in 



1320 



A liask of 250 cc. was liiled to the mark witli a «olutioii of a 



ixtiiie of Na^HPO^ 2 aq ami KH^PO^, calculated lo produce a 

 concentration of phosphate of S'/o during the reaction. A small 

 quantity of Soja-meal was added, mixed with this solution, and the 

 Mask was left for one honr in the bath at 27°. After addition of 

 kiezelgni' (the same weight as that of the Soja-meal) the solution 

 was i-apidly rnn through a pleated filter. F'rom the perfectly clear 

 filtrate portions of 10 cc. were introduced into test-tubes (as above) 

 and placed in the same bath, in which a series of stoppered flasks 

 with urea solutions were bi'onght to 27°. As 2 cc. of these urea 

 solutions were to l)e added to 10 cc. of enzyme-extract, all the 

 niea-solutions had 6 times the requiied final concentration. The three 

 highest concentrations of 4" „, 67o f^"<^l 8" „ were obtained by pi-eparing 

 a solution of 4.8 g. of urea to 10 cc. and bringing 1 cc. of this 

 with 1 cc. of water into the 4"„ tid)e, 1.5 cc. with 0.5 cc. of 

 water into the 67o t^^^e and 2 cc. into the 87o tube. 



The reaction was allowed to proceed for a fixed time, usually 

 2 hours, after whicl) the NH, formed was estimated by connecting 

 the tubes with wider ones, into which had been brought 10 cc. of 

 HjSO^ ^V ^ ^'i<^ some water, running 25 cc. of saturated potassium 

 carbonate and a drop of octylalcohol into the reaclion-tu[)e and 

 passing a current of air for two hours. 



The 1)11 was determined with the electrometer in 10 cc. phosphate- 

 enzyme-solution -j- 2 cc. water at 27°. 



The quantity of Soja-meal was usually 0.2 gram. Only at the 

 lowest im more enzyme and different reaction times had to be taken. 

 The results are then reduced to 0.2 g. of Soja and 120 minutes. 

 (See tables 17 and 18 on following page). 



The conclusions, to be drawn from these results, are the following: 



The amount of action, produced under the same conditions, as to 

 temperature and pu, by the same quantity of urease in urea solutions 

 of different concentrations becomes never really constant, not even 

 in highly concentrated solutions. 



The higher the acidity of the solutions, the more the amount of 

 action increases with increasing concentration. 



These facts are in agreement with the fundamental formula 



— dtV :=. 7)1 dt 



For the initial velocity, when ./• is still equal to a, this formula 



gives the mathematical expression 



d.t a 



=z m 



dt a -\- nc 



