270 MEASUREMENT OF THE CATALYTIC POWER OF CATALASE 
We had only to measure ap and Dp and we could read immediately on 
the slide rule the resulting Kp. We averaged a great number of K's taken 
from different curves. We also calculated the probable error. It proved to 
affect the units only. This must be taken into account. 
Extract in cc. 
Peroxide in cc. 
Number of 
Experiments 
Reaction Velocity 
Peroxide X A' 
Enzym 
1 
2 
2 
4 
41 X 10-4 
164 X 10-4 
I 
2 
7 
no X io~4 
220 X 10-4 
2 
2 
II 
257 X 10-4 
257 X 10-4 
2 
4 
4 
109 X io~4 
218 X 10-4 
3 
2 
4 
396 X 10-4 
264 X 10-4 
4 
2 
I 
535 X 10-4 
263 X 10-4 
4 
4 
4 
261 X 10-4 
261 X 10-4 
4 
4 
47 X 10-4 
188 X 10-4 
Considering the irregularity of the curves due to the poor clockwork and 
PK . 
the possible differences in strength of the enzym solutions, is a fairly 
E 
approximately constant number. But it would take 39 determinations of 
this sort to prove what one determination of reaction time gave us, namely, 
that the reaction follows the law of mass action. 
We tried to compare the curves obtained with mathematically con- 
structed logarithmic lines. (Kapteyn used a similar method for Gaussian 
curves). We constructed several lines 
t = c log 
a — X 
for c varying from o.i to 2 and a = 2 cm. We found in one case: 
Calculated from Curve Amount extract C X E 
0.15 4 CC. 0.6 
0.2 3 cc. 0.6 
0.3 2 cc. 0.6 
0.6 I cc. 0.6 
1.2 ' 0.5 cc. 0.6 
Perhaps this method will be found to be the most practical and accurate. 
The line A — B in which, according to our idea, the first part of the 
reaction must take place, becomes long enough to be measured in very 
feeble enzym concentrations only. Figure 5 shows curves run with 3 cc. 
peroxide and 4, 3, 2, i, 0.5, 0.2, o.i, and 0.05 cc. extract respectively, all 
diluted to 4 cc. fluid. The reaction started at the thick vertical line. The 
latency time caused by the apparatus (fig. 5) seems to be 2 X ^ seconds. 
So we had to subtract 2 from the length A-B. 
Latency time X amount of enzym seems to be more or less constant. 
But to draw conclusions from these facts seems premature. 
