Chemistry. — ”Urease and the radiation-theory of enzyme-action’. 
By Dr. H. P. BARENDRECHT. 
(Communicated in the meeting of May 31, 1919). 
Xe 
11. Direct synthesis of urea by urease out of ammonium 
carbonate. 
According to the above theory the final equilibrium in the action 
of urease on urea will not always be found at complete hydrolysis. 
In the case of a low concentration of urease the synthetic action 
in the outer shell will have free play. 
In an alkaline urease solution, whatever its concentration, the 
enzyme will partially decay in the course of time, as was shown 
in part 9. In this case also a reverse action will manifest itself, 
proportional now to the concentration of urease. 
To test this inference from the hypothesis, the following experi- 
ments were carried out: 
In each of six large cylinders of about 1 Litre capacity 100 c.c. 
of water were introduced, into which 5.786 g. of ammonium car- 
bonate were dissolved. Each of these cylinders was closed by a 
rubber stopper with two borings, the one carrying a straight glass 
tube, provided at the bottom with a bulb with pinholes, the other 
a bent glass tube, allowing the air-current, which was to be blown 
through, to pass into a second, smaller cylinder, in which the am- 
monia was to be absorved. To this purpose each of these smaller 
cylinders contained 186,85 g. of H,SO,74 N (which is equal to 
185 ce. 7 N). The greater accuracy, obtained by weighing the 
absorbing acid, was necessary, considering that the effect looked 
for, was the difference of two large values and would presumably 
be only small. 
In two of the large cylinders 3, in two others 6 g. of Soja-meal 
were introduced. The glass tubes of these cylinders were all closed 
with pieces of rubber tubing and clips. After a few hours those, 
making communication with the absorbing cylinders, were opened 
for a moment, to allow the carbonic acid, evolved by the partial 
change of the dissolved ammonium carbonate to ammonium carba-_ 
mate, to escape through the sulphuric acid. 
