1026 
Chemical cliange and in order tliat Sohönbein’s law be applicable it 
follows immediately tliat the oxidation of sodinm sulphüe which is 
fairly rapid becomes a slow cliange and the velocity of this oxida- 
tion beeomes eqnal to tliat of the oxidation of sodium arsenite, 
becanse the same amount of oxygen will be taken up by the reducing 
agents in the same time. As a matter of fact, trom my experiments 
I have observed tliat in presence of sodinm arsenite or potassinm 
oxalate the velocity of the oxidation of sodinm sulphite becomes 
very small. We assume tliat a molecule of oxygen splits up in this 
reaction into two atoms and each atom oxidises one of the reducing 
agents. Now as a solution of sodium sulphite is much more readily 
oxidised thau a solution of sodium arsenite it becomes difficult to 
onderstand why the olher oxygen atom instead of attacking the 
readily oxidisable nnacted sodium sulphite attacks the much more 
diflicultly oxidisable sodium arsenite. Or if we assume that at first 
a peroxide of the type of Bodlander’s benzoyl peroxide (Ahrens’ 
Sam. 3, 470 1899) is formed as a combination of the sodium sulphite 
with a molecule of oxygen we are still encountered witli the same 
difficulty. In this case we will have to assume that this peroxide 
instead of attacking the readily oxidisable and unattacked sodium 
sulphite will attack the less readily oxidisable sodium arsenite by 
preference. It seems to me therefore that the only course left to us 
is to find out the explanation in the view of the formation of a 
complex of sulphite and arsenite or of sulphite and oxalate and that 
this complex is oxidised as a whole. It is well known tliat complex 
oxalates and sulphites do exist. Ostwald thinks that in order to 
explain positive catalysis by the hypothesis of intermediate compound 
formation it is necessary to show that the intermediate reactions 
actually take place more readilj' than the direct reaction under the 
given conditions because if a reaction goes more slowly via the 
intermediate product than the direct path, it will take the latter 
and the possibility of intermediate products can have no influence 
on the process. “Hence”, adds Ostwald, “I see no possibility of 
explaining retarding catalytic influences by the intermediate products”. 
(Nature, 1902, 65 522). 
I have observed in a previous paper (Proc. Akad. Wet. Amsterdam 
1920) that in the oxidation of sulphites and sulphurous acid the 
sulphite ion is the active agent. If we can decrease the sulphite ion 
we can decrease the Chemical cliange and a solution of sulphurous 
acid which is a weak acid containing few sulphite ions is oxidised 
less readily than a solution of sodium sulphite of the same concen- 
tration. On the addition of an arsenite to a sulphite a complex which 
