of the Theory of Solutions. 489 



Does, then, this assumption of electrolytic dissociation 

 correspond to actual fact ? I am just about to allude to this 

 matter, and I ask the continuance of your attention for a short 

 time in order to show what has followed from a consideration 

 of the narrow but important domain of saponification. 



In 1883, in conjunction with Reicher, I carefully investi- 

 gated the velocity with which bases saponify esters. The 

 first experiments were made with soda and potash, and then 

 we tried calcium hydrate, as we expected a different velocity 

 of reaction. The corresponding equations are 



KOH + CH 3 C0 2 C 2 H 5 = CH 3 C0 2 K + C 2 H 5 OH, 



Ca0 2 H 2 + 2CH 3 C0 2 C 2 H 5 = (CH 3 C0 2 ) 2 Ca + 2C 2 H 5 OH. 



Proportionality between the velocity of reaction and the 

 square of the concentration of the ester in the latter case, and 

 with the concentration alone in the former, might be expected, 

 but we found in both cases practically the same velocity: 



Potash 2-298 ; Calcium hydrate 2*285. 



This curious fact immediately found its explanation in the 

 theory of electrolytic dissociation, for the reaction in both 

 cases is conditioned by the hydroxyl alone, and hence is 

 represented by the equation 



OH + CH 3 C0 2 C 2 H 5 = ChIC0 2 + C 2 H 5 OH. 



Ostwald observed an analogous fact, viz., that greatly 

 diluted acids have the same velocity of saponification. In 

 this case, the action is conditioned by the presence of hydrogen 

 ions. 



Quite recently Wijs has, in my laboratory, investigated the 

 saponifying action of water itself. 



This investigation possesses new interest on account of the 

 question whether the excessively small saponifying power 

 of water is due to the presence of the minute quantity of 

 hydroxyl and hydrogen ions. 



In this case the question is experimentally and theoretically 

 somewhat more complicated. Experimentally, the action of 

 water is disturbed immediately after the commence ment of 

 the saponification by the co-operation of the acid which is 

 formed, and hence must be measured only at the beginning. 

 Theoretically, the increase in hydrogen ions, on account of 

 the formation of acid, must be taken into account in the 

 combined action of hydrogen and hydroxyl ions. In order 

 to determine the quantity of acid in the exceedingly dilute 

 solution (about O'OOOOo-normal), the conductivity, as being 

 the best quantitative method, was employed. 



Phil Mag. S. 5. Vol. 37. No. 228. May 189i. 2 L 



