KI OX/DIZED 
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n 
234 BOTANICAL GAZETTE [SEPTEMBER 
hours. On filtering, a clear, pale yellow extract was obtained, which 
exhibited very active peroxidase properties. 
The peroxidase activity of this extract was determined quanti- 
tatively by the method of BAcH and CuHopat.? To too cc. of a 
solution containing o.2M potassium iodide and 0.05M acetic 
acid 20cc. of the horseradish 
‘A peroxidase extract was added; 
the mixture was kept well stirred 
and at a constant temperature 
of 15° C., and at frequent inter- 
vals portions of 5 cc. were re- 
moved and titrated with o.01M sodium 
thiosulphate solution (with starch indi- 
cator) for the iodine liberated in the oxida- 
tion. The values obtained in this way 
are plotted in the curve OA, fig.1. The 
rate of oxidation of hydrogen peroxide in 
the absence of a ferment is shown by the 
curve OB of the same figure. By sub- 
tracting the ordinates of the curve OB 
from the ordinates of the curve OA we 
obtain the curve OC, which expresses the 
effect of the catalyzer. 
3 For subsequent com- 
parisons the curve OC is 
S Les WUTES also plotted as OC, fig. 2. 
Fic. 1.—Curves of oxidation of potassium ans — poheonce 
iodide by hydrogen peroxide: OA, in bob sence of xtract in the absence of 
horseradish peroxidase; OB, in absence of a cat- @ peroxide showed no 
pe ped aon: lg pe ~ ordinates oxidative activity; on 
cians ae a pager apt lac Seat ad ding portions oe sol ee 
to combine with the iodine in ¢ cc. of reaction mix. tions of potassium iodide 
ture; abscissae represent time in minutes. and starch or to gum 
guaiac free from perox- 
ide no oxidation took place. In this respect it was analogous to an 
ordinary colloidal platinum solution. The platinum may be made 
Q 
2 Bacu, A., and Cuopat, R:, Ber. Deutsch. Chem. Gesells. 35: 2466-2470, 39437 
3946. 1902. 
