549 



of the catalyst in the sulpho-chloride or in the siilphone caused a 

 partial paralysis, as the reaction proceeded mucli more rapidly the 

 moment a small quantity of tlie catalyst in the solution was present 

 in the free state. 



Also, could it be deduced sharply from the progress of the reaction 

 (Proc. 191 3 p. 1069^ that this could be exi)laiued satisfactorily only 

 then when the activating action was sought in what happened 

 between benzene on one side and chloride -|- catalyst on the other 

 side before they had undergone chemical transformation. 



Hence, it was proved experimentally also here that the most important 

 stage of the catalysis is that which lakes place before the union. 



3. If we now consider what can be the significance of the 

 remoyal of the catalysis to the pre-stage of the reaction, it should 

 be remembered that in view of Ostwald's definition a catalyst should 

 be a substance unchanged in Cjnantity and quality after the reaction. 



Guided by this definition we may durbui the reaction assume all 

 kinds of material and energetic changes if only the condition is 

 satisfied that the catalyst remains unmodified before the beginning 

 and after the end of the reaction. 



If now, however, we look for a fiu'ther explanation, that is to 

 say, penetrate further into the mechanism of a reaction, we notice 

 that somewhere during the reaction a catalyst can no longer satisfy 

 that definition. 



Hence, a catalyst can never remain unchanged during the entire 

 course of the reaction ; an ideal catalyst exists no more than an 

 ideal gas or an ideal dilute solution, bnt for all that we have been 

 able to make excellent use of the notion. 



Now, a substance will approach this ideal condition all the more, 

 the smaller the material or energetic displacements will be and it 

 is plain without any further evidence, that similar very small changes 

 will just take place on the approach of the catalyst to the bonds to 

 be activated. 



When there the action ceases, we can understand that these 

 shiftings may be so small that they elude observation (so that for 

 instance, apparently a same equilibrium is reached under the infiuence 

 of diverse catalysts, which in reality cannot be the case.) 



4. If now we want to get a concrete conception of these exceed- 

 ingly small actions, which in the catalysis are both satisfactory and 

 authoritative, we may consult the modern views on our atomic 

 woiid. 



36* 



