VELOCITY OF SAPONIFICATION 135 



activity, and when the acid is strong and sufficiently dilute, 

 is simply proportional to its concentration. 

 Adopting the equation 



& Dexter 7 n p 



/t/2 ^ ester ^ base 9 



for saponification by bases, the constant k 2 thus appears to 

 be independent of the base, and has been found l for ethyl 

 acetate at 9-4 : 



Soda Potash Lime Strontia Baryta Lithia 



k 2 2-37 23 2'28 2-2 2-14 2.21 



when normal concentration is taken as unity. 

 In the same way for acids, with the equation 



U ''ester in n 



7, /(/ 2 ^ ester ^ acid ^ 



the value of k. 2 is independent of the nature of the acid if 

 the latter is strong and sufficiently dilute 2 . At 25 we 

 have : 



Hydrochloric acid Hydrobromic acid Hydriodic acid Nitric acid 

 0-0069 0-0062 0-0066 0-0063 



Chloric acid Methylsulphonic acid 

 0-0065 0-0068 



Next, comparing the behaviour of the different esters, we 

 find a fundamental difference according as the saponification 

 is due to base or acid. 



For saponification by bases we find a relation among the 

 velocities that distantly recalls that among the velocities of 

 esterification, as may be seen from the following numbers, 

 in which the rate of formation for methyl acetate is taken 

 as 100: 



Saponification (NaOH) at 9.4 Esterification 

 Methyl acetate .... 3.49 100 



Ethyl acetate .... 2-31 47-9 



Propyl acetate .... 1-92 45-6 



Isobutyl acetate ... 1-62 38-1 



1 Reicher, Ann. de Chemie u. Pharm. 228. 275 ; Ostwald, Journ. f. prakt. 

 Chew. 35. 112 ; Arrhenius, Zeitschr.f. Phys. CJiem. i. no ; Bugarsky, 1. c. 8. 418. 



2 Ostwald, Journ. f. prakt. Chem. 28.449. 



