386 Dr. J. {Shields on Hydr< 



free base ; thus, 



CH 3 COONa + HOH -<-»- CH 3 COOH + KaOH. 



It has already been stated that the presence of free weak 

 acids has no measurable influence on the velocity with which 

 the saponification takes place. 



This is equally true in the case of sodium acetate, where 

 acetic acid is one of the products of hydrolysis, and is also 

 formed on the saponification of ethyl acetate. Arrhenius 

 (Zeits.f. physikal. Chemie, vol. v. p. 2, 1890) has thoroughly 

 investigated the change of the dissociation ratio of acetic acid 

 on the addition of sodium acetate, and has shown that it may 

 be regarded as nil in presence of large quantities of its salts. 



By referring to the table it will be seen that the experi- 

 ments on sodium acetate lasted for a considerable time, and it 

 is conceivable that the water itself may have played an im- 

 portant part in the saponification of the ester. In order to 

 test this a blank experiment was made with water and ethyl 

 acetate under the same conditions as the experiment with the 

 sodium acetate, and after the lapse of nearly three weeks the 

 solution of the ester was only slightly acid. If, then, pure 

 water, in virtue of its being electrolytically dissociated to a 

 small extent, produces such an inappreciable effect, we can 

 easily conjecture how infinitely slight this effect will be in 

 presence of a strongly dissociated salt like sodium acetate. 



The Influence of the Ester on the existing Equilibrium. 



All the preceding deductions regarding the amount of 

 hydrolysis in aqueous solutions of salts of strong bases with 

 weak acids are based on the assumption that the equilibrium 

 in aqueous solutions, 



KCN + HOH ^— HCTT + KOH 



is not disturbed by the presence of small quantities of ethyl 

 acetate. To justify this assumption, I have made some expe- 

 riments in which the concentration of the ester was varied, 

 whilst the concentration of the salt remained nearly the same. 

 Now, if the presence of the ester produced any change in the 

 state of equilibrium, we should expect an alteration in the 

 concentration of the ester -to be accompanied by a corre- 

 sponding variation in the amount of salt hydrolysed. 



The following tables contain the results of experiments, on 

 an approximately 0*1 normal solution of potassium cyanide, 

 made at 25 o, C, at which temperature & = 6*54. 



ii 



