Section 73. Hydrolysis of Ammonium Acetate. 187 



Or, representing by y and h the ionization and hydrolysis of the salt 

 when in water alone, and by y 1 and h x these same quantities when the con- 

 centration of the salt is the same, but base (or acid) is present in excess 

 at a concentration Cboh, and writing- r for Cboh/Cs we have : 



(I>y = i-r.-^ w and rz\' = *>(r + >.) 



\y/ 1 y /t \y / h 2 v y 



two simultaneous equations which can be solved for h and h since the 

 other quantities may be derived from the measurements. Thus the ratio 

 Yi/yo is equal to Lba/ls (see table 67), and the separate values of y 1 and 

 y are given by the quotients Lba/CsA and Ls/CsA , A being equal to 523. 

 For the exponent n we assumed provisionally the value 1.5, which is 

 that for sodium acetate at this temperature (see section 55, Part V) ; but 

 after the hydrolysis had been computed for the two different salt-concen- 

 trations it was obtained by direct application of equation (1) to the mean 

 of the two sets of results, and was thus found to be 1.45; and with this 

 new value of n the calculations were repeated, although this variation in n 

 produced a decrease in h of only 0.7 per cent of its value both at 23.68 

 and at 9.473 milli-normal. Equations (3) and (4) can be completely 

 solved algebraically for h x or h ; but it is far simpler to use only the 

 incomplete solution obtained by taking the logarithm of equation (3) and 

 eliminating h from it by means of equation (4), whereby results the 

 expression : 



log 1 ~ yi ~ 7 ' 1 =(n 1) log A . 



(1 Yo)' h VHr + h) y 



yo 



This equation can be readily solved for h x by trial, and h can then be cal- 

 culated by (4). 



The results of the calculations are given in table 69. The headings will 

 be understood by reference to the preceding paragraph. In computing 

 the ionization-constant of water, which was done as before by the expres- 



h 2 

 sion Kw = KaKb -\, the concentration was expressed in equivalents per 



liter and the values of K A and Kb used were 5.67 X 10" 6 and 6.28 X 10" 6 

 respectively. The letter A after the value of the ratio r(= C$/Cb) signi- 

 fies that acetic acid, the letter B, that ammonium hydroxide was present in 

 excess. 



