POTENTIALS AT PHASE BOUNDARIES 203 



Since the conductances are here closely proportional to the concen- 

 trations, it is hence demonstrated that distribution law is appHc- 

 able to the partition of sodium salicylate between an oil and an 

 aqueous phase. Consequenth^ no concentration effect can arise. 



On the other hand, when dimethylaniline-HCl was used in such 

 a chain the relations were as follows: 



conductance 



Salicylic aldehyde shaken with 1 molar aqueous solution 



of dimethylaniline-HCl 78 r.m. 



Salicylic aldehyde shaken with 1/50 molar aqueous solu- 

 tion of dimethylaniline-HCl 19. 9 r.m. 



In this case, while the aqueous concentrations were in the ratio 

 of 1 :50, the ratio of the ionic concentrations in the oil phase was 1 :2.5, 

 i.e., the distribution law did not apply here. The ionic content 

 of the oil phase remained constant and unaffected by the concen- 

 tration in the external aqueous phase. 



The same conditions are true for Haber's glass chain. Here 

 the common ion is the H-ion, whose presence in the glass is probably 

 due to the dissociation of the traces of contained water. But since 

 only the pure water, and not the dissolved electrolytes, penetrates 

 into the glass, the H+-concentration of the glass remains constant 

 and unaffected by that of the aqueous phase. 



The case of the usual concentration chain may also be interpreted 

 in the same sense. Being given two phases, viz., metallic silver 

 and an aqueous solution of AgNOs, it may be said that the silver 

 contains freely motile electrons (since it possesses the metallic 

 property of conductivity), and hence it may be said to contain 

 "Ag-ions." The metal represents, as it were, a phase consisting 

 of a silver salt, whose cation is Ag"'"and whose anion is its free electron. 

 The aqueous solution, on the other hand, contains only Ag- and 

 NOs-ions, the electrons do not penetrate into the water phase, they 

 are "not water-soluble." Therefore the concentration of "Ag- 

 ions" in the metal is independent of the Ag+-concent ration in the 

 solution and is invariable. Hence a metal must yield a maximal 

 concentration effect, when it is arranged in the order of an oil 

 chain. The E.M.F. of the chain 



AgNOa 

 Cx 



Metallic I AgNOa 



Ag I C2 



