378 



Dr. J. Shields on Hydrolysis 

 Fig.l. 



3 4 5 



Percentage of Salt hydrolysed. 



reading from the curve, there should be 1'65 per cent, of 

 the potassium cyanide decomposed in a -^ normal solution 

 of that salt. If calculated from the above law, the amount of 

 hydrolysis is 1*58 per cent. 



Now if the salt itself were the cause of the saponification of 

 the ester, the velocity of the reaction which is proportional to 

 the amount of free base present would have been verv nearly 

 directly proportional to the concentration of the salt ; but it 

 has been found approximately proportional to the square root 

 of the concentration, consequently the view that the salt itself 

 produces the saponification is untenable. 



The law which has just been enunciated is what we should 

 expect from the theory ; for if we again take the case of 

 potassium cyanide, we get, neglecting the dissociation ratios 

 as formerly, 



KOH + HCN -7-*- KCN + HOH, 



x .x = (C 2 --#)K ; 



where C 2 is the initial concentration of the potassium cyanide, 



and x the fraction of it which has been hydrolysed. When x 



is very small compared with 2 , the above equation becomes 



