553 



on or ill platimim ; the transfoniialioii : aldehyde = paraldehyde 

 under the influence of sulphuric acid etc. 



Much more frequent will be the cases, such as in the chlorination 

 of nitrobenzene, where the catalyst is found, in regard to one of 

 the substances, a good long way over this most favourable stage; 

 in that case it wall have united with one of tlie components to a 

 more or less firm compound. 



The sulphone formation from bromosulphone-chloride and benzene 

 under co-operation of AlCl^ is an illustrative instance hereof: 



The AlCl^ is combined with the sulphone-chloride and is, therefore, 

 in regard to the chloride, already far removed from the catalytic 

 stage, at 25° it is however not completely paralysed, as according 

 to the course of the reaction it is still capable of activating the 

 second molecule (benzene). 



The sulphone formed now also unites with AICI^ and now it 

 appears also from the course of the reaction that it keeps on activ- 

 ating the benzene, but is, however, no longer capable of influencing 

 the sulfone-chloride. for an excess of the latter exerts no influence 

 on the reaction velocity. (Olivier and Bökseken, Proc. 1913 1. c). 



From this case it is shown how complicated this reaction may 

 become when in the reaction mixture different substances are present 

 which paralyse the catalyst more or less, and that only a clear 

 conception of the catalysis enables us to interpret the observations 

 satisfactorily. 



Represented symbolically, we thus have here (when we assume 

 that the HCl{T>) does not interfere, which has also been proved by 

 Olivier) : 



A 4- B -» C + D 



n 



— Al CI,— 



The AICI3 united to C (the sulphone) can no longer reach A (the 

 sulphonechloride), only the AlCl^ united to ^4 itself can still activate 

 the S-Cl bond, but much less so than free AlCi^ ; only the benzene 

 {B) is still attainable for the AICI^. 



I want to observe here that the paralysis stai'ts here, presumably, 

 from the /S'O^ -group, because this occurs in the sulphonechloride as 

 well as in the sulphone. 



These are just the cases, •wherein the catalyst is united with one of the 

 starting products, but is not entirely paralysed thereby, which have 

 originated the theory of the intermediate products. 



By removing wilfully from the most favourable catalytic stage 



