800 REPORTS ON THE STATE OF SCIENCE.—1912. IL.z. 
1911 The following mathematical formula was deduced by 
* Prud’homme *1* for calculating the solubility of sparingly soluble 
salts from conductivity measurements. If V represent the dilution of 
the salt when ionisation becomes complete, v the dilution of a saturated 
solution, and Ay and A, the respective molecular conductivities at 
those dilutions, then 
u 
A ey A v = (~) x, 
v 
in which n is approximately equal to 3°06. 
B.—Solubility of Liquids. 
Change of volume usually occurs when two liquids are mixed 
1g9g. “gether, and on this fact Herz*® based a method of deter- 
* mining the solubility of liquids in each other. A similar method 
1906. 28 used by Rea,*** by which he estimated the solubility of 
’ halogen derivatives of hydrocarbons in water. He shook 
together known volumes of liquid and water in a graduated vessel, and 
observed the volumes before and after agitation. 
1907 For measuring the reciprocal solubility of liquids 
* Dubroca** has used the method of heating known weights 
of two liquids together and observing (1) the temperature at which 
two layers cease to exist, and (2) the temperature at which, on cooling, 
two layers appear. The mean of these results is taken as the tempera- 
ture at which the mixture of known composition was stable in presence 
of its components. 
1911 Grosschuff *1® determined the solubility of water in various 
* solvents as follows: Known quantities of water and dry solvent 
were heated together in a closed glass bulb until all the water was 
dissolved; the bulb was then cooled until a cloud formed within the 
solution, when it was again warmed and the temperature observed 
at which the cloudiness disappeared. From such data the solubility 
was calculated. 
C.—Solubility of Gases. 
During the period dealt with in this part of the Report compara- 
tively little was done which involved the use of gaseous solutes, and 
for the most part the methods adopted were those which had been 
used generally in earlier work. 
1996 A somewhat novel form of pressure tube was described by 
‘ Walter,** which can be used equally well for determining the 
solubility of either gaseous or solid substances in liquids at high 
temperatures and pressures. 
1897 Roth ?® made use of a form of apparatus which was 
Se". essentially the same as that suggested by Ostwald, which has 
been described and used by Timofejeff * and by Gordon. + 
Slight modifications of this apparatus were sometimes introduced, 
such, for example, as that used by Brawn,’* who reduced the length 
* Zeitschr. physi’al Chem. [1890], 6, 141. 
+ Ibid. [1895], 18, 1. 
