
about two-thirds is present as non-hydrated NH,, the rest being mainly NH^OH 
and a small quantity of ions; in the case of triethylamine only about a third 
is in the anhydrous form, as (C2H.^),N. From these data the true dissociation 
constants of these two bases can be calculated and are found to be at 20^: 
Ammonia K = 5.23 X lo"* 
Triethylamine 64 X 10"*. 
That is to say, the introduction of three ethyl groups into ammonia has in- 
creased the constants only twelve-fold. We should, therefore, expect that the 
introduction of a fourth ethyl group, in tetraethyl-ammonium hydroxide, would 
involve a further increase only to about 150 X io~^, which would mean that it 
was still a very weak base. But as a fact, the quaternary hydroxide is an ex- 
cessively strong base, comparable to potash, for which K is too high to be measured 
and is certainly greater than one. It therefore appears that the first three 
ethyl groups produce only a small increase in the basicity of ammonium hydrate, 
while that produced by the fourth is enormous. It has long been known that 
the quaternary bases were far stronger than the others, but until the true dis- 
sociation constants had been determined it was possible that this might be 
due to the unknown quantity of anhydrous base present in the latter cases but 
not in the former. This is no longer possible; and the sudden increase in the 
quaternary bases certainly seems to point to a difference between their consti- 
tution and that of the hydroxides of the primary, secondary, and tertiary amines. 
If we are not prepared to accept a formula such as Werner's, there are two pos- 
sible explanations. One is that the data on which these calculations are based 
(especially those for triethylamine) may be incorrect. But even if they are 
to be accepted, and this sudden change of basicity really occurs, it can be ex- 
plained on the assumption of analogous structures for the tertiary and qua- 
ternary hydroxides, and without having recourse to any new theories of val- 
ency. If we say that the five valencies of pentavalent nitrogen are all equal, 
this only means that the relation between any five groups and the nitrogen 
atom is determined by those groups themselves, so that (excluding stereoisom- 
erism) isomeric arrangements are impossible. It is nevertheless quite con- 
ceivable, and indeed probable, that three of the nitrogen valencies (those of 
trivalent nitrogen) are essentially different from the other two; and that when 
successive alkyl groups are introduced into ammonium hydrate they fill up 
these three places first. If so, the introduction of a fourth group, which must 
now take up one of the other two positions, may be expected to produce an 
effect on the molecule different from that produced by any of the other three." 

On p. 73 we find an interesting discussion of the diimines. 

"The absence of color in these compounds is important, in view of their 



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3IO New Books 

undoubted quinoid structure. It is commonly assumed that all quinoid com- 
pounds are colored, like the quinones themselves and there is even a tendency to 
suppose that nearly all colored aromatic derivatives contain a quinoid ring. 
But these views require to be reconsidered in view of the recent discoveries on 
the one hand of quinoid substances (like the imines) which are colorless, and 
on the other of colored bodies closely resembling the supposed quinoid) aro- 
matic colored compounds, which cannot contain a quinoid ring because they 
are not aromatic derivatives at all. 

"The causes which determine the absence of color among these quinone deriv- 
atives are not understood. It seems certain that the simple quinoid compounds 
form two series, one colored, like the quinones themselves, and the other not. 
On the other hand, these bodies are capable of a further increase of color, which 
must be accompanied by some structural change. In the triphenyl-methane 
series, for example, the feebly colored Homolka bases go over on treatment 
with acids into the brilliantly colored dyes. This is generally represented as 
the passage of trivalent into pentavalent nitrogen: 

(H^.CeH,),C - C,H, - NH — ► (H^.CeH,),C - C.H, - NH,C1. 

But there is much evidence to show that the change of valency of the nitrogen 
is not sufficient to determine color: thus the diimine salts are colorless. It is 
clear that the influence of a pentavalent nitrogen atom on the color depends 
largely on whether it has a hydrogen atom attached to it: if it has, then the 
effect on the color is much the same as if it was trivalent; if it has not, then its 
effect is usually quite different. The conversion of the group— NX, where X 
is a hydrocarbon radical, into — NXjHCl docs not seem in general to influence 
the color, but its conversion into — NX3CI does so in a very marked way. Of 
this we have an example in the quinone imine derivatives which we have just 
been considering, and another (curiously in the opposite direction) in rosaniline 
dyes, where the change from — NEt, to — NEt,HCl is without effect, w^hile the 
change to NEtjCl destroys the influence of this group on the color altogether. 
This is one of the phenomena which suggest that there is a difference in constitu- 
tion between bodies of the type R3NHX and those of the type R^NX. 

**We must therefore look for some other change of structure in the conversion 
of the Homolka bases into the rosaniline dyes. In this connection certain facts 
recently discovered by Willstatter with regard to the quinone-diimines are of 
great interest. If unsymmetrical dialkyl-/>-phenylenc-diamine is oxidized, 
brilliantly colored substances are produced, known from their discoverer as 
Wurster's salts, which were supposed to be true diimine derivatives, e, g., HN — 
CflH^ = N(CH3)jCl. Further investigation has shown, however, that these 
bodies contain an atom of hydrogen more than this, they are bimolecular com- 
pounds (analogous to the quinhydrones) of one molecule of the oxidation pro- 
duct with one molecule of the unoxidized diamine, and may be written: 

NHjCl . , . NH, 

II I 

CH, ... QH, 

II I 

N(CH3),C1. . . N(CH,),. 

the dotted lines indicating some unknown kind of linkage. If they are further 



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New Books 311 

oxidized to the true diimines the color disappears. Willstatter suggests that 
this peculiar linkage, which he calls meriquinoid (partially quinoid), is the 
cause of color in bodies of this type. An analogous explanation would hold 
for the triphenylmethane dyes, the true dye having a linkage between the quin- 
oid nucleus and one of the other nuclei, which would be absent in the Homolka 
base." 

On p. 92 there is an interesting paragraph in regard to the imido chlorides. 

"In the case of the a-oxy -acids, such as glycoUic add, it was formerly sup- 
posed that the ture imido-acids could be isolated. GlycoUic add gives a normal 
amide CH^OH.CO.NH,; but if its anhydride is treated with ammonia, or its 
imido-ether is saponified, an isomeric substance is obtained, which was origin- 

yOH 
ally assumed to be the iso-amide or imidohydrine CH^OH.C^ 

"Analogous compounds have been obtained from other a-oxy-adds. The 
subject has been reinvestigated by Hantzsch and Voegeln, who have shown 
that the properties of these substances are incompatible with this structure — 
and, indeed, as far as one can see, with any structure. They cannot be converted 
into the amides, a change which one would expect to occur with the utmost 
ease, and their molecular weight is twice that required by the simple formula. 
Their other properties are also most extraordinary. Though they are only 
weak bases, and are not addic at all, their solutions are very good conductors 
of electridty, so that their electrolytic behavior is that of salts. Moreover, 
though they are fairly stable to acids, they are easily decomposed by certain 
salts, such as caldum chloride, with the formation of a glycollate. No satis- 
factory hypothesis has yet been proposed to account for these phenomena." 

It is worth while noting that nitroso-butane, p. 122, has a sublimation point 
below the melting point, 76**. 

Somebody should certainly work out more carefully the conditions determin- 
ing the production of red and yellow salts, p. 174, from the nitrophenols. 

Under fulminic acid, p. 224, we find the following: 

"The overthrow of all two-carbon formulae and the final establishment of 
our knowledge of fulminic add on a firm basis, is due to the work of Nef. He 
showed in the first place that all the evidence was in favor of its containing 
only one-carbon atom in the molecule. Its decomposition products are nearly 
all one-carbon bodies. It is formed, as we have seen, by treating sodium nitro- 
methane with mercuric chloride, and if treated with nitrous add it is converted 
intp methyl-nitrolic add H.C(NO,)NOH. If we take it as proved that there is 
only one carbon atom in the molecule and also consider the fact that on treat- 
ment with hydrochloric add it gives hydroxylamine, only one formula is possible, 
namely H.O.N »= C*'. The real reason which prevented the earlier investiga- 
tors from adopting such a one-carbon structure as this was their unwillingness 
to admit the existence of a dyad carbon atom. But this objection has been 
removed by Nef's other work on dyad carbon, and he has been able to show 
that his formula is alone capable of explaining the very remarkable reactions 
of fulminic add, while all subsequent work on these bodies has only served to 
confirm his views." 

"The one thing needful to establish Nef's formula beyond all doubt is a deter- 
mination of the molecular weight. If it can be shown that fulminic add con- 



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312 New Books 

tains only one carbon atom in the molecule, we have no alternative but to accept 
Nef s view as to its structure. A direct determination of this magnitude is impos- 
sible» but indirect evidence of great force has recently been adduced, from the 
electrolytic behavior of the sodium salt in aqueous solution. The salt can be 
prepared by treating merctuy fulminate in alcohol with sodium amalgam, and 
is fairly stable. On Nef's theory it is the salt of a monoba^c add NaONC; on 
any other, the acid is dibasic, and the salt Na^CONC),. Now van't Hoff has shown 
that the alkaline salts of mono-basic adds in fifth to tenth normal solution give 
a value of the dissociation factor i of about 1.85, and those of dibasic adds 
about 2.5. From this it follows that if sodium fulminate is NaONC, its appar- 
ent molecular wdght in solution should be 35, but if it is Na,(ONC)^ it should 
be about 52. From the depression of the freezing point in fifth-normal aqueous 
' solution, it was found to be 34.9, agreeing with that required for the monomolec- 
ular formula. Again Ostwald found that the increase in molecular conductiv- 
ity in passing from N/32 to N/1024 solution, for the salt of a monobasic add 
was from 4 to 8 units, and for that of a dibasic add about ix. The observed 
increase for sodium fulminate was 5 units. These results make it certain that 
the add is monobasic, and has the formula HONC; and hence Nef's view as to 
its structure must be adopted.'* 

In the chapter on uric add there is a delightful paragraph, p. 318, on the 
work of Medicus. 

"In 1875 Medicus published a most remarkable paper on the constitution 
of this group of compounds. He produced hardly any new facts; but some- 
times on the basis of facts already known, and sometimes, apparently, on no 
basis at all, he suggested formulae for nearly every known compound of the 
group — uric add, xanthine, caffdne, theobromine, guanine, and hypoxan thine. 
The singular point is that with the exception of the position of one of the methyl 
groups in theobromine, all the formulae which Medicus proposed are absolutdy 
correct; although it was not until the most recent work of Fischer, in whidi 
he revised and modified many of his own previous formulae, that they were recog- 
nized as bdng so." 

On p. 378 we get a tentative explanation of the catalytic action of mercury 
on the oxidation of naphthalene by sulphur trioxide. 

"The catalytic influence of the mercury, which occurs in other cases of sul- 
phonation as well, is remarkable, and a very probable explanation of it has 
been given by Dimroth. He has shown that if a mercury salt is heated with 
an aromatic derivative, a compound is formed in which one hydrogen on the 
ring is replaced by mercury. This subsitution is quite peculiar in that the 
position taken up by the mercury is not determined by the substituent akeady 
present: it is always ortho. Now it is found that if benzoic add is sulphonated 
in the presence of merciuy, the amount of meta and para adds produced is the 
same as if the mercury were not there; but in addition a considerable quantity 
of the o-sulphonic add is formed, which is not obtained at all in the absence 
of mercury. This shows that the catalytic influence of the mercury is due to 
the formation and decomposition of a mercury derivative, as it introduces the 
sulphonic group at the position which the mercury (but no substituent) would 
occupy." Wilder D, Bancroft 



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THE PHOTOGRAPHIC PLATE, V 



BY WILDER D. BANCROFT 

The Latent Image I 

When light is allowed to act for a short time upon a 
photographic plate or upon silver bromide precipitated from 
aqueous solution, the silver bromide is changed in some way, 
because a so-called developer causes the silver bromide which 
has been exposed to light to blacken more rapidly than the 
silver bromide which has not been exposed/ We say that 
the light has produced a latent image and our problem now 
is to find out what change has taken place and what the latent 
image is. The difference between the exposed and unexposed 
portions of the plate is one that can be varied within fairly 
wide limits by treating the plate with certain reagents. When 
studying the chemical reactions, it is often advantageous to 
use a collodion plate instead of a gelatine one because collo- 
dion is less readily attacked than gelatine by most reagents. 

The latent image is destroyed by nitric acid, the attack 
being more rapid the more concentrated the acid.' It is also 
destroyed' by chlorine, bromine, or iodine; by ferric chloride, 
cupric chloride, mercuric chloride, or gold trichloride; by 
chromic acid, potassium persulphate, acidified potassium per- 
manganate, or potassium ferricyanide; by hydrobromic acid, 
hydrochloric acid, potassium iodide. In other words these 
substances attack the material composing the latent image 
more readily than they do the unexposed silver bromide. On 
the other hand sodium thiosulphate dissolves the unexposed 
silver bromide more rapidly than the silver bromide which 
has been exposed to light. The same general statement is 
true, though to a varying degree in regard to ammonia, to 
jx)tassium cyanide, and to ammonium bromide.* 

* Cf. Englisch: Eder's Jahrbuch der Photographic, 15, 605 (1901); Schaum 
and Braun: Ibid., 18, 74 (1904). 

' Eder: Sitzungsber. Akad. Wiss. Wien., 114, lla, 1159 (1905). 
' Eder's Handbuch der Photographic, 5th Ed., 3, I, 72 (1902). 

* Eder: Jour. Phys. Chem., 13, 63 (1909). 



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314 Wilder D, Bancroft 

In certain cases the latent image will be destroyed by 
processes taking place in the film under ordinary conditions. 
This phenomenon has been studied with some care by Baeke- 
land from whom I quote.* 

**One of the many practical advantages of the gelatine 
dry plate over the older processes consists in the fact that 
development of the plate can be postponed to any convenient 
time after the exposure. Examples have been recorded where 
negatives were successfully developed a number of years after 
the plate had been exposed in the camera. On the other 
hand, the question has often been raised in how far results 
obtained thus are inferior to those which are produced on 
plates developed immediately after exposure. Direct facts 
have been given indicating a gradual disappearance of the 
invisible photographic image. 

**The study of this question requires more accurate 
methods than those ordinarily resorted to by the average 
photographer and this may account for the reason why this 
question has brought out some quite contrary statements. 

**The gradual disappearance of the latent photographic 
image seems to be a process exactly the reverse of the one 
which produces this image under the action of light. I pro- 
pose to designate this phenomenon under the name of photo- 
retrogression. Very probably we have to deal here with what 
is called in chemistry a reversible reaction, similar to those 
occuring in all phenomena of dissociation and double decom- 
position where under the action of opposing energies which 
try to produce two different systems a condition of equili- 
brium is reached. 

'* That such a condition of equilibrium may exist has been 
shown conclusively by the study of photodecomposition of 
pure chloride of silver in sealed glass tubes, but an almost vir- 
gin field of study and research is still open for the physico- 
chemist who desires to determine the limits and factors of 
photodissociation of various chemical compounds. Such 

* Baekeland: Intemat. Kongress angew. Chemie, Berlin, 4, 403 (1903). 



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The Photographic Plate 315 

study should not be limited to silver salts of which the suscep- 
tibility to the action of light is well known. Much more 
stable inorganic compoimds may undergo profound changes 
as I have been able to show when studying the photooxidation 
of hydrochloric acid. This reaction is so much the more 
remarkable because hydrochloric acid, in presence of oxygen 
oxidizes imder the influence of simlight, whereas we know 
also that chlorine in watery solution evolves oxygen and forms 
hydrochloric acid. We are here in presence of a reversible 
reaction produced imder the influence of light and analogous 
to what occurs in photoretrogression : 

2HCI + O ^± H,0 + Clj. 

"I shall not try to decide here what chemical reaction 
occurs in the production of the latent silver image, nor of its 
photoretrogression. I consider any decisive opinion on this 
subject as idle talk as long as we can not dispose of more 
thorough and complete laboratory investigations than the 
meager work which has been published on this subject. 

*' Without going into further general theoretical specula- 
tion, we may state that photoretrogression was known to 
exist long before the dry plate was invented. In the daguerre- 
otype process the image can only be retained in proper devel- 
opable state diunng a few hours. For the wet collodion pro- 
cess a similar fact is known, although it might be ascribed 
here to the physical condition of the sensitive layer which 
requires a certain degree of moisture. Photoretrogression in 
gelatine dry plates can best be observed in such cases where 
the time exposure has been limited to the very minimum, as for 
instance in undertimed negatives. Even then it may be dif- 
ficult to observe it imless under some particular conditions. 
In all cases where more than enough exposure has been given, 
photoretrogression becomes much less apparent and this is 
perhaps the reason why so many contradictory statements 
have been made on this subject. 

** I have studied photoretrogression on dry plates, films, 
bromide papers, and chloride papers. For all of my experi- 



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3i6 Wilder D, Bancroft 

ments I take a standard negative purposely selected so as to 
show delicate graduations with no high lights and no trans- 
parent parts. I also use a sensitometer scale, similar to what 
is used for ordinary sensitometer tests, and consisting mainly 
of a glass plate divided into numbered squares made up of 
different thicknesses of opaque pigment. As source of light, 
I use a normal candle, the same quality of candle being used 
in all my experiments. 

** In order to minimize the errors of observation, the ex]>er- 
iments have always been repeated at least four times. My 
way of proceeding consists in placing the strip of dry plate, 
film, or paper in direct contact with the negative or sensitom- 
eter scale, and then exposing it during a given time at a con- 
stant distance from the candle light. All ordinary precau- 
tions are taken so that the experiment should only take place 
when the flame of the candle bums under normal conditions. 

**In each series of experiments, some of the dry plates, 
films or papers are developed immediately, the development 
being carried as far as possible; t. e., until the image does not 
gain any further strength. The results thus obtained are 
numbered and stored away for further comparison. An 
equal number of the dry plates, films, or papers exi>osed imder 
the same conditions are stored away in the dark, imdeveloped 
but are treated with the same developer afterwards at specific 
intervals. Proper precautions are taken while storing the 
tests, so as to exclude the possibility of outside influences on 
any of the light-sensitive material. When developing any of 
these tests a developer of strictly the same composition and 
same temperature is taken and development is carried on 
under exactly the same conditions, but in each case, develop- 
ment is carried on as long as the image gains in strength or 
detail, regardless of beginning *fog.' In each case I selected 
a developer which experience had indicated to be best adapted 
for each sensitive material. 

"Some of the experiments were repeated using different 
developers but in each case the results were only compared 
with those obtained by identical developers. I have observed, 



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The Photographic Plate 317 

however, that whenever photoretrogression was apparent, it 
would be shown by each one of the developers, so that the 
nature of the developer seems to play no role in this phenome- 
non. In the first experiments, thus conducted, I came soon 
to the conclusion that certain varieties of films and bromide 
papers, also some chloride papers show photoretrogression to 
considerable extent, even after relatively short intervals, while 
other varieties and specially dry plates do not show it so 
much. This is mainly due to some chemical differences in 
the emulsion as will be explained further. In some varieties 
of bromide paper and films, photoretrogression was quite 
apparent, even after so short a time as forty-eight hours. 
The image developed after this time was invariably weaker 
than the one obtained after exposure; at the end of a few days 
the results became much more decisive and after two month 
in some cases only a faint image was all that the developers 
could bring out. 

"Let me repeat here and insist on what I have stated 
before, that these results become apparent only in such cases 
where expostu'e has been insufiicient and where consequently 
the prints have been undertimed. In such cases, only, devel- 
opment can be carried on to its full limit, and after all silver 
salts, which have imdergone the action of light, have been 
reduced, the image will not gain any further strength, even 
if the developer is left in contact for a considerable time. 
The only effect which such prolonged development may then 
produce is a general gray * fog ' which covers the whole image 
without strengthening it or changing the relative density of 
the different parts of the first developed image. 

**In full timed prints and by these we designate such 
ones as have practically received a slight excess of exposure, 
this condition of affairs does not exist; by developing these we 
reach a stage where development has to be stopped, not on 
accoimt of fear of *fog* but because the shadows and half 
tones will acquire too great a density, which would prove 
objectionable in a negative and which in our experiments 
renders it impossible to distinguish slight differences in the 



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3i8 Wilder D. Bancroft 

results. All experienced photographers will rather give too 
much than too little expostu-e to their negatives. This prac- 
tice is very commendable in view of the fact that thereby the 
effect of photoretrogression is avoided. 

** However, there are many cases where full timed expo- 
sures are not possible, for example, in instantaneous work 
and there photoretrogression may have serious drawbacks. 
It may become objectionable still in some methods of auto- 
matic printing and developing which are carried out now-a- 
days on a large scale by some industrial establishments. As 
the amount of material involved in one of these oi>erations 
may represent thousand of dollars, at a time, it is quite natural 
that in such cases photoretrogression deserves special attention. 

"A few years ago when automatic printing and develop- 
ment or 'photography by the mile,* was first carried on in 
New York, it was brought to my notice that a large roll of 
bromide paper about 500 meters long and 65 cm wide, which 
had been printed automatically by artificial light, could not 
be developed to the proper strength, although the test strip 
which had been printed under identical conditions, but devel- 
oped immediately afterwards, had given excellent results one 
week before. The timing device of the automatic printer, the 
steady quality of the light, the imiformity of sensitiveness over 
the full length of the paper and the conditions of the devel- 
oper were all critically examined. At the time, I had just 
started my investigation of photoretrogression and I was able 
to trace to this phenomenon the difference in results. That 
this was really the cause of all the trouble was proven beyond 
doubt by some direct experiments which were made after- 
wards. 

*' Mr. A. E. Johnstone, of New York, reported to me sim- 
ilar cases which have been observed lately during the develop- 
ment of strips of negative and positive films such as are used 
now-a-days for animated photographic exhibitions. For 
instance, a large roll of films exposed in Europe and of which 
a test strip had been developed there so as to make sure that 
the exposure was correct, was shipped to New York for fur- 



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The Photographic Plate 319 

ther development. On arrival there, it was found that the 
pictures developed were so weak as to make the results unsat- 
isfactory. The same developer was used as in Europe and 
great stress was put on the quality of the chemicals, but with- 
out avail. Finally the imdeveloped portion of the film was 
reshipped to Europe to the party who had developed the trial 
strip, but he could not obtain any better results. 

** Another case was cited to me of an undeveloped film 
which was sent to New York from the Philippine Islands. 
This film had also been exposed in an apparatus for animated 
photographs, and by a competent operator who tested a por- 
tion of the strip for exposure and development. On arrival 
in New York, the image could not be developed, and showed 
all signs of photoretrogression. In this particular instance, 
the film had been submitted for a relatively long time to a 
humid and warm climate, which includes conditions which 
are most favorable for producing photoretrogression as we 
shall see later. 

'*I have tried by direct experiment to determine what 
factors have an influence on photoretrogression. 

Temperature. — Dry plates, films, bromide paper and 
chloride paper were exposed as indicated above. A certain 
number of the tests were developed immediately, a same num- 
ber of them were enclosed in a bottle provided with a glass 
stopper and kept in a refrigerator at a temperatiu^e ranging 
from I ® C to 4^ C. An equal number of the tests were kept 
during one week in a stoppered glass bottle in a box of which 
the temperature was kept at 40° C to 48° C. At the end of 
three days photoretrogression was very apparent for the 
tests kept at a high temperature, whereas it was not notice- 
able even after two weeks for the tests which had been stored 
in the refrigerator. 

Humidity, — Same tests as above were repeated. Some 
were placed in a large earthenware jar provided with a tight 
cover. In the center of the bottom of the jar was placed a 
large cylindrical glass containing sulphuric acid 66^ B^. so as 
to keep a very dry atmosphere. Other tests were placed in a 



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320 Wilder D, Bancroft 

similar jar but, instead of sulphuric acid, the glass this time 
contained cotton, soaked with distilled water so as to satu- 
rate the air of the jar with humidity. The two jars were left 
in a room of which the temperature oscillated between i8°C. 
and 27° C. At the end of two weeks, the tests of both jars 
were developed. All showed photoretrogression, but the tests 
in the humid jar showed it much more than the ones contained 
in the dry atmosphere. 

Chrome alum. — In all above experiments I had the oppor- 
tunity to observe that some dry plates which I used, showed 
less photoretrogression than some films, bromide papers and 
chloride papers. Then again, films and bromide and chloride 
papers of different makes showed results quite different with 
each brand. I soon found out that those papers which were 
most subject to photoretrogression had either a slight acid 
reaction or contained noticeable amoimts of chrome salts. In 
order to determine in how far the presence of chrome salts has 
an influence on this phenomenon, I made a bromide emulsion 
and after dividing it in two portions I added to one of these 
about I % chrome alum of the amount of gelatine used in the 
emulsion. The other portion received no addition and both 
emulsions were used to coat some test plates and papers. The 
tests were dried under the same conditions, and afterwards 
exposed and developed at long intervals. Photoretrogression 
was much more apparent with the tests containing chrome 
alum than with those without this salt. 

Acidity. — In the previous experiment, I noticed that the 
tests which contained chrome alum showed a sUght acid reac- 
tion on litmus paper. In order to determine whether acidity 
or chrome alum has the greater influence on photoretrogres- 
sion, I repeated the experiment in the following way: To 
the whole of the emulsion I added the same amount of chrome 
alum. Then I divided the liquid into two portions. One of 
the portions was used to coat test plates just as it was; the 
other received an addition of some drops of diluted ammonia, 
just enough to produce a very slightly alkaline reaction. An 
initial test showed little or no difference in the sensitiveness of 



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The Photographic Plate 321 

both emulsions, but after a few weeks, photoretrogression 
was less apparent in the tests which were quoted with the 
slightly alkaline reaction. I next compared a neutral emul- 
sion containing chrome alum with the same emulsion, con- 
taining no chrome alum, but enough citric acid so as to give 
it a distinct acid reaction. The acid emulsion without chrome 
alum produced more photoretrogression than the neutral 
emulsion with chrome alum. 

" In all these experiments the tests were carried on in the 
same way and kept under the same conditions for each set of 
experiments, but in certain cases development of all the tests 
of each set had to be postponed for a more or less longer pe- 
riod until such time was reached when the difference in the 
results was sufl&ciently apparent to enable me to draw conclu- 
sions. These experiments explain why certain brands of dry 
plates, films or papers show more photoretrogression than 
others. This phenomenon must undoubtedly be attributed 
to slow chemical action and the chemical conditions of the 
different emulsions determine the speed and intensity with 
which it occurs. 

**It is a known fact that emulsions which are intended 
for films or papers receive almost always an abundant addi- 
tion of chrome alum, so as to render the gelatine coating less 
soluble and to produce at the same time a more viscous 
liquid which is better adapted for certain coating machines. 
Dry plates, on the other hand, require no such addition of 
chrome alum. 

** Furthermore, if emulsions are made by the 'boiling' 
process where the ' ripening ' is obtained by a prolonged appli- 
cation of heat, their final reaction will be neutral or very 
slightly acid and the smallest amount of chrome alum may 
give them an acid reaction. Emulsions * ripened' with the 
ammonia process will almost always be alkaline even after 
long washing, and the addition of a little chrome alum will 
not necessarily give them an acid reaction. 

** I should mention here that emulsions, made with the 
ammonia process but separated by a centrifugal machine. 



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322 Wilder D. Bancroft 

may produce, after reincorporation of the silver bromide with 
fresh gelatine, a neutral or slightly acid reaction which may 
become apparent after the addition of chrome alum. Let me 
also call attention to the fact that these slightly acid or neu- 
tral emulsions give generally papers or dry plates which have 
better keeping qualities and which are less liable to become 
* foggy' with age; it so happens that such emulsions are also 
those which are most liable to show photoretrogression. 

** In the above statements, whenever I referred to chloride 
paper, I meant papers of the Velox class coated with such 
emulsions which contain chloride of silver in the gelatine, but 
without any excess of nitrate of silver or any other soluble 
silver salt, and which are intended to produce images by alka- 
line development and not by printing out methods. 

*'The facts mentioned here add new strength to the sup- 
position that the latent photographic image is due to a chem- 
ical and not to a physical condition. Many hypotheses, none 
of which has been sufficiently demonstrated, have been pro- 
posed to explain this subtile chemical reaction. WTiether 
we try to explain the latent photographic image by the forma- 
tion of free silver, sub-bromide and sub-chloride of silver, or 
again by the existence of oxy-sub-bromides or oxy-subchlorides, 
the above-mentioned facts point out that photoretrogression 
occurs by chemical action. This action is probably the 
reverse of what occurs in the formation of the latent image. 
Whether in this phenomenon oxygen, directly or indirectly 
plays a role, we cannot say yet, and further work in this direc- 
tion may give us a better insight in this matter; but I call 
your attention to the fact that a neutral or alkaline light- 
sensitive layer would be in better condition for absorbing free 
bromine or chlorine or oxygenated derivatives of the same, 
than if it had an acid reaction. 

** As far as regards the influence of heat and moisture, it 
is sufficiently accepted as being of great importance in all 
chemical reactions; in this particular case we are not aston- 
ished to see again the two factors as being of very marked 
influence in photoretrogression. 



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The Photographic Plate 323 

** Photoretrogression, or slow disappearance of the latent 
photographic image, takes place in glass plates, films and 
paper coated with gelatine silver bromide or gelatine silver 
chloride. 

** Photoretrogression is especially apparent in undertimed 
images and much less noticeable in overtimed images. 

"Photoretrogression may, imder special conditions, 
become apparent in dry plates, films or paper, forty-eight 
hoiirs after exposure, and may increase until the latent image 
has nearly disappeared. Photoretrogression occiu-s quicker 
at high than at low temperatures. 

** Photoretrogression is less apparent in neutral or slightly 
alkaline sensitive layers than in such ones which have an acid 
reaction.** 

Barker* found that when plates, made from a well- washed 
silver bromide emulsion are packed after exposure in Swedish 
filter paper and yellow paper, the latent image does not dis- 
appear in eight years. If the exposed plates are packed in 
yellow paper alone, fog is formed. The latent image dis- 
appeared rapidly if as much as 1/480 part of potassium iodide 
had been added when the emulsion was prepared. Potassium 
bromide also increased the rate of disappearance of the image 
though not very much. Ammonium chloride acted in the 
same way. If the emulsion contained 1/240 part of tannin, 
the image could be seen faintly before development. The 
presence of tannin prevents the disappearance of the latent 
image. 

In some photometric work carried on by Brush^ it, was 
foimd that ** photographic action is slow in starting, involving 
considerable light energy which leaves no permanent record. 
If exposure is stopped at this stage, the starting action relapses 
almost wholly within a few minutes and is lost to further 
exposure. Once started, however, action increases rapidly 
to full activity and then remains substantially constant dur- 



^ Eder's Jahrbuch der Photographie, 19, 364 (1905). 
Phys. Rev., 31, 241 (1901). 



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324 Wilder D, Bancroft 

ing further exposure. Relapse of sensitiveness follows expo- 
sure and is very marked at the end of a few hours. 

''Photographic action, when fully excited, continues 
many minutes after exposure, gradually dying out. With the 
adopted period of exposure, this after action amounts to some- 
thing like eight or ten percent of the whole. Within an hour 
or two after action has ceased, relapse sets in andamoimtsto 
about four percent in the first thirty hours, fully half of 
which occurs within the first four hours.'' 

Ltippo-Cramer has also made some experiments on photo- 
retrogression \ 

" I have shown previously that the decay of the photo- 
chemical action is especially marked with iodides of mercur>% 
that this reaction velocity is increased enormously by mois- 
ture, and that the recombination of the dissociated halogen 
with the mercury, taking place under the influence of water, 
is more complete the finer the grain of the emulsion. The 
decrease of the blackening with dry mercurous iodide gela- 
tine also takes place very much more rapidly and more com- 
pletely with a fine-grained unripened iodide than with the 
ripened emulsion. If one exposes one plate of each type until 
they are blackened to about the same degree and then puts 
them away in the dark, it is easy to notice a great difference 
at the end of a day or two. At the end of two days the fine- 
grained mercurous iodide has become very light while the 
coarser emulsion shows only a slight decrease in color. At 
the end of seven days the fine-grained emulsion has entirely 
recovered its original bright color while the coarser mercurous 
iodide is still very dark. 

** Stimulated by this experiment I decided to see whether 
a fine-grained silver bromide emulsion might not show the 
phenomenon of the decay of the latent image even though 
the highly sensitive bromide does not show it to any appreci- 
able extent. As a matter of fact water causes a distinct 
decrease in the darkening of a fine-grained silver bromide emul- 

* Luppo-Cramer: Phot. Correspondenz, 44, 130 (1907). 



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The Photographic Plate 325 

sion caused by exposure to direct sunlight. Nothing of the 
sort can be detected with highly sensitive plates. It is a 
question whether the decrease of the blackening with fine- 
grained plates is really due to a recombination of the halogen 
with the silver similar to that with the iodides. There is no 
doubt but that the latent image fades appreciably in these 
fine-grained emulsions, though slowly as is the case with all 
latent images.* A large number of plates of the same fine- 
grained emulsion as that used in a previous investigation were 
exposed under a negative to daylight for the same length of 
time. Immediately after exposure half of each plate was 
developed, using in every case the same developer at the same 
temperature and developing for the same length of time. The 
developed halves were then put away together with the unde- 
veloped halves. At the end of two months a marked decay 
of the latent image could be detected; at the end of six months 
only the high lights were left. There was no marked dif- 
ference to be detected between plates developed after nine 
months and plates developed at the end of six months. There 
is therefore a distinct decay of the latent image on silver 
bromide gelatine plates when the emulsion is a fine-grained 
one." 

The phenomena of the latent image can apparently be 
duplicated in other ways without exposure to light. A 
dilute solution of a reducing agent will affect a dry plate in 
such a way that the silver bromide can then be reduced by 
the ordinary developer under ordinary conditions. Namias^ 
has shown this for solutions of stannous chloride. 

** In a communication I made to the Chemical Society of 
Milan in 1897 on the chemical reactions involved in the man- 
ufacture of silver mirrors, I made use of a fact which has 
appeared to me to be a very interesting one. 

*' If one takes a carefully cleaned mirror and pours upon 
it a solution of stannous chloride, even one as dilute as 



* Cf. Luppo-Cramer: Phot. Correspondenz, 43, 80 (1906). 

* Phot. Correspondenz, 42, 155 (^1907). 



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326 Wilder D. Bancroft 

I : loocxx), and if one then washes the muror with distilled 
water, the rate of precipitation of silver from an ammoniacal 
tartrate solution is much greater with such a muror. The 
infinitesimal amount of stannous chloride remaining on such 
a plate is suflScient to make the reduction of the silver consid- 
erably easier. The labile equilibrium of the ammoniacal silver 
tartrate solution is at once upset by the action of infinitely 
small traces of such a powerful reducing agent as stannous 
chloride. 

'*When I experimented to see how the same substance 
acted towards silver salts in developing the latent agent, I 
found that its effect was quite marked. In fact a i : 20000 
solution of crystallized stannous chloride, SnCl^.aHjO, in 
distilled water, completely free from air, will produce in a few 
minutes' action on a silver bromide plate a latent action which 
can be detected by developing with an ordinary developer. 
The action of stannous chloride seems to be exactly analo- 
gous to that of light. 

"If one allows a sufficiently concentrated solution (1% 
for instance) to act for an instant, or a more dilute solution 
for a longer time, one obtains a latent image which develops 
with great sharpness. If the action of the stannous chloride 
lasts too long, one gets a result analogous to that caused by 
over-exposure ; the plate fogs and there is no sharpness. This 
is the result, for instance, if the one percent solution is allowed 
to act for two or there minutes. If the solution is allowed to 
act longer, it causes a visible change just as light does.*' 

This result has been observed by Perley^ who has also 
duplicated the action of light by means of a sodium arsenite 
solution or by a diluted solution of an ordinary develoi>er. 

Carey Lea^ has shown that a moderate pressiu'e appar- 
ently produces a latent image. 

**I was able to show many years ago that mechanical 
force could produce a latent image. Lines drawn with a 



* Jour. Phys. Chem., 14, 689 (1910). 
2 Am. Jour. Sci., [3] 43, 528 (1892). 



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The Photographic Plate 327 

glass rod on a sensitive surface could be rendered visible by- 
development in the same way as impressions of light. An 
embossed card pressed on a sensitive film left an invisible 
image which could be brought out by a reducing agent. The 
raised portions of the embossed work exert a stronger pressure 
on the sensitive film than the rest of the card and these por- 
tions darkened when acted upon by a reducing agent. In 
the same way, the lines traced with a glass rod, blackened 
under a developer. In each case, it was the portions which 
had been subjected to pressure which yielded first to the 
reducer. It is therefore clear that in the molecules which 
had received this slight pressure the affinities of the atoms had 
been loosened.*' 

Liippo-Cramer* does not believe a true latent image is 
formed in this way. He says that the pressure phenomena 
*'can be distinguished from real reduction phenomena because 
the latter occur throughout the whole film and are not changed 
in the slightest by any rubbing of the stu-face.'* 

Carey Lea's experiments show that something similar to 
a latent image can be formed by heat.' 

"To determine the eff^ect of heat on silver bromide, 
pieces of bromide paper were placed in a desiccator (of course 
using inactive light), and heated to the extent indicated. 
For each piece so heated a corresponding piece cut from 
beside it in the same sheet was preserved and these two pieces, 
that heated (after complete cooling) and that not heated 
were placed side by side in an oxalate developer. Compari- 
son between these developments indicated the eff^ect of the 
heat. The following results were obtained. 

*' A piece kept for 3 minutes at 145° was strongly affected 
and blackened quickly in the developer, the companion 
piece remaining white. A piece kept for 1 5 minutes at a tem- 
I>erature commencing at 131° and ending at 136° was still 
more thoroughly affected than the foregoing, the longer expo- 



* Phot. Correspondenz, 40, 180 (1903). 

* Carey Lea: Am. Jour. Sci., [3] 41, 262 (1891). 



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328 Wilder D. Bancroft 

sure more than making up for the lower temperature. Com- 
panion piece remained white. A piece kept for 8 minutes at 
a temperature 107° to 108° was distinctly but not strongly 
affected. Companion piece as before. A piece kept for 17 
minutes at a temperature of 100° to 102° was almost unaf- 
fected. A long and careful development brought out a faint 
difference between the piece so heated and its companion 
piece. 

J "It was found that to obtain accuracy in determinations 
such as these, the paper must rest on a glass, and not a metal 
shelf in the desiccator, as the metal shelf is always hotter 
than the air by which the thermometer is affected. In using 
a metal shelf, if the paper curled by reason of the heat, the 
part that rested on the shelf developed darker than that 
which was simply acted on by the air. By substituting a 
glass shelf this difference of effect disappeared. 

"The result of the foregoing and other experiments was 
that the effect of heat on AgBr commences at about 100°, 
that up to 1 08° it is still slight and acts slowly, but that at 
120° to 126° a strong action commences, which further 
increases as the temperature is raised. The analogy with 
allotropic silver is well marked. 

** It may at first seem strange that a temperature of 100® 
should produce a permanent change in a substance which 
will bear a high heat without decomposition, but the explana- 
tion lies in the presence of water in the former case. WTien 
silver bromide is formed in paper and dried in the air, it still 
retains moisture. Even at 100°, this moisture is not driven 
off. A silver haloid requires to be heated to a temperature 
between 130° and 140° for several hours before it ceases to 
lose weight. Therefore in all the foregoing cases, moisture 
must have been present. 

" It remains to be shown that by a sufficiently long expo- 
stue to a moderate heat in the presence of moisture a visible 
decomposition results. For this purpose silver chloride was 
precipitated with an excess of hydrochloric acid, after thorough 
washing was placed in a glass tube of about a centimeter in 



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The Photographic Plate 329 

internal diameter and one half a meter long, and was sealed 
up with a blast lamp. During all these operations the chloride 
was thoroughly protected from light. Five or six cubic cen- 
timeters of pure water were first added to the chloride. It was 
intended to exclude completely the effect of pressure and to 
act on the chloride as far as possible by heat only, and for 
this reason a longer tube was used and one end only was im- 
mersed in the chloride of calcium bath, the other end remained 
cold throughout the operation. 

*'The silver chloride formed itself into a compact plug 
and was forced by the steam which generated below it up to 
the middle of the tube. This effect though not intended, 
ans^Vered very well as the chloride was kept constantly under 
the influence of steam at about 100°. It soon began to darken 
and at the end of three or four hours all the lower part was 
violet-brown, the upper part gray, the change taking place 
entirely through the mass. Some thin smears of silver chlo- 
ride on the lower inside part of the tube were completely 
blackened. 

**0n opening the tube next day there was no escape of 
gas. The water sealed up with the silver chloride had ac- 
quired a faint but distinct alkaline reaction showing that 
enough alkali had been dissolved from the glass to overcome 
any acidity arising from decomposition of the chloride. The 
water contained traces of alkaline chloride. 

'*A similar examination was made with silver bromide 
precipitated with excess of hydrobromic acid and thoroughly 
washed with distilled water. The action of diffuse light on 
silver bromide is very different from that on silver chloride. 
A portion of that prepared, as above mentioned, changed in 
diffuse light very quickly from yellow to greenish yellow, but 
after that first change the alteration was extremely slow and 
in an hour had only reached to a dirty greenish gray. The 
action of direct sunlight was quite different; fifteen minutes 
exposiu^e changed the greenish gray to dark chocolate-brown. 

*' In the tube, the silver bromide did not form a plug ike 
the chloride but separated into balls which remained in the 



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330 Wilder D, Bancroft 

bottom of the tube. By keeping the chloride of calcium bath 
considerably above ioo° the water in the tube was kept 
actively boiling : it condensed in the upper part of the tube 
and returned. Six hours of this treatment only brought the 
bromide to the same greenish color which it would have 
acquired by a few minutes' exposure to diffuse light. 

"The conclusion to be drawn as respects both the silver 
haloids is that they undergo actual decomposition by the 
action of moist heat, but that this effect is much more marked 
in the case of chloride than that of bromide.'' 

Carey Lea also found that sulphuric acid seems to pro- 
duce a latent image. * 

** Dilute sulphuric acid quickly changes allotropic silver 
to normal, and therefore if the parallelism which I have indi- 
cated really exists, marks made on bromide paper with dilute 
sulphuric acid should be capable of development. 

"The experiment was made by drawing characters on 
silver bromide with a glass rod dipped into sulphuric acid 
diluted with twice its bulk of water. After allowing the acid 
to remain in contact for two or three minutes, the paper was 
immersed in running water and washed for an hour or two. 
On applying the oxalate developer nothing appeared. Feel- 
ing confident that an effect must be produced, the experiment 
was repeated several times and the results closely examined. 
On one specimen it was found that the characters had appeared, 
but reversed, that is lighter than the ground which had dark- 
ened by the development being pushed. This at once gave a 
clue; it showed that traces of the acid adhered too strongly 
to be removed by washing and by locally checking the devel- 
opment, interfered with the reaction. Accordingly, next 
time after a very short washing, the paper was immersed in 
water to which a trace of ammonia had been added, and after 
ten or fifteen minutes' action, the ammonia was thoroughly 
washed out. The result was striking: as soon as the devel- 
oper was applied, the characters which had been traced with 
acid came out strongly as brown marks on a white surface. 

* Carey Lea: Am. Jour. Sci., [3] 41, 264 (1891). 



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The Photographic Plate 331 

Cold sulphuric acid even tmdiluted is generally held to 
have no action on silver haloids, but it is well known that the 
hot, strong acid decomposes them. The foregoing experi- 
ments leave no doubt that the cold dilute acid produces an 
initial effect invisible to the eye but revealed by greater ten- 
dency to give way under the action of a reducing agent. 
This action of the acid comes therefore exactly into line with 
that of light and heat. In all three cases an effect is pro- 
duced inappreciably until a reducing agent is applied. But 
m all three cases the agent which produced this invisible 
effect is capable by continued action imder favorable condi- 
tions of bringing about a visible change without the aid of a 
reducing agent." 

In the Waterhouse process for making positives, it has 
been shown ^ that thiocarbamide causes some change in tmex- 
posed silver bromide such that the bromide is readily reduced 
by the developer. In fact the change is so marked that un- 
exi>osed silver bromide, after treatment with thiocarbamide, 
will often reduce more rapidly than silver bromide which has 
been exposed for a short time to light. 

In the preceding pages I have referred to some of the 
more interesting characteristics of the latent image. We can 
now consider some of the theories in regard to the nature of 
the latent image. It has been beUeved that the latent image is 
an oxidation product; a physical modification; a silver nucleus; 
a sub-bromide; a solid solution. 

The theory that the latent image is an oxidation product 
has not met with much favor; but it is always interesting to 
see how much of a case can be made out for any hypothesis, 
so I quote v. Tugolessow's paper in fuU.^ 

**The prevailing assumption in regard to chemical reac- 
tions in photographic processes is that the light-sensitive salt 
(usually a silver halide) is decomposed by light into a sub- 
stance with a lower valence. This behef seems to be based on 



* Perley: Jour. Phys. Chem., 13, 655 (1909). 

* V. Tugolessow: Phot. Correspondenz, 40, 594 (1903). 



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332 Wilder D. Bancroft 

the behavior of sUver chloride (AgCl) which loses weight 
while blackening in the light and changes so as to look like 
silver sub-chloride (Ag,Cl). 

**This might all be right to a certain extent if the only 
action of light on silver chloride was to cause an ever-increas- 
ing blackening. As a matter of fact something else is to be 
noticed. In addition to the change which can be followed by 
the eye, there is also an invisible change taking place which 
we detect in the case of silver bromide and silver iodide by 
means of a developer. There is reason for supposing that the 
invisible change precedes the one which is visible to the eye, 
and we must therefore assume that the production of a lower 
compound from the light-sensitive salt is not the immediate 
result of the action of the light but is merely the last stage in 
a more or less complicated process. The fact that all devel- 
opers are reducing agents and that the haloid salts of silver 
form no saturated compounds, causes us to assume that the 
first action of light is not a reducing one but an oxidizing one. 
The lower stages may result from the decomposition of the 
substance with a higher valence which is first formed. 

** According to this assumption the change of silver chlo- 
ride in the light takes place in two stages; first, an oxidation 
to a higher valence; second, the decomposition of the new 
compound into silver subchloride or even into metallic silver. 
Since the first stage must be accompanied by an increase in 
the weight of the silver chloride, it seemed possible that the 
hypothesis could be checked experimentally. Well-washed 
silver chloride was therefore spread in thin films on watch- 
glasses, dried to constant weight at ioo°, placed in a desicca- 
tor and exposed to daylight. At the end of an hour the glasses 
were weighed again and in all cases a distinct increase in weight 
was noticed. This was sometimes as high as 0.003 g per 
1.995 S AgCl and was almost identical when referred to equal 
surfaces.^ 

'*An experiment with silver bromide led to no satisfac- 

^ When the exposure to light was increased to eight hours a decrease 
in weight occurred. 



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The Photographic Plate 333 

tory blackening^ even below icx)° and the same thing happened 
in a second experiment. Nevertheless, the action of light 
caused an increase in weight of 0.0005 g and 0.0015 g per gram 
of silver bromide. 

*'The increase in weight of the silver chloride is strong 
proof that no decomposition has taken place and that a com- 
bination with some other substance has occurred. Under 
the condition of the experiment, the other substance must 
be the oxygen of the air and the new compound must there- 
fore be one corresponding to silver peroxide. It is known, 
however that silver peroxide decomposes when heated to 150® 
and consequently one would expect that the silver halide 
changed by light would decompose when heated, and that 
the latent image would consequently be developed. 

**To check this hypothesis an exposed collodion plate 
was heated for one to two hours in a drying closet at 125° 
and the result was exactly as expected. It was possible 
in this way to develop the latent image. If the fixing was 
carried out very carefully, it was possible to obtain a negative 
from which one could make quite clear prints upon light- 
sensitive paper.' 

**This experiment is, therefore, to a certain extent an 
argument for the belief that the action of light causes an 
oxidation. Since an oxidation can only take place in pres- 
ence of an oxygen carrier, the light-sensitive substance should 
not be affected by light in the absence of oxygen carriers. 
Since it was not possible for me to study the action of light 
on the halide salts of silver in a vacuum or in an atmosphere 
of an inert gas, I availed myself of a simpler method, but one 
which seemed equally certain to give a conclusive result. 

" I covered the silver chloride with a solution of stannous 
chloride (SnCl2) and exposed the whole to the light. Since 
stannous chloride is a reducing agent, there is no possibility 



* Probably some light got into the dark room though the eye was not 
able to detect any leaks. 

* It is only right to say that the fixing must be done very quickly or 
else the image may disappear. 



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334 Wilder D. Bancroft 

of the silver chloride being oxidized and consequently it was 
to be expected that silver chloride would not blacken in the 
light under these conditions. As a matter of fact the silver 
chloride did not blacken though exposed to the light for 
several days. Even when the water evaporated and crystals 
of stannous chloride separated, there was no change in the 
color of the silver chloride. * 

** Just the opposite was observed when hydrogen peroxide 
was substituted for the stannous chloride, in other words, 
an oxidizing agent instead of a reducing agent. The silver 
chloride darkened more rapidly and more completely than 
in the air or in the water, while silver bromide blackened 
fairly rapidly under the hydrogen peroxide solution, although 
ordinarily it is not easily changed. 

"If the usually accepted view of the photographic pro- 
cess were correct, these experiments should have given the 
opposite results from what they did. The silver chloride 
and silver bromide should have been unchanged in the hydro- 
gen peroxide solution and should have changed rapidly in the 
stannous chloride solution. Since this did not happen, 
it is clear that there can be no question of a reduction of the 
silver salts. 

** If the photochemical changes are a result of oxidation, 
it follows that oxygen carriers would have the same eflfect 
as light upon the silver halides. To test this conclusion, 
silver chloride paper was exposed to the gases set free from 
bleaching powder by acids, chiefly hyjx>chlorous anhydride 
and chlorine. It was assumed that the silver chloride paper 
would blacken as in light, if the silver chloride were oxidized 
under these conditions. As a matter of fact small dark 
spots, having a metallic luster, appeared after ten or fifteen 
minutes' exposure to the gases. If the gases acted for a longer 
time, the paper was bleached again but at the same time 
underwent a great loss of light-sensitiveness. 

**This last experiment indicates that, in addition to the 

* This experiment succeeds better the less stannic chloride (SnCl4) there 
is in the solution. 



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The Photographic Plate 335 

change analogous to that produced by light, the silver chloride 
also undergoes another change which manifests itself in a 
decrease of sensitiveness to light. On the assumption that 
the latter change is due either to an absorption of hydrochloric 
acid by silver chloride or to the formation of a compound 
containing more chlorine, it would be necessary to limit 
the reaction so that silver chloride could react only with 
oxygen. This was accomplished by placing the silver chloride 
paper in an ozonizer and subjecting it to the action of the 
silent discharge. At the end of fifteen minutes the same 
dark spots appeared as before but they did not disappear 
on prolonged exposure to the silent discharge. 

"If the blackening of silver chloride is caused by a re- 
duction, these experiments show that it can only be as the 
result of a decomposition of the higher oxidation stages. 
The close similarity between these results and those due 
to the action of light, points to an identity of steps. So 
far as the silver halides are concerned, we are quite justified 
in breaking away from the generally accepted opinion in 
regard to the photochemical reactions. We should adopt 
the view that the reaction of light on the silver halides is 
primarily an oxidizing and not a reducing one. 

** The phenomenon of solarization and the increased weight 
of exposed silver chloride show that under the influence of 
light there is a direct addition of oxygen to the silver halide. 
The following general formula may therefore represent the salts 
after the action of light : 

AgXv 

(AgX),>0 (X = halide). 
AgX/ 

In this formula n varies inversely with the exposure to light. 

When the action of light is a maximum, n becomes zero and 

the formula is to be written : 

AgXv 

>0. 
AgX/ 

This is the expression for a saturated halide oxygen con^pound 

of silver. 



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336 Wilder D, Bancroft 

**We must assume that the oxygen compounds of silver 
chloride are very instable and that therefore it is scarcely 
possible under ordinary conditions to make a compound 
corresponding to this formula. Yet the oxygen compounds 
of silver bromide must be much more stable than those of 
silver chloride, while the silver iodide compounds are more 
stable than the corresponding silver bromide ones. 

**It is well known that silver bromide is more sensitive 
to light than silver chloride. Consequently we should ex- 
pect silver iodide to be more sensitive than the bromide. 
Judging from the literature this is not the case. In order 
to clear up this contradiction, I made a number of experi- 
ments. Three strips of the same kind of paper was soaked 
in normal solutions of the three salts: the first in a solution 
of potassium chloride, the second in a solution of potassium 
bromide, and the third in a solution of potassium iodide. 
To convert these potassium salts into silver salts, the three 
strips of paper were dipped in a five percent solution of silver 
nitrate, dried, placed side by side in a Scheiner sensitometer, 
and exposed for thirty seconds to the action of daylight. 

'* After the development it appeared that the silver chlor- 
ide paper had scarcely been changed at all, that the bromide 
paper had changed up to the fifth division, and the iodide 
paper up to the fourteenth division. When a longer exposiu-e 
was given, all three strips of paper underwent a change and 
the change in the silver iodide paper was as much greater 
than the change in the bromide paper as the change in this 
latter was greater than the change in the chloride paper. 
Consequently the silver iodide is the most sensitive to light 
and silver chloride the least sensitive.* 

"While studying the action of light on other light-sensi- 
tive substances, a few experiments were made with mer- 
curous salts and with ferric chloride. Ordinary writing 
paper was soaked in a saturated solution of merciu'ous nitrate, 
dried, and exposed under a negative to light. My idea was 
that, if the action of light were an oxidizing one, an insoluble 

* [The experiments do not refer to a ripened emulsion. W. D. B.] 



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The Photographic Plate 337 

basic mercuric salt would form where the paper was illuminated 
and would remain on the paper after the imchanged mercurous 
nitrate had been washed out. 

"The action of Hght produced no visible change in the 
paper; but when the paper had been washed in boiling water, 
the exposed places assumed a yellowish color which then 
changed to a dark gray, making the image fairly distinct. 
Tie theory was confirmed. Under the action of light there 
was formed a colorless, insoluble mercuric salt which was 
changed by a large excess of water into the yellow salt, 
Hg(NO,)j.2HgO.H30. This latter reacted with the excess 
of merciu-ous nitrate in the solution, forming mercuric nitrate 
and mercurous oxide. The mercurous oxide was decomposed 
by boiling water into oxygen and metallic mercury. 

" The action of Ught on mercurous chloride was also studied. 
Sheets of paper were soaked in a solution of mercurous nitrate, 
dipped in a dilute solution of hydrochloric acid, dried, and 
exposed imder a negative to light. The action of the light 
was to be detected by means of the mercuramide compounds. 
Since those of the mercurous salt are black and those of the 
mercuric salt are white, it was expected that ammonia would 
only blacken the parts which had not been exposed to light. 
The experiment did not turn out at first as had been hoped 
for the whole sheet of paper was blackened by ammonia. 
After a short treatment with very dilute hydrochloric acid, 
the high lights became white. This shows that mercurous 
chloride is imquestionably changed to mercuric salt by light, 
but not completely: and consequently the test was spoiled 
by the ammonia reacting with some of the undecomposed 
merciu-ous salt. Since the amoimt of this latter was not 
large, a very short exposure to acid was sufficient to remove 
it, while the acid had practically no more effect on the portions 
which had not been exposed to light. 

** Although there are many more experiments to be made 
on the chemical changes which take place under the influence 
of light, the facts which have been presented justify the con- 



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338 Wilder D. Bancroft 

elusion that the action of light always tends to be an oxidizing 
action." 

The accuracy of these observations has been questioned 
by Liippo-Cramer/ who immersed silver bromide, silver 
chlorbromide and silver chloride dry plates in: water; three 
percent hydrogen peroxide; three percent sodium nitrite; 
and three percent stannous chloride. Hydrogen peroxide 
retarded the blackening in light, while stannous chloride 
and sodium nitrite caused a marked increase in the rate of 
blackening. 

It is only fair, however, to point out that v. Tugolessow's 
experiments were made with silver chloride, bromide, and 
iodide precipitated in paper and that he did not work with 
dry plates. It is also fair to note that Liippo-Cramer' has 
recorded the fact that a five percent sodium nitrite solution 
retards the blackening of silver chloride by light.' 

Chapman Jones* is one of the enthusiastic supporters 
of the belief that the latent image is merely a physical modi- 
fication of silver bromide. 

**It is generally considered that the main question is 
whether a chemical or physical change takes place in the 
silver salt (silver bromide) when a developable image is 
produced. A physical change is an alteration in the nature 
of the substance which does not affect its composition. Silver 
bromide, when physically changed, remains silver bromide, 
but the nature of the combination of molecules into aggre- 
gates is modified. A chemical change consists of an alter- 
ation of the composition of the substance. In this case it 
would be a matter of decomposition; the silver and bromine, 
instead of remaining combined, would be wholly or partially 
separated. Now a chemical change must be preceded by a 
physical change; there must be a movement or commotion 
within the molecule before actual decomposition takes place. 

* Eder's Jahrbuch der Photographic, i8, 335 (1904). 
^ Phot. Correspondenz, 40, 97 (1903). 

' Cf. Perley: Jour. Phys. Chem., 14, 700 (19 10). 

* Science and Practice of Photography, 374, 387, 382 (1904). 



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The Photographic Plate 339 

The question, therefore, is not whether the change is chemical 
or physical, but whether it is physical only, or whether it 
passes beyond the physical stage to an actual decomposi- 
tion. There certainly is some change, and, therefore, there 
is a physical change; but while some consider that this is 
followed by decomposition, others, including the author, 
consider that the balance of evidence is overwhelmingly 
against decomposition/' 

*'If there is decomposition, the amount of silver salt 
that is decomposed must be exceedingly minute, small almost 
beyond imagination. The amount of decomposition might 
be increased many thousands of times before the products 
of decomposition would have accumulated in sufficient quantity 
for direct recognition. The exceeding minuteness of the 
extent of the decompostion is allowed, as it must be, by all 
who advocate the decomposition theory, but it is a very 
weak point in that theory, as will be subsequently shown. 
If the change is regarded as physical only, this difficulty 
disappears altogether, and the quantity of silver salt changed 
into the developable condition is readily recognized and 
weighable. 

**The remarkable stability of the developable image has 
been adduced as an argument in favor of its consisting of a 
substance that is chemically, and not merely physically, 
diflferent from the original silver bromide. But there is no 
reason why a physically changed silver bromide should not 
be as stable, or even more stable, than the sub-bromide. 
The soluble and insoluble varieties of sulphur remain soluble 
and insoluble respectively for long enough. The black 
and red sulphides of mercury are chemically identical, and 
both are stable. The same may be said of the yellow and 
red oxides of mercury. And each of these substances, it 
may be noted, behaves to certain reagents in a different 
manner from the other, though both, in each case, have the 
same composition. Many other examples might be quoted. 
On the other hand, many of the products of chemical change 
are exceedingly imstable. 



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340 Wilder D, Bancroft 

f 
**The stability of the developable image is not much 

argument either for or against either theory of the nature of 
the developable image, but what little weight it has, appears 
rather to favor the physical theory. An exceedingly minute 
amount of metallic silver or silver sub-bromide would prob- 
ably be more readily affected by outside adverse influence 
than a physically modified silver bromide present in relatively 
very large quantity. Moreover, the silver or the sub-bromide 
is in any case, accordingly to the chemical theory, in the 
immediate presence of the bromine that it has lost, and one 
cannot accept this theory without supposing that the bromine 
easily leaves the gelatine and returns to the silver, or else 
that aerial oxygen readily oxidizes the sub-bromide, as these 
are the only explanations of reversal that have been sug- 
gested to fit in with that theory. The stability of the de- 
velopable image becomes, therefore, from this point of view, 
a strong argument in favor of the physical theory, because 
it is necessary that the image shall be unstable according to 
the chemical theory." 

'*The exceedingly minute amount of sub-bromide pro- 
duced by ordinary ex|X)sure, according to the decomposi- 
tion hypothesis, is allowed on all hands to be very, very 
far from sufficient to furnish by itself an image that can be 
seen or discovered in any way, except by allowing it to grow. 
This growth, which means the reduction to the metallic state 
of the silver bromide that has not been affected by light 
by the indirect agency of that which has, is a necessary ad- 
junct to the decomposition theory. The physical theory 
is complete in itself, and needs no supplementing. But 
the physical theory is in no way opposed to the fact that, 
imder some conditions, the image spreads during develop- 
ment, unexposed silver salts being reduced to the metallic 
state. The demonstration that the image spreads in this 
manner, therefore, is no proof of the chemical theory, though 
it removes a difficulty which, if it existed, would at once 
condemn the decomposition hypothesis. 

"But in a gelatine plate, it has never been proved that 



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The Photographic Plate 341 

the image does grow more than an almost negligible amoimt 
(if at all), such, for example, as might interfere in the photo- 
graphing of fine black lines. It is common experience that 
in the development of a gelatine plate a time comes when 
the * development is complete,' *the exposure effect is ex- 
hausted,' 'there is nothing more to get,' *the density ceases 
to increase,' to quote a few common phrases. If the whole 
image, except an indescribably small fraction of it, is the 
result of this growth or spreading, why should the growth 
of the image stop while the developer is still on the plate, 
instead of going on until the reduction of the silver salt is 
complete, and the plate is evenly black all over? It has 
been suggested that this growth cannot extend from granule 
to granule in the gelatine, but only from one part to another 
of the granule, so that only these granules that have been 
affected by light by the production in them of a few molecules 
of sub-bromide are amenable to development. This re- 
finement of the chemical theory appears almost equal to the 
surrender of it. It formed no part of the original idea, and 
that the exigencies of the case should require such a suggestion 
is evident proof of the difficulty foimd in applying the chemical 
theory to the results of every day work. 

** According to the decomposition hypothesis of the nature 
of the developable image, all that the developer has to do 
is to reduce the sub-bromide that is produced by the action 
of light to the metallic state, this silver, by acting on unaltered 
bromide producing more sub-bromide, which is in turn re- 
duced, and so on. The developer, therefore, simply reduces 
silver sub-bromide to the metallic state. This hypothesis 
obliges us to believe that there are some substances that 
can reduce silver bromide but cannot reduce the sub-bromide, 
or else these substances are of such a nature that the action 
of silver on silver bromide to form the sub-bromide cannot 
take place in the presence of their solutions. The first sug- 
gestion seems exceedingly unlikely. With regard to the 
second, it is known that development is not hindered by 
ammonia or by a solution of ferrous citrate and ferrous oxa- 



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342 Wilder D. Bancroft 

late, but by mixing the two, the author has been unable to 
develop a developable image, although the silver salt was 
slowly and in the end copiously reduced. These diflSculties 
and the need for these out-of-the-way suggestions do not 
exist if the physical theory is adopted. It is only what 
would be expected that some substances should be able to 
reduce the silver bromide that has been made less stable 
by the action of light without affecting the unchanged bromide, 
while other substances should be unable to discriminate 
between the altered and unaltered bromide. It is often 
the case that it requires much care to distinguish by chemical 
means between two different physical conditions of the same 
substances. 

**If there is decomposition, that is, if the developable 
image consists of silver bromide that has lost a part of its 
bromine, then, as the function of the developer is to remove 
bromine (leaving the image in metallic silver), exposure 
and development ought to be to a considerable extent inter- 
changeable. But exposure and development are not inter- 
changeable, for exposure beyond a certain point makes de- 
velopment impossible. 

**In some cases, however, it is otherwise. In exposing 
printing-out papers it appears that the exposure may be 
stopped at almost any time, and the image completed by 
development. This developable image, therefore, has not 
the same characteristics as the one we are considering. It 
may be urged that in printing-out papers, organic salts of 
silver are present, and act as sensitizers, that is, absorbers 
of bromine, but gelatine is a sensitizer, too, and will absorb 
large quantities of bromine. 

**One of the most direct pieces of evidence against the 
decomposition hypothesis is furnished by the action of a 
solution of ammonia. This reagent, it is admitted, decomposes 
silver sub-bromide, leaving half the silver as metal. There- 
fore, taking cognizance of this reaction only, the application 
of ammonia to the plate first in development ought approxi- 
mately to halve the speed of the plate, because the amount 



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The Photographic Plate 343 

of the metallic silver produced by its action would be one- 
half the quantity produced by the initial action of the de- 
veloper, which according to this theory, reduces the sub- 
bromide entirely. Or if the speed of the plate is not so much 
affected, certainly development should be retarded by the 
previous application of the ammonia, because it would give 
only half the amount of metallic silver to start with. But 
as a matter of fact, applying the ammonia first, rather quickens 
development, and tends to increase the apparent sensitive- 
ness of the plate. 

"An ordinary solution of ammonia is a good solvent for 
finely-divided silver, the oxygen of the air dissolved in it 
taking part in the reaction. The previous application of 
ammonia should, therefore, not only straightway halve 
the amount of metalUc silver that otherwise would be avail- 
able, but at once begin to get rid of the other half by dis- 
solving it. As the largest possible amount of silver is ex- 
ceedingly minute, thousands of times smaller than the smallest 
quantity directly detectable, and so finely divided, withal, 
as to be invisible, the ammonia should quickly dispose of it. 
Now these effects of ammonia are not imaginary effects; 
they can easily be verified. But as a matter of fact, ammonia 
facilitates development. Ammonia does not act on the de- 
velopable image as it does act on silver sub-bromide. This, 
therefore, is evidence that the developable image does not 
consist of silver sub-bromide. 

"The author believes that all the facts known to bear 
on this subject agree with the supposition that the develop- 
able image consists of particles of silver salt, rendered less 
stable but not decomposed, and that no particle can be de- 
veloped that has not been itself immediately affected by the 
exposure. It should be borne in mind, however, that light 
is not homogeneous, and that its effects vary according to 
its wave length. There may, therefore, be more than one 
change going on during the exposure of a gelatine-bromide 
plate. And it is possible that the nature of a developable 
image varies; it may be different on a gelatine dry plate from 



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344 Wilder D. Bancroft 

what it is on a wet collodion plate, and again different when 
a daguerreotype plate is employed. 

**A11 ideas as to the exact character of the change that 
occurs in the silver salt when light produces a developable 
image are exercises in imagination. It has been suggested 
that the silver bromide is ionized, that the molecular grouping 
in which perhaps it exists is modified, or that a kind of crys- 
tallization action takes place; but these and other ideas of 
the same sort do not serve to correlate the facts that are 
known, and their usefulness is not apparent. 

*'A working hypothesis that the author ventiu'es to 
indicate in the crudest of terms for the sale of clearness vie\^^ 
the silver bromide either in single molecules or molecular 
aggregates as if the silver and bromine were flat figures, say 
like two visiting cards arranged edge to edge in the same 
plane, as they would be laid upon a table side by side. The 
change of this group into a developable condition would 
consist in the rotation of one about the axis common to 
both imtil it was in a plane at right angles to the plane of the 
other, this rotation at the same time screwing the one away 
from the other. Such a system would evidently be less 
stable imder certain conditions than the original. By the 
continued action of light the rotation would continue until 
the two parts were both again in the same plane, and this 
would represent reversal — an undevelopable condition pro- 
duced by a continuance of the change that produces the 
developable condition. The further action of Hght producing 
further rotation, a second developable condition results, 
but less marked than the first, as the increased rotation has 
separated the two parts further from each other. As the 
rotation continues the developable and undevelopable con- 
dition alternate, but rapidly become confused until the 
two parts are really forced asunder and actual decomposi- 
tion results. The student can for himself apply this sugges- 
tion to all the facts of the case." 

Although Namias showed that stannous chloride will 
apparently produce a latent image on a dry plate, he does 



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The Photographic Plate 345 

not admit for a moment the accuracy of the sub-bromide 
hjrpothesis.^ 

" How does stannous chloride produce a latent impression? 
The advocates of the chemical hypothesis will find in these 
experiments of mine a new argument in favor of their view. 
They will certainly say that stannous chloride is a powerful 
reducing agent and that it therefore reduces silver bromide 
to sub-bromide. It is easy, however, to show that the amoimt 
of this reduction must be infinitely small. A plate, 9 cm X 12 
cm, may be assumed to have at least o.i gram silver bromide 
in the film, and this plate will be completely changed by the 
prolonged action of 50 cc of a stannous chloride solution 
(i : 200,000); in other words by the action of 0.00025 gram 
stannous chloride, assuming that all the stannous chloride 
in the solution enters into the reaction; unquestionably 
only a small portion of the total stannous chloride reacts. 
This amount of stannous chloride is only sufficient to reduce 
o.oooi gram silver bromide to sub-bromide. At most, 
therefore, only one one-thousandth of the total amount can 
have been converted into sub-bromide. 

**For ten years I have combatted the sub-bromide 
hypothesis on the basis of many exjjeriments and this one 
serves to strengthen my theoretical views. Since so little 
sub-bromide is formed, one may well ask how the reduction 
of all the silver bromide is brought about. 

"I will not go further with these theoretical consid- 
erations and I return to the experiments. If a plate or 
if silver bromide paper be dipped in a three percent stannous 
chloride solution and then dried, it will give an image by 
direct printing if exposed long enough to the light. The 
image is not dissolved by thiosulphate. In this way one can 
use plates and papers which would otherwise be worthless 
on account of fog and one can obtain pictures by a printing- 
out process. In no other way have I been able to obtain 
such sharp pictures with silver bromide without development. 



* Namias: Phot. Correspondenz, 43, 155 (1905). 



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346 Wilder D. Bancroft 

I have used oxalic acid and oxalates several years ago as 
sensitizers for silver bromide and they produce images fairly 
readily; but the image is dissolved almost completely by 
thiosulphate. 

"The reduction by light in presence of oxalic acid is, 
therefore, not so thorough as in presence of stannous chloride. 
In the first case the action of light forms silver sub-bromide 
only and this substance dissolves to a great extent in thio- 
sulphate. In the second case light must reduce the silver 
salt to metallic silver because thiosulphate scarcely attacks 
the image at all. The blackening of silver bromide by Ught 
takes place very rapidly when stannous chloride is present." 

Namias has discussed the question of the latent image 
at some length in his book.* 

** Without question one of the most marvelous things 
in photography is the formation of the latent image. The 
halide salts of silver — chloride, bromide, and iodide — are 
specially noticeable for the characteristic of changing in 
consequence of a very short exposure to light, thereby forming 
a latent image, the existence of which can only be shown 
by development. It is hard to say what change the silver 
salts imdergo during a very short exposure to light. It is 
so slight in amount that it escapes our senses and all physical 
or chemical methods of investigation. 

**To accoimt for the formation of latent images, we have 
recourse to hypotheses, and these hypotheses are of two 
kinds. According to one point of view the action of light 
produces a real and definite chemical change. According 
to the other point of view we are dealing with a physical 
or molecular change. It is possible to make out a strong 
case for either point of view. 

**The hypothesis that we are dealing with a chemical 
change is at first sight the most plausible one. We know 
that when silver chloride, bromide and iodide are exposed 
to light for a sufficient length of time, halogen is set free and 



Namias: Chimie Photographique, 102, no (1902). 



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The Photographic Plate 347 

they become black. There is produced a chemical decompo- 
sition which can be followed. The total amoimt of decompo- 
sition, increases as the exposure is increased. It, therefore, 
seems legitimate to assume that the decomposition which one 
can see when the action of light has been prolonged sufficiently, 
is the reaction which takes place to an infinitesimal degree 
when the exposure to light is very short and that it is this 
decomposition which gives use to the latent image. 

*'In support of this hypothesis is the fact that chlorine, 
bromine and iodine destroy the latent image when allowed 
to act on a plate which has been exposed to light. It looks 
as though this destruction of the latent image were due to 
a regeneration of the substance which had been decomposed 
by light. 

**The upholders of the chemical theory claim that the 
very brief action of light causes the formation of a very small 
amoimt of sub-chloride, sub-bromide, or sub-iodide of silver. 
If AgCl, AgBr and Agl are the formulas of the chloride, 
bromide, and iodide of silver, respectively, the formulas 
of the corresponding sub-halides will be Ag2Cl, Ag^Br, AgjI. 
There is satisfactory evidence of the existence of these sub- 
salts and one may claim that the blackening, at least in the 
first stages of exposure, is due to the formation of sub-halides 
rather than to the precipitation of metallic silver. The 
amount of the sub-halides constituting the latent image is, 
however, very small. According to Eder the amount of 
bromine set free from a surface of ten square centimeters of a 
silver bromide gelatine emulsion cannot be more than a 
millionth of a gram. Since this amount of emulsion will contain 
at least 0.25 gram of silver bromide, it follows that the amoimt 
of sub-bromide formed according to the chemical hypothesis 
will only be a little more than a millionth [hundredth-thous- 
andth?] of the silver bromide in the sensitive plate.* 

*'The fact that some substances which react readily 
with chlorine, bromine or iodine (chemical sensitizers) facili- 



[Eder gives the figure as one in a thousand. W. D. B.] 



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348 Wilder D. Bancroft 

tate the formation of the latent image would seem to prove 
the chemical nature of the change produced by light. It 
is not easy to explain the action of these substances so long 
as one claims that the change is purely molecular and that 
none of the chlorine, bromine or iodine is eliminated. 

"We have now given some of the evidence in favor of 
the chemical hypothesis. There are certainly as many and 
as good reasons for accepting the hypothesis that the invisi- 
ble change produced by light is entirely physical or molecular. 
Let us consider the daguerreotype for a moment. The 
latent image is formed on a plate of silver covered with silver 
iodide, and it is developed by means of mercury vapor. The 
action of the mercury is purely physical, the mercury con- 
densing on the places which have been ex|X)sed to light. 
Must we admit that a chemical change in silver iodide has 
taken place in order to account for its having acquired the 
property of retaining mechanically the vapor of merciuy? 
Most certainly not. 

"Moser's experiments have a bearing on this question. 
A coin was placed on a glass or a metal plate and left there 
for several hours. If one breathes on the plate where the 
coin had been, or passes the vapor of iodine or merciuy over 
it, there is a differential condensation on the places which 
have been in contact with the coin and an image of the coin 
is thus formed. What appears more strange is that one 
can obtain an image and can develop it in this way, even 
without actual contact between the coin and the plate. It 
is enough if the coin is near the plate. 

** These facts have nothing to do with the action of light, 
but light will produce similar phenomena. In fact, if one 
exposes a plate of silver, copper or glass to an intense light 
for several hours, one notices that water vapor from the breath 
or mercury vapor will develop the parts which have been 
exposed to the action of light. 

**In the cases thus cited the change which makes it 
possible to develop parts of the glass or metal plate is piu'ely 
a physical one. Why not, then, admit that with the daguerreo- 



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The Photographic Plate 349 

type plate the change, which makes it possible for the silver 
iodide to condense the merciiry vapor, is also a purely physical 
one? 

"If we admit this for the daguerreotype plates in which 
the light-sensitive material is silver iodide, why should we 
not also assume a purely physical phenomenon to account 
for the change taking place in other light-sensitive prepara- 
tions of silver halides, even though the latent image is de- 
veloped with a liquid instead of a vapor and by a chemical 
process instead of a physical one?" 

"If we adopt the hypothesis of a physical modification, 
we may be asked how we account for the destructive action 
of chlorine, bromine, or iodine on the latent image. It is 
not easy to find a completely satisfactory answer to this; 
but if the destructive action of chlorine, bromine, or iodine 
is in keeping with the chemical hypothesis and confirms 
it, we cannot say the same for the action of other substances 
such as potassium iodide for instance. We do not know 
how to account for the action of potassium iodide on the 
sub-halide and yet we know that this salt destroys the latent 
image imder some conditions. 

"The spontaneous disappearance of the latent image, 
makes the acceptance of the chemical hypothesis very difficult ; 
and this decay of the image is common to all negatives, though 
the time necessary varies with different plates. We know 
that with daguerreotype plates the latent image disappears 
in a very short time. This disappearance takes place quite 
independently of any external action. It is precisely in the 
daguerreotype process, that the latent image disappears 
rapidly even though this is the process in which a chemical 
explanation of the phenomenon is hardest to find. In order 
to account for the disappearance, it is not permissible to 
postulate that the sub-iodide, formed by the light, takes 
up iodine again. If we grant that a small amount of the 
iodine is set free by the light, it will react at once with the 
silver plate to form more silver iodide. It is hopeless to 
fall back on the action of substances in the sensitive film 



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350 Wilder D, Bancroft 

because there is no silver nitrate nor any other substance 
which might decompose gradually and tend to reverse the 
action of light." 

**The invisible change which moderate pressure produces 
upon the silver halides, must be a polymerization. All 
forms of energy produce the same effect when they act to 
a limited extent. The hypothesis, that the first action of 
different forms of energy on silver bromide causes a pK)lymeri- 
zation, gives us a plausible explanation for development by 
reduction. In development by reduction, which is the usual 
method for bromide dry plates, the latent image becomes 
visible because the halogen (chlorine, bromine, or iodine) 
is removed more rapidly from the portions exposed to the 
action of Ught (or of any other form of energy) than from 
the other portions. There is a setting free of silver which 
is the substance forming the visible image. If now we jx)stu- 
late for silver bromide two formulas, AgBr, and Ag^Br,, 
the second being a polymer of the first, it seems reasonable 
to assume that the silver bromide corresponding to the second 
formula is more readily decomposed in consequence of the 
atoms of silver being in some way partially connected in the 
molecule and also the atoms of bromine, so that the affinity 
between silver and bromine is diminished thereby, with the 
result that decomposition should apparently take place more 
readily. 

**Let us now consider another phenomenon which fin- 
nishes another argument for the molecular or physical hy- 
pothesis. We know that the latent image on a silver bromide 
gelatine plate becomes, when developed, more dense at the 
points where action of light has been most intense. We 
know also that under normal conditions the image shows 
no tendency to spread sideways. If we claim that the in- 
visible modification produced by light is a sub-bromide, 
we must admit that the chemical modification is limited to 
an infinitely small fraction of the sensitive film, because 
we have already seen that only an infinitesimal amount of silver 
sub-bromide is formed. It is, therefore, necessary to account 



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The Photographic Plate 351 

for the reduction of the silver bromide to metallic silver ex- 
tending through the whole thickness of the film. To do 
this we must admit that a physical action plays an important 
part in the development and that, in consequence of an 
attraction between the silver (reduced from the sub-bromide) 
and the unchanged silver bromide, the image can develop 
to a greater depth. If we are going to speak of an attraction 
or of any other physical action, why should this action take 
place in different amounts at the points in the plate which 
have received different exposures, and why should the action 
make itself felt in the depths of the film and not at the side 
of the image? 

**We believe that it is hopeless to search for a rational 
explanation of these facts if we assume the chemical hy- 
pothesis. We could also cite other facts which have had 
an influence in making us abandon this hypothesis. 

**In an article published in Archiv wiss. Photographie, 
for 1899, Professor Abegg resuscitated the hypothesis that 
the formation of the latent image is due to the precipi- 
tation of an infinitesimally small quantity of metallic silver, 
which then acted as a nucleus and facilitated the reduction 
of the surrounding silver bromide. In confirmation of this 
hypothesis, Abegg established the fact that dilute nitric 
acid tends to destroy the latent image by reacting with the 
metallic silver. Before that, it had always been supposed 
that nitric acid did not have such an action and this was looked 
upon an an argument in favor of the sub-bromide hypothesis 
because this was supposed not to be attacked by nitric acid 
while metallic silver is attacked. Further, we know from 
Eder's experiment that, if an unexposed silver bromide 
gelatine plate is immersed in a developing bath and is brought 
in contact with a silver wire, reduction takes place at the 
point of contact. This proves that metallic silver really 
has the power of facilitating the reduction of silver bromide 
with which it may be in contact. In addition, an experi- 
ment by Abney supports thisi view. Abney showed that 
if a finished negative is placed in contact with an unexposed 



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352 Wilder D. Bancroft 

emulsion and if the two are then placed in a developing bath, 
the image is re-enforced by reduction of the silver bromide 
in the superposed film. Another interesting fact, recently 
discovered, may be cited in support of Abegg's theory. If 
an exposed dry plate is fixed in a hyposulphite bath before 
it has been developed, and is then plunged into a silvering 
bath such as is used in the collodion process, an image appears. 
It is claimed that this happens because the hyposulphite 
has dissolved the unchanged silver bromide, leaving intact 
the infinitesimal quantity of silver set free by the light. This 
silver causes the deposit on itself of silver from the bath. 

**In spite of the excellent reasons in support of this 
chemical theory, which is much superior to the one based 
on the assumption of the sub-bromide, it will not be accepted 
by everybody. Why should one admit that this infinitesimal 
quantity of metallic silver forms regularly throughout the 
whole depth of the film which is to be developed? Why 
does the silver reduced by light exert an attraction on the 
silver bromide to be reduced in the developing bath only 
downwards through the film and not sideways from the pK)uits 
which have been exposed to light? We might make many 
other objections but there is always the difficulty of accounting 
for the way in which development takes place, when we 
adopt any theory which presupposes an attraction. In 
order to be free from the objections just cited, any theory, 
molecular or chemical, must postulate that the change which 
makes the silver salt developable occurs in all the particles 
of silver salt exposed to light and not merely in a few of them. 

"This is exactly what is postulated by our theory, which 
assumes a molecular change, which change may be a polymeri- 
zation as we have pointed out, or may be something entirely 
different. 

*' The experiments, recently made by the Messrs Lumi^e 
as to the action of light on dry plates which had been cooled 
to a very low temperature ( — 190®) by means of liquid air 
have shown that the rate of formation of the latent image is 
much decreased by a lowering of the temperature. To 



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The Photographic Plate 353 

produce the same image the time of exposure must be increased 
fifty to four hundredfold that necessary at ordinary tempera- 
ture. This would be a reason for doubting that the change 
was a physical one, and for claiming that the change must 
be a chemical one because the chemical phenomena are the 
ones that are the most affected by temperature. These 
experiments do not however, tell against our hypothesis of 
a molecular change, because the temperature also has an 
effect on molecular modifications. 

"The energy which produces the molecular change must 
not be considered as merely starting the reaction without 
being absorbed, but it must be considered as being absorbed 
and as actually doing work. Though this work may be small, 
it nevertheless decreases the total amount of work which 
would be necessary to decompose a silver salt which has 
not been exposed to light. 

"The silver halides are very remarkable in that the 
equilibrium of their molecules may be disturbed by any form 
of energy. They are still more remarkable because the slight 
disturbance produced by the first action of light or of any 
other form of energy, changes the manner of reacting with 
certain substances in such a way that it becomes possible 
to replace the invisible image by one that can be seen.'* 

Namias assumes that silver bromide is polymerized 
by light. On the other hand, Hurter and Driffield^ believe 
that light depolymerizes the salt. 

"The application of thermo-chemical data to the theory 
of development, having shown that the whole of the energy 
required for the decomposition of silver bromide may possi- 
bly be, and probably is, derived from the changes which 
the developer undergoes during development, it would ap- 
pear to be possible to dismiss the old theory of the constitution 
of the latent image long held by many authors. 

"The idea that some portion of the silver bromide is 
decomposed by the light into a sub-bromide and free bromine. 



» Phot. Jour., 22, 149 (1898). 



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354 Wilder D. Bancroft 

is not necessary for the explanation of the phenomenon o 
development. It is quite sufficient to assume that the light 
causes some change in the molecular structure of silver bro- 
mide; that it changes, for instance, a complex molecule 
Ag^Br^ into simple ones. We may assume that the light 
does some work of disgregation, as Clausius would say; not 
involving a complete change in chemical com|x>sition, such 
as the formation of a sub-bromide, but work, such as is done 
during the change in the crystalline structure of sulphur 
or of calcium carbonate; work which requires a much smaller 
amount of energy than the complete separation of atoms 
of bromine from the molecule of silver bromide would in- 
volve. 

** There is absolutely no experimental proof that the 
change which silver bromide undergoes when exposed to 
light of such small intensity, and for such small periods of 
time, as suffice for the production of photographic negatives, 
produces any visible effect or any measurable chemical trans- 
formation. All that can be proved is that silver bromide 
is more rapidly attacked by the developer than unexposed 
silver bromide; but the character of the change (whatever 
its nature) and its progress in course of time are identical 
for the exposed and for the unexposed silver bromide. 

**When silver bromide is treated with a solution of 
potassium iodide, chemical decomposition takes place, the 
bromine and iodine are exchanged, and we then have silver 
iodide. This reaction takes place also in the case of silver 
bromide in the sensitive film. If silver bromide which has 
been exposed to light (i. e., impressed with a latent image) 
consisted of sub-bromide, this sub-bromide would either 
remain as such, when treated with potassium iodide, or it 
would yield a sub-bromide. In either case it ought to yield,, 
upon development, a visible image; but the treatment of a 
latent image with potassium iodide completely destroys 
the image, and we must therefore conclude that the latent 
image consists of bromide of silver, possibly in an allotropic 
modification. 



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The Photographic Plate 355 

"If a film containing exposed silver bromide be treated 
with potassium bromide, no effect whatever is produced; 
the latent image can be developed in its full vigor after the 
potassium bromide has been washed out. 

** Again, if a sensitive gelatino-bromide plate be treated 
with a dilute solution of bromine in water, the film loses 
its sensitiveness to light, that is, the plate becomes exceedingly- 
slow. If the sensitive plate had a latent image impressed 
upon it by suitable exposure to light before it was treated 
with bromine, this latent image would no longer be capable 
of development; the difference in rapidity of attack by the 
developer on the exposed and unexposed silver bromide 
would have vanished. 

** This peculiar behavior of the film under the influence 
of free bromine, shows that if the action of the light upon the 
sensitive film were continued so long as to bring about actual 
decomposition, and so produce a certain amount of free bromine 
the bromine thus liberated would eflface the latent image, 
and render the film almost insensitive. This is exactly what 
happens when the exposure is continued so long as to pro- 
duce the phenomenon of reversal. 

**That any ordinary camera exposure is inadequate to 
produce a material decomposition of the silver bromide on 
the plate can be shown by other experiments and considera- 
tions. A standard candle consumes 120 grains or 7.77 grams 
of spermaceti per hour, or about 0.0021 gram per second. 
The energy evolved by the combustion of 0.002 1 gram sperm- 
aceti (i gram = loooo units of heat) is 21 gram-units (small 
calories). If the whole of this energy were produced in the 
form of chemically active light and evenly distributed over 
a sphere of i meter radius = 125,663 square cm, the amount 

of energy per 100 square cm of surface would be ^ — = 

0.016 gram-units of heat. 

** While it is possible on a sensitive plate to produce a 
deposit of 26.5 milligrams of metallic silver per 100 square 
cm area by an exposure of 10 C.M.S., the amount of energy 



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356 Wilder D. Bancroft 

received by this area, assuming the whole energy yielded by 
the candle to be taken into consideration, as in the above 
calculation, is lo X 0.016 =0.16 units in 10 seconds. Now 
the decomposition of silver bromide, equivalent to 108 milli- 
grams of silver, requires energy amounting to 23 gram-imits 
and the energy necessary for 26.5 milligrams of silver is 5.6 
imits, so that the candle, even if the whole of its energy of 
combustion were active in decomposing silver bromide^ 
could only decompose 2.9 percent of the amoimt which ex- 
periment shows can be actually rendered amenable- to de- 
velopment. As a matter of fact, however, only a small 
fraction of the energy of the candle is transformed into radiant 
energy; and again, a very small fraction of the radiant energy 
constitutes ethereal -waves of sufficiently short wave length 
to affect silver bromide. It is thus rendered quite evident 
that the candle can only furnish an infinitesimal part of the 
energy necessary to produce 26.5 milligrams of metallic 
silver per 100 square cm with an exposure of 10 C.M.S., and 
that the whole of this energy is, in all probability, provided 
by the developer. 

**We have, moreover, furnished the proof, as far as this 
can be done, that the composition of the latent image is^ 
as nearly as possible, AgBr; and in a paper, pubhshed in 
February, 1891, we showed that no bromine is liberated in 
the course of development. As this paper may not be readily 
accessible, we will briefly repeat our experiment therein 
recorded. 

**A gelatino-bromide plate (6V2 by 4*/^ inches) was 
exposed to the light of two standard candles, one on either 
side of the plate at a distance of half a meter, for 33 minutes. 
The plate was then well washed with pure distilled water 
to remove any bromine which might either become free as 
such, or which might, by action on the gelatine, have formed 
hydrobromic acid. The result was that no soluble bromine 
could be detected in the wash water. 

*'The plate was then developed with ammoniacal pyro- 
gallol for 30 minutes and washed. The developing solution 



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The Photographic Plate 357 

and the wash water were together oxidized with nitric acid 
and the bromide precipitated, washed, filtered, and weighed 
as metallic silver. The weight foimd was 197.7 milligrams. 

**The plate was then fixed in pure thio-sulphate, well 
washed, and the film stripped. The amount of metallic 
silver contained in the film Was determined and found to be 
194.4 milligrams. The amount of bromine in the developer 
was thus slightly more than the equivalent of the metallic 
silver found in the developed plate. Hence we must con- 
clude that the chemical composition of the latent image is 
AgBr; and this silver on the plate had been brought into 
a readily developable form. 

*'The behavior of exposed silver bromide to a solution 
of potassium iodide only furnishes qualitative results. 

"The behavior of expK)sed silver bromide to a solution 
of |>otassium bromide is shown by the following experiments. 
A plate which had received a series of graduated exposin-es 
was cut into two parts. One part was soaked for 20 minutes 
in a solution of potassium bromide, and then washed for 
40 minutes. The other part was soaked in water for 60 
minutes. Both parts were then developed and gave the 
following result. 

Experiment i 



=^ - - . - _r i: 


- - - - - ^ - - ' ^ 


^ ' ' ^ -^ - — 




, Density. 


Plate D, 


Exposure C. M. S. 1 

1 


Soaked in KBr | 


Soaked in water 


0.625 
1.25 

2-5 

5 
10 1 


0.065 
0.360 
0.870 

1.305 
1.740 


0.060 

0.385 
0.910 

I 365 
1.820 


20 


1 2.190 I 


2.230 


40 


2.515 ! 


2.510 



** That, in course of time, the rate 6f action of the developer 
upK>n unexposed silver bromide is the same as upon exposed, 
is shown by the following comparative results : 



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358 



Wilder D. Bancroft 
Table III 



Plate 



Time of development 



2 min. 



D, 


0.745 


1^. 


0.760 


1>, 


0.790 


G 


0.660 


H, 


0.505 


Dt 


0.650 



4 min. 


8 min. 


1. 165 


1.765 


1.370 


2.140 


1.290 


1.890 


I 095 


1.600 


1.200 


I 965 


1.270 


I 945 



Unexposed 
Unexposed 
Unexposed 
Exposed 2.5 C. M. S. 
Exposed 10 C. M. S. 
Exposed 20 C. M. S. 



j **In the case of the unexposed plates, the developer 
contained no bromide, while bromide was used in the case 
of the ex|x>sed plates. It will be seen, however, that the 
growth of density with time is nearly the same in both cases. 
When unexposed and expK)sed silver bromide are de- 
veloped together, this equal rate of growth is not so easily 
detected since the action of the developer U|x>n the imexposed 
silver bromide is then comparatively small, but the ratio 
does approximate to equality, as is shown by the following 
experiments, in which the exposed and the unexposed plates 
were developed together. 

Table IV 



Plate D, developed 



Unexposed 

Exposed 1.25 C. M. S. 
Exposed 2.5 C. M. S. 
Exposed 5 C. M. S. 



0.175 
0.370 

0.725 
1 .040 



4 mm. 

0.300 
0.615 
1. 100 
1.520 



Ratio 

1. 71 
1.66 

I 51 
1.46 



*' These experiments show that the difference between 
imexposed and exposed silver bromide is of the same character 
as the difference between two successive exposures; it is 
a difference of degree only, and not of kind. 

"Our previous experiments and calculations indicate 
that it is highly probable that the difference in the amoimt 
of energy contained in the exposed and unexposed silver bro- 
mide is very small, and that the rapidity with which the 



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The Photographic Plate 



359 



developer attacks the unexposed films of plates, varying 
conside ably in speed, is almost identical, showing that there 
is a trifling difference, if any, in the amount of energy con- 
tained in the imexposed silver bromide, whatever the speed 
of the plate. The rapidity of attack of unexposed silver 
bromide in plates varying in speed is shown in the following 
table : 

Table V 




- - - - 


- - -rr -r:^- 


- 


Density developed in 


2 min. 

( 


4miB. 


8 min. 


\ 0.790 
1 0.760 

i 0.745 


1.290 
I 370 
1. 165 


1.890 
2.140 
I 765 



Unexposed 
Unexposed 
Unexposed 



** If, then, the silver bromide in rapid plates is of the 
same composition and contains the same amount of energy 
as that in slow plates, the difference in the speed of gelatino- 
bromide plates must be due more to their physical consti- 
tution and optical properties than to any difference in the 
silver bromide.*' 

In commenting on this paper, Mr. Bothamley^ said: 
''One point, of which I was astonished to find that 
Messrs. Hurter and Driffield took no account in their paper, 
is the very great tendency of gelatine to combine with bromine. 
Mr. Driffield referred to a view held by various people to the 
effect that when light acts upon silver bromide there is forma- 
tion of sub-bromide, and, as I thought he said, a setting 
free of the bromine; I can only say, in connection with that, 
that I do not know any chemist who has given attention 
to photographic questions and who holds any view of that 
kind. The evidence, as far as we have it at present, seems 
to me to be something like this: Gelatine is known to be 
capable of combining with great rapidity with large quantities 
of bromine. I have myself prepared these bromo-derivatives 



* Phot. Jour., 22, 157 (1898). 



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36o Wilder D. Bancroft 

of gelatine and it is quite easy to get solid compK)unds con- 
taining close upon 30 percent of bromine, and in the formation 
of these derivatives a very large amount of heat is developed. 
Now I will try to explain concisely the view which, as I under- 
stand it, is held by those who consider that a chemical change 
takes place in the production of the developable image. 
We know quite well, that in many cases, perfectly pure com- 
pounds show little tendency to undergo chemical change; 
for example, that combination will not take place between 
carbonic oxide and oxygen, if they are both quite dry. In 
the case under consideration, we have light as the active 
agent, and silver bromide as the substance that may undergo 
change. I am bound to admit, of course, that the evidence 
as to whether pure silver bromide alone is affected by light 
or not is rather vague, and the statement of different observers 
are rather contradictory; but there is an experiment of Schu- 
mann's which seems not to have attracted the attention 
it deserves. He covered one-half of a glass plate with gela- 
tine, leaving the other half bare; then he put that plate in 
the bottom of a vessel in which he produced by precipitation 
some silver bromide, so that the precipitated silver bromide 
gradually settled down on the glass plate and come in con- 
tact with the glass of one-half and with the gelatine upon the 
other half. The plate was then lifted out, very carefully 
washed by gentle diffusion of water, dried, exposed to light, 
and treated with a developer; there was foimd to be practically 
no change in the silver bromide which had been in contact 
with the bare glass; but there was an abundant formation 
of reduced silver in the silver bromide that had been in con- 
tact with the gelatine. Therefore, in considering any question 
of the formation of the latent image, we must take into ac- 
count the function of the gelatine. Everybody knows how 
different the phenomena are when silver bromide is in collo- 
dion and when it is in gelatine, and the view that I and others 
hold is that in a gelatino-bromide plate we have an intimate 
association of silver bromide and gelatine, and that when 
light falls upon the silver bromide it throws the molecules 



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The Photographic Plate 361 

of it into a violent agitation, and thereby, as Mr. Chapman 
Jones has ahready said, into unstable equilibrium. If the 
action of light is sufficient to produce a developable image 
it is because the condition of unstable equilibrium has reached 
such a point that part of the bromine, at least, ceases to be 
in chemical union with the silver and simultaneously com- 
bines with the gelatine; we do not believe that there is any 
setting free of the bromine in the ordinary sense of the term 
'setting free.' Now, Messrs. Htu-ter and Driffield describe 
an experiment which they consider proves that the composi- 
tion of the latent image is the same as that of the silver bro- 
mide, and the experiment consisted in treating a plate with 
a reducing agent and showing that there passed into the 
reducing agent or developer an amount of bromine equiva- 
lent to the amoimt of silver that had been reduced. Now 
what, I want to point out is that the experiment does not prove 
that all the bromine was in combination with the silver, 
because the reducing agent which would reduce the bromide 
of silver would most probably also reduce the bromo-gelatine; 
and it does not in any way disprove the view that I have 
endeavored to explain that silver sub-bromide and bromo- 
gelatine are formed, because the amount of bromine would 
be the same, and it would equally pass into the developer 
in the two cases. With regard to the statement that if you 
take an exposed gelatino-bromide plate, and treat it with 
potassium iodide, ycu destroy the latent image. Some few 
years ago, in preparing a paper on '*The Latent Image,'* 
for a camera club conference, I treated two or three exposed 
gelatino-bromide plates, with a five percent solution of potas- 
sium iodide for a considerable time, washed out the potassium 
iodide, treated the plates with the developer, and casual 
observation would have led one to suppose that the develop- 
able image had been destroyed; some later work, however, 
threw doubts upon that conclusion; it seemed possible that 
the latent image was there, but that the time required for 
its development was very long, and I found that by allowing 
the ferrous oxalate developer to act for a good many hours 



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362 Wilder D, Bancroft 

I was able to develop an image. Recently, Schumann has 
made an experiment in which he has fomid that the ordinary 
belief that an emulsion of silver iodide in gelatine will not 
give a latent or developable image is contrary to actual 
fact, and that if such an emulsion is subjected to light of very 
high refrangibility you can get an image and develop it just 
as in the case of silver bromide. Therefore, coupling these 
facts with the well-known fact that there are certain chemical 
reagents which will cause the disapi>earance of the develop- 
able image, while other chemical reagents will not, I am 
bound to-day that, while I do not commit myself to any 
definite opinion as to the precise compK)sition of the image, 
it seems to me that the evidence in favor of some chemical 
change is very considerable, and certainly that the exf>eri- 
ment of measuring the amount of bromine that goes into the 
developer does not prove anything to the contrary." 
To this, Messrs, Hurter and Driffield* replied: 
"Professor Bothamley has directed most of his remarks 
to chemical changes, which he believes to be induced by the 
light, and which he supposes to be so profound as to actually 
reduce the silver bromide to some sub-bromide. Whatever 
may be the formula of this sub-bromide, it means the com- 
plete separation of some bromine from silver. Professor 
Bothamley does not say that the energy necessary for this 
reaction is supplied, even in part, by the supposed formation 
of a bromine compound of gelatine, but this must be the 
meaning of his remarks as to the facility of the formation 
of a bromine compound of gelatine and as to the amount 
of heat developed. His belief summed up appears to be 
that the latent image is formed by the transference (under 
the influence of light) of bromine from the silver bromide 
to the gelatine, with the consequent formation of some sub- 
bromide of silver, the possible existence of which, as a labora- 
tory product, we do not deny. But we have always under- 
stood these sub-bromides to be colored bodies, and the latent 

» Phot. Jour., 22, 151 (1898). 



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The Photographic Plate 363 

image resulting from ordinary photographic exposures is 
not colored. Professor Bothamley will readily admit that 
bromine when combining with gelatine will do so either by 
forming a substitution product (when hydrobromic acid will 
appear as well) or by forming a simple addition product. 
Our quantitative experiments are quite decisive as to the 
non-production of hydrobromic acid, and to prove that 
there is, at any rate, no substitution product. They are, 
however, not decisive as regards the formation of an addition 
product, and this fact was stated in our original communica- 
tion in 1890. 

"But whichever product be formed, the great question 
still remains — whence is the energy derived which separates 
the bromine from the silver? The possible formation of 
a bromine compound of gelatine may reduce the amount 
of energy required to bring about this separation to about 
one-half of the 23 calories, since the heat involved on substi- 
tuting bromine for hydrogen is, at most, 1 1 calories per atom 
of bromine taken from the silver; and 14 calories if an addi- 
tion product be formed. The greatest difficulty with regard 
to the sub-bromide theory, therefore, still remains, namely, 
the energy difficulty; and it remains even if the combination 
of bromine with gelatine were a proved fact, which, as far 
as we are aware, it is not; it is simply an opinion.*' 

Bredig^ suggests that light may disintegrate the grains 
of silver bromide physically. The disintegrated particles 
would have a higher solubility than the others owing to the 
decrease in size. It seems reasonable to postulate that they 
would also be reduced more rapidly by the developer. Bredig 
is careful to point out that, although this hypothesis apparently 
describes the facts, it is quite possible that others may be 
equally satisfactory. 

So far as I can understand Colson's rather vague account, 
he seems to think that gelatine is thrown into a state of molec- 
ular thrills by light quite as much as the silver bromide.* 

* Eder's Jahrbuch der Photographie, 13, 365 (1899). 
' Cblson: La Plaque photograpfaique, 19 (1897). 



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364 Wilder D, Bancroft 

** It has thus been proved that the reaction of the hydro- 
gen of the gelatine with oxygen or with chlorine retards the 
development of the latent image on a bromide gelatine plate. 
The part played by the organic matter is therefore very im- 
portant. This throws new light on the formation of the 
latent image and on the way that the developer acts. Let 
us consider the action of any form of energy on the bromide 
gelatine plate. The impression is not visible but can be made 
so by development. The absorbed energy has then done 
a certain amoimt of work in the film, has started a change 
which will be completed by the developer. It is preliminary 
molecular work which precedes the decomposition. By 
increasing the vibratory movement of the molecules, it makes 
it possible for part of the hydrogen of the gelatine to come 
out and react with the substances for which it has a great 
aflSnity, oxygen, chlorine, bromine and iodine. 

** We usually explain the action of the developer by saying 
that it reacts with the oxygen of the water, while the hydro- 
gen thus set free reacts with the bromine of the bromide 
which has been made ready for decomposition by the light. 
We say that organic matter acts merely as an inert support. 
Since it does not react, by definition, no further attention 
is paid to it. 

"The facts, which I have brought out, lead us to a more 
complete explanation. The oxidation of the developer, at 
the expense of the oxygen of the water in contact with the 
molecules of gelatine and bromide, causes an evolution of 
energy. This finishes the work started in the silver salt 
and the organic matter by light or any other form of energy. 
It makes the hydrogen of the gelatine combine directly with 
the bromine of the bromide or with the oxygen of the water 
thus setting free more hydrogen which may react with the 
exposed bromide. 

*'The mechanism is a direct and logical consequence 
of the great principle of the transformation and conservation 
of energy: 

I. Increased excitation of the molecular movement 



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The Photographic Plate 365 

of the gelatine and bromide by luminous, calorific or thermal 
energy. This gives rise to the latent image which lasts for 
a certain time. We shall see other instances of this in phos- 
phorescence, in the old experiments of Niepce de Saint- 
Victor, etc. 

2. Another increase of the molecular movement of the 
gelatine and bromide by the energy set free during the oxida- 
tion of the developer. This evolution of energy, produced 
by oxidation, is increased, as we call it, by what we call an 
evolution of heat. This stimulus causes the separation of 
the molecules of hydrogen in the gelatine and of the molecules 
of bromine in the bromide. At the same time it makes the 
bromine combine with the hydrogen coming from the de- 
composition of water by the developer, and with the hydro- 
gen coming from the gelatine. 

"I lay stress on this new way of regarding the action 
of the developer because the whole of photography rests on 
the action of the developer. 

"I call attention also to the fact that this theory, which 
follows quite naturally from the conception of molecular 
movement, is in itself sufficient without having to invoke 
what is called the chemical theory of the latent image, accord- 
ing to which it is assumed that the first action of light always 
produces a sub-bromide. This hypothesis is not only not 
necessary but it is contradicted by many facts. For instance, 
there is absolutely no color to the latent image when exposure 
is normal. A gray tint begins to appear only when the 
normal exposure has been exceeded. By that time there 
has been a reduction of bromide to sub-bromide; but, imder 
these conditions, the developer gives rise to a reversed image, 
to a positive instead of a negative. The moment when the 
direct action of light causes a visible image is the moment 
when the developer begins to produce a reversal. This is 
the phenomenon of solarization.'' 

Sheppard and Mees* have the following to say in regard 
to explanations of this type. 

' Investigations on the Theory of the Photographic Process, 201 (1907). 



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^ 



366 Wilder D. Bancroft 

''Analogy with elastic phenomena has suggested to 
many observers the idea of a 'strain' in the halide. In 
particular, J. C. Bose* has brought forward a 'molecular 
strain' hypothesis in explanation of the changes of conduc- 
tivity, e.m.f., and surface tension of surfaces exposed to 
stimulus — mechanical stress or pressure, light, Hertzian 
waves, etc. It is maintained with regard to the photographic 
process that it gives a simple explanation of various obscure 
phenomena of the photographic action, such as the relapse 
of the latent image, recurrent and abnormal reversals, and 
dependence of the photo-eflFect on the time rate of illumina- 
tion. 

" This is not the place to criticize in detail Professor Bose's 
theory of 'molecular strain' in its applications to coherer 
action, response to stimulus, etc., but, as bearing on photog- 
raphy, we may suggest that there is a suspicion of a vicious 
circle in the argument. The elastic behavior of matter in 
bulk is transferred to the molecules, whereas a consistent 
molecular theory should surely afiford an explanation of 
elastic phenomena themselves. Generally it may be said 
of the physical theories that they shirk a real explanation 
by treating the phenomenon to be explained as a quality of 
the physical modification of the halide, much as the narcotic 
powder of opium was attributed by mediaeval mediciners 
to a 'somniferous principle' peculiar to the drug. Mean- 
time the primary fact requiring explanation seems to be 
somewhat neglected — ^namely, the acceleration of reduction 
by the developer." 

In the next paper of the series, I shall discuss the hy- 
pothesis of the silver nucleus and the hypothesis of the silver 
sub-bromide. 

Cornell University 



* Proc. Roy. Soc., 1902; Phot. Jour., 26, 146 (1902). 



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THE FUNCTION OF THE WALLS IN CAPILLARY 

PHENOMENA 



S. L. BIGELOW AND F. W. HUNTER 

The purpose of this investigation was to determine 
whether the material of which a capillary tube is made has 
any effect upon the height to which a liquid will ascend in 
it. The literature upon capillarity, which is extensive, does 
not furnish the desired information. G. Quincke* believed 
that water rose to diflferent heights in tubes of different kinds 
of glass. P. Volkmann^ subjected this conclusion to an ex- 
ceedingly careful investigation and decided that the nature 
of the glass made no difference. Inferences may be drawn 
from the measurement of flat drops on different surfaces, 
but direct measurements of capillary ascension in tubes 
other than glass do not appear to have been attempted, 
probably on accoimt of the fairly obvious difficulty arising 
from the fact that such tubes are not transparent. 

It occtured to one of us that such measurements could, 
however, be made with great facility by applying a simple, 
well-known principle. The height of a column of liquid 
in a capillary tube is determined by the radius of the tube 
at the meniscus, and the size or shape of the tube below the 
meniscus makes no difference. Accordingly, if a tube of any 
convenient radius, say 3 mm be closed at the top by a thin 
plate of any material, through which a small hole is bored; 
if the whole be immersed in a liquid, and then gradually raised; 
a meniscus should form in this small hole, and the whole tube 
should remain full of liquid, until the height of the column 
is equal to that which would have been obtained with a long 
enough tube of the material of the plate, and of imiform bore 
the same size as the hole. When this point is reached, the 
meniscus should break away from the lower surface of the 

* Wied. Ann., 52, i (1894). 
Mbid., 53. 633 (1894). 



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368 5. L. Bigelow and F. W. Hunter 

plate and the tube should empty. We foimd the facts agreed 
with this simple deduction in the most gratifying manner. 

Apparatus 

A cross section of the essential part of the apparatus 
we constructed for measuring capillary ascensions is shown 
on an enlarged scale in Fig. i. The complete arrangement 
is shown on a diminished scale in Fig. 2 with the plate removed 
and as it appears while a height is being determined. A is 
the plate with the small capillary hole in it, resting on the 
glass tube B. This is carried by an arm C, which is raised 
or lowered by a ratchet and pinion mechanism such as is used 
for the coarse focussing adjustment on microscopes. Thus 
the tube and plate may be lowered imtil entirely submerged 
in the liquid in the beaker, and then it may be raised until 
the meniscus at the small hole breaks and the tube empties. 
At first we cemented the plates to the tubes, but cements 
dissolve and the solutions having different siuiace tensions 
are apt to produce irregular results. We discarded cements, 
put a rubber stopper on the tube and laid our plates on that. 
Only then did we realize that a further application of the 
principle on which we are basing our whole method made 
rubber as superfluous as cements. Suppose there is a crack 
between the plate and the top of the tube. It will fill with 
the liquid by virtue of the capillary forces, and will stay 
full and will not " leak " unless its width is equal to, or greater 
than, the radius of the hole in the plate. It is a very easy 
matter to grind off the top of the tube and to use flat plates 
so that the break, when it comes, comes always at the hole. 
We, therefore, merely laid the plates on the tubes and pro- 
ceeded to make our observations. This simplification may 
appear trifling, but it is not, in fact, for three reasons. First, 
it much diminishes the time required to prepare for an ex- 
periment; second, it makes it much easier to clean the plates 
between experiments; third, it enables us to avoid substances 
which might contaminate our liquids or their surfaces. 

After the liquid had fallen, we removed the plate, brought 
the point D to the surface of the liquid in the beaker, utilizing 



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Function of the Walls in Capillary Phenomena 369 



«3I 



I 



:czj 




-D 



SI y 



Fig. I 



B 
Fig. 2 



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370 5. L. Bigelow and F. W, Hunter 

the reflection of the point on the surface in the usual manner, 
and then brought the point E onto the edge of the glass tube. 
These points are carried by extensions independently movable, 
on one of which extensions is a scale in millimeters, on the 
other a vernier. We thus read the height to one-tenth of a 
millimeter, the limit of acciu"acy of our present instrument. 
We have in mind the construction of another with a microm- 
eter screw to measiu"e to o.oi mm. 

Two corrections must be applied to the height thus 
measured. First, the liquid falling out of the tube raises 
the level of the liquid in the beaker. From the diameters 
of the beaker and the tube and the height of the column, 
this correction is easily calculated. We found it more ex- 
peditious in most cases, however, to make a preliminary 
experiment to determine about the height to expect. We 
then repeated more carefully, and, after having raised the 
plate to within two millimeters of the breaking point, set 
the point D, then raised gradually till the break came, re- 
moved the plate and set the second point E. The second 
correction is as follows: the meniscus in the plate remains 
near the top at first, but when a height is reached within 
the thickness of the plate of the maximum height, the meniscus 
descends until it hangs by the lower edge, as indicated in 
Fig. I. We assumed, for obvious reasons, that just before 
breaking it was hemispherical, with a radius equal to that 
of the hole. We, therefore, subtracted this radius from the 
measured height. It would have been more accurate had 
we subtracted 2/3 of the radius, but this refinement falls 
at the limits of our experimental errors. 

It should be mentioned that we lay no particular stress 
on this ratchet and vernier instrument, and recognize that 
a cathetometer telescope would have certain advantages. 
It would take longer to make the readings with the telescope, 
but they would be somewhat more accurate. 

For drilling the holes in the plates, we used a jeweller's 
lathe and drills, holding the drill stationary and revolving 
the work. We examined the holes and measured them 



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Function of the Walls in Capillary Phenomena 371 

with a good microscope, a stage micrometer and micrometer 
ocular. We had the customary diflSculties in our efforts 
to secure strictly round holes. None of them were round 
within the limits of oiu* measuring instruments, but they 
were as nearly round as the bores of the tubes used by previous 
investigators of capillary phenomena. 

Our measiu'ements of the diameters of the holes were 
within 2 microns of right. On each hole we measiu"ed 10 
to 12 diameters and took the average. The difference be- 
tween the maximum and minimum diameters on one hole 
was never less than 5 microns. If this difference exceeded 
20 microns, we did not use the plate. With the very thinnest 
metal plates and with salt plates, we were obliged to content 
ourselves with somewhat less regular holes. With some 
salts the deviation equalled 8 percent of the smallest diameter. 
Not infrequently, when we thought we had prepared a use- 
ful plate, we observed differences between maximum and mini- 
mum diameters as large as 60 microns. The holes in the 
plates were inspected and measured under the microscope 
before and after each group of observations, and if measur- 
able differences were observed that group of observations 
was discarded. This was an absolutely necessary precaution 
in our work with soluble salt plates, and a reasonable pre- 
caution in our work with such metals as zinc and copper, 
owing to our method of cleaning. 

Metal plates were washed by immersion in dilute sul- 
phuric acid (i : 3) for from 30 to 60 seconds, then transferred 
to distilled water, dried with filter paper and then dried at 
a distance of 20 cm above a bunsen flame. They were then 
washed in benzene, dried with filter paper and then again 
at the same distance above a bunsen flame. The salt plates 
were merely dried as rapidly as possible with filter paper 
after removal from the solution. 

We seciu"ed the desired temperature and held it constant 
within 0.5® by standing the beaker in a large shallow jar of 
water to which we added hot or cold water as needed. 

After having developed the method as described above, 



/ 



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372 5. L. Bigelow and F, W. Hunter 

we discovered that Oersted* had devised a similar apparatus 
based on the same principle, in 184 1. In Oersted's apparatus, 
one arm of a U tube carried a plate with a hole in it. A side 
arm enabled him to alter the level of the liquid in the other 
arm of the U tube. He raised the level here till liquid was 
forced out through the capillary and meastu-ed with a cathetom- 
eter the liquid pressiu"e required. He also lowered the level 
in the other arm until the meniscus broke away, as in our 
work. This is a less convenient application of the principle 
than ours and less free from possible errors. He determined 
that an amalgamated copper tube and a glass capillary tube 
raise water to the same height. He also determined the 
capillary ascension of mercury in an amalgamated copper 
tube and that is all. The article is but three pages long. 
He expresses his intention of continuing this line of investi- 
gation, but we have not foimd anything further by him. 
He died in 1844. It is indeed strange that no one else appears 
to have utilized his apparatus. 

Results 

Although we felt reasonably certain that the thickness 
of our plates could make no difference, we carried out a set 
of experiments to prove the fact. Our results are contained 
in Table I. This, and the succeeding tables containing our 
results, are self explanatory, and require but few remarks. 
All measurements are expressed in millimeters. The first 
column contains the thickness of the plates, the second the 
radius of the capillary hole in the plate, the third, the highest 
ascension obtained, the fourth, the lowest, the fifth, the number 
of separate observations, the sixth, the average, and the 
seventh, the product of this average into the radius. The 
values in the seventh column should then be constant. Each 
horizontal line represents an entirely separate group of ex- 
periments, in many, if not most instances, carried out on 
different days. A microscopical inspection of the hole pre- 
ceded and followed each of these groups. 

* J. C. Oersted: Pogg. Ann., 53, 614-16 (1841). 



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Function of the Walls in Capillary Phenomena 373 

Our glass plates were sections cut ofif a capillary tube 
and groimd down to the given thickness with fine carborun- 
dum and a solution of camphor in turpentine. 

Table i 
Copper Plates — Water. Temp. 20.5-21*' 



Thickness 
of plate 



0.07 
0.14 
0.15 
O.IO 

0.20 

0.68 
0.81 
0.83 
1. 13 



tadins of 
.hole 


Highest 


Lowest 


No. of 
readings 


0.316 


47-9 


47-3 


3 


0.250 


60.3 


59-3 


4 


0.243 


62.3 


62.3 


2 


0.243 


62.8 


61.5 


4 


0.296 


511 


50.8 


4 


0.289 


521 


52.0 


4 


0.293 


51 9 


512 


5 


0.285 


53-8 


53-8 


2 


0.240 


62.7 


62.6 


3 



Average 


hr. 


47.61 


1504 


60.11 


15 


03 


62.31 


15 


15 


62.31 


15 


15 


50 -95 


»5 


08 


52.10 


15 


05 


51-72 


15 


i6 


53 78 


15 


32 


62.70 


15 


05 



Av. 



15. 115 



Table 2 
Platinum Plates — Water. Temp. 20.5-21*' 



0.08 
0.08 
0.08 



0.24 
0.24 
0.24 
0.24 
0.24 
0.24 
0.24 



0.283 


52.3 


51-7 


5 


52.15 


0.269 


54-6 


54-4 


4 


54 58 


0-314 


47-2 


46.4 


5 


46.83 



14.76 
14.69 
14.70 



Av. 14.72 



Table 3 
Zinc plates — Water. Temp. 20.5-21^ 



0.304 
0.306 
0.293 
0.271 
0.308 
0.309 
0.306 



505 


50.0 


49 


3 


49 I 


51 


2 


511 


56 





55-6 


49 


5 


49.2 


49 


5 


48.9 


50 


I 


49 7 



5 
3 
4 
5 
5 
5 
4 



50.24 


15- 


49-15 


15- 


51 14 


H 


55-81 


15- 


49-25 


15- 


49-19 


15- 


49-93 


15- 



27 
04 
98 

12 

17 
20 
28 



Av. 15 . 15 



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374 



5. L. Bigelow and FW. Hunter 



Table 4 
Nickel Plates — Water. Temp. 20.5-21*' 



Thickness ' Radius of I tt,- i,^*. r ^„^«f 
of plate hole j ^*«^"' ^^^^ 



No. of 
readings 



0.53 


0.304 


49 4 


49 3 


3 


53 


0.299 


50.0 


49 


5 ■ 


5 


0.53 


0.306 


49 2 


48 


5 


5 


0.53 


j 0.274 


55-2 


54 


6 


5 


0.53 


0.269 


56.2 


55 


4 


5 


0.53 


' 0.305 


49 8 


49 





5 


053 


1 0.275 


55 2 


54 


9 


4 



Average 


hr. 


49 


37 


1501 


49 


81 


14 


89 


48 


90 


14 


96 


54 


74 


15 


00 


55 


70 


14 


98 


49 


34 


15 


05 


54 


99 


15 


12 



Av. 15.00 



Table 5 
Silver Plates — Water. Temp. 20.5-2 1*' 



Thickness 
of plate 



0.28 
0.28 
0.28 



Radius of 
hole 



Highest 



0.261 
0.260 
0.258 



56.2 

57.3 
57-3 



Lowest 

55.6 
57 o 
57 I 



No. of 
exps. 



Average 



hr. 



4 
5 
5 



55 


98 


14 


.61 


57 


26 


14 


89 


57 


18 


14 


■75 



Av. 14.75 



Table 6 
Aluminium Plates — Water. 



Temp. 20.5-21^ 



0.87 


0.301 


0.87 


0.298 


0.87 


0.299 


0.87 


0.312 


0.87 


0.302 


0.87 


0.306 


0.85 


0.295 


0.86 


0.299 



49 
49 
49 
47 
49 
49 
50 
49 



48 
48 
49 
47 
49 
48 

49 
48 



4 
3 
6 

7 
5 
6 
6 
3 



49 
49 
49 
47 
49 
49 
49 
49 



00 14 

10 14 

30 14 

50 14 



43 
16 
69 
07 



14 
15 
14 
14 



75 
63 
74 
82 

93 
04 
66 
68 



Av. 14.78 



Table 7 
Glass Plates — Water. Temp. 20.5-21* 



1.87 
1.90 



0.312 
0.312 



47.2 
47.2 



46.8 
47 I 



4 
3 



47.04 
47.15 



14.68 
14.71 



Av. 14.69 



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Function of the Walls in Capillary Phenomena 375 

Table 8 
Celluloid Plates— Water. Temp. 20.5-21°. 



Thickness 
of plate 


Radius of 
hole 


Highest 


Lowest 

57.7 
60.9 

59.1 
58.0 


No. of 
exps. 

4 
5 
7 
7 


Average 


hr. 


0.75 
0.75 
0.75 
0.75 


0.243 
0.233 
0.236 
0.236 


58.3 
61.5 
61.6 
60.3 


57 91 
61.30 
60.04 
59.21 


14.07 
14.29 
14.17 
13-97 



Av. 14.12 



Table 9 
Beeswax Plates — Water. Temp. 20.5-21° 



1.70 

I 15 
1.50 
1.65 



0.340 


38.8 


38.3 


5 


; 38.48 


315 


423 


40.3 


10 


! 41.45 


0.316 


41.4 


40.9 


6 


41.08 


0.310 


42.1 


41.4 


5 


41.92 



13.08 
13 05 
12.98 
12.99 



Av. 13.02 



Table 10 
ParaflSn Plates — Water. Temp. 20.5-21° 



2.5 
2.0 
1.8 
1.8 



0.258 I 
I 0.305 I 



0.268 
0.272 



I 



37.5 
31.5 
37.2 

36.4 



36.5 


5 


37.10 


30. 1 


6 


30.91 


36.4 


5 


36.87 1 


36 4 


I 


36.4 1 



9-57 
9.43 
9.88 

9.90 



Av. 9 . 69 



In Table 11, we have condensed the results given in de- 
tail in Tables i-io, and have entered the substances in the 
order of the average values for rh obtained with them. This 
order is strikingly similar to that of the electromotive series 
of the metals. Aluminium falls out of place, doubtless owing 
to a protective coating of oxide upon it. We have included 
the highest and the lowest value for each substance to make 
it perfectly clear that our results overlap. Though the values 
for the different metals are not far apart, yet the lowest 
value for zinc is larger than the highest value for silver, and 
the highest value for glass is less than the lowest for nickel, 
etc. 



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376 



5. L. Bigelow and F, W. Hunter 



Table ii 

Plates of different substances. Temperature 20.5^-21* 

rh values for water 





High 


Low 


Average 


Zinc 


15 28 


14.98 


1515 


Copper 


15 


32 


15 


03 


15 " 


Nickel 


15 


12 


14 


89 


1500 


Aluminium 


15 


04 


14 


63 


14-78 


Silver 


14 


89 


14 


61 


14 -75 


Platinum 


14 


76 


14 


69 


14.72 


Glass 


14 


71 


14 


68 


14.69 


Celluloid 


14 


29 


13 


97 


14.12 


Beeswax 


13 


08 


12 


98 


13 02 


Paraffin 


9 


90 


9 


43 


9.69 



It both surprised and interested us to find that with 
substances commonly spoken of as "not wetted," namely, 
with celluloid, beeswax and parafiin, we could not only get 
ascensions, but high and regular ascensions. Our results 
with these substances agree with each other as well as the 
results with plates of other materials, as may be seen by refer- 
ence to Tables 8, 9 and 10. 

We believe that our results are numerous enough, and 
have been obtained with suflScient care, to justify the state- 
ment that water rises to different heights in capillary tubes 
of different materials. This is a somewhat more pregnant 
statement th^ it might at first appear to be. The surface 
tensions, (;-), of liquids are frequently calculated from measiu^- 
ments of capillary ascensions, employing the well-known 

rhs 
formulae ;- = — , (s = specific gravity), when the angle 



of contact between liquid and wall is o, and 7- = 



rhs 
2 cos^ 



when 



that contact angle (0) is greater than o. A polemic arose 
between Volkmann,* who maintained that the contact angle 



» p. Volkmann: Wied. Ann., 17, 353-90 (1882); 53, 633-66 (1894); $6, 
457-91 (1895); 62, 507-17 (1897). 



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Function of the Walls in Capillary Phenomena 377 

between clean water and clean glass was o, and Quincke/ 
who maintained that under certain circumstances this angle 
had a measurable value. 

Volkmann, employing many precautions in his experi- 
ments, obtained the value, ;- = 7.40 for the surface tension 
of water at 20°. We claim no such high degree of accuracy 
as Volkmann 's, for our separate results, yet oiu- average for 
water and glass (see Table 7) was 14.69, and half this, or 
7.35 would then be the value of ^; a satisfactory agreement. 
Now if that is the value for the surface tension of water at 
20°, what are we measuring when we obtain our higher values 
with practically all the metals we have tried, and when we 
obtain our lower values with celluloid, beeswax and parafiin? 
The surface tension of one liquid at one temperature must be 
a constant, and since we obtain different values, it cannot be 
surface tension which we are measuring. It is possible that 
the contact angle between water and glass is not o, and that 
this angle is more nearly o between water and those sub- 
stances with which we obtained higher ascensions. This 
view is the more probable as other methods for measuring the 
surface tension of water, the drop method, the bubble method, 
the ripple method, all give somewhat higher values than those 
obtained from the ascensions of water in glass capillary tubes. 
But one has not much more than stated the problem when 
he has demonstrated that the angle is o in some cases and 
greater than o in others. What interests us is, why is the 
angle different in different cases, or as we prefer to state it, 
why is the ascension of a given liquid different in tubes of 
different materials? This is a field in which but little, if any, 
direct experimental evidence has thus far been obtained, 
owing to the lack of a convenient experimental method. 

A liquid rises and is held at a definite height in a capil- 
lary tube through the action of two forces, first, the cohesion 
between the like particles of the liquid which, in the siu^ace 
layer is denoted by the phrase ** surface tension" and second, 

* G. Quincke: Wied. Ann., 2, 145-94 (1877); 27, 219-28 (1886); 52, 1-22 
(1894); 61, 267-80 (1897). 



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378 



5. L. Bigelow and F, W. Hunter 



the adhesion between the liquid and the walls. The arrange- 
ment may be likened to a chain with two links, and when such 
a chain is strained to the breaking point it is the weaker link 
which gives way. So, here, whichever is the weaker, adhesion, 
or cohesion must break first. The cohesion of a given Uquid at 
one temperatiu"e must be considered as constant, not varying. 
We find the phenomenon of '* breaking" at different strains, 
therefore we must be meastudng the force of adhesion. The 
force of cohesion must be greater in all our experiments, 
except those giving the highest results, and in those cases we 
have no sure means of knowing which of the two forces it is 
which gives way. Because of these considerations, we have 
intentionally avoided the use of the conventional values for 
}' and have expressed our results in terms of the product of 
the radius into the height into the specific gravity, which is a 
measure of weight held up, and leaves open the question as 
to what relation these values bear to surface tension. For 
the above reasons, we call these values of ours adhesion values. 
We wished to determine whether the capillary ascensions 
of other liquids than water were different with tubes (plates) 
of different materials. Tables 12-17 give the detailed results 
with benzene of specific gravity (s) 0.879 at 20.5®. Table 
18 summarizes the results. It will be observed that the cap- 
illary ascensions show differences greater than can be attri- 
buted to experimental errors, and furthermore, that the order 
in which the substances fall is practically the same as with water, 
with the exception that silver and copper have changed places. 

Table 12 
Benzene Sp. gr. 0.879. Temp. 20.5^ ± o°.2 
Glass plates h in mm 



No. 


Thick- 


of 


nessof 


pUte 


plate 


I 


1.87 


2 


1.90 


3 


2.77 



Radius of 
hole 



0.312 
0.312 
0.312 



Highestj Lowest 




6.675 5.866 



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Function of the Walls in Capillary Phenomena 379 

Table 13 
Benzene Sp. gr. 0.879. Temp. 20.5° ± 0*^.2 
Platinum plates h in mm 



No. 
of 

ptAte 
3 

4 

5 



Thick- 
ness of 
plate 



Radius 
of hole 



Highest 



Lowest 



No. of 
readings 



Average 




hrs. 



0.08 
0.08 
0.08 



0.283 
0.269 
0.314 



I 24.2 

! 25.6 

! 21.8 



239 
25.2 
21.6 



6.839 6.012 



Aluminium plates 



Table 14 



2 


0.87 


0.298 


23.2 


22.7 


4 


23 05 


6.87 




3 


0.87 


0.299 


23.1 


22.9 


5 


2308 


6.90 




4 


0.87 


0.312 


22.4 


22.0 


5 


22.29 


6.96 








Av. 


6.909 


6-073 


Table 


15 








Copper plates 










3 


0.15 


0.248 


27.6 


27.4 


5 


27-54 


6.83 




5 


0.20 


0.302 


22.9 


22.7 


5 


22.82 


6.89 




6 


0.68 ! 0.290 


23.7 


234 


5 


23 -57 


6.84 








Av. 


6.852 


6.023 


Table 


16 








Nickel plates 










A.B. 


0.53 


0.333 


20.9 


20.7 


4 


20.81 


6-93 




A.A. 


0.53 


0.333 


20.9 


20.8 


5 


20.88 


6-95 




A.C. 


0.53 


0.336 


20.9 


20.5 


6 


20.76 


6.98 








Av. 


6.953 


6. 112 


Table 


17 








Silver plates 










I 1 0.28 


0.261 1 27.6 


275 


4 


27-53 


7.18 




2 0.28 


0.260 1 27.7 


27.6 


5 


27.62 


7-18 




3 0.28 


0.258 1 27.1 


26.6 


5 


26.82 


6.92 




K.i.j 0.29 


0.352 1 19 9 


19.5 


5 


19.64 


6.91 




K. 


2 


! o.3< 


^ 


0.315 


21 .9 


21.5 


1 5 


21.81 


6.87 





Av. 7.014 6.165 



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380 S. L. Bigelow and F, W. Hunter 

Table 18 
rhs values for benzene. Temp. 20.5** ± 0.2^ 



Silver 

Nickel 

Aluminium 

Copper 

Platinum 

Glass 



6.16 
6. II 
6.07 
6.02 
6.01 
5.87 



We next undertook to determine the capillary ascen- 
sions of saturated water solutions of several salts in tubes of 
the solid solute. We obtained fair-sized plates by grinding 
down crystals, without reference to the position of the crys- 
tal axes. We felt that regard for the axes was a refinement 
which might advantageously be postponed tmtil we knew 
more of what to expect in this new field. We saturated our 
solutions at higher temperatures and then cooled them to 
the temperature of the experiment, always having a consid- 
rable excess of the solid present in the beaker. We deter- 
mined the specific gravities with a pycnometer at the temper- 
ature of the experiment in the usual manner. Otherwise, our 
procedure was in every particular as already described. We 
have results obtained with saturated solutions of copper sul- 
phate, gypsum, common salt (halite), potassium dichromate 
and alum, and plates of platinum and of the solute. Upon re- 
peating the work we have, however, obtained different values 
and deem it expedient to withhold these results tmtil we can 
determine the cause of the discrepancy. 

Conclusion 

We have described a new and convenient method for 
determining the capillary ascension of liquids in "tubes "of 
any substance. 

We have demonstrated that the capillary ascension of water 
(and of benzene) is different in tubes of different substances. 

We consider it probable that the capillary ascension of 
liquids is primarily a measure of the adhesion between the 
liquid and the substance of the wall. 

University oj Michigan, 
January 9, igti 



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THE DIELECTRIC CONSTANTS OF SOME LIQUID 

HYDRIDES 



BY R. C. PALMER AND HERMAN SCHLUNDT 

Measurements of the dielectric capacity of liquid hydrides 
have been extended/ and values are reported here for the die- 
lectric constants of liquid phosphine and stibine, and liquid 
and solid ammonia. 

The dielectric constant of liquid ammonia was determined 
independently in 1899 by Goodwin and Thompson,' and 
Coolidge,' but we have fotmd no record of a value for solid 
ammonia. As the dielectric constant of the solid was fotmd 
to be much lower than that of the liquid, and the value of 
the liquid increases with lowering of temperature, a maximum 
value must intervene. Like many other substances the change 
in dielectric capacity of ammonia is abrupt and occiu*s at the 
melting point. The maximum value of the liquid, at — 77®, 
was determined. 

We were restricted, in our experiments, to the use of 
solid carbon dioxide and ether under diminished pressiu-e for 
obtaining low temperatures. We fotmd the preparation and 
liquefaction of ammonia and phosphine relatively easy opera- 
tions in comparison with stibine. Since the boiling point of 
liquid stibine is only — 18°, and its melting point, — 91.5°, 
lies above the temperature of the cooling bath used, it seemed 
rather strange at first to meet with failures in seciu-ing the 
required quantities of this liquid. Beautiful mirrors of anti- 
mony appeared upon the walls of the connecting tubes, but 
only a few drops of liquid would accumulate in the condenser. 
Evidently the large volume of hydrogen generated simultane- 
ously swept the stibine through the small U tube condenser 
too rapidly. By modifying the generator and using a tiny 



» Cf. Schaefer and Schlundt: Jour. Phys. Chem., 13, 669 (1909)- 
» Phys. Rev., 8, 38 (1899). 
• Wied. Ann., 69, 125 (1899). 



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382 R. C. Palmer and Herman Schlundi 

spiral condenser the desired quantity of liquid stibine was 
ultimately obtained. 

The measurements were made with the well-known appa- 
ratus of Drude as modified by Schmidt.* As the hydrides in 
question are gases at ordinary temperatures and atmospheric 
pressure, the measiu-ements were conducted with the liquids 
in sealed cells. The U form of cell previously used* answered 
very well here. The cells were calibrated with the standard 
solutions of benzene and acetone, and acetone and water as 
given by Drude.' At least two independent determinations 
were made with different samples of each of the liquids and 
in cells whose dielectric capacity differed somewhat. The 
cells were recalibrated for each determination with freshly 
prepared samples of the solutions used as standards. The 
length of the stationary electric waves produced by the appara- 
tus in air was determined and found to be 71.5 cm. 

Preparation of Compounds, — In preparing the hydrides 
stress was laid on securing pure samples in the liquid state. 
After the different parts of the apparatus, — generator, drying 
trains, condenser, measuring cells, manometers, etc., had been 
sealed together, dry air was passed through the apparatus for 
an hour or two, and finally the apparatus was exhausted with 
a Geryk pump. The chemical action was then started and 
the gas condensed in a small condenser surrotmded by Thil- 
orier's mixture which could be kept under greatly reduced 
pressure if desired. The final measurements were conducted 
with samples that had been redistilled in vacuo. 

The ammonia used in these experiments was prepared by 
allowing a concentrated solution of potassium hydroxide to 
drop upon a quantity of ammonium chloride in a suitable 
generator. The gas was dried in the usual way, and after 
condensation the liquid was distilled into the calibrated measur- 
ing cells, which had been previously sealed to the condenser. 
The cells were finally sealed off and transferred to the Drude 



* Dnide's Ann., 9, 919 (1902). 

* Jour. Phys. Chem., 13, 671 (1909). 
' Zeit. phys. Chem., 23, 270 (1899). 



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Dielectric Constants of Some Liquid Hydrides 383 

apparatus where several sets of readings were made with each 
sample at several temperatures. 

The samples of liquid phosphine used were free from the 
hydride, PjH^. Two of the specimens were prepared by the 
interaction of potassium hydroxide solution and phosphonium 
iodide, and a third was obtained by the interaction of alumin- 
ium phosphide and water as given byMatignon.* The gase- 
ous phosphine was dried by passing through towers contain- 
ing phosphorus pentoxide, after passing through a cooling 
condenser to remove traces of PaH^. The liquid phosphine 
was finally transferred to the cells by distillation in vacuo. 
With the exception of the rubber stopper of the generator all 
connections were glass seals.' 

The samples of pure liquid stibine used were prepared by 
the method of Stock and Doht,* as later improved by Stock 
and Guttman.* An alloy consisting of one part antimony 
and two parts magnesium by weight was first prepared. The 
metals powdered to pass through a 40 M sieve were thoroughly 
mixed, placed in an iron tube, and heated in an atmosphere of 
hydrogen to a bright red heat, being finally kept at a dull red 
heat for about one hour. The alloy thus formed was easily 
removed from the tube, being in the form of a brown powder. 

In preparing the stibine, the finely powdered alloy was 
gradually shaken into cold diluted hydrochloric acid. sp. gr., 
1.06, which had previously been boiled to free it from air. 
The acid was kept cold during the reaction by shaking the 
generator which was immersed in a mixtiu-e of ice and brine. 
Before passing through the drying tubes of calcium chloride 
and phosphorus pentoxide the gas passed through moist glass 
wool and water in a U tube to absorb traces of hydrochloric 
acid that might be carried over mechanically from the gener- 

* Comptes rendus, 130, 13 14, 1393 (1900). 

' Complete details of preparation and photographs of the apparatus 
used as well as detailed data on the measurements are given by R. C. Palmer 
in his thesis for the degree of Chemical Engineer, University of Missouri, June 
19 10. 

* Ber. chem. Ges., Berlin, 35, 2270 (1902). 

* n>id., 37, 885 (1904). 



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384 R' C, Palmer and Herman Schlundt 

ator. With the exception of a piece of pressure tubing con- 
necting the generator and drying train all connections were 
glass seals. Stock and Guttman experienced no diflficulty in 
liquefying and solidifying stibine in a simple form of conden- 
ser immersed in liquid air. To liquefy stibine with Thilor- 
ier's mixture kept under diminished pressure we foimd it 
necessary to cool the gases in a spiral condenser ending in a 
small bulb at the bottom whose outlet passed up through the 
spirals and was surroimded by them. The liquid stibine was 
colorless and of high refractive power, and was easily trans- 
ferred to the cells by distillation. The cells were finally sealed 
oflF at constricted places. We met with no accidents in these 
operations. Stock and Guttman state that gaseous and even 
liquid stibine have a tendency to dissociate with explosive 
violence. To prevent any explosion in sweeping back through- 
out the whole apparatus when the measuring cells were sealed 
off, a stopcock was placed between the condenser and the cell. 

Only a faint antimony mirror appeared in the capillary 
tube where it was sealed off. The unstableness of stibine, 
however, was always manifest by the plating of antimony 
mirrors in different parts of the apparatus during an experi- 
ment. 

Results, — The values obtained for the dielectric constants 
are summarized in the following table: Unless otherwise 
specified the values refer to the substances in the liquid state 
imder their own vapor pressure at the temperatiu-e given. 



Substance Temp. ° C 


D.C. 


Temp, cocff. 
Percent 


Ammonia 20.5 


15.55 


- 


" '- - — - -^ ' 24.5 


14 9 


— 


(max. value)- - . L -. — 77 


25.4 


--0.4 


'* (solid) . ^ ^ J . — 90 


4.01 


— 


Phosphine *• • * • -^ * ^ — 60 


2.55 


-fo.i8 


• —25 


2.71 ' 


— 


** (calculated) • • • ^ ^^ 20 


2.91 


— 


Stibine • • . * ^ -^ -^80 


2-93 


— 


• - - --t —50 


2.58 


—0.4 


(calculated) - -* -^ - ^ 20 


1.76 





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Dielectric Constants of Some Liquid Hydrides 385 

The value obtained for liquid ammonia at 20.5°, 15.55, 
agrees fairly well with that of Coolidge, who fotmd 16.2 at 
14®, and also with the result of Goodwin and Thompson, 
namely 21-23 at — 34°. From the dielectric constants at 
20.5° and — 77° the calculated temperature coeflScient is 
— 0.4% per degree rise in temperatiu'e referred to the maxi- 
mum at — 77°. The value of the dielectric constant for 
liquid ammonia at 20.5°, namely 15.55, if calculated to — 34® 
by means of the temperature coeflScient determined gives 
the value 21.4. This agrees fairly well with the value deter- 
mined by Goodwin and Thompson for this temperature, 
namely 21-23. It should be stated in this connection that 
the cells used for making the measurements were designed 
for substances with low dielectric constants. Consequently 
the values determined for liquid ammonia are not as acciu*ate 
as the apparatus is capable of giving. 

The temperature coeflScient of liquid phosphine was 
found to be positive, and has a value of 0.18% referred to the 
value at — 60°. The dielectric constants for phosphine and 
stibine at 20° were calculated by assuming that the change 
in value is a linear function of the temperature. 

The electrical conductivity of phosphine and stibine in 
the liquid state was tested and these solvents were found to 
be non-conductors like benzene. 

It is hoped to complete this series of determinations by 
measuring the dielectric constant of liquid arsine. 

Discussion, — It is seen from the results that the dielec- 
tric constants of the liquids determined, decrease with increase 
of molecular weight. Tereschin^ showed that in a large num- 
ber of cases of homologous series, such as organic acids, alco- 
hols, etc., the dielectric constants decreased with increased 
molecular weight. This inorganic series, ammonia, phos- 
phine, and stibine, may show this same relation although not 
an homologous series in the usual sense. 

It was noted by Schlundt' that there is always a marked 

» Wied. Ann., 36, 807 (1899). 

» Bull. Univ. Wis. Sd. Series, 2, 353 (1901). 



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386 R. C. Palmer and Herman Schlundi 

diflference in the physical properties of the first two members 
of any homologous series, and that this difference always held 
for the value of the dielectric constant. This marked dif- 
ference is also shown for the dielectric constants of liquid 
ammonia and liquid phosphine, the values being 15.55 ^^d 
2.91 respectively at 20® C. This fact asstmies especial impor- 
tance when it is considered that the nitrogen, phosphorus, 
and antimony compotmds may be classed as organic as well 
as inorganic. 

As regards the Nemst ^-Thomson' rule very little can be 
said for the values determined, since the ionizing power of 
these liquids as solvents, with the exception of ammonia, 
have never been studied. Liquid ammonia is an excellent 
example of the Nemst-Thomson rule since its dielectric con- 
stant is comparatively high and its ionizing power as a sol- 
vent is quite marked. It would be expected that liquid 
phosphine and liquid stibine having low dielectric constants 
would show very little ionizing power. But in view of pre- 
vious work' on liquid hydrogen halides which have low dielec- 
tric constants but do possess marked ionizing power, this 
property cannot be predicted for liquid phosphine and liquid 
stibine. 

Chemical Laboratory ^ 

University of Missouri, 

December, igio 



* Zdt. phys. Chem., 13, 531 (1894). 
'Phil. Mag., [5] 36, 320 (1893). 
•Jour. Phys. Chem., 13, 669 (1909). 



\ 

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STUDIES IN THE ELECTROCHEMISTRY OF THE PRO- 
TEINS, VI. THE CONDUCTIVITIES OF SOLUTIONS 
OF THE CASEINATES OF POTASSIUM AND OF 
THE ALKALINE EARTHS IN MIXTURES OF 
WATER AND ALCOHOL. 



BY T. BRAILSFORD ROBERTSON 

(From the Rudolf Spreckels Physiological Laboratory of the 

University of California) 

L Introduction 

If one-half a cubic centimeter of a 0.0125 solution of 
KOH, neutralized either to phenolphthalein or to litmus 
by the addition of casein, be added to 10 cc, i. e,, to 20 volumes 
of 99.8 percent alcohol, no precipitation of protein occiu-s, 
although the solution which is thus obtained is appreciably 
more opalescent than a solution of equal concentration in 
water containing no alcohol. Even if, instead of employing 
a solution of potassium caseinate in water, we employ a 
0.0125 solution of KOH in 75 percent alcohol, containing 
1.6 or 2.5 percent of casein, adding V^ cc of this to 10 cc of 
99.8 percent alcohol, still no precipitation of the caseinate 
occurs, although it is now dissolved or forms a stable sus- 
pension in a 98.6 percent solution of alcohol. The caseinate 
can, however, be readily precipitated by adding to this mix- 
ture an equal volume of ether and allowing it to stand for 
a few hours. 

Very different is the behavior of the caseinates of the 
alkaline earths. If to 100 cc each of 60, 70, 75 percent, etc., 
solutions of alcohol we add ^/^ cc of a 0.012 N solution of 
Ca(OH), neutralized to phenolphthalein by casein, distinct 
precipitation of the caseinate occurs, on shaking, when the 
final concentration of alcohol in the mixture is about 55 
percent. The same is true for an equally concentrated 
solution of barium hydroxide neutralized to phenolphthalein 
by casein. For strontium caseinate, the limiting concentra- 
tion of alcohol at which precipitation occurs is much higher. 



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388 71 Brailsford Robertson 

about 70 percent. In all cases precipitation is much accel- 
erated by energetic shaking of the mixture. 

It is of interest to compare the marked difference between 
the behavior of the caseinates of the alkalies and of the alka- 
line earths upon the addition of alcohol to their aqueous 
solutions, with the numerous other differences which subsist 
between the caseinates of the alkalies and those of the alka- 
line earths. 

Thus the aqueous solutions of the ** neutral" or ** basic'* 
caseinates of the alkalies and ammonium are clear, do not 
(except lithium caseinate) show any increase in tiu-bidity 
on warming, and are not precipitated by the addition of 
finely divided insoluble substances or by passing through 
a clay filter, while the aqueous solutions of the caseinates of the 
alkaline earths are opalescent, show a marked increase in tur- 
bidity on heating their solutions to 35°-45°C which dis- 
appears on cooling and are precipitated from their solutions 
by the addition of finely divided insoluble substances 'or 
by passage through a clay filter.* 

The ** neutral" and ** basic" caseinates of the alkalies, 
upon solution in water, depress its freezing point and the 
amotmt of the depression is that of a solution of the molecular 
concentration as the alkaline solution which is employed 
as solvent. The depression produced by calcium caseinate 
is nmch less, being less than half as great.' 

Equally concentrated solutions of the hydroxides of the 
alkaUes and ammonium dissolve casein at approximately 
the same rate. Solutions of the hydroxides of the alkaline 
earths dissolve casein nmch more slowly.' The rate of the 
solution of casein by solutions of the hydroxides of the alka- 
lies is accelerated by raising the temperatiu-e above 36°; the 
rate of the solution of casein by solutions of calcium hydroxide 
is materially diminished by a similar rise in temperature.* 

* W. A. Osborae: Jour. Physiol., 27, 398 (1901). 

»T. Brailsford Robertson and Theo. C. Burnett: Jour. Biol. Cbem., 6, 
105 (1909). 

* T. Brailsford Robertson: Jour. Phys. Chem., 14, 377 (1910). 

* T. Brailsford Robertson: Jour. Biol. Chem., 5, 147 (1908). 



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Studies in the Electrochemistry of the Proteins 389 

The caseinates of the alkaline earths are precipitated 
from their solutions by the addition of small concentrations 
of the chloride of the corresponding alkaline earth.* 

The caseinates of the alkalies are not precipitated by the 
addition of similar quantities of the chlorides of the alkalies. 

I have alluded to the fact that the limiting concentra- 
tion of alcohol at which strontium caseinate is precipitated 
is considerably higher than that at which calcium and barium 
caseinates are precipitated. This is curious because we 
should expect, as a rule, to find the salts of strontium possessed 
of properties intermediate between those of calcium and 
barium. It is, therefore, the more interesting to observe 
that this is not the only respect in which the caseinates of 
strontium exhibit behavior differing from that of the casein- 
ates of calcium and barium and approaching the behavior 
of the caseinates of the alkalies: for casein dissolves much 
more rapidly in solutions of strontium hydroxide than it 
does in equally concentrated solutions of calcium or barium 
hydroxide;* the solutions of strontium caseinate are less 
opalescent than equally concentrated solutions of calcium 
or barium caseinate, and the dissociation-constant of "basic" 
strontium caseinate is much larger than those of barium or 
calcium caseinate and is intermediate in magnitude between 
these and the dissociation-constants of the "basic** casein- 
ates of sodium and ammonium. This, however, is not a 
general phenomenon where protein salts of the alkaline earths 
are concerned, because the dissociation constant for the stron- 
tium salt of " insoluble '* serum globulin is not very appreciably 
different from those of the calcium and barium salts.* 

It appeared of interest to determine the conductivities 
of solutions of the caseinates of potassium and of the alka- 
line earths in alcohol-water mixtures, not only with a view 
towards a further comparison of the caseinates of the alkalies 
and of the alkaline earths but also with a view towards a 



* T. Brailsford Robertson: Jour. Phys. Chem., 13, 469 (1909). 
' Ibid., 14, 377 (1910). 
' Ibid.. 15, 166 (191 1). 



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390 T. Brailsford Robertson 

further understanding of the chemical mechanics of the 
precipitation of proteins by alcohol. 

II. Experimental 

The mode of preparation of the casein and the technique 
of the conductivity determinations were the same as described 
in previous communications.* All of the conductivity de- 
terminations were made at 30° C. The resistance-capacity 
of the vessel employed was 0.1949. The conductivity of the 
distilled water, in reciprocal ohms per cc was 4 X lo"* and 
it has been subtracted from each of the tabulated conductivi- 
ties. 

In five hundred cc of N/io KOH were dissolved 62.5 
grams of casein, thus forming a solution of "basic" potassium 
caseinate, neutral to phenolphthalein. To 50 cc portions 
of this solution were added, respectively, o, 20, 40, etc., cc 
of alcohol and the mixtures were diluted to 200 cc with water. 
Each of these solutions was then diluted with alcohol solu- 
tions, of corresponding concentrations, to the desired con- 
centration of caseinate. The solutions in ** 75 percent alcohol" 
were made up by adding 99.8 percent alcohol to 50 cc of the 
original solution of caseinate tmtil the volume was 200 cc, 
and diluting with a 75 percent by volume solution of 99.8 
percent alcohol. 

The following were the results obtained : 



^ T. Brailsford Robertson: Jour. Phys. Chem., 14, 528 (1910). 



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Studies in the Electrochemistry of the Proteins 391 




00 


M 

»>4 


00 M 


.r = conduc- 
tivity in re- 
ciprocal ohms 
per cc at 30® 


XXXXX 

M M M M M 

0.0,0.0,0, 



00000 

8882S 

M Oa On M 01 
ON M c#i Cn 


Equiv. cone. 

of KOH 
neutralized 

by casein 


10 Oa Cn vo 0^ 

^ >o 4^ 
XXXXX 

^^ M M M M 

0, 0, 0, q 0. 

a a » tt tt 


X -= conduc- 
tivity in re- 
ciprocal ohms 
per cc at 30** 



I 

41 


1 M K) Oa ^ 

1 On 1-4 M VO H4 

1 K) ONOJ M Cn 


IXXXXX 


s 

C3 


1 M M M M H4 
l9 S R S R 


§ 


1 1 1 1 1 1 
1 • • • • 



®oB7? 



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392 



71 Brailsford Robertson 



Twenty grams of casein were dissolved in 200 cc of 0.05 N 
KOH. To twenty-five cc portions of this solution were 
added 10, 20, etc., of alcohol and the mixtures thus obtained 
were diluted to 100 cc. The solution in 75 percent alcohol 
being obtained by adding 99.8 percent alcohol to 25 cc of 
the original solution of caseinate until the total voliune 
of the mixture attained 100 cc. 

Table II 
Concentration of KOH neutralized to litmus by casein = 0.0 125 



Percent alcohol by volume 



X = conductivity in reciprocal ohms 
per cc at 30® 



O 
10 
20 
50 

75 



866 X IO-* 

663 X IO-* 

513 X lo-' 

254 X lo-' 

80 X IO-* 



Fifteen grams of casein were dissolved in 250 cc of 0.048 N 
Ca(OH)j, thus forming a solution of "basic" calcium caseinate. 
To 25 cc portions of this solution were added o, 10, 20, etc., 
cc of alcohol and these mixtures were diluted to 100 cc. It 
was foimd preferable to poxu* the caseinate solution into 
the alcohol (previously somewhat diluted) rather than to 
poxu* the alcohol into the caseinate solution for otherwise 
coagula were formed where the concentrated alcohol first 
met the caseinate solution and these coagula redissolved 
with difficulty. 

The following were the results obtained : 

Table III 
Concentration of CaCOH), neutralized to phenolphthalein by 
casein = 0.012 N 



Percent of alcohol by volume 



X = conductivity in reciprocal ohms 
per cc at 30® 



O 
10 
20 
30 
40 
50 



177 X 


lO' 


75 X 


lO' 


37 X 


lO" 


22 X 


lO' 


16 X 


lo- 


12 X 


lO' 



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Studies in the Electrochemistry of the Proteins 393 

Fifteen grams of casein were dissolved in 500 cc of 0.024 
N Sr(OH)j, thus forming a solution of "basic*' strontium 
caseinate. To 50 cc samples of this solution were added 
o, 10, 20, etc.,cc of alcohol and the mixture were diluted to 
100 cc. 

The following were the results obtained : 

Table IV 

Concentration of Sr(OH), neutralized to phenolphthalein by 

casein = 0.012 N 



Percent of alcohol by volume 



O 
10 
20 
30 
40 
50 



X = conductivity in reciprocal ohms 
per cc at 30® 

251 X lO"* 

124 X IO-* 

63 X IO-* 

42 X io-« 

32 X IO-* 

23 X IO-* 



Fifteen grams of casein were dissolved in 250 cc of 0.028 
N Ba(0H)2, thus forming a solution of "basic** barium 
caseinate. To 25 cc portions of this were added o, 10, 20, 
etc. cc of alcohol and these mixtures were diluted to 100 cc. 

The following were the results obtained : 

Table V 

Concentration of Ba(0H)2 neutralized to phenolphthalein by 

casein = 0.012 N. 



Percent of alcohol by volume 



I X = conductivity in reciprocal ohms 
per cc at 30® 



o 
10 
20 
30 
50 



167 X 
66 X 
30 X 

17 X 



IO~ 
lO" 



lO" 
IO~ 



7 X 10- 



The solutions of calcium and barium caseinates in 50 
I>ercent alcohol were very opalescent, that of the Ba casein- 



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394 ^' Brailsford Robertson 

ate being as opaque as milk. The solution of strontium 
caseinate in 50 percent alcohol was much less opalescent. 
In the solutions of ** basic " potassium caseinate it was observed 
that the opalescence imderwent a marked and relatively 
sudden increase at a concentration of alcohol lying between 
60 percent and 75 percent by volume, although, as we have 
seen, precipitation of the caseinate did not occur at even 
very much higher concentrations of alcohol. 

III. Diseussion of the Results and Additional Data 

{%) The applicability of the Ostwald dilution-law to solu- 
tions of the caseinates in alcohol-water mixtures. 

In previous communications I have shown* that the 
Ostwald dilution-law for a binary electrolyte may be written : 

___ 1.037 X 10-' ^ , 1.075 X 10-* 

tW ; X -|- -^z r .- X* {I) 

where m is the equivalent-molecular concentration of the 
electrolyte, x is its conductivity in reciprocal ohms per cc, 
G its dissociation constant and v^ and v^ are the ionic velocities 
in cm per sec. per potential gradient of i volt per cm. In 
the same commimications I have shown that this law, in 
the form 

_ 1.037 X 10-* 1.075 X 10-* , , . 

m —7 V X -f- ;r — ; r-;- X \^2) 

where m is the equivalent-concentration of base combined 
with the protein and p is the number of equivalent gram 
molecules of caseinate which is produced by the neutrali- 
zation of one equivalent gram molecule of base, holds good 
for aqueous solutions of the ** neutral'* and ** basic'' casein- 
ates of sodium and ammonium and for solutions of the " basic '* 
caseinates of calcium, barium and strontium. From these 
and other data I have concluded' that in the formation of 
the ''basic** caseinates two (or four) molecules of base are 



* T. Brailsford Robertson: Jour. Phys. Chem., ii, 542 (1907); 12, 473. 
(1908); 14, 601 (1910). 

' Ibid., 14, 528, 601 (1910). 



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Studies in the Electrochemistry of the Proteins 395 

bound up in one molecule of caseinate and that the salt which 
is thus formed dissociates into two (or foiu-) quadrivalent 
ions. 

Applying equation (2) to the results enumerated in 

Table I and computing the constants ^'^?^ . ^^ and 

^' , — ; r^ for each concentration of alcohol from all the 

results by the method of least squares, we obtain : 
For the solutions containing o percent of alcohol : 

m = 12.41 X -f i666 x^ (3) 

For the solutions containing 10 percent of alcohol : 

w = 15.97 ^ -f 3325 ^' (4) 

For the solutions containing 20 percent of alcohol : 

m = 21.14 ^ + 5880 x^ (5) 

For the solutions containing 30 percent of alcohol : 

m = 27.23 X -f 10858 x^ (6) 

For the solutions containing 40 percent of alcohol : 

w = 34-^3 ^ + 18931 x^ (7) 

For the solutions containing 50 percent of alcohol : 

m = 42.91 X -f 35937 ^' (8) 

For the solutions containing 60 percent of alcohol : 

w = 53.49 ^ + 78335 ^' (9) 

For the solutions containing 75 percent of alcohol : 

m = 29.95 X + 1219800 x' (10) 

Inserting in these equations the observed values of x, we 
can compute the "theoretical" values of m, that is, the 
equivalent concentrations of KOH neutralized by the casein 
which should, provided that in all of these solutions, potas- 
sium caseinate dissociates into two ions (or into ]onr ions 
all capable of mutual interaction, Cf. part V of these "Stud- 
ies" Journal of Physical Chem.) correspond to the observed 
conductivities. In the following table the observed and 
calculated values of m are compared : 



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396 



T. Brailsford Robertson 



% 



o 

•§ 



tt 

^ 
^ 






X^ 



O (H O 



+ + 1 












c 



o 

o 



a 

8 



o 
o 



M d M P4 H4 M 



O 0/ 



xt 






o 

o 
u 



o 



o 









+ + 



1^ f^ CM r*o r>» 



+ « 

c 
o 









O M 



O r* M I i-i 



** C8 


O fO fO fO t^ 


I1 1 


»0 CS vO to "-• 


S-3 




U 




■b-g 




-. ^ 


O lO ro i-i O 


S o 


»0 W O to "-I 



<3 



O 

8 



c 
a; 
u 

o 



8 



O IH tH fi o 

I + + 



I Ci 



+ ^ 



O -^ ^ fOvO 



O »0 fO »H SO 

to « vo to •-• 






c 
o 



o 

8 



O jU 
^ CO 

Xs 

u 



O 1) 

- > 

5-g 



xg 



5-^ 



lO M M ro lO 



-o'S 




-•a 


lOvO 


Xf, 




£-3 




u 




•vo 




O V 




■" s 


O »o 


xS 


lO <H 


S JD 




ft o 







<1 


« 00 « 


P^ 



I to •^ s 
I vO to ' 





»i^ 


M M 


to •-• 


• to 


< 


+ 


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-f -f 


+ 








<J 


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»H 


'^ « 


Tj-t^ 


p^ 


xg 


lO <H vO 


to •-« 




6g 










'^s'^ 










2 ^ 










5-§ 


o 


lO to 


Ml vO 






to •-« 





O « •-• to M I « 

I 1++ i + 



lO « \o to «-• 



O »0 to "-I vO 

»o « \o to «-• 
« I-I 



O « O to •-« I w 

I ++i + 



O to to '^ t^ W 

•o w \o to »H 



O »0 to "-I o 
»0 <H vO to •-< 

« l-l 



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Studies in the Electrochemistry of the Proteins 397 

It is evident that the correspondence between the ex- 
perimenta results and those which are indicated by the 
Ostwald dilution-law for a binary electrolyte is all that could 
be desired for the solutions containing from o to 60 percent 
of alcohol. For the solutions containing 75 percent of alco- 
hol, the divergences between theory and experiment are, 
however, considerably greater than could be accoimted for 
by experimental error and probably indicate that the law 
does not hold good for these solutions. The sudden altera- 
tion in the relative values of the constants which occurs when 
the j>ercentage of alcohol attains this magnitude indicates, 
whether the Ostwald law be considered as holding good or 
not, a profound change in the molecular and ionic condition 
of the protein. 

It would appear, however, that we are justified in con- 
cluding that potassium caseinate dissociates in alcohol-water 
mixtures containing from o to 60 percent of alcohol in the 
same manner as it does in aqueous solutions. 

(m) The influence of the concentration of alcohol in the 
solvent upon the conductivities of solutions of potassium 
caseinate, 

I find that the conductivity {=.Xy) of a solution con- 
taining any given concentration of casein combined with 
KOH in the proportion requisite, in aqueous solution, to 
secure neutrality to phenolphthalein, when dissolved in an 
alcohol-water mixture containing y percent of alcohol by 
volume is connected with the conductivity {=Xq) of a similar 
solution in water by the formula 

^y=5^ (II) 

where A is a constant which varies but slightly, if at all, 
with the concentration of the caseinate. This constant is 
determined in the following manner: If the logarithms to 
base 10 of x corresponding to j/ = o, 10, 20, 30, 40, 50 and 
60 percent be tabulated in order and each successive value 
of log X be subtracted from the one lying immediately above 



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398 T. Brailsford Robertson 

it, the differences thus computed are observed to be appreci- 
ably constant and equal to ten times the log, to base 10 of A. 
For all of the determinations enumerated in Table I (omitting, 
in the computation, the solutions containing 75 percent alcohol) 
the average value of A is 1.0265. For the various concen- 
trations of potassium caseinate the values of A are as follows : 



Tabl 


e VII 


Concentration of KOH neutralized 
by casein 




0.0250 




0.0125 
0.0063 




0.0031 
0.0016 





I. 1279 

I .0270 
1.0265 
1.0252 

1.0257 

Average, i . 0265 

In the accompanying table (Table VIII) the experi- 
mental values of x and those computed from the formula 

Xy = -^y are compared. Two ** calculated*' values of Xy are 

given, the first calculated value of Xy being computed from 
the average value of A for the concentration of caseinate 
in the solutions under consideration, the second being com- 
puted from the average value of A for all the determinations 
enumerated in Table I, with the omission, of course, of those 
for the solvent containing 75 percent of alcohol. 

The same relation also holds good for solutions of *' neu- 
tral* ' potassium caseinate in alcohol- water mixtures, in this 
case the values of A were computed from the results (except 
that for 75 percent alcohol) enumerated in Table II, the 
average difference in log^, Xy for 10 percent increase in y 
being computed by adding together the three observed dif- 
ferences (between jc^, corresponding to y = o percent and 
10 percent, 10 percent and 20 percent, 20 percent and 50 
percent) and dividing their sum by 5. In this way A is 
ascertained to possess, for these solutions, the average value 



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Studies in the Electrochemistry of the Proteins 399 



en O O 



4^ 0^ K) M 

00000 





Oa -r*" Cn ^ vO 
10 Od Cn 10 -^ 




ON 


10 0^ 4^ Cn ^ vO 
i-i K> K> Cn K> Cn 

K> 0^ ^ Cn ^ sp 
04 4k. Cn OOCn 00 


Hi 
ON 

Cn 

M 
.^ 

Cn 



jcy X lo* calc. 
A = 1.0279 

3Cy X 10* calc. 
A = 1.0265 



O 
crffl 

8S 



B £. 






^ ONCn 

cn O O 



vO 004^ 



1-4 i-i 10 

10 oooj 



i-i i-i K) 
04 vO -^ 



4k. C^ 10 M 

O O O O Q 



Oa 0>) Cn On 00 
M \0 1-^ OOvO 



O.) 4k. cn On 00 
M O 10 OOvO 



C^i 4k. cn On 00 
M M OJ OOvO 



jcy X 10* obs. 

Xy X 10* calc. 
A = 1.0270 

Xy X 10* calc. 
A = 1.0265 



Wo 



^ ONCn 

Cn O O 



^ O) 10 M 

00000 



I-I 1-4 M 10 10 o>) 4^ 

ONOC*i^ M^^ 00 


xy X 10* obs. 


1-4 M M K> K) C^i 4^ 

^ OJ ^ M 00^ 00 


xy X 10" calc. 
A = 1.0265 



M O 00 



M K) K) Od 4^ 
^ K) 00^ 00 



jpy X 10* calc. 
A = 1.0265 



Wo 

crfflS 
.o^bS 
8 8 2 2- 



f 



^ ONCn 
Cn O O 



4^ 00 10 1-4 

00000 



M 1-4 1-4 10 

I vO H4 ^ vO Cn 



^ 004»- M OnvO vO 00 



4^ Cn ^ 

b bo-i^ 



1-4 M K) K) 

\0 to Cn O Cn 



00 Cn ^ 

ON-i*. b 



Cn 10 <v| M 00 



M M M 10 

\0 I-I C/1 vO Cn 



O 0000 00 00 



jcy X 10* obs. I 



j jpy X 10* calc. 
j A = 1.0252 

Xy X 10* calc. 
A = 1.0265 



*-4 ONCn ^ Od K> M 

CnOOOOOOO 

K>C*AC>a4»' ONOOOcS 

bbvooiob^oo 


Xy X io» obs. 


MOAOACn OnOOOOa 

^bvbb-^co-ijbo 


Xy X lo" calc. 
A = 1.0257 


M lOC^4k> OnOOOOo 
VO NO ^ boC*A K) ON 00 


Xy X 10* calc. 
A = 1 .0265 



o 
o 

d 

cr-n 
^W 

o 



o 
o 

B 

b2 



2.N o 

cr 1-^ 

O 



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400 



T. Brailsford Robertson 



1.0248. In the following table the actual and computed 
values of Xy are compared : 

Table IX 
Concentration of KOH neutralized by casein = 0.0125 



o 

lO 

20 
50 
75 



Xy X io~* observed 

87 
66 

51 

25 

8 



Xy X 10— • calculated 

87 
68 

53 
25 
14 



The law does not, however, hold good for solutions of the 
caseinates of the alkaline earths in alcohol- water mixtures; 
this is evidenced by the lack of constancy in the first differ- 
ences of logi^ Xy corresponding to equal increments of y. In 
the accompanying table are given the values of log^, Xy corre- 
sponding to various values of y for the solutions of calcium 
caseinate, computed from the results enumerated in Table III. 

Table X 



ni 01 aiconu 
irolume 


Logio ^y X 10* 


DiflFerencc 





I 24797 





10 


0.87506 


0.37291 


20 


0.56820 


0.30686 


30 


0.34242 


0.22578 


40 


0.20412 


0.13830 


50 


0.07918 : 


0.12494 



In the following table are given the corresponding data 
for strontium caseinate derived from Table IV : 

Table XI 



y = perceni 01 aiconoi 
by volume 


Logio Xy X 10* 
1.39967 


Difference 





10 


1.09342 


0.30625 


20 


0.79934 


0.29408 


30 


0.62325 1 


0.17609 


40 


0.50515 


o.ii8io 


50 


0.36173 


0.14342 



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Studies in the Electrochemistry of the Proteins 401 

It is perhaps not without significance that in the above 
table the first two differences are much more nearly alike 
than the succeeding differences. In solutions containing o to 
25 percent of alcohol strontium caseinate is further from 
precipitation than corresponding solutions of calcium caseinate 

and, as we have A, in the equation Xy = ^, approaches 

constancy. Having regard to the observed failure of the 
solutions of potassium caseinate in 75 percent alcohol to 
conform to the law, and to the fact that at an alcohol-concen- 
tration lying between 60 percent and 75 percent solutions 
of potassium caseinate imdergo a great and relatively sudden 
increase in opacity, we may, I think, conclude that the pre- 
cipitation af a caseinate by alcohol is heralded by a failure of 

the solution to conform to the law ^y = ^> connecting the 

percentage af alcohol in solution with its conductivity, 

{Hi) The interpretation of the law Xy = ^. 

As we have observed, the value of A is not only constant 
for all dilutions of potassium caseinate, but also is very nearly 
constant for all of the proportions of alcohol to water employed 
as solvents. Provided A was rigorously constant we would 
obviously obtain the relation : 

_^HsO ^constant 

^alc. H9O 

for any given proportion of alcohol to water. This is the 
relation, suggested by Cohen, ^ connecting the conductivi- 
ties of inorganic salts in mixtures of alcohol and water. Roth,* 
however, foimd that this rule does not strictly hold good for 
solutions of KCl in mixtures of alcohol and water, but that 

the quotient --"*^- decreases somewhat with increasing 
dilution. In the accompanying table, the values of — ?^— 

^•Ic. H9O 

are given for each of the proportions of alcohol to H3O em- 
ployed. 

» Cohen: Zeit. phys. Chem., 25, 31 (1898). 
' Roth: Ibid., 42, 209 (1903). 



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402 



T, Brailsford Robertson 





4-» 


BB o 


00 « N O « 1 

O^ O^00 00 00 ■ 






1 


« • 


« « W W W 






.H 








, o 

1 "V 






** 




5 «4^ f-^ 




g . 




o 


8og 


O »0 fO M \0 


1 




•8 

1 ^ 


Equivalent 

centratioi 

KOH neu 

izedb: 

caseit 


SS888' 
6 6 6 6 6> 


I- 






HH 00 VO W W 


< 






J 


1 




"ti 




fO W N W W 1 






§ 




« « <s « w 

























' o 


ivalent cc 
ntration o 
^H neutra 
ized by 
casein 


i 

O »0 fO »-• vO 






5 


0.025 
0.012 
0.006 
0.003 
O.OOI 


*J 1 


X 




^8« 


i 


s. 


s 







'S 1 


P3 








•n ' 


< 




^ 







H 




9. « 


vO »00 fO rO 


•0 ' 




4J 


t^ t^ t^ t^ t^ 







1 a 


>< « 




< 




Jf 


;« 








& 






\ 




o 










1 M 


C3 1 








1 


. CO 

n of 
tral 

1 


10 to M \0 1 






uivalent 

entratio 

OH neu 

ized b 

caseiz 


0.025 
0.012 
0.006 
0.003 

O.OOI 








§•«« 


1 






1 


'1 


f*5 M •-< On 


V 1 

u 






eo CO fO PO cs 


u 




a 


H4 M M M M 






s. 






-0 




o 


Cv^ • 




ja 






uivalent co 
en t ration o 
OH neutra 

ized by 

casein 


»0 fO •-« \0 


8 




, o 


0.025 
0.012 
0.006 
0.003 

O.OOI 


•< 




1 
1 


^"« 


1 


1 



9, 


<8. 


R!J2^^8. 




6 






O »0 fO •-• VO 
00088 

6 6 6 6 6 



CO I u 






w*- 






eS J. 

§3.2 

O €i 
033 o 



t^ Ov t^ »0 O 
i-i 00 t^ tJ-nO 



O "O <o 
»o « vp 
« i-i Q 

000 



88 



00000 



^ i-i 00 On ^ 
00 t^vO ^ »0 

fi <0 fO fO f5 



O »o <o •-« O 

10 CM vO f<5 •^ 

« M 

00000 
6 6 6 6 6 



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Studies in the Electrochemistry of the Proteins 403 
It will be observed that the values of — ^*9— are ap- 

^alc. H,0 

preciably constant for each proportion of alcohol to water, 
for the solutions containing o to 60 percent of alcohol, but 
that in the solutions containing 75 percent of alcohol the 
value of this ratio does not even approximate to constancy 
but decreases rapidly. There is, it is true, a slight but regular 
diminution in the value of this ratio, even in the solution 
containing o to 60 percent of alcohol, in passing from an equiv- 
alent concentration of neutralized KOH of 0.0250 to 0.0016, 
but, except in the solutions containing 75 percent alcohol, 
the diminution is not more than a few percent. 

We have seen (eqims. 3 to 10) that the Ostwald dilution- 
law, in the form expressed in equation (2) holds good, at 
any rate for solutions of potassium caseinate in alcohol- 
water mixtures containing o to 60 percent of alcohol. 

From the symmetry of the equation : 

it would follow, were A strictly constant for all dilutions, 
that the proportion of alcohol to water employed as solvent 
for the caseinate affects only v^ + v^, i. e., the migration- 
velocities of the ions, not the dissociation-constant (=G) 
or the number of equivalents of caseinate resulting from the 
neutralization of one molecule of KOH (=p). Since the 
alteration in A with dilution of the potassium caseinate is 
so small for solvents containing o to 60 percent of alcohol, 
we may conclude that in these solutions it is for the greater 
part the migration-velocity of the caseinate ions which is 
affected by the percentage of alcohol in the solvent. From 
the values of the constants in equations 3-9, it is apparent 
that the migration velocities of the caseinate ions are pro- 
gressively diminished by increasing alcohol-concentration from 
o percent to 60 percent. From the facts that the law Xy = 

T- no longer holds good and the ratio — ^^9— is not constant 

in the solutions containing 75 percent alcohol, we may con- 



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404 



T. Brailsford Robertson 



elude that in these solutions the degree of dissociation of the 
caseinate or the niunber of equivalents of casein produced 
by one equivalent of KOH or both undergo a profound modi- 
fication. The values of the constants in equation lo indi- 
cating an increase in the magnitude of v^ + v^ and a very 
great decrease in the magnitude of the dissociation-constant. 

In the following table the values of (v^ + v^) and of — corre- 
sponding to the equations 3-10 are enumerated: in the fourth 
column is given the percentage dissociation of the caseinate 
in the solution containing 0.025 N KOH bound by casein. 



Potassium caseinate 80 



Percent of 






alcohol by 


pi-vi -h If 


volume 







83.6 10 


10 


64 


9 10 


20 


49 


I 10 


30 


38 


10 


40 


29 


9 10 


50 


24 


2 10 


60 


19 


4 10 


75 


34 


6 lo- 



Table XIII 




X IO-* equivalents of KOH per gram 




Percent of caseinate 


G 


disiociated in solu- 




tion containing 


p 


0.025 equivalents 




of potassium 


1 0.0923 


82 


0.0767 


80 


0.0760 


79 


0.0682 


78 


0.0633 


77 


0.0513 


74 


0.0365 


68 


0.0007 


17 



The degrees of dissociation of the caseinates in the solutions 
containing 60 percent and less than 60 percent of alcohol is 
evidently but little effected by the percentage of alcohol in the 
solvent, the major part to the effect of the alcohol upon the con- 
ductivity being attributable to the decreased mobility of the casein- 
ate ions, 

(iv) The viscosities of solutions of ''basic'' potassium 
caseinate in alcohol-water mixtures. The striking resem- 

X I 

blance between the formula ^ = .^ and the Arrhenius- 

Xo Ay 

Euler formula: ^ = a* for the dependence of the viscosity 

of a solution upon its concentration where rj^ is the viscositX 



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Studies in the Electrochemistry of the Proteins 405 

of the solution, ij^ that of the solvent, n is the concentration 
of the solution and a is a constant, forcibly suggests that 
the decrease in the conductivity of potassium caseinate 
solutions, due to the addition of alcohol between alcohol- 
percentages of o and 60 may be attributed for the greater 
part to the hampering of the protein ions by the increased 
internal friction of the solvent/ 

Accordingly the following determinations were made: 
31.25 grams of casein were dissolved in 250 cc of N/io KOH, 
To 25 cc portions of this were added o, 10, 20, etc. cc of alcohol, 
the volume of each mixture being made up to 100 cc, the 
solution containing 75 percent alcohol being made up 
by adding 99.8 percent alcohol until the volume of the mixture 
was 100 cc. 

A series of exactly similar solutions were made up in 
which, however, 25 cc of N/io KOH were employed instead 
of 25 cc of caseinate solution. 

The viscosities of these solutions were determined at 
30*^ in an Ostwald viscometer, for which the time of outflow, 
for water, was 90 seconds. The times of flow, were read 
with a stop-watch. The viscosities were calculated from 

the formula — =^ ^— where i^o ^s the viscosity of distilled 

water, t) that of the solution imder investigation, = s^ and t^ 
are the density and time of outflow, respectively, of distilled 
water and s and / are the density and time of outflow, respec- 
tively of the solution. The densities of the solutions were 
determined by means of a normal hydrometer, reading the 
density to within 0.0002. 

Taking the viscosity of water at 30*^ to be 0.00798 dynes 
per cc* and its density as 0.996, the following were the re- 
sults obtained : 



^ In this connection the work of H. C. Jones and collaborators on the 
conductivities of solutions of inorganic salts in alcohol-water and acetone-water 
mixtures should be consulted. Am. Chem. Jour., 28, 329 (1902); 32, 521 (1904); 
34, 481 (1905); 36, 325» 427 (1906); 37. 405 (1907); Zeit. phys. Chem., 61, 641; 
62, 41 (1908); Am. Chem. Joiu-., 41, 433 (1909); 42, 37 (1909); cf. also Walden: 
Zcit. phys. Chem., 55, 207 (1906); Heber Green: Jour. Chem. Soc. 

» Thorpe and Rodger: Phil. Trans., 185 A, 307 (1894). 



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4o6 



T, Brailsford Robertson 



Tablb XIV 
Concentration of KOH neutralized to phenolphthalein by casein 

0.250 N 



Percent of ' . . j„„^. ^^, ^^ 
-i«^u^i K« ^ *o dynes per cc 



17 in dynes per cc > Difference due to 
for solution caseinate 






0.00816 


0.01668 


0.00852 


10 


0.01065 


0.02049 


0.00984 


20 


0.01376 


0.02484 


0.01108 


30 


0.01694 


0.02814 


0.0II20 


40 


0.01913 


0.03237 


0.01324 


50 


0.02064 


0.03400 


0.01336 


60 


0.020II 


0.03200 


O.OII89 


75 


0.01735 


0.02345 


0. 00610 



Walden (1. c.) has found that for solutions of tetraethyl- 
ammonium iodide in thirty organic solvents the product 
of the molecular conductivity of the salt at infinite dilution is 
proportional to Vi + v^ (the sum of the migration-velocity of its 
ions) and the viscosity of its infinitely dilute solution is nearly 
constant, indicating an inverse proportionality between the 
viscosity of the solution (or, which comes to the same thing 
at infinite dilution, the solvent) and the migration-velocities 
of the ions which it contains. In the accompanying table 
are given the values of piv^ + i'2)'?»owcnt ^or the various 
solutions investigated. 

Table XV 



Percent of alcohol by volume 



o 
10 
20 
30 
40 
50 
60 

75 



/>(^i + ^.)'?«,lveiit 




0.68 X lo-' 




0.69 X 10-* 




0.68 X IO-* 




0.64 X IO-* 




0.57 X 10-* 




0.50 X 10-* 




0.39 X 10-* 




0.60 X 10-* 





It is evident that the product of the ionic mobility of 
potassium caseinate at infinite dilution and the viscosity of 



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Studies in the Electrochemistry of the Proteins 407 

the solvent varies much less than either of these quantities 
taken alone, indicating in a qualitative sense at all events, 
that the ionic mobility of the caseinate is in the main determined 
by the viscosity of the solvent. The observed increase in the 
ionic mobility of the caseinate ions on increasing the alcohol- 
content of the solvent from 60 percent to 75 percent, is, in 
view of the fact that the viscosity of the solvent passes through 
a maximum at 50 percent to 60 percent alcohol and rapidly 
decreases between 60 percent and 75 percent, especially 
confirmatory of this view. It will be observed that the 
viscosity of the solvent is notably increased by the addition 
of the concentration of casein employed and this effect, of 
course, varied very considerably with dilution, yet the 
Ostwald law holds good. We can only conclude from this 
that the viscosity of the solution, due to the casein per se, 
does not affect the mobility of the caseinate ions.* 

(v) The molecular condition of potassium caseinate in 
75 percent alcohol. 

We have seen that the behavior, optical and electrical, 
of potassium . caseinate dissolved in alcohol- water mixtures 
undergoes an abrupt change^ in passing from 60 percent to 
75 percent alcohol-content. The degree of dissociation, which 
is but little effected by lower concentrations of alcohol 
undergoes a profound diminution in 75 percent and the 
opacity of the solution imdergoes a concurrent increase. These 
phenomena suggest a polymerization of the caseinate molecule 
and an accompanying increase in the weight of casein involved 
in the carriage of one atomic charge. Accordingly, experi- 
ments were imdertaken with a view to ascertaining the effect 
of increasing alcohol-content of the solvent upon the electro- 
chemical equivalent of casein. 

The experiments were carried out upon solutions con- 

* Cf. also Sackur: Zeit. phys. Chem., 41, 672 (1902); T. Brailsford 
Robertson: Jour. Phys. Chem., 12, 473 (1908). 

' Not only is the opalescence of the solution greatly increased but also 
the change in the refractive index of the solvent due to the introduction of I 
gram of casein, is considerably diminished. T. Brailsford Robertson: Jour. 
Biol. Chem. 



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4o8 T. Brailsjord Robertson 

taining 50 percent and 75 percent of alcohol, made up in the 
manner described above. The electrochemical equivalent of 
casein, combined with potassium, in aqueous solution has 
previously been determined, and the methods employed in 
this were identical with those employed in the previous in- 
vestigation.* 

The alteration in the percentage casein-content of the 
solution, due to deposition of the casein upon the anode was 
estimated from the change in the refractive index of the 
solution. The volume of the solution employed being al- 
ways 25 cc, the actual amount of casein deposited was obtained 
by dividing the alteration in percentage by 4. The change 
in the refractive indices of alkaline 50 percent and 75 percent 
alcohol solutions, due to the addition of casein had been 
previously determined by me' and I have, furthermore, 
shown that the change is directly proportional to the per- 
centage of casein dissolved in these solvents. 

The quantity of electricity which had traversed the 
solution was estimated by a silver titration voltameter, con- 
taining N/io AgNOj, placed in series with the solution under 
investigation. 

The results obtained are tabulated below, the figures 
in the 6th column being obtained from those in the 5th column 
through multiplication by the Faraday constant. 

There is evidently a very marked increase in the weight, 
or decrease in the valency of casein ions in solutions of basic 
potassium caseinate when the added alcohol attains 75 per- 
cent, leading to doubling of the weight of casein required to 
transport one atomic charge of electricity. 

From these facts and from the failure of Ostwald's dilu- 
tion law to adequately represent the behavior towards dilution 
of solutions of *' basic" potassium caseinate in 75 percent 

* T. Brailsford Robertson: Jour. Phys. Chem., 15, 179 (191 1). 

* T. Brailsford Robertson: Jour. Biol. Chem. For immediate reference 
the figures are repeated here: In 50 percent alcohol, change due to i gram 
per 100 cc «=» 0.00149 ± 0.00005. In 75 percent alcohol, change due to i gram 
100 cc =» 0.00125 ± 0.00006. 



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Studies in the Electrochemistry of the Proteins 409 



pr «. .^ ;* 

M O <V 

o ^ rt B 

O 3; 



g*g g- 



•^ s 



1 



cn O O 



Q. 



w w 

O Cn 

§5 

o o 

H-hf 

o o 
b b 

8^ 



O O 

P P 
Cn O 

H-F+- 
o o 

88 

K) O 



o a 
era 

o "^ 





*^ 


.-1 ON 






-. 


vO 00 


S B 


4>^ 00 


Ȥ3 


M M 


3 "^ 

3 


s s 


^ ^ 





S 






O 



E. 
< 

(^ 

s. 

?^ 
o 

X 

w 
B 



o 

•n 

s 



^3. I 
0:1 

B O 



•2„ 

E 14 
2 p 

ft '^ 2 
= 2 

B H'b- 

9fl5 2. 

^=^5 8 
3- 



•^ K> K) 


Grams 
carry 
ionic 


OA V$ 0* 

OS Q OA 
OA On OS 




^ **• ^ 


H-hf Ff 


ft B 
?^ft 


On M M 


J s 


vO vO 00 


^ s 


Cn 0* OJ 


rt (» 2. 




B 



n 

I 



§ 



?1 
o 

a; 






5' 
II 
o 
b 



r 
« 

X 
< 



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4IO T. Brails ford Robertson 

alcohol and the optical appearance of these solutions it ap- 
pears probable that they partake rather of the character of 
suspensions than of true solutions and that the transport 
of electricity by the caseinate in 75 percent alcohol is a phe- 
nomenon of "electric endosmose.** 

The precipitation of a protein by alcohol is evidently 
heralded by, and is probably attributable to polymerization 
and greatly decreased dissociation of the protein salts. 

Conclusions 

(i) Potassium caseinate is not precipitated by the 
addition of alcohol to its solution up to 98.6 percent, but the 
solutions undergo a marked increase in opacity at a concen- 
tration of alcohol lying between 60 percent and 75 percent, 

(2) The caseinates of the alkaline earths are precipitated 
by the addition of alcohol to their (aqueous) solutions. Cal- 
cium and barium caseinate are precipitated when the con- 
centration of alcohol attains about 50 percent. For the 
precipitation of strontium caseinate, a somewhat higher con- 
centration of alcohol is required, about 70 percent. 

(3) The conductivities of solutions of varying casein- 
content in various alcohol-water mixtures have been deter- 
mined. 

(4) Solutions of potassium caseinate (proportion of 
KOH to casein = 80 X 10"* equivalents per gram) in alcohol- 
water mixtures containing from o to 60 percent of alcohol 
obey Ostwald's dilution-law for a binary electrolyte. Solu- 
tions in 75 percent alcohol do not obey the law. 

(5) The conductivity (=^y) of a solution containing 
any given concentration of the protein potassium caseinate 
is connected with the percentage (=y) of alcohol in the 
solution (from o to 60 percent) and the conductivity {^=x^) 

of a solution containing no alcohol by the formula x^ = v^. 

(6) The value of A is very nearly the same for all con- 
centrations of potassium caseinate, and for all proportions 
of alcohol to water, between o and 60 percent, the average 



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Studies in the Electrochemistry of the Proteins 411 

being 1.0265, and departures from the average less than two- 
tenths of a percent. 

(7) This law also holds good for solutions of ** neutral" 
potassium caseinate (50 X 10"* equivalents of KOH per 
gram) in alcohol-water mixtiu-es containing less than 75 
percent alcohol. 

(8) The law also holds good for solutions of strontium 
caseinate from o to 20 percent of alcohol, but it does not 
hold good for solutions containing higher percentages of 
alcohol, nor for solutions of calcium or barium caseinates 
in alcohol-water mixtures nor for solutions of potassium 
caseinate in 75 percent alcohol. 

(9) It is concluded that the precipitation of a caseinate 
by alcohol is heralded by a failure of the solution to con- 

form to the law Xy = ^° . 

(10) In solutions of "basic'* potassium caseinate (80 X 
10"* equivalents of KOH per gram) containing from o to 
60 percent of alcohol, the relation 

— ^— = constant 

^alc. H,0 

holds good for any given proportion of alcohol to water. This 
relation implies that the effect of added alcohol (up to 60 
percent) upon the conductivity of a caseinate solution is 
almost entirely attributable to its effect upon the mobility 
of the caseinate ions and not to any effect upon the dissocia- 
tion or polymerization of the caseinate. It is the relation 
foimd by Cohen to hold good for the conductivities of solu- 
tions of inorganic salts in alcohol-water mixtures. 

(11) In solutions containing 75 percent alcohol, the 
relation 

^"*^ = constant 

does not hold good. It is inferred that in this concentra- 
tion the alcohol exerts a considerable influence upon the 
dissociation or polymerization or both, of potassium caseinate. 



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412 T. Brails ford Robertson 

(12) The relative ionic mobilities at infinite dilution 
and degrees of dissociation of "basic" potassium caseinate 
in alcohol- water mixture have been computed. 

(13) The viscosities of solutions or *' basic" potassium 
caseinate in alcohol-water mixtures and of these solvents 
have been determined. 

(14) The relative ionic mobilities of ** basic" potassium 
caseinate at infinite dilution in alcohol-water mixtures tend 
to be (but are not exactly) inversely proportional to the 
viscosities of the solvents. 

(15) The mobility of the caseinate ions is not affected 
by that proportion of the viscosity of the solution which is 
due to the caseinate itself. 

(16) It is inferred that up to and including 60 percent 
alcohol the major part of the effect of added alcohol upon 
the conductivity of ** basic" potassium caseinate solutions 
is attributable to the greater or less degree to which the 
viscosity of the solvent diminishes the mobility of the casein- 
ate ions. 

(17) The electrochemical equivalents of casein combined 
with 80 X lo"' equivalents of KOH per gram and dissolved 
in 50 percent and 75 percent alcohol have been determined. 
The weight of casein required to transport one ionic charge 
has been deduced, with the following results: In o percent 
alcohol the weight of casein required to transport one atomic 
charge is 2336 ± 183 grams; in 50 percent alcohol the weight 
of casein required to transport one atomic charge is 2906 ±193 
grams; in 75 percent alcohol the weight of casein required 
to transport one atomic charge is 4363 ± 695 grams. 

(18) It is inferred that in 75 percent alcohol the major 
part of the effect of the added alcohol upon the conductivi- 
ties of ** basic" potassium caseinate solutions is attributable 
to polmerization of the caseinate and to a profound decrease 
in its degree of dissociation. 

(19) It is concluded that the *' solution*' of potassium 
caseinate in 75 percent alcohol is probably to be regarded 
rather as a suspension than as a true solution and that the 



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Studies in the Electrochemistry of the Protein 413 

transport of electricity by the caseinate in 75 percent alcohol 
is probably a phenomenon of "electric endosmose** rather 
than of true electrolytic conduction. 

(20) The precipitation of protein salts by alcohol is 
attributed partly to polymerization and partly to greatly 
decreased dissociation of the salts. 

(21) This explains the observed fact that alcohol pre- 
cipitates protein salts as such from their solutions and not 
the imcombined proteins, since, previously to their precipita- 
tion, the combined base or acid is bound up in an undissociated 
molecule. 



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Dos Oedem. By Martin H. Fischer. 24 X 16 cm; pp. vii + 223. Dresden: 
Verlag von Theodor Steinkopff, J 910. Price: paper, 6 marks. Cloth, 7 marks. — 
This is a scientific study of the conditions under which water is taken up by 
living tissue. As it is essentially a problem in colloid chemistry the author 
studies the action of water and of solutions on fibrine and on gelatine. He then 
points out the parallelism between these cases and that of the adsorption of water 
by protoplasm. Special cases of oedema come next, followed by chapters on 
turgor and on the secretion of urine. 

Of special interest to the physical chemist are the pages, 84-96, in which 
the author takes exception to the osmotic pressure theory as applied to plant 
cells. He claims that there is no evidence of the existence of semipermeable 
membranes around most cells. He believes that that the swelling and the 
shrinking of plant cells is due to the adsorption or loss of water by the colloids 
forming the plant cells. One advantage of this point of view is that it eliminates 
the difficulties which confronted the osmotic pressure theory when it tried to 
account for the growth of a plant. It has always been a puzzle how salts could 
be carried through a layer of cells when the membranes were impermeable to 
these salts by definition. This difficulty disappears with the disappearance of 
the semipermeable membranes. 

Since sodium citrate decreases the absorptive power of gelatine for water, 
the author concludes that it ought to check oedema, and he actually reduces 
glaucoma of the eye by injecting sodium citrate solution. 

Since fatness is largely a matter of excessive adsorption of water by the 
tissues, it seemed to the reviewer that sodium citrate should be a cure; but that 
conclusion is not yet warranted by the facts. 

This is an admirable book and reflects great credit on the author. If he 
continues to turn out scientific work of this grade, we shall all be proud of him. 

Wilder D. Bancroft 

Dcr Kautschuk und seine Prtifttng. By F. W. Hinrichsenand K. MemmUr. 
16 X 23 cm; pp. 263. Leipzig: Verlag von S. Hirzel, 1910. Price: paper, 8 
marks; bound, 9 marks. — ^The authors discuss the general properties of rubber 
and then take up the chemical analysis and the mechanical tests. These last 
two sections are very probably the ones that will interest the rubber chemists 
the most. Those of us who play with golf balls instead of making them will be 
more interested in the first section. 

The authors discuss: the properties of the latex; the constitution of the 
hydrocarbons; the other substances in crude rubber; the physical properties of 
crude rubber; the chemical properties of rubber; the theory of vulcanization; 
the properties of vulcanized rubber. 

The authors have taken into account the articles published in the Zeii- 
schrift far Kolloidchemie and have treated the coagulation of the latex and the 
vulcanization of rubber as problems in colloid chemistry. Their book is conse- 
quently the best one on the subject and is indispensable to anybody who is 
interested in colloid chemistry. Wilder D. Bancroft 



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New Books 415 

Dynamos and Motors. A Text-Book for Colleges and Technical Schools, 
By William Suddards Franklin and William Esiy. Direct-Current and Alterna- 
ting-Current Machines. 14 X 22 cm; pp. viii + 489. New York: The Mac- 
millan Company, igog. Price: $4.00 net. — ^The chemist nowadays has to 
handle dynamos and motors, and it is consequently essential that he should 
know something about how they work. He will find this book a very satis- 
factory one either for reference or for study. 

There is a section on general theory and then the subject is discussed under 
the headings: direct-cmrent generators and motors; elementary theory of alterna- 
ting currents; alternating current generators and motors; station arrangements 
and operations. J]t Wilder D. Bancroft 

^ ^EinfUhnmg in die technische Elektrochemie. By Paid Askenasy. Erster 
Band: Electrothermie. Unier Mitwirkung der Herren R. Amberg, A. Helfenstein, 
F. Hiller, A. Koenig, G. Leithailser, B. Neumann, herausgegeben von Paul 
Askenasy. 15 X 25 cm; pp. 249. Braunschweig: F. Vieweg und Sohn, igio. 
Price: paper, 9 marks; bound, jo marks. — ^The volume consists of a series of 
articles on special topics, each written by an expert in that line. Helfenstein 
writes on ftunaces for calcium carbide and for f errosilicon ; Neumann on iron 
and steel; Amberg on carborundum and graphite; Askenasy on zinc; Hiller on 
alundum and carbon bisulphide; Koenig on nitric add and on ozone. 

The volume is good as a whole, though it is uneven. Helfenstein 's article 
on large furnaces for carbide and ferrosilicon is excellent. The articles on 
carbortmdum, graphite, alundum, and carbon bisulphide do not seem to rep- 
resent first-hand knowledge, but are fairly good compilations. The article on 
nitric acid is not very good and that on ozone is very bad. This last does not 
give any idea of the real situation. The articles on iron and on zinc are about 
what would be expected. 

While this may sound like faint praise, it should be remembered that there 
is no book on applied electrochemistry which amounts to anything at all. This 
is the first attempt by anybody to write a real book on appUed electrochemistry 
and, as such, it has the field to itself. Wilder D. Bancroft 

Analytische Chemie. By W. Ostwald. Fifth Edition. 75 X 2j cm; pp. 
2JJ. Leipzig: Wilhelm Engelmann, igio. Price: bound, 8 marks. — The first 
edition appeared in 1894; the second in 1897; the third in 190 1; the fourth in 
1904; and the fifth, the present one, in 19 10. The chief difference between this 
edition and the preceding ones is that we are introduced to phases in the begin- 
ning of the first chapter. This is interesting as showing how long it takes even a 
bom teacher like Ostwald to get down to an actual statement of facts as they are. 
From time immemorial all teachers of chemistry have defined the term 'mixture' 
in the first session. During that period of time they have always considered a 
mixture of two pure substances and consequently they have never presented the 
matter in a general form or in the form based on the student's experiment. 
Ostwald takes the facts as they are and speaks of a mixture of two phases in- 
stead of a mixture of two cnbstances. He then discusses the separation of 
phases and does not reach the definition of a pure substance until the second 



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41 6 New Books 

chapter. This may seem like a trifle; but it is not. It is both a revolution 
and a revelation. 

In other respects there is not much change. Methyl orange still poses as a 
fairly strong add in defiance of the facts and will probably continue to do so 
through all future editions. After all, who cares? Wilder D. Bancroft 

Physical Chemistry. Its Bearing on Biology and Medicine. By James C. 
Philip. J 4 X 20 cm; vi + ji2 pp. Sew Y'ork: Longmans, Green & Co., igjo. 
$2.1 o. — ^This is chiefly an elementary physical chemistry with no special char- 
acteristics. The best thing about it is that the author does state some of the 
difficulties. Thus, on p. 66, we read that "evidence has, however, been brought 
forward showing that an individual plant may in certain cases be able to vary its 
internal osmotic pressure according to that of the surrounding medium." 

"Again (p. 84), there is a very striking fact that the inorganic constituents 
of the blood corpuscle are notably different from those of the plasma: the cor- 
puscles fluid is comparatively rich in potassium and phosphate, while the plasma 
is poor in these, but rich in sodium and chloride. From the fact that the cell 
receives its nutrient from the external medium, it appears that the membrane 
cannot be absolutely impermeable to potassium salts, and yet their retention 
in the cell would seem to be impossible if permeability of the membrane is con- 
ceded. We are therefore driven to assume some specific intervention of the 
living membrane or some special affinity between the cell protoplasm and the 
potassium salts." 

"The value of the plasmolytic method has lately been questioned by Oster- 
hout. In experiments with Vaucheria he found that plasmolysis occurred with 
sodium chloride solution as dilute as o.oooi N, the addition of caldiun chloride 
however to the sodium chloride solution, although it raises the osmotic pressure, 
prevents the contraction of the protoplasm from the cell walls. If one molecule 
of caldum chloride is present for every 100 molecules of sodium chloride, the 
cells may be immersed in o. i N sodium chloride solutions without suffering 
plasmolysis. It looks therefore as if, in some cases at least, sodium chloride 
exerts a specific effect on the protoplasm bringing about a contraction which is 
indistinguishable from plasmolysis caused by purely osmotic action." 

Wilder D. Bancroft 

Notions fondamentales de Chimie organique. By Ch. Moureu. Trois^me 
idition, revue et mise au courant des derniers travaux. 14 X 23 cm; pp. J54. 
Paris: Gauthier-Viliars, igio. Price: paper, 8.50 francs. — This is intended 
as a text to be used in connection with a brief introductory course in organic 
chemistry. Under general theory the author discusses: molecules and atoms; 
isomerism; homologous series; and stereochemistry. The remaining chapters 
are entitled: hydrocarbons; oxygen compounds; nitrogen compounds; metallo- 
organic compounds; heterocyclic compounds. To the reviewer it seems as 
through it would be desirable either to teach a student less organic chemistry 
or to give him a good deal more. It is difficult to see how anybody could master 
the facts as given and know anything except how to pass an examination. As 
this is the third edition, the book evidently does i*\\ a need. The second edition 
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MOLECULAR ATTRACTION. IX 

MOLECULAR ATTRACTION AND THE LAW OF GRAVITATION. 
BY J. E. MILLS 



General Outline of the Paper 

1. The usual idea of molecular attraction. 

2. Statement of the recently discovered law governing 
molecular attraction. 

3. The law expresses the relation between the energy 
added and the distance apart of the molecules. 

4. The law is independent of the mass of liquid taken. 

5. Tentative deduction of the law governing the molec- 
ular attractive force. 

6. Further evidence that the molecular attractive force 
varies inversely as the square of the distance apart of the 
attracting particles. 

7. The law of gravitation applied to molecular at- 
traction. 

8. Application of the law of gravitation to the vaporiza- 
tion of a liquid. 

9. The numerator of the law governing the molecular 
attractive force. 

ID. The law governing the abstraction of molecular at- 
tractive energy from the ether. 

11. The law governing the abstraction of gravitational 
energy from the ether. 

12. Possible identity of the laws of molecular and gravita- 
tional attraction. 

13. The difficulties that arise in explaining gravitation. 

14. Newton's law of gravitation is not a necessary conse- 
quence of the motion of the heavenly bodies. 

15. Newton's law of gravitation is not a necessary conse- 
quence of the motion of freely falling bodies. 

16. Newton's law of gravitation is not a necessary conse- 
quence of the motion of bodies retarded during their fall. 



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4i8 /. E. MUls 

17. Direct measurement of the attraction of two masses. 

18. Comparison of all of the attractive forces. 

19. The nature of mass. 

20. Proposed modification of the statement of the law of 
gravitation. 

21. Facts in accord with the suggested changes. 

22. Summary. 

1 . The usual idea of molecular attraction. — Newton thought 
that the force of gravity was exerted by each individual 
particle of a mass and made the statement: "Gravitatem in 
corpora universa fieri.*** It is said that he attempted to 
apply the law of gravitation to explain chemical affinity and 
the molecular cohesion to be observed in all liquid and solid 
bodies, but I have not been able to verify this statement. 
Certain it is that the subject was investigated later by Helm- 
holtz and Clerk Maxwell and has been discussed by numerous 
investigators. The conclusion that the two following facts 
existed proving that gravitation could not be the cause of 
molecular cohesion seems to have been almost universally 
accepted. First: The molecular cohesion was a far greater 
force than the gravitational force. Second: The sphere of 
molecular action was small. If the molecular force obeyed 
the law of gravitation the sphere of molecular action could not 
remain small but must include the entire mass taken. This is 
true because the number of the molecules increases as the 
cube of the distance from a centrally chosen molecule and the 
gravitational attraction diminishes only as the inverse square 
of that distance. The fact that the molecular sphere of 
action is small seemed to demand that the molecular force 
decrease with the distance at least as rapidly as the inverse 
fourth power. 

The writer desires to point out some recently discovered 
facts which seem to indicate that the groimds for this con- 
clusion should be very carefully reconsidered. 

2. Statement of the recently discovered law concerning 



Principia, Book III, Prop VII, Coral, 2. 



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Molecular Attraction 419 

molecular attraction, — In an extended investigation of molec- 
ular attraction the writer has proved that the following law 
holds true for normal non-associated liquids : 

T g 

I. 3iv_:ri^ = constant, or ^ = /(N^— Nd). 

Here L is the heat of vaporization of i gram of the liquid, 
Eg is the energy spent in overcoming the external pressure 
as the liquid expands to the volume of the satiu"ated vapor. 
L — Eb is therefore the so-called internal heat of vaporiza- 
tion and is called X, d and D are the densities of the liquid 
and saturated vapor respectively at the temperature of the 
vaporization. The constant given by the equation is called 

I have said that the above law was proved true. I use 
the word proved advisedly. Thirty-eight liquids of very 
dififerent chemical constitution have been investigated* over 
a very wide range of temperature extending usually from 
near the freezing point of the liquid to the critical temperatiu"e. 
For thirty of these liquids the very accurate measurements 
made by Dr. Sydney Yotmg' and his co-workers were avail- 
able. The proof cannot be quoted here. The eighth paper 
above cited gives a brief summary of the results obtained. 
I believe the truth of the law is now established beyond 
question. 

Originally the above relation was theoretically derived. 
The facts prove that the relation is true and its truth is not 
dependent therefore upon the truth of the theory by which 
it was derived. Emphasis is laid upon this fact as some 
seem to ignore the difference and to believe that the con- 
clusions of the writer are based upon theoretical grounds. 



» Jour. Phys. Chem., 6, 209 (1902); 8, 383, 593 (1904); 9, 402 (1905); 
10, I (1906); II, 132, 594 (1907); 13, 512 (1909); Jour. Am. Chem. Soc., 31, 
1099 (1909); Phil. Mag., Oct., 19 10. These papers need revision badly. The 
eighth paper should be read first, then the last two papers mentioned. The re- 
maining papers can then be briefly examined in the order in which they were 
written, making allowance for some necessary changes. 

» Sd. Proc. Royal Dublin Soc., 12, 374 (19 10). 



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420 /. E. Mills 

3. The law expresses the relation between the energy added 
and the distance apart of the molecules. For a mass of liquid 
of M grams, containing n molecules each of molecular weight 
w, if 1; is the volume of the liquid and V the volume of the 
saturated vapor, and s^ the distance apart of the molecules 
of the Uquid and s^ the distance apart of the molecules of the 
saturated vapor, we have, 

-, nm nm ^Iv ^/v 

nm = M,r= ^ , r = —,.. = ^-, ., = ^^. 

Therefore 

N</ = A/ „ = 8 r- = c • Sinularly •Vd= — . 

The above relations assume (see page 423). 

A. That the molecules are evenly distributed throughout 
the space occupied by them. 

B. That the number of molecules does not change. 
Substituting the above values of d and D in equation i 

we have 



'->^"<rd- 



The heat required to change a liquid into its saturated 
vapor can be directly measiu-ed and the energy necessary 
to overcome the external pressure during the given expansion 
can be calculated accurately. The internal heat of vaporiza- 
tion must therefore denote the total energy necessary to add 
to the liquid in order to effect the given change in the distance 
apart of the particles. Equation 3 expresses therefore the 
relation between the distance apart of the molecules and the 
energy which it is necessary to add to them in order to bring 
about the given change in their distance apart. 

4. The law is independent of ihe mass of liquid taken. 
— It is also an experimentally established fact that the heat of 
vaporization of M grams of a liquid is just M times as great 
as the heat of vaporization of i gram of the liquid. Moreover 
the density of the liquid and the density of the saturated 
vapor at a certain temperature and pressure are likewise 



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Molecular Attraction 421 

independent of the number of grams of liquid taken. Conse- 
quently we can combine the newly discovered law governing 
molecular attraction with this fact and write, 

4. M>l = M/£'(Ni— »Vd). 



M>1 



= M,'3,-(I i). 



5. TentcUive deduction of the law governing the molecular 
attractive force. It is well known that the total energy re- 
quired for any change is dependent only upon the force over- 
come, and the distance through which the force is overcome, 
and is quite independent of the method or mechanism of the 
change. Denoting the energy by E, the force by /, and the 
distance by s, we have, 

6. n-=ff.ds. 

In the expansion of a liquid the molecular attractive 
force of any molecule extends doubtless in various directions 
and to numerous molecules situated at different distances. 
In determining the total energy required for any given change 
in volume the action of every molecule upon every other 
molecule (at least within the molecular sphere of action) 
must be included in the summation. In order to avoid 
introducing any assumptions no attempt is made at present 
to imwind this tangle of individual molecular forces. But 
it is clear that if the action be viewed as a whole and the 
summation as regards distance be taken between the limits 
cs^ and cs^ that the force must follow the law : 

7. / = ---^-,- . 

SO that since Vj the mass only is moved, 

as required. It will be noticed at once that for any particular 
liquid /i' is a constant and 'Vw is a constant. The meaning 



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422 y. E. Mills 

of equation 7 is, therefore, that the numerous individual 
forces acting between the molecules as they expand from the 
distance apart s^ to the distance apart s^ can be replaced by a 
resultant force acting between the limits cs^ and cs^ and this 

resultant force will vary as - ^ , We will denote c/i^'Vi 

by fJL and write 

as a law governing the resultant molecular force. 

Equation 9 is deduced and stated as a law governing the 
resultant molecular force. If however M denotes any mass of 
liquid M might be taken equal to the mass of a molecule m, 
c would become equal to i and the molecular force proceeding 
from the individual molecule would therefore be 

. titn Constant 

the constant varying with dififerent substances. Since the 
proof of the ftmdamental equation 4 (or 5) has been obtained 
only for molecules in bulk this extrapolation of equation 9 
is open to some doubt. The reasonableness of the deduction 
will however appear later. 

6. Further evidence that the molecular attractive force 
varies inversely as the square of the distance apart of the at- 
tracting partices, — Surface action under ordinary circum- 
stances can be disregarded and the heat of vaporization is 
therefore independent of the shape of the containing vessels. 
(This fact is in itself significant. It is not due, as has been 
supposed, to an inverse fourth power law of the molecular 
attraction but to the mutual absorption of the attraction by 
the attracted particles. At least I believe the facts later 
cited warrant this statement. Whatever the explanation, 
the fact is that the shape of the containing vessels can be d s- 
regarded). It is therefore physically possible and mathe- 
matically convenient to have the liquid spherical in sha}>e 
and to make it expand to a larger sphere in changing to its 



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Molecular Attraction 423 

saturated vapor. To further simplify the treatment we will 
assume : 

A. That the molectdes are evenly distributed throughout the 
space occupied by them, — ^This assumption is probably always 
more or less imtrue. But if the molecules are shifted from 
their ideal position by reason of the attractive force, the 
particles would gain in kinetic energy exactly so much as they 
would lose in potential energy. We may therefore, without 
error, consider them to be shifted back into their position of 
even distribution. 

B. That the number of molecules does not change, — 
Except for associated substances or substances tmdergoing 
decomposition, it is generally believed, and the belief rests 
upon considerable experimental evidence, that the number of 
molecules in the liquid and in the gaseous condition are the 
same. The equation is not true where this condition is violated. 

While I have called the foregoing statements assumptions 
they are really more in the nature of limitations and do not 
seriously detract from the strictness of the proof to follow. 
Thus even if statement A is not true the subsequent proof 
will hold provided the term ** distance apart of the molecules" 
is tmderstood to mean their average distance apart. State- 
ment B limits the application of the proof to chemically 
stable non-associated liquids. 

Under these conditions if s^ is the average distance apart 
of the molecules of the liquid and s^ the average distance 
apart of the molecules of the vapor, it is readily seen from the 
symmetry of the figure that if any molecule is distant xs^ 
before expansion, after expansion it will be distant xs^. And 
a little consideration will show clearly that in integrating 
equation 6 we are summing up a large number of individual 
actions each of exactly the same character and each repre- 
sented by 

II. U = Cf.ds, 

XS2 

X being a constant during each integration but varying in 



J 



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424 /. E, Mills 

value for every individual integration. Since x is a constant 
during each integration and the law of the force remains the 
same during all of the integrations, it is possible to replace all 
of the n* — n diflFerent x's by their sum, which we will call c 
and perform but one integration. Therefore the law of the 
molecular attractive force must be 

/ = - ,, . 

so that 

.3. MA ./«'■';''-. ,<.-M,...,(l-'). 

c can hardly be considered a function of the distance 
apart of the molecules, but is apparently a function of the 
number within the sphere of molecular action. If c is not a 
function of the distance apart of the molecules the force between 
the molecules must vary inversely as the square of their distance 
apart in order to produce the observed law. 

From the point of view of the writer c is dependent on 
the absorption or neutralization of the ** lines of force** pro- 
ceeding from a molecule. The sum total of these is always a 
constant and the distance at which they are neutralized is 
proportional to the distance apart of the molecules, c be- 
comes therefore a constant for any particular substance. 

The idea that the force of molecular attraction cannot 
vary inversely as the square of the distance apart of the at- 
tracting particles is so universal that I stop here to lay an 
added emphasis on the above proof. The molecular at- 
traction can vary inversely as the square of the distance 
apart of the attracting particles. The idea that the inverse 
square law of the distance is impossible for molecular forces 
is founded on the error that the forces must vary as the prod- 
uct of the masses of the attracting particles. 

I would also call attention to the fact that I am not now 
trying to explain why the inverse square law of the molecular 
attraction is true. I have pinposely so far said nothing 
about the mechanism of the action. If some one supposes 



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Molecular Attraction 425 

that the inverse square law is due to the mutual action of 
positive and negative forces emanating from a molecule each 
varying as the inverse fourth power of the distance, the sup- 
pK>sition need not, so far as I can see, necessarily contradict the 
inverse square law. If the final explanation of the inverse 
square law proves to be connected with the fact that Des- 
cartes* idea that the total quantity of motion in the universe 
(including the ether which Leibnitz and modem science failed 
to include) is a constant, my present statements are not 
to be taken as contradictory of such an explanation. I am 
simply using the nomenclattu-e at present adopted to express 
a fact. The explanation of the fact I am not just here dis- 
cussing. 

Some one may also be troubled by a possibility already 
noted by the writer in a previous paper, namely, that it is 
not certain, that the energy per se of a molecule in the liquid 
condition is equal to the energy of a molecule of its own vapor 
at the same temperature and under the same pressiu-e. There- 
fore it is possible that some of the energy needed for over- 
coming the molecular attraction during the vaporization of a 
liquid is drawn from the liquid itself. There is certainly this 
possibility, and it should be carefully borne in mind that the 
laws that I am considering in this paper deal with the energy 
which it is necessary to add to a liquid during its vaporization 
and with the corresponding force exerted throughout the molecular 
distances conditioned by the vaporization. The possibility of 
an internal source of energy therefore in no degree lessens the 
finality of the conclusions as made, I might add also that 
such a concealed source of energy could hardly escape detec- 
tion imless it followed a law similar to the one under dis- 
cussion. 

7. The law of gravitation applied to molecular attraction, — 
The amount of energy that would be required to effect a given 
expansion if the molecular attraction obeyed the law of 
gravitation can be readily found. Helmholtz in 1854 in- 
vestigated the amount of energy that would be given out by 
the contraction of the sun in order to determine if the energy 



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426 /. E. Mills 

continually radiated from that body could be thus obtained. 
In this investigation he assumed that the particles of which 
the sun was composed were at the same temperatiu^e before 
as after the contraction, the excess of energy having been 
radiated off into space. He also assumed that the force 
acting between the particles of the sun's mass obeyed the 
Newtonian law of gravitation. Hence the investigation was 
essentially the same as the one at present desired. In order 
to make possible a better mathematical treatment Helm- 
holtz assumed that the sim was homogeneous in density. 
Helmholtz* found that the total heat, W, given out by the 
contraction of a homogeneous sphere from radius CR^ to R^ 

under the mfluence of a force, / = -. — , between the 

elements {dili) of the mass, was equal to 



17. W = .AK«(^ -c~ )MoS 



where M^ is the total mass of the sphere. 

In applying the above investigation as given by Helm- 
holtz to the contraction of the saturated vapor into the 
condition of the liquid it is to be noted that since the volume 
of a sphere, V, n r ', is equal to its mass divided by its density 

we have, CR^ = \i^> and R^ = \i^^. Also during the 

contraction of the satiu-ated vapor to the volume of the 
liquid the total work done against the attractive forces is 
equal to M(L — EJ = M >l = W. Therefore substituting 
these values in equation 17 we obtain 

18. M(L — Eg) =M>1 = W = 0.9682 K»M*'»(»>&—Nd). 

It should be noted that the actual value of this constant 
as well as the constant of equation 25 depends upon the 
original assumption of Helmholtz that the sphere was uniform 
in density, I do not see how the transformation from a 



* See Moulton's "Celestial Mechanics,'* page 58, or Jour. Phys. Chem., 
II, 147 (1907). 



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Molecular Attraction 427 

sphere of uniform density to one of uniformly distributed 
particles could eflfect any change in the nature of the energy 
relations involved. 

So long as a constant mass is taken equation 18 will reduce 

to the form of equation i, namely ,-_ — ir^= constant. If, 

however, the mass is varied, equation 18 informs us that 
acting under the law of gravitation the work done should 
vary as the 5/3 power of the mass. It should require 3.2 
times as much heat to vaporize 2 grams of liquid as to vaporize 
I gram. As a matter of fact, we know that it requires only 
twice as much heat to vaporize 2 grams as to vaporize i gram. 
8. Application of the law of gravitation to the vaporization 
of a liquid. — It is interesting to take the equation derived by 
Helmholtz for calculating the energy given out by the con- 
traction of the sun under the action of gravitational force, 
and by changing the constant, apply the equation to the 
contraction of a saturated vapor into the condition of a 
liquid. For the piu-pose of illustration isopentane is chosen. 
In Table i below is given for isopentane the density of liquid 
and saturated vapor ^ and also the internal heat of vaporiza- 
tion of I gram.' The equation of Helmholtz has been shown 
to reduce to the form given in equation 18. If 0.9682 K' be 
taken equal to 105.46, and i gram of liquid is used, equation 
18 reduces to the yet simpler form, 

19. W = 105.46 ('V^ — 'Vd) calories. 

I give below in Table i under the heading **W" the 
values obtained from equation 19. Similar comparisons are 
given for ether and for benzol using for the constants 103.76 
and 109.26 respectively. It is inconceivable to me that the 
agreement between W and L — Eg could be accidental. 
A full investigation of equation 19 for the thirty-eight sub- 
stances examined is given m J, Am. Chem. Soc, 31, 1099 
(1909). 



' Sci. Proc. Roy. Dublin Soc., 12, 374 (19 10). 
* Jour. Am. Chem. Soc., 31, 1099 (1909). 



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428 



J. E. MUls 



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Molecular Attraction 429 

The formula used by Helmholtz to represent the energy 
given out by the contra4:tion of the sun does, by changing the 
constant and keeping the mass of liquid constant, represent the 
energy given out by the contraction of isopentane from the gaseous 
to the liquid condition. And not only isopentane but essen- 
tially as well all of the non-associated liquids examined, 
for similar comparisons for all of these substances have al- 
ready been published. I have here republished the results 
for isopentane, ether, and benzene, as coming from Helm- 
holtz 's formula only to emphasize the statement that I do 
not go beyond the facts when I declare that, as regards varia- 
tion with the distance, the law of molecular attraction is identical 
with the law of gravitation, and precisely the same formula is 
applicable to both, 

9. The numerator of the law governing the molecular force. 
— ^The facts to be noted are as follows : 

MM' 

1. The gravitational law of force is / = K-_- = 

s^ 

— ^ . This law used to calculate the energy given out on the 

contraction of molecules leads to an equation of the form, 
energy = cM*'»(Ni— 'Vd). 

2. The equation actually governing the energy given 
out on the contraction of molecules is: energy = M^ = 
/I'MCVS — ^Vb). As before noted, this equation, if universally 

tint 
true, indicates that for the molecular force, / = ^ • 

3. If a constant mass is taken and the constant suitably 
altered, the gravitational law, energy = c M*'»(*Vi — ^Vd), be- 
comes identical with the molecular law, MA = /x'MCVS — *sfD). 

4. The molecular sphere of action is small. The gravita- 
tional law of the force would. make the molecular sphere of 
action include the entire mass taken. 

5. Every molecule is subject to the action of attractive 
forces and itself exerts an attractive force and the attraction 
between the molecules is therefore of a mutual character. 

Considering first the meaning of the expression for the 



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430 y. E. Mills 

j molecular force, , , it will be seen that // is a constant for 

I any particular substance, and m is likewise a constant for any 

i particular particle, and therefore for any molecule, / = 

^ — '— . The molecular force radiating or proceeding from 

* a molecule is not therefore increased by increasing the number 

of surrounding molecules. The sum total of the force of a 
: molecule at a given distance is a constant, and if so much 

I of the force is used up in attracting other molecules there 

1 • • remains an exactly equivalent amount less of the force. 

Molecular force can therefore be viewed as an attribtUe of the 
molecule in exactly the same way that chemical force is an 
I attribute of the atom. Just as the chemical force is used up 

(absorbed or neutralized) by a combination of one atom with 
another so the force of molecular attraction is absorbed or 
neutralized by the surrounding molecules. An atom of 
sodium has a certain amount of *' chemical affinity" and an 
atom of chlorine has a certain amount of *' chemical affinity." 
When these combine the active affinity of each disappears 
and the sodium cannot continue to attract other chlorine 
atoms or the chlorine to attract other sodium atoms. The 
attraction of the combined sodium and chlorine can be re- 
garded as absorbed, neutralized, destroyed, or shielded (the 
word used makes little difference, seeing that the mechanism 
of the action is not understood) from other sodium and chlorine 
atoms. The sphere of action of the chemical force is very- 
small although the force of "chemical affinity" is very great. 
The absorption of the molecular attraction by the attracted 
particles in the same way makes the sphere of molecular 
action small, even though the inverse square law is obeyed by 
the molecular force so long as its power is operative. 

Again, the total molecular force varies as a constant 
times the mass. The constant depends upon the nature of 
the substance and remains the same constant however much 
of the substance is taken. The mass is a constant property 



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Molecular Attraction 431 

of every molecule of a particular substance but varies with 
the number of molecules, that is with the mass, taken. 

The foregoing discussion of the law of the molecular 
force proposed has shown that the law very readily explains 
the facts noted under the headings 3, 4, and 5, above. It 
only remains to show that the complex molecular interaction 
can now be considered and that the fundamental equation 
can be rigidly deduced from the law of force given provided 
we assume: 

C. That the attraction of any molecule is absorbed at a 
distance proportional to the distance apart of the molecules, — 
Since the direction of the force is mathematically a matter of 
no concern we can regard all of the attractive force of one 
molecule as concentrated upon another molecule at distance 
cjj. After expansion this molecule is distant cs^ and the 
energy required for the expansion is 

J s^ c Vj, 5^/ 

To pull n molecules from each other the total energy is simply 
n times as great and we have therefore for the total energy, 
M X, required to overcome the molecular attraction in vaporiz- 
ing a mass of liquid M, containing n molecules, each of molec- 
ular weight w, 

M^ = a'nm^<ik\ — ^ ). 
V^, sj 

Substituting the values given in equation 2 this equation 
reduces readily to the form 

22. m;1 = M/(N^— »Vd). 

In conclusion therefore, I think that there can be but 
little doubt that the molecular attraction follows the law, 

. __ Cfx'^'^m m _ fim 

ID. The law governing the surrender of energy from the 
ether, — Taking into consideration the fundamental nature 



21. 



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432 /. E, Mills 

of the attractive forces it is certainly probable that equation i, 
X = ii'C^ — *VD), will represent under all circumstances, the 
temperature remaining constant during the expansion, the 
work done against the force of molecular attraction in moving 
molecules further apart. Now the further the molecules are 
moved apart the less becomes the value of D, and D will 
finally become zero when the molecules have been moved an 
infinite distance apart. Making, therefore, D equal to zero, 
and remembering that the density, rf, is equal to^'^m/s we can 
write : 

24. ^00-^== constant (For M grams the constant is M//'*^»i) 
as the very simple form for the law under discussion. This 
statement means simply this: 

In any normal substance the internal heal given out as the 
molecules approach each other, multiplied by the distance apart 
of the molecules t is equal to a constant. The significance of 
this statement is very great. The potential energy of molec- 
ular attraction, since it does not reside in the particles them- 
selves, must reside in the medium surrounding the particles, 
that is in the ether. (See under heading 18.) Potential 
energy of attraction is therefore energy due to the position of 
attracting particles of matter in the ether, and the potential 
energy of attraction is a property of the ether. The above law 
therefore governs the surrender of molecular attractive energy 
from the ether. 

1 1 . The law governing the surrender of gravitational energy 
from the ether. — ^The law governing the abstraction of gravita- 
tional energy from the ether can likewise be put into a very 
simple form. Taking equation 17 and making CR^ infinite, 
we have for the energy, E^, given out on the contraction of 
the mass from an infinite distance, since 

25. Eqo ^ = constant. For M grams the constant is 0.9682 K^M*'«*^iw 
or 

0.9682 K^M^ 



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Molecular Attraction 433 

where n is the number of molecules in the mass taken. (See 
also the remark after equation 18.) 

Comparing equation 24 with equation 25 it will be seen 
that for any given mass the law governing the surrender of 
molecular attractive energy from the ether is of precisely the 
same form as the law governing the surrender of gravitational 
attractive energy from the ether. The only difference is in 
the constant involved and this difference depends upon the 
mass taken. 

12. Possible identity of the laws of molecular and of gravita- 
tional attraction, — ^The evidence advanced has pointed clearly 
and almost conclusively to the belief that the three following 
laws governing molecular attraction and energy changes 
caused by that attraction are true. 

(a) / = iT , where / is the molecular force. 

(6) ^^ s ^ constant = fi' '^w» M, where >loo is the inter- 
nal energy given out on the coming together of the molecules 
from an infinite distance to distance s, 

(c) M^ = M/C^— '^D)— the fundamental law as ex- 
perimentally proved. 

The usual ideas concerning gravitational attraction lead 
to the following corresponding laws for that force : 

MM' M^ 

(a') / = K' — — = K'-^ for homogeneous substances. 

(6') E«,5 = constant = 0.9682 Km'^^^^m = ^'^^^^-^^\ 

(c') E = o.9682K^M''»(»^i — » >/D) . 

The similarity of these laws — ^they are identical except 
for the mass and the constant involved — must make one 
pause and think and think again. Are not the laws really 
identical? Is not the difference due to some misconception 
or misconstruction on our own part? Notice that a drop of 
liquid under the action of molecular forces arranges itself 
into a sphere. The radius of the sphere may be many thou- 
sands of times greater than the radius of the so-called *' sphere 
of molecular action.** Notice that the earth also and the 



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434 /• ^' MMs 

planets under the action of the gravitational force assume a 
spherical form, except in so far as modified by their rotational 
movements. Was not the earth at one time merely a large 
drop of liquid and was not its shape determined by the same 
law that determined the shape of the smaller drop? 

The gravitational attraction applies to every mass and 
to every measurable particle of every mass, in the imiverse. 
Is it possible that the mere subdivision of this mass into 
molecules should alter the nature of the law? The molecular 
attraction applies to every molecule in the imiverse. Is 
that law altered by the collection of the molecules into an 
appreciable mass? Would the contraction of a sun made of 
isopentane differ as regards the nature of the laws concerned 
from the contraction of a few grams of isopentane in the 
laboratory? Are there in reality two forces with laws al- 
most, but not quite identical, which apply to the one opera- 
tion — ^the aggregation of matter? The idea is not reasonable 
and there is but little evidence for it 

If the two forces, gravitational and molecular, are identi- 
cal, which law of force above given is the correct law? / 
think that the statement of the law of gravitational force as made 
by Newton needs some modification and thai it is possible to 
bring the law of molecular and gravitational force into harmony 
with the facts and with each other, 

I only ask that the statement made be judged by the 
evidence that is, or that can be, presented. It should, at the 
outset, be understood clearly that the gravitational law as 
expressed by Newton and commonly interpreted since his 
day, cannot, unmodified, be made to apply to molecular 
attraction for the following reasons: 

1. The sphere of molecular action would not be small 
and the liquid could not be regarded as homogeneous through- 
out. 

2. The heat of vaporization of a liquid would not vary 
as the mass of the liquid taken. 

3. The boiling point of a liquid would vary with the 
amount of liquid taken and with the shape of the vessel. 



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Molecular Attraction 435 

4. Surface tension phenomena generally would vary 
with the amount of liquid and the shape of the vessel. 

5. The gravitational force as calculated for molecular 
distances by Newton's law is not great enough to account for 
the observed phenomena of cohesion. 

It should be further remembered that since Newton in 
1682 deduced the law of gravitation, all of the attempts — 
and they have been numerous — ^to formulate a sufficient cause 
for the law have completely failed. The attempts have 
ended not alone in failure to formulate a cause for the law, 
but in emphasizing, most distinctly, the difficulty of forming 
such a conception at all. May not the real cause of the 
trouble lie in the fact that scientists have been trying to ex- 
plain how a force can be infinitely multiplied and absolutely 
unaffected by intervening matter, when force with such 
properties has really no existence? The whole situation 
merits careful consideration. 

13. The difficulties that arise in explaining gravitation. — 
The difficulties that arise in attempting to explain gravita- 
tional force (as that force was understood by Newton and by 
scientists since his day) Jiave been most excellently sum- 
marized by W. B. Taylor,^ and only the unusual length of 
this paper prevents my quoting his statement of the *Xon- 
ditions of the Problem" in full. Without reviewing the 
entire discussion I would place additional emphasis on three 
facts required by the usually accepted laws of gravitation. 

First, — ^The attraction exerted by a particle can be 
infinitely multiplied merely by the introduction of other 
particles. If by some act of creation new particles come into 
existence the former attraction of every particle in the uni- 
verse is thereby increased. Is it not unreasonable to suppose 
that a particle could exert its attractive pull upon one thousand^ 
or one million^ or one hundred million, particles and yet always 

* "Kinetic Theories of Gravitation," Smithsonian report, 1876. The 
entire paper should be read by those interested in the cause of gravitational 
force. 



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436 y. E, MiUs 

have just as much of its force remaining to exert on other particles 
brought within the same distance? 

Second, — A particle at the center of the earth attracts a 
particle at the surface of the earth, or a particle at the center 
of the sun excuMy as if there were no intervening matter. Is U 
reasonable that the introduction of particles of matter into the 
space surrounding a molecule slwuld be absolutely without in- 
fluence on the wave motion or emanation {or more spiritual 
essence) which acts as if it proceeds from the molecule and gives 
rise to the phenomena of attraction? And that this filling in 
of the space surrounding a molecule with other particles of matter 
{or centers of energy, if you choose) should be able to continue, 
ad infinitum, without disturbing the attractive radiation pro- 
ceeding from the body? 

Third, — ^The attraction is propagated supposedly with an 
instantaneous velocity, but with a proved velocity^ at least 
50,000,000 times that of light; that is, the proof holds imless 
there is some imknown compensating action. 

To the reader these difficulties may well appear insur- 
mountable. They have proved equally as insurmountable 
to every student of the subject.. Newton, himself, in his 
oft-quoted third letter to Bentley, dated Feb. 25, 1692-3, 
stated: ** That gravity should be innate, inherent, and essen- 
tial to matter, so that one body may act upon another at a 
distance, through a vacuum, without the mediation of any- 
thing else, by and through which their action and force may 
be conveyed from one to another, is to me so great an absur- 
dity, that I believe no man who has in philosophical matters 
a competent faculty of thinking can ever fall into it. Gravity 
must be caused by an agent acting continuously according 
to certain laws; but whether this agent be material or im- 
material, I have left to the consideration of my readers.** 

Twenty-five years later, **as if driven back from every 
assault to the only retreat, which in earlier years he had 
stigmatized as *so great an absurdity' that no competent 
thinker could *ever fall into it,' he despairingly asks: *Have 

* Taylor: "Kinetic Theories of Gravitation." 



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Molecular Attraction 437 

not the small particles of bodies certain powers, virtues, or 
forces, by which they act at a distance What I call ** at- 
traction" may be performed by impulse, or by some other 
means unknown to me. I use that word here to signify only 
in general any force by which bodies tend toward one another, 
whatsoever be the cause.' And beyond this point, no human 
research has yet been able to penetrate.*'^ 

There is no need to review the fruitless effort expended 
in trying to get an explanation of the gravitational law since 
the time of Newton. Faraday^ clearly and repeatedly asserted 
his belief that no force with the properties usually ascribed to 
gravitation could exist. The question of the truth of the 
gravitational law cannot be finally settled by an appeal to our 
minds as to the relative difficulty or ease of the conception, 
though such an appeal is not without value. Let us proceed 
fiulher to examine in detail the evidence for the law. 

14. Newton's law of gravitation is not a necessary conse- 
quence of the motion of the heavenly bodies. — Kepler deduced 
from the observations of Tycho Brahe and his own three 
empirical laws governing the motion of the planets about the 
sun. 

Newton perceived that these motions of the planets 
about the sun and the motion of the moon might be deter- 
mined by the action of a force differing in no substantial 
respect from the force of gravity as exhibited on the earth. 
He investigated this briUiant conception and finally stated the 
universal law of gravitation as causing the observed planetary 

,MM' 
motions, g = k — .^ . 

Newton did not know the mass of the earth, or of the moon, 
or of the sun, or planets. He could not therefore prove the 
numerator factor of his law correct so far as the masses of the 
heavenly bodies are concerned, and we are to-day as totally 
without proof. All of Kepler's laws follow on the assumption 
of a central acceleration varying inversely as the square of the 

* Taylor: "Kinetic Theories of Gravitation," page 5. 

* "Essay on the Conservation of Forces," and other writings. 



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438 /. E, Mills 

distance from the center. The fact that this central accelera- 
tion varies as the product of the masses of the attracting 
bodies was a pure assumption, so far as the heavenly bodies 
are concerned, made because Newton saw clearly that all 
masses appeared to be concerned in such mutual attractions. 

The mass of the earth was really determined for the first 
time by Maskelyne in 1774 who weighed the earth against a 
mountain (by measuring the deflection of a plumb-line) and 
obtained its weight on the assumption that the law of gravita- 
tion as stated by Newton was true. Since that time various 
investigators have made use of four methods for determining 
the mass of the earth but in all of these methods the truth of 
Newton's law of gravitation is assumed. Really only the 
attraction or acceleration between various masses is directly 
determined and the mass is calculated on the assumption that 
Newton's law of gravitation is correct. 

When we consider the various methods of obtaining the 
masses of the other heavenly bodies we find always a similar 
condition. The relative amount of the attractions are deter- 
mined and the masses are calculated on the basis of Newton's 
law. Astronomical data gives absolutely no evidence to show 
thai gravitational attraction varies as the product of the masses 
of the attracting bodies. It does prove that a force of a definite 
and apparently unchanging magnitude emanates as if from 
the center of each heavenly body within the limit of investiga- 
tion and that this force varies inversely as the square of the 
distance from its origin. The magnitude of the force exerted 
depends upon some property of the body. 

Astronomical data does apparently fiuther prove that 
this force of gravity cannot be shielded, or refracted, and 
that its action is instantaneous throughout all ascertained 
distances. Thus the passage of the moon between the sun 
and the earth does not alter in the slightest degree the relative 
motion of the sun and the earth and therefore apparently 
does not disturb the attraction which exists between them. 
This remarkable circumstance (equally true for all similar 
cases) has doubtless kept many from questioning the truth 



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Molecular Attraction 439 

of Newton *s statement of the gravitational law. An ex- 
planation of the actually observed facts is suggested later. 

15. Newton's law of gravitation is not a necessary conse- 
quence of the motion of freely falling bodies. — If bodies, initially 
at rest near the earth *s surface, fall freely towards the earth 
under the influence of the gravitational attraction the follow- 
ing laws apply : Let v = velocity acquired, a = acceleration 
produced by gravity, t = time, s = distance traversed. Then, 

26. V = at; a ^^ — ; cw = — . 

2 2 

These laws and these laws alone are sufficient to determine 
the motion of bodies near the earth free to fall under the 
action of gravitational attraction. Motion on an inclined 
plane and the motion of pendulums can be regarded as falling 
imder this head. It should be noticed particularly that the 
mass of the body nowhere enters into thee quations. That 
is to say a feather, a gram of aluminum, and a poimd of lead, 
in a vacuum, all fall at exactly the same rate, and that rate 
is in no sense dependent upon their relative mass. It should 
be borne in mind that if during its fall the mass of the lead were 
altered to that of the aluminum, or to that of the feather, the 
change of nuiss could not be detected by any observation upon the 
motion of the lead.^ It is therefore perfectly clear that no 
observation of the motion of a body falling freely towards the 
earth will give any evidence as to the mass of the body. This 
statement as has already been shown applies also to the motion 
of the heavenly bodies. 



^ Objection has been raised to this statement on the ground that the 
alteration of mass is a purely hypothetical question and also on the ground 
that the conservation of energy must be considered. I do not believe that the 
alteration of the mass is a purely hypothetical question. I suspect very strongly 
that it does actually take place and I am here giving one reason why we have 
heretofore failed to detect it. As regards the conservation of energy, if the 
kinetic energy of a body is due to its motion, my very point is that this motion 
is not changed. If as I think more likely the kinetic energy of a moving body 
is more or less a property of the ether surrounding the body then the energy 
is adjusted when the ether condition is adjusted — that is probably completely 
only when the system becomes static. 



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440 /. E. Mills 

Newton's calculation showing that the moon "fell" 
towards the earth required no knowledge of the mass of the 
moon or of the earth. It did prove that the earth's attraction 
extended to the moon and that this attraction varied inversely 
as the square of the distance from the center of the earth. A 
cannon ball at the distance of the moon once given the velocity 
of the moon would follow its orbit very nearly. The differ- 
ence observed would be due to the fact that the moon and the 
earth revolve around their common center of gravity which 
would be changed by the substitution of the cannon ball for 
the moon. Now oil the supposition of Newton's law of gravita- 
tion the relative mass of the moon and earth can be obtained 
from this fact. Similarly the relative mass of the planets is 
obtained from the divergence from Kepler's third law. It is 
thus a little curious that our knowledge of the relative masses 
of the heavenly bodies is largely due to their divergence 
from the verj'^ laws Newton's law was advanced to explain. 
The divergence of course likewise takes place in accordance 
with Newton's law. 

1 6. Newton's law of gravitation is not a necessary conse- 
quence of the motion of bodies retarded during their fall. — Imagine 
two equal masses of say 99 grams each connected by a cord 
and balanced by passing the cord over a nearly frictionless 
pulley free to revolve. Now motion in such a system can be 
started by placing a small rider, let us say of 2 grams, upon 
one of the masses. The mass will descend under the action 
of the gravitative force exerted by the earth upon the mass 
of 2 grams. The velocity acquired will however be only 
i/ioo of the velocity acquired by the 2-gram mass if it be 
allowed to fall freely. And in general, it can be thus shown 
that the force of gravity is proportional to the mass of the at- 
tracted body. The same fact may also be demonstrated by 
measuring the gravitational attraction upon any body and 
then determining the inertia of the body when it is subjected 
to motion in a horizontal plane. Always the force of gravity 
appears to be proportional to the inertia of the body. But this 
fact, so far from constituting a proof of Newton's law of 



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Molecular Attraction 441 

gravitation, is a proof only of the law of molecular force given, 

^ _ constant X mass 
namely, force = ^ . 

17. Direct measurement of the attraction of two masses, — 
When Newton proposed his magnificent generalization he 
had no proof whatever that the gravitational attraction did 
vary as the product of the masses of the attracting bodies. 
The attraction of two bodies, the masses of which could be 
independently determined, was not measured by any ex- 
perimenter for nearly a hundred years after the law had 
been proposed. Newton saw that the attraction of gravity 
apparently extended to all bodies, that it apparently could 
not be shielded, deflected, or absorbed in any way, and that 
the earth's attraction, at least for bodies near the earth, 
varied as the mass of the bodies. From these facts Newton 
made his generalization. 

In attempting to find the constant of gravitational at- 
traction the attraction of two masses has been directly 
measured by a number of experimenters using several different 
methods. The experiments are difficult in the highest degree 
and naturally the results did not at first agree well with each 
other. But the difficulties have been gradually overcome 
and reliable measurements have now been made of the at- 
traction of two masses at known distances under circumstances 
j)ermitting of the elimination of the numerous disturbing 
elements. The fact that these experiments were performed 
under diverse conditions, with masses of varying size and 
substances, at varying distances, and yet give agreeing (con- 
sidering the difficulty of making accurately the measure- 
ments involved) values for the gravitational constant k, 
constitutes the sole proof existing to-day, so far as the writer 
is aware, of the truth of Newton's statement that substances 
universally attract as the product of their masses. The proof 
that has thus accumulated cannot be lightly put aside. An 
interesting account of these experiments is to be found in 
**The Laws of Gravitation,*' by A. S. Mackenzie. 

The agreement shown by these experiments is one fact 



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442 /. E, Mills 

that must be explained in explaining gravitation. I will 
refer to these experiments later. 

1 8. Comparison of all of the attractive forces. — ^The nature 
of the gravitational and of the molecular attraction is a very 
fundamental question. The nature of matter, of inertia or 
mass, the nature of the other attractive forces, and the nature 
of the ether must all be considered to some extent at the same 
time. The table below gives the usually accepted belief as 
to the action of the attractive forces. The general resemblance 
between these forces is so striking, I think, as to warrant a 
very serious consideration of any idea which leads to the 
belief that all of the forces do not follow the same law. Are 
they not perhaps all, in fact, one and the same force? Are 
not the apj^arent exceptions to a complete similarity between 
the action of the forces due to our lack of knowledge, or to a 
wTong understanding and interpretation of the facts in- 
volved? In seeking an answer to these questions the inter- 
pretations suggested below of certain facts are new, and in 
order to prevent confusion a general discussion of the table 
precedes the more detailed consideration of the facts. 

All of the attractive forces appear to proceed from some 
particle or mass of matter as a center and to be exerted upon 
some other particle or mass of matter across an intervening 
space which is supposed to contain ether. Thus always in 
the action of the attractive force at least two particles are 
concerned and these two particles possess, because of their 
mutually attractive force, a so-called potential energy, which 
can be obtained from the system by causing the particles to 
approach. Without making any further supposition what- 
ever, fundamental mechanical principles being true, as to 
the nature of the particles, of the ether, or of the attractive 
force, it is clear that this potential energy does not reside in 
the two particles from which the force appears to proceed, 
for these particles can be supposed at rest and therefore de- 
void of all energy per se, (If when the particles are at rest, 
they possess internal motion, it can hardly be supposed that 
the internal motion is changed by their approach. Yet 



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Molecular Attraction 



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444 /• ^' Mills 

perhaps this possibility should not be regarded as eliminated.) 
This potential energy, since it does not reside in the particles 
themselves, must reside in the medium surrounding the 
particles, that is in the ether. Potential energy of attraction 
is therefore energy due to the position of attracting particles 
of matter in the ether, and the potential energy of attraction is 
a property of the ether. This view is pretty generally accepted. 

It is equally clear that this energy of the ether exists or 
exists in an available form, solely on account of the presence 
of the attracting particles. The attraction must therefore be 
caused by some interaction between the attracting particles and 
the ether, WTiile two particles and the ether are necessary 
to the phenomena of attraction, it is quite clear, ^ that the two 
particles are not necessary for the interaction between the 
matter and the ether. That is, eocA particle alone must interact 
with the ether in su^h manner as to produce a modified condition 
of the ether in its neighborhood. Two or more ** modified con- 
ditions" of the ether produce an attraction between the 
particles causing the ** modified conditions," and the attrac- 
tion is due to some connection between these modified ether 
conditions. // is clear that if one particle alone in the ether be 
considered, the total effect of its interaction with the ether is a 
proper measure of its potential attractive energy, which under 
these conditions becomes a constant and definite property of the 
particle. 

Without knowing, or at present considering, the mech- 
anism of the interaction between the ordinary particle 
and the ether yet a further conclusion can be drawn. Con- 
sider two particles at an infinite distance apart, each particle 
being surrounded with its modified sphere of ether. Prob- 
ably these ** modified spheres of ether" proceed from a particle 
somewhat as does light from a central source of light. Under 



* The author holds the belief that two particles of ordinary matter or of 
ether cannot exert any action upon each other acrofe an absolutely empty 
(devoid of matter and of ether) intervening space. To attempt to justify this 
belief would lead to an examination of the foundations of thought, mathematics, 
and science. Such an examination would lead us too far from the immediate 
object of the present paper and cannot be undertaken here. 



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MolectUar Attraction 445 

the influence of their mutual attraction caused by these 
modified spheres of ether the two particles commence to 
approach each other and gain in kinetic energy. The ether 
loses therefore a corresponding amount of energy and must 
suffer change to a corresponding extent. The loss of this 
energy by the ether must be to that extent a reversal of the 
"modified condition of the ether'* caused by the particles of 
matter; for the cause of the attraction, as has been seen, 
lay in this modified condition of the ether and when the cause 
produces a change the cause must itself suffer an equal op- 
posite change. If this does not happen there would be a 
creation of energy. In fact the modified spheres of ether can be 
regarded as produced by the interaction between the particles 
and the ether a^id as representing so much available energy , a^nd 
if some of this energy is used up^ the amount of energy remaining 
must be diminished by an exactly equivalent amount. The 
attractive force, which is a manifestation of this energy, 
must be subject to a corresponding limit. That is, the at- 
tractive forces, whatever their nature , whether chemical , molec- 
ular, magnetic, electrical, or gravitational, which proceed from a 
particle are definite in amount. If this attraction is exerted 
upon another particle the amount of the attraction remaining 
to be exerted upon other particles is diminished by an exactly 
equivalent amount. 

Strenuous objection has been raised to this sentence and 
I have been accused of confusing force and energy. I am 
not confusing the two. I think force in its last analysis has 
to do with the quantity of motion transferred per unit of 
time. I do not consider this idea of force heretical. When 
the totality of a force is considered per unit of time (as is here 
done) it will be seen that the quantity of motion transferred 
can be increased only by increasing the velocity of the moving 
particles or by altering their distance apart (or their number 
per imit of volume, which is the same thing). Both of these 
operations (alteration of velocity or distance apart) would 
require the expenditure of additional energy. Where the 
energy is fixed and a definite system is considered the total 




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446 /. E. Mills 

force is also constant. I have been cited to the hydraulic 
press, etc., as illustrations of how force can be multiplied. 
The total force in a hydraulic press has to do with the total 
motion exchanged among the molecules of the liquid used. 
For a given press the total force of the system is constant unless 
the amount of liquid used, the temperature of the liquid, or 
the distance apart of the molecules are altered, and all of 
these alterations require the expenditure of energy. When we 
keep the conditions in the press the same the force exerted 
at one end is multiplied at the other because we consider 
only a part of the total force and that part as acting on differ- 
ent areas. There can really be no multiplication of the total 
force except as above stated. I see no reason whatever for 
attributing ** powers*' to a molecule which are not possessed 
by any mechanism whose real nature we are able to imder- 
stand. The disturbance set up by the interaction of a mole- 
cule and the ether is in my opinion perfectly definite in amotmt 
for a given condition of the molecule and the ether, and this 
disturbance represents a certain amoimt of energy and a 
certain total and perfectly definite transference of energy 
per tmit of time, which definite amount of force can be used 
(that is, exerted on ordinary matter), but once used does not 
continue available. 

In my opinion the idea that a definite electrical charge 
on a definite particle represents a definite amount of energy 
necessitates the above conclusion regarding the constancy of 
the electrical force proceeding from the charged body, 
similarly as regards magnetic forces. Hence it will be noticed 
that the gravitational force offers the only pronounced ex- 
ception to a general resemblance of the forces. Perhaps it is 
best in this connection to call attention to the following 
points : 

I. As regards the positive and negative tendencies of the forces, chemical, 
magnetic, and electrical forces show decided evidence of directive action. It is 
usual, moreover, to distinguish between positive and negative electricity, positive 
and negative poles of a magnet, and positive and negative elements, as indica- 
ting some difference in the kind of attractive force which they exert. As evi- 
dence of variation in the intensity of the molecular forces with their spatial 



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Molecular Attraction 447 

arrangement around the molecule, might be cited the phenomena of crystalline 
form, of water of crystallization and molecular combinations in general, and 
also those cases where a liquid appears to show a definite and symmetrical 
structure. The evidence that the molecular forces show positive and negative 
tendencies is not convincing and so a question mark is inserted in the table to 
indicate our lack of knowledge. With gravitational force there is no evidence 
showing positive and negative tendencies of the force. 

2. Some might be inclined to doubt the statement that temperature has 
no effect upon chemical affinity. This fact is however almost beyond doubt.* 
Almost equally beyond doubt change of temperature has per se no effect on 
magnetic and electrical forces, but being unable to cite direct experiments upon 
this point the writer has used question marks in the table. 

3. The velocity of propagation of a chemical reaction is of course an 
altogether different quantity from the velocity of propagation of the chemical 
force itself. There is no evidence as to the rate of propagation of either chemical, 
molecular, or magnetic forces. The velocity of propagation of gravitational 
force is discussed in the reference already given.* Electromagnetic waves 
travel with a velocity of 186,000 miles per second. I have taken this as indica- 
ting the speed of propagation of electrical force through the ether. 

4. The law of variation of the chemical force with the distance apart of 
the atoms is unknown, but that this force does vary as some function of the 
distance apart of the atoms concerned has, I think, been already shown by the 
work of Richards' and Traube.^ The latter says: **Wi€ von mir zuerst festgestelU 
wurde, ist der Raum eines Atoms keine Konstante, sondern dndert sick von Stoff 
zu Staff und ist um so kleiner, je grosser die Affinitdi des betreffenden Atomes zu 
den Atomen isty mit welchen es in unmittelbarer Verbindung stehi. Die Kontrak- 
iion der Atome ist daher ein unmiUelbares Mass der Affinitdi." Concerning 
Traube's claim to priority in this discovery see remark by Richards.* While I 
prefer not to accept the conclusion of these investigators that the atoms them- 
selves suffer a contraction, I cannot doubt from the evidence that they have 
brought forward that the chemical attraction between atoms is one of the de- 
ciding factors as to the distance apart of these atoms when combined into a 
molecule. That is to say, the distance apart of the atoms is some function of the 
chemical affinity. The problem is as yet too complicated to permit of finding the 
law of the attraction, and at present I must limit myself to the statement that 
the inverse square law of the distance is possible also with this force. 

The rather widespread idea that the inverse square law is not possible 
for chemical force rests upon the same error already discussed for molecular 
force. The investigators* have not taken into consideration the mutual ab- 
sorption or cancellation of the force by the atoms when they unite. 



* Trans. Am. Electrochem. Soc., 14, 35 (1908). 
' Taylor: "Kinetic Theories of Gravitation." 

» Proc. Am. Acad., 37, 1 (1901); 15 (1902); 38, 7 (1902); 39, 23 (1904). 

* Zeit. anorg. Chem., 40, 380 (1904). 

» Proc. Am. Acad., 39, 23, 583 (1904). 

* See for instance Helmholtz: Jour. Chem. Soc., 39, 277 (1881). 



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448 /. E. MUls 

In considering the numerator factor of the forces three 
circumstances are worthy of attention: 

First. Except for the gravitational force, the numerator 
factor of the force is supposedly bound up with the nature of the 
force itself, — Thus when we speak of the ** electrical** force 
the numerator factor has to do with the ** electrical'* charge; 
when we speak of the ** magnetic** force the numerator factor 
is the *' magnetic** strength of the pole; when we speak of 
"chemical** or ** molecular** attraction, the numerator factor 
is supposedly dependent upon the ** chemical'* aflfinity or the 
nature of the ** molecule;'* when however we speak of gravita- 
tional force, it is usual to regard the numerator factor of the 
force as ** mass,** and as a property therefore distinct from and 
independent of gravitation. Is not ** mass** really a ** gravita- 
tional'* charge? 

Second. — ^Just as the condition of an electrical charge can 
be considered as dependent upon two factors, a capacity 
factor C, and an intensity factor, the voltage V, so possibly 
the ** gravitational charge" or mass, would be dependent upon 
two similar factors. Similarly for the numerator factors 
of all of the forces. 

Third. — If one attempts to consider what changes must 
be made in the numerator factor of the forces in order to derive 
a common expression for all of the forces, one starts with the 
broad idea that a force is measured by the effect which it pro- 
duces. There is no law as to the conservation of force, but 
there is a law as to the conservation of energy. Granting the 
conclusion already drawn that the modified sphere of ether 
surrounding a particle represents a definite amount of energy 
belonging to the particle and that this potential energy of the 
particle is transformed into kinetic energy of motion by some 
interference of two such spheres, then it is clear that this 
interference of these modified spheres of ether constitutes the 
force of attraction acting between the particles. Now since 
force is transference of energy the total attractive force of a 
particle is definite in amount. If therefore a portion of this 
attraction is expended upon one particle there remains exactly 



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MolectUar Attraction 449 

an equivalent amount less to be expended upon the remaining 
particles. Conseqtiently the attractive force exerted can be 
measured by the amount of the neutralized force. From this 
point of view the usual ideas of the attractive forces could be 
expressed : 

amount of attraction neu- . , amount of attraction neu- 



Force 



tralized at unit distance tralized at unit distance 



It seems perfectly reasonable that the attractive force 
should vary with the amotmt of the attraction absorbed at 
imit distance but why should the force vary as the product 
of the amounts so absorbed? Moreover the above expression 
makes the mass of a particle proportional to the amoimt of the 
attraction absorbed. Is this idea of mass further supported 
by the facts? 

The close relationship of magnetic and electrical forces is 
well known. The probability of a very close relationship or, 
identity, of chemical and electrical forces is now hardly 
doubted by any one. Many chemists at heart consider 
molecular and chemical forces as of probably identical origin 
and character. Recent work shows that the motion of elec- 
trical charges may accotmt for mass. Is it then too much 
to suspect that gravitation belongs also within the fold? And 
is it too much to ask that more serious attention be given to 
the possible ultimate identity of all of these forces? 

19. The nature of mass. — Each of the three following 
definitions of mass are sometimes given : 

A. Mass is quantity of matter. 

B. The unit of mass is that quantity of matter which 
will coimterpoise in a balance a certain standard mass known 
as a standard poimd or gram. 

C. Mass is inertia — resistance to motion. This is the 
modem definition and finds expression in the formula, 
energy = M. a. s, = Vj MV^, or mass X acceleration X dis- 
tance traversed = y, mass X (velocity acquired) ^ 

As regards definition A, compare a mass of i gram of 
lead with a mass of i gram of aluminum. There is not, so 



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450 /. E. Mills 

far as the author knows, one iota of evidence, save in the 
suggestiveness of the periodic table of the chemical elements, 
as to whether the gram mass of aluminum and of lead contain 
equal or imequal amounts of the ** ultimate material*' of 
which both may be composed. And there is no way of 
finding out imless the aluminum and the lead can be de- 
composed into the ultimate constituents of which they are 
made. The first definition should, therefore, for the present, 
be banished from science. 

Definition B is founded on the fact that mass is pro- 

, . - . weight , . , r 

portional to weight, or equal to 7 ~y~ , and is therefore a 

deduction from Newton's law of gravitation. 

Adopting the third definition that mass is inertia, or 
resistance to motion, it is certainly reasonable to consider the 
resistance to motion in the ether to be in principle the same 
as the resistance to motion in other media. If one tries to 
move a particle from a bar of iron, or from a piece of lead, 
the resistance to the motion is great. WTiy? Because the 
attraction of the particle for the surrounding particles is very 
great. If this attraction is overcome it becomes very easy to 
move the particle. If one tries to pull a boat to land, the 
inertia of the boat does not depend entirely upon its mass 
but upon the resistance the water offers to its motion. 

The motion of matter through the ether must be similar. 
The inertia of a body is the amount of resistance offered by the 
ether to the motion of the body. The usual idea of the motion 
of matter through the ether has more or less neglected three 
facts, each of great importance. 

I. The ability of a particle to accelerate other particles 
towards its own position {i, e., to attract) must depend on the 
inertia of the particle as one factor, — Mach declares* that the 
concept of mass as inertia renders unnecessary the special 
enunciation of the principle of action and reaction. Why 
did not Mach go one step further and apply his statement 
to the gravitational force? 

* Science of Mechanics, page 220-5. 



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Molecular Attraction, 451 

Consider a particle with the abiUty to attract but possessed 
of no inertia, and attempt to apply the principle that action 
and reaction must be equal and opposite. The particle 
without inertia and its attractive mechanism would be at 
once moved to the position of the attracted particle at the 
first effort to preserve the principle of action and reaction. 
A little consideration will show clearly that the attraction, the 
inertia, and the principle of action and reaction, are but phases 
of the same phenomenon. Their relationship will appear more 
clear from a concrete example. Suppose a man in a boat 
by means of a rope attempts to pull a man on land into the 
water. The man in the boat, no matter what his strength, 
cannot produce an effect greater than that allowed by the 
inertia of his boat. His greater effort would only result in 
drawing his own boat the faster towards land, while the man 
on land retains, perhaps, almost his same position, due to the 
fact that he can suitably brace himself so as to produce in 
himself a relatively great inertia. If the man on land is im- 
movably braced to the earth the principle of action and re- 
action is not violated. The entire earth will be slightly moved 
so that the center of gravity of the entire system — earth, 
water, and boat — is preserved. 

If both men are in boats both boats would move. The 
inertia of one boat, times the distance through which it 
moves, is equal to the inertia of the other boat times the 
distance through which it moves, or obviously, Is = I's'. 

Now consider carefully the boats and the rope. If the 
rope is slack there is no pull (attraction) between the boats 
and there is no inertia actively displayed. If now the man in 
boat I' pulls the rope supposed attached to boat I, he ** at- 
tracts'* boat I and causes at the same time a display of interia 
in his own boat. If the rope is attached to boat I' and the 
pulling is done by the man in boat I then boat I "attracts" 
boat I' and inertia is brought into play in boat I. In each 
case the pull upon the rope (the attraction) is possible solely 
because of the inertia of the boat from which the pull pro- 
ceeds. The attraction and the inertia are different ends of the 



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452 J, E. Mills 

same rope. The man in either boat might say "I can pull 
(attract) the other boat because of the inertia of my own 
boat.*' A man on land would say : ** The rope is stressed, both 
boats are attracted, and both boats possess an inertia which 
depends on the boats themselves and on the surroimding 
water.'* 

The case is exactly similar when two particles attract 
each other except for the fact that while the rope is the ether, 
the ether likewise represents the water, and is therefore one 
factor determining the inertia (the other factor being the 
nature of the particles, probably their size, if they are " ulti- 
mate** particles). Therefore, while in the case of the boats 
there is no necessary relation between the strength of the 
man in the boat and the inertia of his boat, in the case of the 
attracting particles, the attraction of a particle and its inertia 
are proportional, both being determined by the ether surround- 
ing the particle. 

Quite possibly the total attractive force of a particle 
depends upon the total ether surrounding the particle. Its 
inertia towards any given attraction depends upon the ether 
encountered in its motion and is therefore a function of its 
** front.** Its acceleration is produced by the pressiu-e of the 
ether from "behind.** Different masses at the same distance 
from the attracting body have the same acceleration because 
the ratio of the ether pressure ** behind'* to the ether re- 
sistance in '* front'* is the same. 

2. Light, heat, magnetic and electrical phenomena, also 
molecular and gravitational as well, show that under certain 
circumstances ether can react strongly with ordinary matter. 
Yet the ether is said to offer no resistance to the motion of a 
heavenly body or to the motion per se of other bodies. This 
is a remarkable, and a remarkably neglected, state of affairs. 

3. The mass or inertia of a body is said to depend upon 
its resistance to motion in a horizontal plane and the idea and 
measure of mass is said to be altogether independent of the 
law of gravitation. This is not true as will appear upon 
closer inspection. The horizontal plane is defined with 



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Molecular Attraction 453 

reference to the center of gravity; that is, the horizontal plane 
is made to follow the ciu-vature of the earth. Then motion 
in this plane is supposed to be free from the influence of the 
earth's attraction. This is unfortunately untrue, since the 
body will continue in motion upon the plane thus defined 
(even were there no air and normally no friction) only with one 
particular velocity. If the body is given too small a velocity 
it will at once press upon the plane and if it be given too great 
a velocity it will at once leave the plane. When the body is 
given such velocity that it will retain its position upon the 
so-called ** horizontal" plane it is virtually falling aroimd the 
earth.* Our measure of mass, therefore, so far from being 
free from the influence of the surroimding field of force is 
essentially determined by that field of force. 

The idea that mass, even when it occurs in the expres- 
sion V2 Mv^ as one of the terms defining energy, cannot be 
defined or measured so as to get rid of gravitational attraction 
as a determinative factor will probably meet with opposition. 
It is well, therefore, here to recall the historical dispute over 
this expression between Descartes and Leibnitz and their 
followers — a dispute which lasted for seventy years and con- 
tinues even yet to break out periodically. Descartes thought 
that the quantity of work in a body should be measured by 
the quantity of motion (MV), Leibnitz that it should be 
measiu-ed by the vis viva (MV). Mach in his wonderful 
book "The Science of Mechanics*' gives a history of the dis- 
pute well worth reading and says: "Similarly, the capacity 
of a moving body for work, whether we measure it with 
respect to the time of its action by its momentum or with 
respect to the distance through which it acts by its vis viva, 
has no significance referred to a single body. It is invested 
with such, only when a second body is introduced, and in the 
first case, then, it is the difference of the velocities, and in 
the second the square of the difference that is decisive. 
Velocity is a physical level, like temperature, potential func- 



* This fact hardly needs proof here. The application of the fact alone 
is new. For proof see almost any book on analytical or celestial mechanics. 



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454 J' E, Mills 

tion, and the like.'*' (English translation, page 325.) This 
statement and the grounds for the statement should be care- 
fully digested. 

Some one will ask: ** If the ether offers a resistance to the 
motion of matter why does not the earth, etc., bum up on 
account of the energy that would be developed through 
friction?'* The answer is that if two bodies approach each 
other imder the action of gravitational attraction, energy is 
developed and is stored up in the bodies or in the surrounding 
ether. It is thus that kinetic energy is made. In my opinion 
a body without any attractive force would not have mass 
in the usual sense of that term. If in motion its energy would 
be measiu-ed by m'v and not by V2 MV where w' is a capacity 
factor differing from mass as usually defined. Moreover, 
since gravitation acts continuously, ordinary mechanical 
principles holding true, we know that the action must be 
dynamic in its nature. There is a continual exchange of 
energy between the matter and the ether. Uniform motion 
in a circle simply means that the body is giving out exactly 
so much energy as it absorbs. However, I am not discussing 
the possible mechanism of the gravitational action in this 
article, except where it is essential to do so to avoid a mis- 
imderstanding of my point of view. 

In conclusion, therefore, I think that mass is proportional 
to the resistance offered by the ether to the motion of a body 
and that the amoimt of this resistance is proportional to the 
amount of the attraction absorbed under a specified condition. 
The attraction and the mass are a sort of action and reaction 
due to the same cause, or rather they both depend upon the 
amotmt and the condition of the ether with which the body 
comes into contact. Mass is a gravitational charge. A 
body alone in space could not possess mass any more than a 
body alone in space could possess an electrical charge. Per- 

' Mach agrees with Leibnitz and accepted scientific usage and thinks 
Descartes has been proved wrong. But it is worthy of note that if the ether has 
momentum Descartes may yet be right and his idea may be the more universal 
and fundamental of the two. I think this point may prove of importance in 
discussing the mechanism of gravitational action. 



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Molecular Attraction 455 

hap. n^ M- ^ the ^viutiooa, i^uU. 5f , co^d be 

thought of as a positive charge (it has to do with the attrac- 
tion), mass in the kinetic formula, V, Mv^, as a negative 
charge (it has to do with the inertia). They are obverse 
and reverse of the same thing. 

Perhaps this particular idea of mass is not essential 
to the reconciliation of the laws of gravitational and molec- 
ular attraction, but I have felt that the succeeding statements 
could not be properly understood without some explanation 
of my point of view regarding mass. 

20. Proposed modification of the statement of the law of 
gravitation, — In order to make the statement of the law of 
gravitation accord with the law of molecular attraction, 
if the views expressed in this paper are correct, two changes 
in oiu: usual conception of the gravitational law are neces- 
sary: 

First, The total attractive energy of a given body is to be 
considered a constant. — It is a property which belongs essen- 
tially to the body and to its surrounding ether. This energy 
is changed into kinetic energy upon the approach of other 
bodies and may then be given out as heat, etc. 

Second, Mass in the usual sense is a relative and not an 
absolute property of a body. — It is proportional to the at- 
tractive forces to which the body is subjected. 

The first change has to do with the totality of the attractive 
force. The second has to do with the distribution of this 
perfectly definite force. 

As regards the totality of the force, if the particle or 
mass be supposed so surrounded with other matter that its 
total field of force is neutralized at distance s, then we may 
write as the law governing the force exerted by the particle, 

_ am 

27. Force = -^ » 

where /£ is, as before, an intensity factor, and where w is a 
factor identical with, or proportional to, ordinary mass. 



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456 y. E, MUls 

This statement is intended to hold both for molecular and for 
gravitational force. We could conceive that the total force 
proceeding from a particle was absorbed by one neighboring 
particle (as was done in section 9) at the distance s, and so 
long as we are considering the total acting force or total 
obtainable energy, no error is committed But as a matter of 
fact we know full well that the total attractive force of one 
particle is not confined to a single neighboring particle. How 
then is this perfectly definite force distributed? Certainly 
to all of the particles in the immediate neighborhood, quite 
possibly to every particle of matter in the imiverse; for the 
statement made that equation 27 applies to the gravitational 
force is not to be regarded as necessarily a contradiction of the 
idea that every particle of matter in the universe attracts 
every other particle. It is only to be regarded as necessarily 
a contradiction of the idea that every particle of matter in the 
universe attracts every other particle as if no other particles 
existed. The difference can be made clear by analogy. The 
attractive force is a property of the ether and one molecule or 
body by affecting the condition of this ether may affect every 
other molecule or body. Just as a fat bather at Atlantic 
City may cause the water to rise in the ocean and produce an 
infinitesimal influence extending throughout the entire ocean 
even to a bather at Brighton Beach. But if some sea spirit 
by a process of integration, or otherwise, collects this wide- 
spread influence, he will find it definite in amount, and to 
consist of two factors — a capacity factor determined by the 
size of the aforesaid fat bather, and an intensity factor deter- 
mined by his average depth of immersion. There is just so 
much ocean displacement and if one sea spirit makes use of a 
portion of that displacement he diminishes the total by an 
exactly equivalent amount. The mistake that has been made 
in the interpretation of the gravitational phenomena is not 
necessarily* in the statement that every particle attracts 

* Perhaps the attractive influence is exerted fairly directly, perhaps by 
proxy. It is interesting in thinking of the possible mechanism of the force to 
consider how forces such as electricity, magnetism, osmotic pressure, ordinary 
pressure, etc., become apparent only at a surface. 



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Molecidar Attraction 457 

every other particle, but in the failure to see that this state- 
ment can only be true by the adjustment of a definite influence 
so a^ to include he universe within its scope. If the universe 
were a completely static system quite possibly the attractive 
influence proceeding from a particle would penetrate through- 
out the imiverse and this definite amoimt of attraction would 
be felt by (would be neutralized by) every other particle 
in the imiverse in proportion to its mass and inversely as the 
square of its distance. Newton's law that the force between 

two particles = k — p would be exactly true. But no 

less true would it be that if all of the attraction proceeding 
from the particles were summed up, it would be definite in 

amount and could be expressed by / = ^. Under this 

MM' 
completely static system both Newton's law, / = fe — ^, 

and the modification proposed, / = —7, are equally true, one 

having to do with the totality of the force of the particle w, 
the other having to do with the distribution of this definite 
force. 

If now the million million particles immediately sur- 
rounding m be moved closer to w, the remaining universe 
staying as before, the modified law proposed as governing 
the total force of the particle m would remain unchanged, 
Newton's law governing the distribution of the force could be 
applied as before after the system had become static. But 
it would have to be applied to a new system. The mass of 
all the particles in the universe with respect to m would have 
changed. It might be possible to express this change merely 
as a change in ''W but of this I am very doubtful. The 
particles immediately surrounding m would now absorb more 
of its attraction than they did before. More remote particles 
would absorb less. Such at least is my conception of the 
relation between the usual law of gravitation and the law 
foimd to hold for molecular force. 



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458 /. E. Mills 

21. Fads in accord with the suggested changes. — i. The 
connection between gravitation and mass or inertia is ex- 
plained as being causal, or if one objects to the word ** causal," 
they are merely different aspects of the same phenomenon. 

2. Since from the point of view outlined, mass or inertia 
is a necessary part of the gravitational attraction, the fact 
that the ether itself has no mass in the usual sense and is like- 
wise devoid of attractive force is worthy of note. 

3. It has been long known that ether imder certain 
conditions can react with matter, as evidenced by electrical, 
magnetic, gravitational, molecular, and light phenomena. 
That ether should offer no resistance to the motion of matter 
is an apparent fact that needs explanation none the less 
because scientists try to keep quiet about it. I have here 
suggested that the ether does offer resistance to the motion 
of matter, and that this resistance has to do with the field 
of force surrounding the body. I have shown that the usual 
definition and measure of mass is not independent of, but is 
dependent upon, the surroimding field of force. 

4. Uniform motion in a circle has always proved a stumb- 
ling block.* The usual explanation as to why the ''falling 
body*' does not approach the center is perhaps satisfactory, 
but why the accelerated body does not increase in velocity 
under the action of the constant acceleration (in accordance 
with the law, velocity = acceleration X time) is far more 
difficult to understand. I think perhaps a more satisfactory 
explanation could be given by supposing that increased 
velocity of the body was prevented by the resistance that the 
ether offered to its motion. 

5. A basis is offered for explaining the fact that ap- 
parently gravitational force cannot be shielded, absorbed, or 
deflected, in any way. The idea is that the mass is a relative 
property and changes exactly in proportion to the change 
in the gravitational force. I took care to point out that in a 
vacuum a pound of lead, a gram of aluminum, and a feather 
all fell at the same rate, and that if the mass of lead changed 

• "Science of Mechanism," English translation, page 160. 



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Molecular Attraction 459 

to the mass of the feather during their fall no observation upon 
the motion of the bodies could detect the change. Apply this 
observation in toto to a heavenly body. If by any means 
the mass of one heavenly body with reference to another was 
altered no observation upon the relative motion of the bodies 
could detect the change. 

6. A basis is offered for explaining the fact that ap- 
parently gravitational force is propagated with infinite veloc- 
ity, the explanation lying of course in the fact that the 
infinite velocity is only apparent. The alteration of mass 
and force takes place together and the finite velocity of 
propagation cannot be measured by the supposed method. 

7. The gravitational force cannot be infinitely multiplied 
by the introduction of other particles into the field of force. 
The original field of force is simply readjusted, the total at- 
tractive force of each particle being perfectly definite in 
amount. 

8. The law of gravitation comes into harmony with the 
law of the molecular attractive force. That the two forces 
are identically the same forces I have not yet proved. It 
may later be possible to show some relation between the 
constants of both forces. There are difficulties in the way of 
such identification. Perhaps the real solution of the identity 
lies yet deeper. The chemical force may be the **left over" 
interatomic force; the molecular force the **left over*' chemical 
force; the gravitational the '*left over" molecular force. All 
may be one force governed by the same law — a readjustment 
of a definite force taking place with each combination. The 
fact that the intensity of the force seems to increase enor- 
mously from gravitational to molecular, from molecular to 
chemical, from chemical to interatomic (as judged by radium, 
etc.) lends some color to this supposition. Possibly electrical 
and magnetic forces are different manifestations of this same 
fundamental force — electricity being closely connected with 
the chemical force and magnetism with the molecular force. 

9. It is impossible here to more than mention the 
similarity in the behavior of the electrical force and the 



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460 /. E. Mills 

gravitational-molecular. The electrical force is said to vary 

charfire X charsre 
g^ — ^_ _ ^ jj^^ jjj spite of this fact it is well recognized 

that an electrical charge on a definite particle represents a 
definite amoimt of energy and that the above law — owing 
to the disturbance of the field of force — is not capable of 
indefinite extension. I think electrical and magnetic forces 
could be regarded as following a law similar to the one govern- 
ing the molecular force. 

10. The fact that a body attracts as though its mass were 
collected at its center seems quite possible of explanation 
imder the law of force given. 

1 1 . The fact that chemical changes, and physical changes 
of temperature and energy content, have no effect upon 
weight is, from the point of view given, a matter for some 
surprise. One explanation of this fact has been suggested 
by Comstock.* 

12. The Cavendish experiment, and similar experiments, 
seem to indicate that consistent results under diverse con- 
ditions are obtained by writing the law of attraction, K --, . 

I am not satisfied as to the explanation of these experiments. 
I would only point out here : 

(a) That the experiments were nearly all performed 
with the idea of finding the gravitational constant, and the 
consequent density and weight of the earth, and usually 
without any intention of investigating the truth of the gravita- 
tional law. 

(6) The essence of each experiment consists in the 
determination of the earth's attraction for two masses and a 
subsequent comparison of the attraction of the masses. The 
siibseqtient comparison of the attraction of the masses takes place 
in the earth's field of force, 

(c) If the phenomena of electrical and magnetic attrac- 
tion are considered as parallel phenomena it will be realized 



* Jour. Am. Chem. Soc., 30, 683 (1908). 



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Molecular Attraction 461 

that the conclusion from these experiments, that substances 
attract always as the product of their masses, is yet open to 
much doubt as regards its imiversal application. 

13. Using the usual nomenclature the electrical force can 
be written 

ee' 



_ ^^^ c harge X charge ^ ^, 
The gravitational force can be written similarly, 



Now if the forces are really identical we would have, 

^,. ee' ^^ mm' ee' 

K' — r- = K — ; or , = constant, 

s^ s^ mm' 

a condition which is satisfied if e/m = constant and e'/m' = 
constant. From the point of view expressed in this paper 
the same result is reached yet more simply, the mass and the 
charge being measures of the same quantity in different 
imits. It would seem therefore that the important fact 
that the ratio of the charge of an electron to its mass is a 
constant can be cited as in agreement with the views ex- 
pressed in this paper. 

In conclusion, I desire to say that in making the state- 
ments expressed in this paper I have not been actuated by 
any desire to startle or to change accepted usage. Starting 
originally with a research upon molecular attraction I have 
been led to the ideas expressed above as the best explanation 
of all the facts involved. Many things should be done that 
I have not yet been able to do. Particularly some quan- 
titative method of testing the identity of gravitational and 
molecular forces should be devised. I am anxious to have my 
views corrected where they are wrong and to have them 
developed where they prove to be right. Any criticism or 
help publicly or privately given will be greatly appreciated 
by the author. 

22. Summary, — ^Attention is called to a law recently 
discovered by the author governing molecular attraction. 



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462 /. E, Mills 

The significance of this law is discussed and the law of the 
force deduced from it is compared with the law of the gravita- 
tional force. Careful examination of the facts would seem 
to indicate that perhaps the laws of gravitational and molec- 
ular force should be identical. It is shown that the gravita- 
tional law as proposed by Newton cannot apply to the molec- 
ular force and it is suggested that Newton's statement of the 
law of gravitation should be modified so as to become / = 

—^, when the total force of mass m is considered; that is, 

gravitational attraction should be regarded as a definite 
property of matter, and not as a property indefinitely de- 
pendent upon the product of the masses. The evidence for the 
law of gravitation as stated by Newton is discussed and the 
difficulties involved in the usual view of gravitation are pointed 
out. 

Incidentally the other attractive forces, chemical, elec- 
trical, and magnetic, are discussed. The view is taken that 
possibly all of these forces are identical in origin and char- 
acter. It is thought that the mass of a body is proportional 
to the attraction exerted by it and that mass is a relative 
and not an absolute property of matter. The bearing of the 
ideas suggested upon a few points is briefly discussed. 

Camden ^ S. C, 
September ly, 1910 



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APATITE AND SPODIOSITE' 



BY FRANK K. CAMERON AND W. J. MCCAUGHEY 

Apatite is a constituent of all rocks. ^ Consequently its 
presence, to some extent, should be expected in every soil, 
and this expectation has been confirmed by the microscopic 
examination of a large number of samples of various types 
from many parts of the United States.' It is slightly soluble 
and is hydrolyzed by water, the natural apatites yielding an 
alkaline solution but one also containing phosphoric acid. 
It has therefore an importance in soil investigations. It is 
a carrier of an essential plant nutrient and it is often a guide 
to the genesis of a particular soil. In the investigation* of 
the phosphates of lime which is in progress in this laboratory, 
apatite is being studied, and in this paper attention is directed 
to some observations which have been made upon this com- 
pound and the related substance, spodiosite. 

Apatite has been reported as made artificially in several 
ways: by the action of phosphorus trichloride on caustic 
lime,^ by passing hydrochloric acid over red hot tricalcium 
phosphate,® by melting tricalcium phosphate in sodium 
chloride,' and by melting tricalcium or trisodium phosphate 
in calcium fluoride or a mixture of these salts.* It has also 

* Published by permission of the Secretary of Agriculture. 

^ Rosenbusch u. Wulfing: Mikrosk. Physiog. Min. u. Gest., 4 Auf. Bd. I, 
H. 2, 108 (1905); Emmons: Economic Geology, 3, 611 (1908). 

' From the