190 HYDROGEN ION CONCENTRATION 



and hence 



RT , ci • a RT , ci . /5 



TT = -—- in = — In 



F Co F cj 



Therefore, whenever a = ^, then tt = 0. 



By determining analytically (by conductivity measurements or 

 similar methods) Ci and C2, we derive the following two equations de- 

 fining the three quantities, t, a and /S: 



RT ci ' a 



TT = -— - In 



F C2 



Ci • a C2 „ C2 ^ / 



= y/ a • p 



or 



C2 ci |8 ci 



If we compare the former equation 



RT , ci RT , k2 



TT = — In — — In -- 



F Co F ki 



with the present equation which we will now write in the form of 



RT , ci , RT , 



we see at once that 



k2 



— = ot 

 ki 



and that likewise for the second ion-species it is 



ki 



Thus we see that the distribution coefficient of an ion-species 

 bears a definite, and a thermodynamically calculable, relationship 

 to the above defined values k2 and ki. 



This principle can be restated as follows: 



The oil-solubility (in terms relative to water-solubility) of an ion- 

 species bears a thermodynamically deducible relationship to its elec- 

 trolytic solution tension in the oil. A truly amazing conclusion! 



The relation of solubihty to electrolytic solution tension can also 

 be derived in the following way: 



