1916] REED—OXIDASE REACTIONS 309 
the rate at which hydrogen peroxide is decomposed by platinum 
black which had previously been subjected to active oxygen (by 
using it as an anode), and AC indicates the rate obtained with 
platinum black which 
had previously been sub- 
jected to active hydro- 
. ; Nc] 
gen (by using it as a S 
cathode); it is apparent > 
that the latter treatment 6 
greatly accelerates the 
catalase action. Thus 
while electrolytic oxida- 
tion or reduction of the 
platinum apparently has 
no effect on the peroxi- 
dase action of the metal, 
the catalase action is 
very greatly modified. 
That this treatment has 
no effect on the peroxi- 
dase action may be ex- 
plained by following the 
oxidation potential of 
the platinum during the 
reaction. In a previous 
paper (/oc. cit.) it was 
pointed out that in oxi- 
dations by hydrogen 
peroxide, where colloidal 
platinum played the 
part of a peroxidase, the 
peroxide served to main- 
tain the potential on the 
a /0 
MMUTES 
Fic. 3.—Curves of oxidation potential of a 
platinum cathode in a o.1M solution of hydro- 
gen peroxide: upper curve AB represents drop 
in potential on an electrode which had previ- 
ously been treated with active oxygen by using 
it as an anode; lower curve CB represents rise 
in aagani on an. — Debes had _ 
ously b using 
it as 4 cathode; ordinates represent Ndite 
abscissae, time in minutes. 
catalyzer at a maximum, although the substance undergoing oxida- 
tion would tend to pull down the potential. 
If this be true (since 
previous treatment with either active hydrogen or oxygen has no 
effect on the peroxidase action) the same potentials should be 
