i86 



Conductivity of Aqueous Solutions. Part VI. 



The excess of the second value over the first value gives the un-ionized 

 salt, AC(1 y h), that has been produced out of free acid and base: 

 this added to the quantity (ACy) of ions similarly produced gives the 

 quantity of salt in the hydrolyzed state when it is alone present in water; 

 and this divided by the concentration (C) gives the fraction hydrolyzed 

 (h ). The results of the computations are given in table 68. 



Table 68 -Hydrolysis of ammonium acetate and ionization-constant of zvater at 100. 



It will be seen from table 68 that the hydrolysis h is only a little 



greater at 10 than at 25 milli-normal. From each of these values the 



ionization-constant of water (Kw =ChX Con) has been calculated, and 



the results are given in the last column, the concentration being here 



expressed in equivalents per liter. The calculation was made by means of 



h 2 . 

 the mass-action expression K-w = KaKb in which Ka and Kb are the 



ionization-constants of the acid and base respectively, and h and y are the 

 hydrolysis and ionization of the salt in water alone. This expression is 

 readily obtained by multiplying together the two ionization-equations 



ChCa i jy CbCoh 



K-a and A B ~c~Z~~ , substituting iw for Ch X Coh, yCs for Ca 



and for Cb, and Cs,h for Cha and Cboh, and transposing. It will be noted 

 that the two independent values of K\? agree almost completely. 



In order to calculate the hydrolysis at 156 from the conductance data it 

 is necessary, since the hydrolysis is not reduced to zero even by the largest 

 quantity of acid or base added, to unite with the empirical relation between 

 the concentrations of ions and un-ionized molecules, the mass-action 

 relation between the concentration of the ions and the products of the 

 hydrolysis. These two expressions, if y represents the fraction of the salt 

 existing as ions and h the fraction hydrolyzed into free acid and base and 

 Cs and Cboh are the concentrations of the salt and of the added base (or 

 acid) respectively, are 



(yCs)" 



and 



C s (l y h) 



(yCs 2 ) 

 (Cboh -\-C s h)C$h 



= const. 



K A K: 



1 +/*v 



K 



<TC7 



\v 



(1) 



const (2) 



