RELATIONS TO OTHER SCIENCES 281 



and therefore 



dx 



But this is exactly the velocity equation for the ester catalysis, (Ester) 

 being substituted for (Base) : 



dx 



37 = fc X (Ester) X (H) 



And so if the ester could form salts with acids its saponification could 

 undoubtedly be due to the saponification only of its salt or positive 

 ion. This important link in the chain of argument has been supplied 

 by the discovery of Baeyer and others that the esters do form well- 

 defined salts with acids, very unstable ones, but still salts. They are 

 almost certainly salts of quadrivalent oxygen bases or oxonium salts. 

 Coehn has proved that they are true electrolytes by showing that the 

 positive ion of dimethyl pyronium hydrochloride moves to the nega- 

 tive pole when the solution is electrolyzed. 



Now if we start from the idea that it is only the positive ion of 

 methyl acetate which is saponified by water, we can put for the reac- 

 tion: 



CH 3 C0 2 CH, +H 2 -> CH 3 C0 2 H +CH 3 OH 



dx 



fa = fcsap X (Posit. Ester Ion) X (H 2 0) 



as was proved experimentally for the imido-esters. For the combin- 

 ation of methyl acetate with water to form an oxonium base and for 

 the ionization of this base, we have 



OH 



I 

 CH 3 CO-O-CH 3 +H 2 0<=>CH 3 CO-O-CH 3 and 



I 

 H 



OH 



I + 



CH s CO-O-CH 3 rCH 3 CO-0-CH,+OH 



I I 



H H 



and consequently 



(Posit. Ester Ion) = ^? X (Ester) X (H) 

 K 



By the substitution of this value for the concentration of the posi- 

 tive ester ion in the above equation, we obtain for the velocity of 

 saponification of methyl acetate by water alone 



i^base 



?MP = k sap X -- X (Ester) X (H) X (H,0) 



