LEWIS. AUTOCATALYTIC DECOMPOSITION OP SILVER OXIDE. 783 



At least we may conclude in regard to the decomposition of silver oxide, 

 that since there are substances besides silver which act as catalyzers the 

 autocatalysis is probably not of the same nature as that of pre(;ipitation 

 from a supersaturated solution, and further there is some ground for be- 

 lieving that the velocity which we measured is either that of the reaction 

 20 — Oj or that of the diffusion of the factors or products of this reactiou 

 to or from the catalyzing substance. 



We should expect the catalytic power of the silver to be proportional 

 to the extent of its surface, while we have found it to be proportional to 

 the amount of silver. But probably these two quantities are very nearly 

 proportional, since the silver is produced as a slightly cohesive mass which 

 readily falls into a tine white powder. If the grains are of fairly uniform 

 size, the surface exposed is proportional to their number, or, in other 

 words, to their mass. 



Summary. 



A satisfactory thermostat for high temperatures is described, together 

 with a method of measuring the velocity of decomposition of silver oxide. 



This velocity of decomposition at constant temperature increases as the 

 reaction proceeds, passes through a maximum, and falls gradually to zero. 



The phenomenon is due to autocatalysis, and the catalyzing agent is 

 metallic silver. 



The reaction proceeds with great regularity, and the curve of reaction 



velocitv comes verv close to the curve of the equation, v =: —- ;„ 



i (1 + e^')- 



which is the equation of the simplest case of autocatalysis. 



The influence of the purity and the method of preparation of the silver 

 oxide upon its decomposition is discussed. 



The temperature coefficient of the reaction velocity is determined. 



Evidence, both experimental and theoretical, is offered in favor of a 

 comprehensive theory of such catalytic action. 



