224 HYDROGEN ION CONCENTRATION 



The simplest case to be had is that in which but one diffusible 

 electrolyte is present, such as 



According to the principle developed above the right to left ratio 

 of the H+-concentrations, must be equal to the left to right 

 Cl~-concentration ratio, thus: 



[H+]2 [Cl-ji 



[H+]i [Cl-]2 



But since on the right side [H+]2 = [Cr]2, it follows that 



[H+[! = [Cii? = [H+]i X [Ciix (1) 



Let us now see how we can define more closely the distribution of 

 ions in the simplest possible case. Let us take this system: the 

 solution inside of a collodion thimble is that of a chloride of a non- 

 diffusible, but molecularly dispersed, base in concentration a. 

 Also, the H+ and Cl"~ ions are present in this inner solution in the 

 concentrations hi and ch. In the outer solution we have HCl in 

 the concentration h2 = CI2, but no "colloid" is present. The elec- 

 trolytes are assumed to be completely dissociated. The values h2 

 = CI2 are known while hi and ch are taken as the unknown values. 

 The following relations exist : 



^& 



and also 



a + hi = cli 

 hi = CI2 

 hi _ CI2 

 h2 cli 



a + hi = cli (1) 



hi . cli = ch^ (2) 



From (1) and (2) the following quadratic equation for ch is 

 obtained : 



cU* - a cli - cl2« = 



ff 



cli = ^ + Vt + ch^ (3) 



