1024 
Primary change 
Induced change 
Sodium sulphite 4 - oxygen 
Sodium sulphite + oxygen 
Sodium sulphite oxygen 
Sodium sulphite -f oxygen 
Sodium sulphite -f- oxygen 
Sulphurous acid 4- oxygen 
Stannous chloride -f oxygen 
Manganous hydroxide -f oxygen 
Cobaltous hydroxide -)- oxygen 
Acetaldehyde -(- oxygen 
Formaldehyde -f- oxygen 
Benzaldehyde -f~ oxygen 
Ferrous ammonium sulphate + oxygen 
Ferrous ammonium sulphate 4- oxygen 
Ferrous ammonium sulphate -f- oxygen 
Ferrous hydroxyde + oxygen 
Ammoniacal cuprous hydroxide + oxygen 
Sodium arsenite -f oxygen 
Sodium nitrite f oxygen 
Sodium oxalate -j- oxygen 
Sodium formate + oxygen 
Ferrous ammonium sulphate -f- O- 
Ferrous ammonium sulphate + O; 
Ferrous ammonium sulphate + Q 2 
Sodium arsenite + oxygen 
Sodium arsenite + oxygen 
Sodium arsenite -)- oxygen 
Sodium arsenite + oxygen 
Sodium arsenite -)- oxygen 
Sodium oxalate -J- oxygen 
Sodium tartarate -f oxygen 
Sodium citrate -)- oxygen 
Sodium arsenite -f- oxygen 
Sodium arsenite -f- oxygen. 
In all these cases at first the primary change, that is, the oxidation 
of the easily oxidisable snbstance takes place and t.his primary 
change induces or promotes the secondary or the induced change 
that is, the oxidation of the difficultly oxidisable snbstance. 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 negativo 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 negativo catalysis is 
