Primary change Induced change 
Sodium sulphite + oxygen Sodium arsenite + oxygen 
Sodium sulphite + oxygen Sodium nitrite + oxygen 
Sodium sulphite + oxygen Sodium oxalate + oxygen 
Sodium sulphite + oxygen Sodium formate + oxygen 
Sodium sulphite + oxygen Ferrous ammonium sulphate + O, 
Sulphurous acid + oxygen Ferrous ammonium sulphate + O, 
Stannous chloride + oxygen Ferrous ammonium sulphate + Op, 
Manganous hydroxide + oxygen Sodium arsenite + oxygen 
_Cobaltous hydroxide + oxygen Sodium arsenite + oxygen 
Acetaldehyde + oxygen Sodium arsenite + oxygen 
Formaldehyde + oxygen Sodium arsenite + oxygen 
Benzaldehyde + oxygen Sodium arsenite + oxygen 
Ferrous ammonium sulphate + oxygen | Sodium oxalate + oxygen 
Ferrous ammonium sulphate + oxygen | Sodium tartarate + oxygen 
Ferrous ammonium sulphate + oxygen | Sodium citrate + oxygen 
Ferrous hydroxyde + oxygen Sodium arsenite + oxygen 
Ammoniacal cuprous hydroxide + oxygen | Sodium arsenite + oxygen. 
In all these cases at first the primary change, that is, the oxidation 
of the easily oxidisable substance takes place and this primary 
change induces or promotes the secondary or the induced change 
that is, the oxidation of the difficultly oxidisable substance. In other 
words, the potential chemical change between oxygen and sodium 
arsenite is activated by the previous oxidation of sodium sulphite. 
The oxygen divides itself, as it were, between the two reducing 
agents and the proportion in which it divides itself between the: 
two reducing agents is the next point of“ interest. 
It is well known that a solution of sodium arsenite is not oxidised 
by atmospheric oxygen under ordinary conditions, On the other hand 
a solution of sodium sulphite is readily oxidised to sodium sulphate. 
Now if we mix the two together both the oxidations take place 
simultaneously. At the same time a curious phenomenon takes place. 
The velocity of the oxidation of sodium sulphite becomes very small 
in. presence of sodium arsenite, that is, sodium arsenite which is 
undergoing a slow oxidation acts as a powerful negative catalyst in 
the oxidation of sodium sulphite. Similarly a solution of an oxalate 
which also undergoes slow oxidation in presence of sodium sulphite 
which itself is being oxidised, decreases to a marked extent the 
oxidation of sodium sulphite by atmospheric oxygen. It appears, 
probable, therefore that the phenomenon of negative catalysis is 
