952 



Dr. S. A. Shorter : Contribution to the 



Hence, i£ the addition of Ci raises not merely the solubility 

 of C 2 , but also the ratio of this solubility to the concentration 

 of d, the addition of C 2 raises the chemical potential of C . 

 An example of this is afforded by the system water (C ), 

 zinc chloride (.Ci), and zinc oxide (C 2 )* (except in the case 

 of very large values of sj , as will be seen from Table II. 



Table II. 

 Ordinary Temperature. 



100 s r 



100 s a . 



S 2 /V 



8-22 



•0137 



•0017 



23-24 



•138 



•0051 



51-5 



•604 



•0117 



569 



•723 



•0127 



62-85 



•884 



•0141 



96-00 



1-792 



•0186 



144-8 



2-64 



•0182 



2030 



1-59 



•0078 



We have thus three cases of solubility influence : — 



(1) Solubility Lowering : the addition of C x to the two- 



phase system precipitates C 2 , the addition of C . 

 causes more 2 to dissolve. In this case S 01 -<0, 

 S 02 <0, and S 12 >0. 



(2) Solubility Raising : the addition of Ci causes more 



C 2 to dissolve, the addition of C precipitates C 2 .. 

 In this case S i<0, S 02 >0, and S 12 <0. 



(3) Solubility Raising : the addition of either C or C\ 



causes more C 2 to dissolve. 



If C and Ci are perfectly miscible liquids, the distinction 

 between cases (1) and (2) is merely an arbitrary one depend- 

 ing on which component is called the solvent. 



The system water (C ), hydrochloric acid (Cj), and lead 

 chloride (C 2 ) affords an example of each of these three cases f. 

 For small values of s l9 'ds 2 /'ds 1 is negative, but becomes 

 positive for higher values of s 1? and increases still more as 

 Si increases. Hence from the value s 1 = to the value at 

 which s 2 is a minimum, we have case (1) ; from this latter 

 value to the value at which s 2 /si is a minimum we have 

 case (3); for still higher values of sj. we have case (2). 



* Annual Tables, vol. i. (1910;, p. 399 (1912). 

 t Kothmund, loc. cit. p. 176. 



