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to earbonie acid, is shown to be non existent. Ammonium carbo- 
nate + carbonic acid form a powerful buffer-mixture, which can 
maintain constancy of py, the indispensable condition for constant 
enzyme activity in a urea solution during hydrolysis by urease. 
Fresh confirmation of the above formula for the rate of hydrolysis 
is afforded by many experiments with this buffer-mixture. 
7. The estimation of initial velocities of bydrolysis, equal con- 
centration of urease being allowed to act on different concentrations 
of urea at constant py and 7’, produces results, which appear 
unexplainable without the radiation-theory. 
The lower the py, the more these initial velocities increase on 
increase of the concentration of the urea. With high py, there is 
first an increase and then a decrease on raising the urea concentration. 
These facts are shown to be in perfect accordance withthe radiation- 
theory. 
8. The influence of neutral substances is investigated experimentally 
and theoretically. Both decrease and increase of enzyme action by 
the same substance are explained by the influence the neutral body 
has on the dissociation-constants of water or of urease or of both 
of them. 
9. The hypothesis is put forward that urease radiation, weakened 
by spreading or in any other way, causes synthesis. 
Experimental evidence of this is afforded by the fact, that at high 
pa, Where the urease is shown to be decaying, reversion of the 
hydrolysis is several times observed. 
10. A second inference from this conception, that outside the 
sphere of hydrolytic action around a urease molecule there. must be 
a region of radiation, weakened by spreading, and therefore of 
synthesis, explains the fact, established by a series of new experiments, 
that, diluting the urease concentration beyond a certain value, its 
specific activity is decreased. For evidently the synthetic action of 
undecaying urease can only be manifesied, if the spheres of hydrolytic 
action do not intersect each other sufficiently. 
11. A third inference, that in any urease solution, in which the 
enzyme is decaying through the combined action of alkalinity, tempe- 
rature and time, a synthesis of urea from ammonium carbonate, 
proportional to the urease concentration, will be observed, is tested 
experimentally and confirmed. 
12. Description of an apparatus for the simple determination 
H-ion concentration at constant temperature. 
The determination of the hydroxyl-ion concentration, which is 
needed for the calculation of the dissociation-formula of urease, is 
