Chemistry. — " L'rmsf' (Oid the radiation-theory of enzipNe action'\ II. 

 By Dr. H. P Barkndrecht. (Commnnioated by Prof. .1. H()f,sekk,n.) 



(Communicated in the meeting of March 29, 1919). 



Ill order to secure a more complete coiistaiicv ol" pf^ a more 

 extensive investigation, this time with 0,01 \\, of nrea, was carried 

 out some months later, when Ihe (echniqne of (he estimations was 

 more fully worked out and refined. 



At least Iwo sei-ies, with different />//, were completed on the same 

 day, starting fi-om the same neutral phosphate extract of Soja-meal. 

 On another day one of them was repeated together with a third one 

 with a new />//. In this way the uncertainty as to the comparabi- 

 lity of the enzyme quantities, prepared on difïeient days, was 

 obviated. 



P'or want of space these tables cannot be communicated here. 



71C 1 



The value of )n, now calculated with the formida loff -I- 



0,434 1— V ^ 

 i),0[y = mt, was constant in each table again, within the limits of 

 the unavoidable experimental errors. 



In continuing these investigations at still highei- p^ a falling off 

 of the constant m was generally observed towards the end of the 

 reaction. This is, what might have been expected for different reasons. 



From the well-known chart of the H-ion concentration data of 

 SöRBiNSRN it is clear, that the phosphate mixtures are oidy efïicient 

 buffers up to about p^ = 8. 



It was for instance established by the present author, that, while 

 10 c.c. of a 9,6 V„ phosphate mixture, diluted with 2 c.c. of water, 

 produced an 8 7. l)hosphate mixture of /;h = 8,1J, dilution with 

 2 c.c. of NH, sV N (i.e. the amount of NHg formed by the hydrolysis 

 of 12 c.c. of 0,01 7o "J'^ft- solution) made pn=8,25. 



At lower p„ this change in p^ is oidj about 0,01 or 0,02. 



Evidently by the increase of alkalinity during the hydrolysis in 

 a solution of 0,01 "/„ ui-ea the in already diminishes a little in the 

 case of a large p^^. 



iVloreover, as indicated above, the radiation theory itself predicts 

 a decrease of the activity of the enzyme as soon as the total con- 

 centration of urea -j- H-ion (or more accurately, as soon as ?/? -f- ''^) 

 has become so small, that the radiation does not all reach a urea 



