1043 



was contested by Ericson-Auren and Fai.maer M, Tammann *), Marc'), 



SeNTER *), Wn.DERMAzNN ^) etc. 



Since, according to the diffusion theory, in chemical reactions 

 which occur merely at the boundarj^ between two phases, the 

 phenomenon is essentially one of diffusion, it is useless to fry and 

 determine the order of reactions from the rate at whicii they proceed ; 

 this method of argument is only applicable, according to kinetic 

 considerations to the piobablity of collisions in homogeneous systems 

 and loses its significance when applied fo heterogeneous syslems. 

 Moreovei-, if the velocity is controlled by a diffusion process, one 

 will get a coefficient of the velocity similai- to that for a uni-molecular 

 reaction and the coefficient will be independent of the actual order 

 of the more rapid chemical reaction, whicli accom[)anies the process. 

 Consequently it is impossible to establish a relation between the order 

 of a leaction and its temperature coefficient in heterogeneous systems. 



(<7) Temperature coefpcients of niicatalysed reactions. 



Another consequence of the diffusion theory is that the temj)era- 

 ture coefficient for an elevation of 10^ should be of the order 'J .3 i.e. 

 of the same order of magnitude as the temperature coefficient of 

 diffusion (compare Ohölm ")). We shall now see if experimental 

 results confirm this inference from the diffusion theory. The following 

 is the summaiy of results. (See table J next page). 



These results support the diffusion theory of reaction velocity in 

 heterogeneous medium. In this connection it is inteiesting to observe 

 that elevation of temperature np to a certain limit is found to l)e 

 without influence on the decomposition of some alcoholic compounds 

 by sodium amalgam (Löwenherz, Zeit. Phys. Chem. 1900, 32,480; 

 1902, 40, 400) and on the velocity of dissolution of Casein '\n 

 alkalies (Robertson, Jour. Phys. chem. 1910, 14, 377). 



On the other hand, the following summary of results shows that 

 the conclusion as to the effect of temperature, is not corroborated 

 in these cases. (See table 2 next page). 



It has already been pointed out that velocities of diffusion only 

 determine the rate of reaction when no other processes interfere 

 and specially when no slow processes, taking place in the homogen- 



1) Zeit. Phys Chem. 1906, 56, 689. 



2) ibid. 1910, 69, 257. 



«) ibid. t908, 61, 385; 1909, 67, 470. 

 *) Jour. Phys. Chem. 1905, 9, 311. 



5) Zeit. Phys. Chem. 1909, 66, 445. 



6) ibid. 1905, 50, 309; 1910, 70, 385. 



