432 



The reduction took place altogether regularly without any consider- 

 able paralysis, as a sign that the H^ contained some 0, after all. 

 Yet the difference in velocity with the H, containing ± 5 "/„ 0, 

 is very striking as may be seen from the subjoined table. 



^ , .• r ^, ^ in ,^ on Duration No. of the 



^,0 Gas-absorption of the 5 10 15 20 ^^ graphic re- 



''' • cinnamic acid methylester min. min. mm. , mm. .reduction presentation 



Difference I— III 46 85 



131 



181 



When we also observe, that the oxydation of the H, j)roceeds 

 rather slowly (11) we draw the conclusion, that the two reactions: 

 the oxydation of the H, and the reduction of the ester, influence 

 each other very favourably. 



This might lead us to suppose that owing to the presence of the 

 oxygen the palladium is continually freed from a paralysis-layer, 

 so that the number of atoms becoming available for the reduction- 

 reaction is greater than when no 0, is present. But if this were so, 

 the paralysing of the catalyser, when no reducible substance is 

 present would be unintelligible. It may be, that the solvent, the 

 80 Vo alcohol, which no doubt will be acted upon by the oxygen 

 and converted into aldehyde, plays an important part. 



A closer investigation will have to elucidate this question, but it 

 appears at any rate that this catalytic reduction is far more com- 

 plicated, than would appear at first sight. 



It is certain that the velocity of the hydration proper : 



Hj -|~ substance to be reduced = reduction-product, 



can be considerably modified by a by-reaction, so that we feel still 

 more positive in concluding, that we have not measured the velocity 

 of this reaction. 



.The question, whether we shall ever be able to measure this 

 velocity of reaction when using colloidal catalysers cannot be 

 solved yet. 



It would be indispensable for us to l)e able to introduce these 

 catalysers into the reaction-mixture in such a state and to bring 

 about the course of the reaction in such a manner, that the forma- 



