1904.] Studies on Enzyme Action. 209 



Effect of some Reducing Agents on the Reaction. 



Measurements have been made with phenylhydrazine acetate, hydro- 

 xylamine hydrochloride, sulphuretted hydrogen, and formaldehyde, the 

 results with the two former being interesting from their known 

 property of combining with aldehyde and ketone groups. 



Sulphuretted Hydrogen. This body proved to be quite remarkably 

 poisonous to the action, a solution containing 1/2,500,000 gramme-mol. 

 reducing the rate to a half. The poisonous effect also depends greatly 

 upon the period of incubation, the longer the incubation the greater 

 the retardation. The constants also increase considerably during the 

 action ; this phenomenon is very likely due to the gradual oxidation of 

 the H 2 S by the H 2 2 . 



The numerical results are appended : 



Table VIII. 



Time 

 Substance used and concentration. of incubation. Constants. 



Sulphuretted hydrogen, m/500,000 10 mins. 0*0062 0-0085 



m/500,000 90 0-00180-0075 



m/1,000,000 10 0-00730-0080 



m/1,000,000 90 0-00250-0080 



m/2,500,000 10 0'0076 O'OIOO 



m/2,500,000 90 0-00540-0098 



Without sulphuretted hydrogen 0*0190 



It was observed by Faraday that platinum no longer brought about 

 combination in detonating gas containing a little H 2 S, and Bredig has 

 shown that this gas is remarkably poisonous to the catalysis of H 2 2 

 by colloidal platinum.* 



Sulphuretted hydrogen has a slightly poisonous action on the lower 

 organisms, but is a very energetic blood-poison, probably acting on the 

 haemoglobin, which it changes into a compound containing sulphur, f 



Hydroxylamine. This body has a considerably retarding effect, the 

 constants decreasing slightly during the action. 



Table IX. 



Salt used. Constants. 



Hydroxylamine hydrochloride, ?*/20,000 ... 0-00080-0005 



?i/40,000 ... 0-00470-0041 



Without hydroxylamine 0'0180 



Part of the hydrochloric acid remains uncombined and exerts a 

 retarding action, but this is very small in so dilute a solution, and 

 nearly the whole retardation is due to the hydroxylamine. 



* Bredig, loc. cit., p. 65. 

 t Loew, loe. cit., p. 56. 



