850 



SCIENCE 



[N. S. Vol. XLII. No. 1094 



ticular, the effect of sodium sulphate on 

 the "melting point" of hydrated sodium 

 ehromate, and the effect of strontium bro- 

 mide on strontium chloride, were both care- 

 fully studied. 



Another investigation allied both to that 

 just mentioned and to the work on com- 

 pressibility, is the effect of pressure upon 

 the solubility of salts. Theoretically as 

 well as experimentally this is not a new 

 subject, but there is still great need for the 

 procuring of accurate data. A small but 

 practicable apparatus was devised, making 

 possible the determination of this effect as 

 far as 600 atmospheres pressure, and pre- 

 liminary results have already been obtained 

 upon a number of typical salts. These in- 

 vestigations also are still being continued. 



Turning now to the electrochemical side 

 of our activities: during the past three 

 years we have studied anew the precautions 

 necessary in order to determine exactly the 

 weight of silver deposited from its solu- 

 tions by the galvanic current — a problem 

 which has a distinctly practical bearing, 

 in that the weight of deposited silver is one 

 of the most satisfactory measures of the 

 quantity of electricity flowing through the 

 solution. There can be little doubt that 

 this weight is in precise accord with the de- 

 mands of Faraday's law of electrolysis, 

 that is to say, is directly dependent upon 

 the atomic weight of silver; but disturbing 

 circumstances enter into the actual deter- 

 mination and one of the most important 

 outcomes of this work was to show once 

 more that the silver under some circum- 

 stances may carry down with it appreci- 

 able amounts of the solution from which it 

 was deposited, thus increasing its appar- 

 ent weight and leading to a somewhat er- 

 roneous estimate of the relation between 

 quantity of electricity and quantity of 

 substance. This investigation is being eon- 

 .tinued not only at this laboratory, but also 



at the Bureau of Standards and at Prince- 

 ton University. 



The electromotive forces manifested by 

 metals and amalgams in appropriate solu- 

 tions have a significant bearing on the 

 energetic side of chemistry, being con- 

 cerned not only with the important effect 

 of concentration on chemical change, but 

 also with chemical affinity itself. On this 

 account these electromotive forces have not 

 been neglected in the Gibbs Laboratory, 

 the behavior of concentrated thallium amal- 

 gams and alloys of sodium and lead having 

 received attention. The interesting details 

 of these experimental researches are too 

 technical and too elaborate for a brief 

 statement of this kind. 



Yet another electrical phenomenon in- 

 vestigated was the dielectric behavior of 

 non-conducting organic substances. The 

 dielectric constants of nearly a score of 

 very pure organic substances were deter- 

 mined by means of a modification of a 

 standard method, which was improved and 

 made much more sensitive and accurate. 



In keeping with the plan to study and 

 compare all the important physical prop- 

 erties of typical chemical substances, the 

 densities, melting points and boiling points 

 of many substances mentioned above, which 

 had been purified with very great care, 

 were determined, taking pains about accu- 

 racy in the thermometric measurements 

 not usual in chemical laboratories. It is 

 especially interesting, in view of the diffi- 

 culty of complete purification, to have all 

 these various properties determined on the 

 same uniformly pure samples of material, 

 so that the true correlation between the 

 different properties can be discovered; for, 

 obviously, if one sample containing one 

 set of impurities is used for determining 

 density, and another sample with another 

 set of impurities is used for determining 

 the boiling point, any relation which may 



