1137 



is really the general equation of nrease-action at constant lempe- 



rature and constant H-ion concentration. 



nc 

 If -— — is small, compared to a, evidently the reaction curve 

 0,434 ' -^ 



must be expected to be practically a straight line. On the other hand 



the logarithmic curve of the simple law of mass action will appear 



to represent the course of the leaction in more acid solutions, where 



nc 



predominates largely over a small value of a. 



0,434 



By changing the proportion of NaJlPO^ 2 aq and KH^PO^ in the 

 87, phos|)hate mixtures a great range of constant H-ion concen- 

 trations could be covered. To secure the constancy of p^^ throughout 

 the course of the reaction, it was necessary to work always with 

 0.02 7,, or better still with 0.01 »/„ urea solutions. Since 12 c.c. of 

 0.01 7o contain oidy J. 2 mg. of urea, this means, that in all these 

 experiments the degree of hydrolysis of 1.2 mg. urea had to be 

 determined by single measurements, a serious disadvantage, which, 

 however, had to be put up with in view of the dominating impor- 

 tance of constant H-ion concentration. 



The same high degree of accuracy, as was absolutely necessary 

 in the determination of the constant n, is not to be expected here, 

 nor, happily, is it required. 



A second object of these experiments was to determine m in the 

 solutions of different acidity, when equal or comparable amounts of 

 enzyme were present or in other words to investigate /// as a function 

 of pH- 



To get comparable amounts of enzyme in the solutions the following 

 simple method proved to be efficient. 



Some 500 grams of powdered Soja-beans were kept stored for 

 this purpose in a stoppered bottle, shut off from the influence of 

 light in a cupboard, and simply mixed now and then by shaking 

 in the course of these experiments, which lasted several months. 



The quantity of Soja-meal required was always weighed off and 

 extracted on the day of the experiment with the same nearly neutral 

 solution of 7.28 gr. of Na,HPO, 2 aq + 2.32 gr. of KH,PO, per 

 100 cc. of water. This extraction was performed by mixing Soja- 

 meal and phosphate-solution in a stoppered flask, shaking through 

 thoroughly, leaving it for one hour in the water-thermostat at 27°, 

 adding kiezelgur of the same amount as the Soja-meal, and filtering 

 rapidly through an ordinary pleated filter. Invariably, without any 

 difficulty, a clear solution was obtained, slightly opalescent if large 

 quantities of Soja-meal had been employed. The working solution 



