206 



Dr. G. Senter. 



[June 2, 



Acids. 



Sulphuric acid.., 



Tartaric ... 



Oxalic ,, ... 



Succinic ... 



Lactic ... 



Acetic ... 



Table III. 



Inhibiting quantity. 

 1/245 normal solution. 

 1/75 

 1/630 

 1/30 

 1/9 

 5/6 



Hydrogen 

 ion concentration. 

 1/245 normal. 

 1/280 

 1/1000 

 1/700 

 1/265 

 1/266 



It is clear that in this case, also, the retarding effect is, in the first 

 instance, proportional to the chemical activity of the acid, though 

 oxalic and succinic acids have a greater toxic action than would be 



expected. 



Effect of Alkali upon the Reaction. 



The influence of sodium hydroxide upon the reaction has been 

 determined. It has been found that the velocity is not very appreciably 

 influenced by solutions weaker than 1/2000 normal, but that in stronger 

 solutions a retardation of the velocity is brought about. The retarda- 

 tion, unlike that caused by acids, depends upon the period of incubation, 

 but the change is not a permanent one, since on neutralisation the 

 original velocity is regained. Details are given in my former paper.* 



Effect of Neutral Salts. 



Numerous investigations of the influence of neutral salts on enzyme 

 action have been carried out, but little of a general character can be 

 deduced from the results. Dilute solutions have often a slightly 

 accelerating action, which passes into a retardation in more concentrated 

 solutions. 



I have investigated the influence of halogens of the alkalis and 

 alkaline earths, of the alkali sulphates, and of sodium acetate and 

 carbonate. Only the halogen compounds exert a considerable retarda- 

 tion; the effects due to the others seem to be more of a secondary 

 nature. 



Some typical results are given below : 



Lithium chloride, ra/400 



Sodium chloride, w/400 



w/800 



Potassium chloride, m/400 . 



w/800 . 



Ammonium chloride, w/400. 



Potassium bromide, w/800 . 



w/2000. 



Ammonium bromide, m/800. 



Table IV. 



Constants. Constants. 



'0059 Ammonium bromide, m/2000. . '0136 



-0055 Barium chloride, w/200 '0052 



0-0093 m/400 O'OOSO 



'0057 Strontium chloride, w/200. ... -0056 



'0095 /400. ... -0090 



-0058 Calcium chloride, w/200 '0051 



'0094 fw/400 -0084 



-0075 Sodium fluoride, w/400 . . '0170 



0-0128 w/800 0-0246 



-0074 Control experiment '0280 



* Senter, loc. cit. } p. 301. 



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