484 
it becomes verj difticuU to deterrnine the tempemture coëfficiënt 
acciirately. It appears Iherefore that the reaction is aiito-cataljtic. 
Mathêws and his colleagues (Jour. Phys. chem. 1913, 17 , 211 ; 
Jonr. Amer. chem Soc. 1917, 39 , 635) fonnd that ultraviolet liglit 
markedly accelerates this reaction, and also established the fact that 
this is not a case of auto-oxidation. For this i-eaction, thej^ could 
not find a posilive calalyst; copper sulphate, which is known to be 
a powerful catalvst under ordinary conditions exerted no appreciable 
effect in nltra-violet light. On the other hand the negative catalysts 
like hydroqninone, plienol etc. exerted a retarding effect in presence 
of nltra-violet light. So it appears tliat tliere are very few positive 
catalysts, hut very many negative ones for tliis reaction when carried 
out in light or darkness. 
The explanation of the negative catalytic effect of organic snb- 
stances in general on this reaction is this; 
The reaction consists in the oxidation of SOj radical into SO^, 
and the snlpliite ion is the active agent. It is well known that several 
organic substances forrn complexes with sulphnrous acid and sulph- 
ites ; these complexes are stable so far as oxidation is concerned 
and hence the organic substances act as negative catalysts by dimin- 
ishing the concentration of sulphite ion by combining with it. 
In foregoing papers I ha\ e proved that the phenomenon of nega- 
tive catalysis is very common, whilst there are very few positive 
catalysts. According to Luther’s view a negative catalyst must have 
a positive catalyst as its counterpart, but this is not probable since 
there are so few positive catalysts and so many negative ones. 
Hence it appears that Luther’s view which emphasises that nega- 
tive catalysis cannot take place in a reaction which is entirely free 
from positive catalysts, is not substantiated by experimental evidence. 
Summary. 
n. Cane sugar, lactose, glucose, camplior, and menthol are nega- 
tive catalysts, whilst naphthalene, and anthracene are without action 
on the oxidation of sodium sulphite. 
h. The weak organic acids and their sodium salts exert practic- 
ally the same effect. Benzoic, oxalic, salicylic acids and their sodium 
salts exert greater negative effect than tlje weak acids and their 
salts. It is very peculiar that the acid and its salt should exert the 
sarae effect. 
c. The temperature coëfficiënt of the reaction is about 2 and it 
