324 H. B. TAYLOR. 
The values of A obtained for such a preparation of cata- 
lase are given on the preceding page. 
A solution of catalase obtained in the manner described 
above was used for determining the effect of different con- 
centrations of enzyme on tbe rate of decomposition of 
hydrogen peroxide. The method used to determine the 
concentration of hydrogen peroxide in the experiment was 
as follows:—the enzyme solution was mixed with hydrogen 
peroxide at a temperature of 25° C., so that the resulting 
concentration of hydrogen peroxide was M/300. From 
time to time 5 ccs. of this solution were added to 1 ce. of 
a saturated solution of mercuric chloride and filtered, the 
filter washed with water and the filtrate titrated with 
potassium permanganate solution of a concentration N/400. 
If the values of X are calculated as for a first order reac- 
tion, and compared with the concentration of the enzyme, 
the rate of decomposition is found to be proportional to the 
concentration of enzyme as shown below. 
Table V. 
Temperature 25° C. 
Concentration of Concentration of Kx 104 K/Cs 
hydrogen peroxide. | enzyme. 
M/300 : 10 15 1:50 
25 62 2°48 
50 126 2°52 
(© 188 2°50 
100 256 2°56 
This proportionality between the values of A and the 
concentration of the enzyme agrees with the result given 
by Senter? for blood-catalase. 
The effect of hydrogen peroxide on the velocity constant. 
The solution of catalase, used for the remainder of the 
experiments given in this paper, was obtained by dialysing 
1 Zeit. fur Physik. Chemie, 1903. 
