HOMOGENEOUS IONIC EQUILIBRIA 229 



represents an upper limit and it is possible that the true value may be 

 much below this limit. The high value of the ionization, however, ren- 

 ders any precise determination of the limiting value of the mass-action 

 function uncertain, and, indeed, if conductance data alone are considered 

 it is even uncertain that a definite limit greater than zero is approached. 4 * 

 The strong acids and strong bases are ionized to practically the same 

 extent at higher concentration ; and if the ionization functions in the case 

 of these two types of electrolytes approach the same limits at low con- 

 centrations, the conductance of a salt as measured will be found some- 

 what lower than the true value if hydrolysis becomes appreciable. On 

 the other hand, if the functions of acid and of base approach values which 

 differ considerably, then the result will be to increase the conductance of 

 the solution above that of the unhydrolyzed salt. If, for example, the 

 ionization constant of the acid relative to that of the base were 10~ 3 , 

 then, at a salt concentration of 10~ 5 N, the hydrolysis would have a value 

 of 0.95 X 10" 3 or approximately 0.1 per cent, which would raise the con- 

 ductance of the solution approximately 0.3 per cent. In view of the 

 entire lack of experimental data relating to the limiting values of the 

 ionization constants of the strong acids and bases, conductance measure- 

 ments with salts at concentrations below 10~* normal cannot be inter- 

 preted with certainty. 



In solutions of salts of weaker acids and bases, hydrolytic equilibria 

 appear to be fairly well established. This lends support to the view that 

 the ionization constants of the weaker acids and bases, as well as that 

 of water, are not materially affected by the presence of larger amounts 

 of salt. The agreement of the values for the ionization constant of 

 water as determined from a measurement of the conductance of solutions 

 of salts of weak acids and bases, with that as determined by other 

 methods, indicates that the fundamental assumptions underlying the 

 theory of hydrolytic equilibria are substantially correct. In these equi- 

 libria, the ionization of the salt is involved. If, as some assume, the 

 salts are completely ionized at all concentrations, then the ionization y 

 of the salt should vanish from the hydrolysis equation, which would 

 materially affect the values obtained for the ionization constant of water. 

 At the present time, however, data making such a comparison possible 

 are not sufficiently precise to enable us to draw any certain conclusions. 



Among other typical equilibria involving electrolytes are those in 

 which a strong acid or a strong base is partitioned between two weaker 



" Naturally, if this view were adopted, it would be necessary to recast our notion* 

 relative to the nature of electrolytic equilibria. 





