850 REPORTS ON THE STATE OF SCIENCE.—1912. VII. 
The complex problem presented by the dissolution of homogeneous 
1uixtures was investigated by Thiel.'*t He distinguished five different 
cases, gave examples of each, and considered how the solubility varies 
with the composition of the solid mixture. 
McLauchlan *** attempted to explain the results of his work on solu- 
bility influence* on the basis of chemical interaction taking place in 
solution. 
Determinations of distribution coefficients carried out by Vawbel 187 
led that author to conclude that the abnormalities he observed were due 
to the formation of hydrates in solution. 
The opinion is held by some chemists that, in the case of slightly 
soluble substances, electrical conductivity may be regarded as a measure 
1904 of solubility,} and for the purposes of such calculations Kohl- 
* rausch published a large number of conductivity measurements. } 
Gardner and Gerassinoff 1®° pointed out that in the case of salts which 
are easily hydrolysed the above assumption is not true, and in support 
of their statement quoted the fact that the conductivity of barium car- 
bonate is lowered by the presence of sodium hydroxide, whereas that of 
barium sulphate remains unchanged. 
When a gas dissolves in a liquid, Henry’s law is obeyed provided the 
gas is not dissociated in solution, or if it associates with the solvent, it 
does so in such a manner that each aggregate contains only one molecule 
of the dissolved gas.§ For those cases in which the gas is dissociated 
in solution Richardson ?‘* arrived at a suitable equation for calculating 
the solubility: a mathematical expression correlating variation of solu- 
bility with change of temperature was obtained, which is dependent 
solely on the difference of the heats of solution of the dissociated and un- 
dissociated gas. 
Schirr *** investigated the problem of the rate of dissolution of salts. 
Tn his studies, all but one of the crystal facets of the solute were covered 
by paraffin, || and he was able to detect three different periods of dis- 
solution. The rule of Noyes and Whitney was found to be true only 
for sparingly soluble substances. In the following year Bruner and 
1905 Tolloczko*** criticised these suggestions and reaffirmed the 
“~“* formula proposed by Noyes and Whitney. 
On the basis of Jahn’s theory, Hoffman and Langbeck ?°° derived 
formule from which it is possible to calculate the effect of various elec- 
trolytes and non-electrolytes upon the solubility in water of benzoic and 
allied acids. 
In addition to the many attempts made to arrive at a mathematical 
expression which would properly represent solubility relationship for 
more than a few chosen cases, a good deal of attention centred on the 
association theory of solution. Lowry ?** attempted to extend the con- 
* Vide V. ¢. ii. 
+ From time to time attempts have been made to compute the degree of dis- 
sociation from solubility graphs—vide Kremann (Monatsh., 25, 1215; Zeitschr. Elektro- 
chem., 12, 259) ; Roozeboom and Aten (Zeitschr. physikal. chem., 53, 463); Van Laar 
(Proc. K. Akad. Wetensch. Amsterdam, 8, 699); Findlay and Hickmans (J. Chem. 
Soc., 91, 905). t Vide II. R. 203. 
§ Vide Van’t Hoff’s Lectures on Theoretical Chemistry, Part II., p. 28. 
|| Vide Part I. R. 56 and 59. 
