129 
Results : 
TABLE 24. 
c.c. NH; yo N in: 
| a | Corrected | NH; 
| First | Second | ts “for 
cylinder ‚cylinder | Mean ‚NH; out SE 
| | of Soja | into urea 
| | | 
Amm. carb. alone 1352.1 | 1352.7 | 1352.4 | 
Amm. carb. + 6 g. of Soja, 2days 1351 
Amm. carb. + 6 g. of Soja, 3 days 1350.9 
Amm. carb. + 6 g. of Soja, 4days 1350 135055: | 1350.3 | 1349.3 J. 1 
| | | 
| | | 
| 
Amm. carb. + 12 g. of Soja, 2days | 1349.9 | | 
Amm. carb. + 12 g. of Soja, 3 days | 1348 
Amm. carb. + 12 g. of Soja, 4days 1348.7 1348.6 | 1348.7 | 1346.7 | a: 4 
| | 
weakened by being dissolved for such a long time in an alkaline 
medium and therefore a gradual displacement of the equilibrium to 
the side of urea was to be expected. 
These experiments show clearly, that a small part of the ammonium 
carbonate disappears through the action of urease and that this part 
is proportional to the amount of urease present. Both facts are in 
accordance with the above theory of the synthesis of urea. 
12. The determination of H- and OH-ion concentration. 
Since the theory and results, communicated in this paper, will 
both have emphasized the dominating importance of frequent and 
therefore simple py determinations in enzyme research, it may be 
useful to give the following details of the apparatus used for this 
purpose. 
It was nearly the same as that, described by the author as “A 
simple Hydrogen Electrode” in Biochem. J. 1915, 66. 
The accuracy was improved by the addition of a little cup with 
saturated KCl solution, in which both the hydrogen-electrode and 
the tube of the calomel-electrode dipped. The latter was changed, 
as shown in Fig. 16 in order to avoid all capillaries and rubber 
connections. After a measurement the small flask, containing the 
calomel-electrode proper, was turned round and the dipping tube 
enclosed in a small tube with saturated KCl solution, as will be 
seen in the figure. 
9 
Proceedings Royal Acad. Amsterdam. Vol. XXII. 
