137 
out the analogy between chemical catalysts and light. His conclusion 
was, that: “probably the effects of increase of temperature, of light, 
and of chemical catalysts in a reaction are intimately connected and 
are possibly identical in nature”. They all appeared to act by shift- 
ing the equilibrium between “active” and ‘inactive’ molecules. 
SUMMARY. 
1. The enzyme urease acts by a radiation, which is only absorbed 
by its substrate, urea, and by H-ions. 
2. The mathematical formulation of this conception is 
et 
— dt, 
z+ nc 
— df =m 
in which 2 is the concentration of urea at the time ¢, c the con- 
centration and » the absorption-coéfficient of the H-ions, m a constant, 
proportional to the concentration of urease, if H-ion concentration 
as well as temperature are kept constant. 
Integration gives the formula 
ne 
- log —— + ay = mt, 
ence ae 
in which a is the initial concentration of urea, and y the fraction 
of a, still present at the time ¢. 
3. By numerous experiments this equation is shown to represent 
the kinetics of urease action at constant py and temperature. It 
explains the nearly straight lines of the hydrolysis in alkaline solu- 
tions equally well as the practically logarithmic curves in acid ones. 
+. Comparing equal concentrations of urease at varying H-ion 
concentration, the constant m is found to be dependent on the py; 
i.e. the activity of a given concentration of urease is a function of 
the pa of the solution. 
Plotting m as a function of py, the resulting curve is strikingly 
similar to the characteristic curves for the undissociated fraction of 
an amphoteric electrolyte as a function of pz. 
This connection can be formulated mathematically and leads to 
the conclusion, that urease is an amphoteric electrolyte, whose 
activity is greatest when undissociated. The curve obtained represents 
the excess of activity of undissociated over dissociated urease. 
5. This mathematical formulation leads to an approximate deter- 
mination of the dissociation-constants of urease, which are calculated 
to be not far from those of carbonic acid and ammonia. 
6. The accelerating action on urease, ascribed by previous authors 
