62 BOTANICAL GAZETTE [JULY 
however, the oxidation potential did not fall so low, and it remained 
approximately constant until the peroxide was exhausted.* 
as 50 
SUNUTES 
Fic. 3.—Curves showing oxidation of potas- 
sium iodide; lower curves OA, AB, BC, represent 
successive oxidations by platinum black which had 
been charged with oxygen at the beginning of each 
oxidation; curve OE represents oxidation by aah 
nates represent drops of o.01M N: * S20; ashe 
to combine with the iodine in 5 cc. of the reaction 
mixture; abscissae represent time in minutes. 
From these results it 
may be concluded that in 
the oxidation of formic 
aldehyde by hydrogen 
peroxide in the presence 
of platinum black two 
reactions are concerned: 
the platinum combines 
with oxygen from the 
hydrogen peroxide, as it 
combined with oxygen 
when subjected to anodic 
oxidation; this compound 
of platinum then gives up 
its oxygen to the for- 
maldehyde, producing 
formic acid. 
In a similar manner it 
was possible to show that 
the catalytic action of 
platinum black on the 
oxidation of potassium 
iodide by hydrogen per- 
oxide was due to an 
intermediate platinum- 
oxygen compound. A 
freshly platinized plati- 
num crucible, which had 
just: been subjected to 
active oxygen in the man- 
ner described in the pre- 
vious experiment, was 
%3 The oxidation potential in hydrogen peroxide is much lower than would be 
expected from its activity as an oxidizing agent (Lewis, Jour. Amer. Chem. Soc. 36: 
1696), which is probably due to the fact that it may act as both an oxidizing and 
as a reducing agent 
