V.B. ON SOLUBILITY. 819 
found to be increased by pressure, whereas under similarly changed 
conditions the solubility of ammonium chloride was decreased. 
The non-obedience to Henry’s law of solutions of carbon dioxide 
in water was attributed by Jakowkin* to the existence of double 
molecules of solute—(CO,),—when in the gaseous state, and of only 
simple molecules—CO,—when dissolved in water.* 
1997. . From the observations of Spezia *? it would again appear that 
* imcrease of pressure does not always occasion an increased solu- 
bility. In the case of quartz this author could detect no change in 
weight of the solute after it had been kept in water at 27° for several 
months under a pressure of some 1,800 atmospheres. 
1900 From the fact that solutions of ammonia in aqueous salt 
solutions do not obey the Henry-Dalton rule of partial pressure, 
Konowalow 7* came to the conclusion that the ammonia enters into 
combination with the salt in solution. 
Increase of pressure was found by Van der Lee™ to raise the 
critical temperature of complete miscibility of phenol and water, a result 
which is quite in harmony with Van der Waals’ theorem when applied 
to solutions. + 
190 Cassuto '*1 gave results of measurements of solubility of 
oxygen, hydrogen, nitrogen, and carbon monoxide in water when 
under pressures varying from 1 to 10 atmospheres. He showed that 
between 19.5° and 23.4° C. Ostwald’s coefficient of solubility + for 
oxygen and nitrogen decreases more rapidly than the pressure increases. 
At pressures near to the atmospheric pressure the solubility coefficients 
are nearly constant for constant temperatures. 
1909 Cohen and Sinnige *°° °° studied the influence of pressure 
* upon the solubility in water of the salts CdSO,,8/3H,O and 
ZnSO,,7H,O; the range of pressure being from 1 to 1,000 atmospheres. 
An increased pressure was found to produce a marked increase of solu- 
bility with the cadmium salt but quite a slight decrease in that of the 
zinc salt. 
With regard to the influence of pressure upon the mutual solubility 
of a pair of liquids, work similar to that recorded by Van der Lee § 
was carried out by Timmermans,*** who showed that in general a 
pair of liquids may be made to pass through all stages of miscibility 
by varying the external pressure. It is thus possible to pass con- 
tinuously from dilute to concentrated solutions by simply varying the 
pressure. On this basis the author proposed to elaborate a theorem 
by applying to concentrated solutions conceptions similar to those of 
Van der Waals. 
1910 Continuing his work on the influence of pressure upon solu- 
* bility, Cohen,*** with Inouye and Euwen, found that the 
solubility, both of sodium chloride and of mannitol, steadily increases 
as the pressure is increased from 1 to 1,500 atmospheres, the total 
solubility-incréase being about 5 per cent. 
* See also Section VI. + Vide Part I., R. 181. 
{ Ostwald’s coefficient of solubility r=¥, in which v=volume of liquid which 
dissolves volume V of gas at known temperature and pressure. 
§ Vide this Section 1900. 
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