HOMOGENEOUS IONIC EQUILIBRIA 225 



the electrolyte on the ionization constant of water. The results of the 

 various methods are summarized in the following table. 



TABLE LXXXIV. 



THE HYDROGEN-ION CONCENTRATION (X 10 7 ) IN PURE WATER AS DETER- 

 MINED BY VARIOUS INVESTIGATORS. 



Investigator Method of Determination 18 25 



Arrhenius ...... Hydrolysis of sodium acetate by 



ester-saponification ................. 1.1 



Wijs ........... Catalysis of ester by pure water ........ 1.2 



Nernst ......... Electromotive force of gas cell ...... 0.8 



Lowenherz ..... Electromotive force of gas cell ......... 1.19 



Kohlrausch and 

 Heydweiller . . Conductance of pure water ....... 0.36 0.80 1.06 



Kanolt ........ Hydrolysis .................... 0.30 0.68 0.91 



When a salt is dissolved in water, interaction takes place between 

 the ions of the salt and the ions of water with the resultant formation 

 of un-ionized molecules of acid, or of base or of both, depending upon 

 the strength of the acid and the base. Assuming the law of mass-action 

 to hold in the mixture for both acid and base, and assuming that the 

 salt is highly ionized and that its ionization function is known and is 

 the same in the mixture as it is in a solution of the salt alone, the con- 

 centration of the various constituents in the mixture may be obtained 

 from a solution of the reaction equations: 



H+ X X- = # 

 (53) M + X OH- = 



and the condition equations: 



MX + HX + X- = C a , 



(54) MX + MOH + M+ = C 6 , 



M+ + H + = X- + OH-, 



where K a , K^ and K W are the ionization constants of acid, base, and 

 water, respectively, and C a and C^ are the total concentrations of acid 



and of base, and the other symbols represent the concentrations of the 

 various constituents concerned in the reaction. Let us assume that the 

 acid is stronger than the base, in which case H + is greater than OH~. 

 Let Y represent the fraction of base present in the form of ions. Since 



