264 MEASUREMENT OF THE CATALYTIC POWER OF CATALASE 
lecular, and follows the law of mass action, the well-known formula of 
van't Hoff will apply: 
k(a — x) 
in which 
dt 
a = available amount, 
X = decomposed amount, 
t = time, 
k = reaction velocity. 
I a 
Integration of this form k = —log enables us to find the reac- 
o.4343t a - X 
tion velocity from a single determination. Concerning catalase a great 
variety of opinions exists in regard to the constancy of the reaction velocity. 
If the reaction velocity were proved to be practically constant, we should 
find, if X approaches its maximum value (let us say a) : 
1000 
k = 
04343t 
or, k will be inversely proportional to t. In this case only would one be 
justified in measuring the so-called reaction-velocity, taking this as a 
comparative number for the "real" reaction-velocity, i.e., ^ — : — . 
reaction time 
Excepting Bredig, who first called attention to this fact, F. A. F. C. Went^^ 
is the only author, so far as we know, who has tried to determine directly 
the time in which a reaction took place. He studied starch hydrolysis by 
the enzym of Aspergillus niger. His numbers are interpolated but still 
show marked properties. 
In all cases, more or less scattered determinations (see, for example, 
figures in W. M. Bayliss^^ on glycerol-glucoside) must furnish the basis for 
the calculations. In our special case of catalase action, an autographic 
method which marks the time in which the reaction is ended offers a solution 
of this difficulty. Furthermore, this gives us opportunity to collect a far 
greater number of figures. As we learned after we had worked out the 
apparatus, the idea of an autographic record was not new. 
C. Foa (I.e.) used a Mosso-plethysmograph and a revolving drum with 
soot paper to determine the action of different phenols on oxidase. He 
published his graphs without using them for calculation. A. Schultze 
(cited by Foa), used a self-recording manometer for measuring the CO2 
output in yeast activity. M. Antropoff studied autographically the 
periodical decomposition of peroxide by mercury. (Stephane Leduc^^ has 
explained his results in a peculiar way.) 
19 Verh. Kon. Akad. Wet. Amsterdam 27. 1918. 
^'^ General physiology, 2nd edition. London, 191 7. 
Theorie physico-chimique de la vie. Paris, 19 10. 
