HETEROGENEOUS EQUILIBRIA 245 



spondence found between the values of y^ an d Y c m aqueous solutions 



appears, therefore, to be a property of electrolytic solutions in other 

 solvents also. 



3. Solubility of Non-Electrolytes in the Presence of Electrolytes. 

 The solubility of non-electrolytes in water is, in the majority of cases, 

 depressed by the addition of an electrolyte. The effect of the added 

 electrolyte on the solubility depends upon the nature of the substance in 

 question, as well- as upon that of the added electrolyte. If reaction takes 

 place between the two, the solubility is naturally influenced by this 

 reaction. 



For certain substances, the solubility is very nearly a linear function 

 of the concentration of the added salt, in which case it may be expressed 

 by the equation: 



(62) S = S + BS C 



where S is the solubility of the non-electrolyte in pure water, S is the 

 solubility in the presence of the salt at the concentration C, and B is the 

 solubility coefficient, which is a constant if the solubility varies as a 

 linear function of the concentration. In general, however, the solubility 

 function is not a linear one. The change in the solubility for a given 

 addition of electrolyte is, as a rule, the greater the smaller the amount of 

 electrolyte added. The solubility is more accurately expressed by the 

 equation: 



q 



.(63) log -=- = PC, 15 where p is a constant. 



O 



In the following table are given values for the solubility of hydrogen 

 in aqueous solutions of different electrolytes. 18 In pure water, the solu- 



TABLE XCIII. 



SOLUBILITY OF HYDROGEN IN AQUEOUS SOLUTIONS OF ELECTROLYTES AT 

 DIFFERENT CONCENTRATIONS AT 25. 



C= 0.5 1 2 3 4 



CH 3 COOH ......... 0.0192 . 0.0191 0.0188 0.0186 0.0186 



CH,C1COOH ...... 0.0189 0.0186 0.0180 ........ 



HN0 3 ............. 0.0188 0.0183 0.0174 0.0167 0.0160 



HC1 ............... 0.0186 0.0179 0.0168 0.0159 ____ 



H2 4 ............. 0.0185 0.0177 0.0163 0.0150 0.0141 



KOH .............. 0.0167 0.0142 ........ 



NaOH ............. 0.0165 0.0139 0.0097 0.0072 0.0055 



"Rothmund, Ztschr. f. Electroch. 7, 675 (1901) ; Ztschr. f. phys. Chem. 69, 524 

 (1909) ; Nernst, ibid., 38, 494 (1901). 



"Geffcken, Ztschr. f. phys. Chem. 49, 257 (1904). 



