100 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



The conductance of potassium chloride solutions between the concen- 

 trations of 10'* and 2 X 10~ 5 normal may be represented well within the 

 limits of experimental error, by means of the Equation 11 23 in which 

 the constants have the value: ra = 0.52, D 1.703, A = 129.9, and 

 K = 10 X 10- 4 . Washburn's value for K is 200 X lO' 4 . Actually, this 

 represents an upper probable limit for the value of the constant K. 

 The value 10 X 10~* would appear to be too small. Salts in the alcohols 

 have values of the mass-action constant considerably greater than this. 

 Since, in general, the value of the mass-action constant increases with 

 the dielectric constant, we should expect that the value of this constant 

 in the case of aqueous solutions would be greater than in the alcohols. 

 It should be noted, however, that the experimental results might still 

 be represented within the limits of experimental error if a value con- 

 siderably greater than 10 X 10~ 4 were assumed for the mass-action con- 

 stant. It is possible, therefore, that the salts in water may have a value 

 of the mass-action constant as high as 100 X 10'*. On the other hand, 

 so far as the actual data are concerned, it cannot be definitely demon- 

 strated that the mass-action law is approached as a limiting form in 

 aqueous solutions of strong electrolytes. Even the value of 200 X 10~ 4 

 for potassium chloride appears to be distinctly lower than the value of 

 the constants for certain much weaker electrolytes in aqueous solution, 

 as, for example, acids of intermediate strength. 



In the case of the strong acids and bases, sufficient data are not 

 available to determine the order of magnitude of the limit which the 

 function K' approaches. If the data relating to hydrochloric acid are 

 correct, the ionization of this acid in a 10~ 4 normal solution is as low 

 as that of potassium chloride at the same concentration, assuming that 

 the value of A for hydrochloric acid is 380.0. Actually this value of 

 A is somewhat too low and the value 382.0 is probably more nearly 

 correct. It would appear, therefore, that the strong acids may approach 

 a value of the mass-action constant as low or lower than that of the 

 salts; or, in other words, values lower than 200 X 10~ 4 . No data are 

 available from which the ionization of the strong bases may be calculated 

 at low concentrations. 



The limiting values which the ionization constants of the strong acids 

 and bases approach at low concentrations is of considerable practical 

 importance, since the hydrolysis of salts depends upon the relative values 

 of these constants and that of water. If the values which the mass- 

 action constants of the bases and acids approach at low concentrations 

 are sufficiently small, then the salts of these acids and bases will be 



Kraus, Joe. cit. 



