30 
small quantity of alkali, which will leave a py of moderate value 
practically unchanged, will cause a distinct rise in a py of about 8. 
This is clearly borne out by the results, obtained by the addition 
of ammonia. 
The urea, however, increases the py to an equal degree, whatever 
its original value. 
This increase is therefore evidently not due to an alkalinity of 
urea. A substance, however, which possesses no alkalinity, can only 
lower the H-ion concentration, if it lowers the OH-ion concentration 
just as much. 
This effect may be expected from all neutral substances, when 
added in such an amount to the solution, that the concentration of 
H,O is appreciably diminished, provided their ionising power is 
much less than that of water. In such a case the dissociation product 
Cu XX Con or, as it is usually called, the dissociation-constant of 
water &, will show a diminution. 
Similar changes of the dissociation-constant of water have been 
studied before, for instance by LÖWENBERz *) in a paper on “The 
influence of the addition of ethyl-aleohol on the electrolytie disso- 
ciation of water”. 
In view of this influence on ky the study of urease action in 
solutions, mixed with some alcohol, promised interesting results. 
The alcohol, employed in these experiments had been freed from 
carbonic acid by boiling in a flask, attached to a reflux condenser. 
The same 8°/, phosphate buffer-mixtures and Soja extract were 
used as before in the determination of m in part 4 of this paper. 
The amount of alcohol, to be mixed beforehand with the phosphate, 
was calculated so as to obtain a concentration of 5°/, in the final 
solution. 
For the sake of comparison the same Soja-meal was used as in 
the previous experiments. Those beans had been powdered a year 
ago and the meal had shown already some signs of weakening. 
Especially in alkaline solution its constancy of activity had been 
found to be diminished. Therefore in the experiments with high 
Pu the m of the first stage had to be taken rather than the mean. 
And this value was multiplied by the ratio of the activities at the 
same py, found formerly and now. 
The values, obtained in this way for m in the alcohol solution 
are plotted in figure 6 /, in which for the sake of comparison the 
original curve for m of fig. 3 is also reproduced. 
1) Zeitschr. physik. Chem. 1896, 20, 283. 
