20)6 



Conductivity of Aqueous Solutions. Part IX. 



From the values of the hydrolysis and ionization given in tables 123 

 and 124, the hydrolysis-constant Kn (equal to %l ) can be readily 



calculated by the mass-action relation 



K 



A 7 h, in which h 



(1 K)7 



represents the hydrolysis of the salt in water alone at any concen- 

 tration C , y is the fraction of the unhydrolyzed salt C (1 h ) which 

 exists as ions, and 7<w, -Ka and Kb are the ionization-constants for 

 water, the acid, and the base, respectively. This equation is readily 

 derived by combining the three simple mass-action equations, ChCoh =K-w, 

 Ch Ca = K aCha, and Cb Coh = ^bCboh, substituting for Cb and C\ the 

 expression C (l h )y and for Cha and Cboh the expression C h , and 

 taking the square root. The values of the hydrolysis constant A' H thus 

 calculated are given in table 125. The values at the two concentrations 

 will be seen to differ by from 12 to 9 per cent. As those at the higher 

 concentration are influenced to a less extent by impurities and contami- 

 nation, a double weight has been assigned to them in deriving the final 

 mean values. It is not improbable that these values are still too high ; 

 but it is unlikely that the error exceeds 5 per cent. 



Table 125. The hydrolysis-constant for the ammonium salt. 



104. THE IONIZATION OF WATER. 



The ionization-constants of water (Kw = Cn Coh) can be calculated 

 from the hydrolysis-constants given in table 125, and the ionization- 

 constants of the acid and base given in section 102. Table 126 contains 

 the values of this constant for water, and also those of its square-root, 

 which last represent the concentration of the hydrogen and hydroxide 

 ion in pure water (in equivalents per liter). 



Table 126. The ionization-constaut of zvater and the 

 hydrogen or hydroxide-ion concentration. 



