306 BOTANICAL GAZETTE [OCTOBER 
and the activation by enzymes of oxidations in the presence of 
hydrogen peroxide (peroxidase action) are closely correlated and 
may be referred to a common cause. 
A study of the relations existing between the catalase and 
oxidase actions of colloidal platinum and of certain plant extracts 
has led the writer to a different conclusion. ‘The present paper 
contains an account of the experiments with colloidal platinum. 
In a previous paper" it was pointed out that the direct oxidase 
action (that is, in the absence of peroxides) of colloidal platinum, is 
dependent upon the amount of oxygen combined with it; that the 
reaction can be completely inhibited by electrolytic reduction, and 
again renewed by recharging the platinum with oxygen at an anode. 
It was also pointed out that the peroxidase action is essentially 
the same process; namely, in the presence of hydrogen peroxide 
the metal is kept fully charged with oxygen, while it is at the same 
time actively giving up oxygen to the substance undergoing 
oxidation. : 
The amount of oxygen which could be combined with the 
platinum electrically was only sufficient to bring about a very 
small amount of oxidation as compared with that effected by a low 
concentration of hydrogen peroxide. It was expected, therefore, 
that the amount of oxygen in combination with the platinum, when 
it was introduced into a solution of hydrogen peroxide and an 
oxidizable substance, would have very little effect, either on the 
rate of reaction or on the amount oxidized. Several measurements 
proved this to be the case. 
Two platinum disks of exactly the same size, 2 cm. in diameter, 
were cut from the same piece of foil, sealed into glass tubes for 
convenience in handling, and platinized by the usual method. 
Care was taken to continue the platinizing for the same length of 
time with the same current, so that equal amounts of colloidal 
platinum were deposited on each electrode. These were then 
attached to opposite poles of a 110-volt circuit delivering one ampere 
and connected by placing in the opposite arms of a U tube con- 
taining dilute salt solution. In this way one electrode was subjected 
to active oxygen, the other to active hydrogen. 
4 Reep,G.B., Bor. Gaz. 62:53-64. figs. 4. 1916. 
