35 
This table and curve B of Fig. 8 would predict a decrease in m 
brom 1<3; forno "BTA, fot pp = 1,24, thatsis-from- 1 to 
0.725, whereas according to table 42 experiment produced a decrease 
from 1 to 0.82. 
The interpretation of this difference is, that the 4, and ky are 
also appreciably diminished by 10 °/, alcohol, that therefore the “rest- 
curve” of urease in this solution has to be placed above the curve 
B of Fig. 8. 
The curve C in Fig. 8 and the fourth column in table 19 
represent the values which 7 would have, if both ka and k, had 
. increased by 20°/,, 4, having, as in curve B, the value 10-142, 
Attention may here be drawn to the fact, that if a neutral body 
like aleohol, diminishes the dissociation constants of urease as well 
as of water, the new curve for m intersects the original one, which 
means, that in such a case a considerable decrease of activity 
is to be expected at low py (in the present case below py = 7.85) 
and by the same agency, the addition of alcohol, an increase at high py. 
The influence of neutral salts may be illustrated by the example 
atb: KCI. 
Here, as in all previous cases, 5°/, means 5 gram in 100 c.c. of 
the reacting solution. 
In 8°/, phosphate solutions the py was found not to be raised, 
but to be diminished in a constant degree by 5°/, KCI. 
Pu 
without KCl 6.13 6.89 (220 
with 5 °/, KCl 6.00 6.79 (ga G2) 
difference 0.13 0.10 0.10 
Nevertheless in the ammonium carbonate solution KCl had pro- 
duced a considerable decrease of urease activity. Without KCl 
m = 0,0031, with 5°/, KCl m= 0.0022. 
The conclusion, to be drawn from these facts, is, that a neutral 
salt like KCl increases all dissociation constants, that of urease as 
well as that of water. : 
We thus have here again and in a marked degree, a change in 
the nature of urease, a general decrease in its activity, brought 
about by an increase of its dissociation-constants. 
The raising of the dissociation-constant of water by salts had 
already been observed in this study in the determination of the 
hydroxyl-ion concentration in 8°/, phosphate solutions, the dissocia- 
tion-constant of water having been found to be 10-1878, instead 
of 10-1584, as it is in pure water. 
3% 
