J315 



Tlie action of urease on a solution of urea soon pioduces so con- 

 siderable a lowering of the H-ion concentration, that the course of 

 the hydrolysis is seiiously ciiecked. To regard (he accelerating- effect 

 of a stream of CO,, passed throngh this solution, as u pi-oof of the 

 specially favourable influence of CO., is an unnecessary assumption, 

 as long as full account is not taken of the power, CO, has to 

 compensate the depression of the H-ion concentration. This was not 

 done by previous authors. 



It was, however, knowji, that nature often makes use ofbicarbo- 

 nates and carbonic acid as well as of phosphate mixtures as buffers 

 to maintain the necessary constancy of the true reaction in the 

 living cell. The buffer action of bicarbonates in blood is a case in 

 point, which has attracted much attention of late. 



Before reaching the point of view, that the urease radiation is 

 only absorbed by the substrate urea and the H-ious, the author 

 assumed, that the products of the enzyme-action — here ammonia 

 and carbonic acid — also absorbed the radiation to some extent and 

 in this way interfered with the rate of hydrolysis. 



At the same time it was taken into consideration, that by passing 

 a continuous and abundant stream of CO, through a urease solution 

 containing much ammonium-carbonate and not too large an amount 

 of urea, the H-ion concentration might easily be ujaintained constant; 

 for generally the true reaction of a solution of a bicarbonate, saturated 

 with carbonic acid, is not changed by some variation in its con- 

 centration. 



It was therefore that in 1915 and 1916 a considerable amount 

 of experimental work was carried out with ammonium-carbonate 

 and carbonic acid as buffer-mixture, a short account of which will 

 now be recorded and explained by the theory afterwards developed. 



The ammonium-carbonate eniployed was Kahlbaum's Ammonium- 

 carbonat, "zur Analyse mit Garantie-Schein". 



By dissolving ammonium carbonate in water, as Fenton ^) has 

 shown, an equilibrium of ammonium-carbonate and ammonium- 

 carbamate is oütained. Fenton's method of estimating both these 

 compounds and urea in one solution by the use of sodiumhypo- 

 chlorite and sodiundiypobromite was tried by the present author 

 with a view to establish what was the original product of the 

 hydrolysis of urea by urease. 



The velocity with which both animonium-cai'bonate and ammonium 

 carbamate tend to equilibiium, is, however, too great. These efforts 



1) Proc. Roy. Soc. 1886. 39. 386. 



