1916] REED—OXIDASE ACTION 6r 
case, by titrating samples at frequent intervals with HCl. The 
results are indicated by the curve OA, fig. 2. The freshly plati- 
nized platinum crucible was then placed in a similar mixture of 
formic aldehyde, alkali, and hydrogen peroxide, and the rate of 
oxidation under the new conditions determined as before. The 
results are shown in the curve OB, fig. 2. By subtracting the 
ordinates of the curve OA from the ordinates of OB we obtain the 
curve OC, which expresses the effect of the catalyzer. For 
subsequent comparison the curve OC is also plotted as curve 
OD, fig. tr. 
As has been shown, the speed of the reaction between aldehyde 
and oxidized platinum, in the absence of any other source of oxygen, 
is a function of the amount of oxygen which can be furnished by _ 
the charged platinum; and it is evident from an inspection of the 
reaction curve OA of fig. 1 that by starting with a sufficiently 
high concentration of oxygen on the platinum the initial velocity 
could be made equal to the velocity of the catalyzed peroxide 
reaction represented by OD. As the curves indicate, the former 
reaction in the absence of a continual supply of oxygen slows 
down much more rapidly than the peroxide reaction; but it is 
clearly possible to prevent this by recharging the platinum with 
oxygen at sufficiently short intervals. It seems evident, there- 
fore, that the hydrogen peroxide acts by recharging the plati- 
hum with oxygen as soon as a portion of the oxygen has been 
temoved by the formaldehyde. This is of great theoretical interest 
as an explanation of the means by which the catalyzer produces 
its effect, that is, by combining with one or both of the reacting 
substances. 
Measurement of the oxidation potential of this platinized sur- 
face when connected as a cathode through a formic aldehyde 
mixture similar to that previously used led to the same conclu- 
sions. When freshly charged with oxygen the platinum exhibited 
a high potential, but on contact with the aldehyde solution this 
rapidly dropped to equilibrium at very nearly zero potential. In 
the presence of hydrogen peroxide and the aldehyde mixture, 
™ REE p, G. B., Measurement of oxidation Samoa and its significance in the 
- Study of adtdisen Bot. Gaz. 61:523-527. figs. 2. 1916 
