954 



Dr. S. A. Shorter : Contribution to the 



has been obtained previously and tested experimentally *. 

 A similar equation will evidently apply to the case of a 

 single solid component in equilibrium with a solution in a 

 solvent medium containing any number of components. 



We will now consider the relation between solubility in- 

 fluence and vapour pressure. Let us first assume that C 

 and Cx are volatile and 2 is involatile — a case often occurring 

 in practice. We will assume that the binary vapour mixture 

 obeys the partial pressure law. From equations (39), (10),. 

 and (28) we obtain the relation 



1 ds 2 



s 2 d$i 



Vim**) 



B*2 



v (n , 0)^+^(^,0)^ 



(46) 



If we assume that the vapours obey the ideal gas laws, and 

 if we introduce the molecular concentrations, the above 

 equation reduces to 



a log iii 



i_ac 2 



c 2 dci 



dc 2 



d log Qo d log fli 

 "dc 2 "dc 2 



(47) 



c 2 — c 5 



where c 2 is the molecular saturation concentration. 



There are no experimental data available for the quanti- 

 tative verification of the above theory. The theory is verified 

 qualitatively, however, by the experiments of Kablukow, 

 Solomonow, and Galine f, who have investigated the effect 

 of the addition of various salts on the pressure and composi- 

 tion of the vapour of mixtures of alcohol and water. These 

 investigators find that the partial pressure of the alcohol is 

 raised by the addition of potassium chloride, bromide, and 

 iodide, but lowered by the addition of mercurous chloride. 

 Now the addition of alcohol raises the solubility of the last 

 of these salts, but lowers the solubilities of the others. These 

 facts are, of course, in agreement with the above theory J. 



If only the component C is volatile, we can deduce only 

 qualitative relationships between solubility influence and 

 vapour pressure. If the addition of Ci lowers the solubility 



* See Duhem, loc. eit. vol. iii. p. 129 ; Braun, Wied. Ann. xxx. p. 250 

 (1887) ; von Stackelberg, Zeit.fur Phys. Chem. xx. p. 337 (1896). 



t Zeitsch.fur Phys. Chem. xlvi. p. 399 (1903). 



X This qualitative relationship, which is perhaps not readily apparent 

 from equation (47), is easily deduced from general considerations or from 

 equations (28) and (39). s 



