1904] Studies on Enzyme Action. 207 



Owing to the direct oxidising action of H 2 2 upon the iodides, it has 

 been found impossible to complete the series by making measurements 

 with corresponding solutions of these compounds. This point will be 

 again referred to under the experiments dealing with iodine. 



From the results given above it is evident that the retarding effect 

 due to the halogen compounds is due to the halogen ion alone, since 

 it is quite independent of the other ion present. It may be mentioned 

 in this connection that according to Bredig* the catalysis of hydrogen 

 peroxide by colloidal platinum is retarded by KC1 and NH 4 C1, though 

 not appreciably so by other neutral salts. 



The results with sodium fluoride are particularly interesting, since it 

 has long been regarded as a poison for micro-organisms, but without 

 effect on enzymes, f According to Pavy, j however, it has a slightly 

 deleterious action on enzymes, and this is quite borne out by the results 

 given above. 



Alkali Sulphates. Experiments were carried out with potassium, 

 sodium, and ammonium sulphates, in concentrations varying from 

 m/50 to m/400. The results are as follows : 



Table V. 



Salt used. Constants. Salt used. Constants. 



K 2 SO 4 , w/50 0-0265 :N T a 2 SO 4 , m/50 0'0360 



m/200 0-0235 w/200 "0308 



m/400 0-0245 m/400... 0-0288 



(NH 4 ) 2 SO 4 , m/50 -0280 Control experiment ; no 



m/200 '0250 salt present '0288 



m/400 .... -0260 



From the results given it is evident that, while K 2 S0 4 and (NH 4 ) 2 SO 4 

 exert a slight retarding action, Na 2 S0 4 in m/50 solution has a con- 

 siderable accelerating effect, which practically disappears in m/400 

 solution. As having a possible connection with this result it may be 

 recalled that, of the three sulphates, only the sodium salt crystallises 

 with water (10 molecules). 



Sodium Acetate and Sodium Carbonate. The results are as follows : 



Table VI. 



Salt used. Constants. Salt used. Constants. 



Sodium acetate, m/100 '0272 Sodium acetate, m/1000 .... '0345 



m/200 -0270 m/2000 .... -0340 



m/400 '0250 Control experiment "0280 



Control experiment '0180 



Salt used. Constants. 



Sodium carbonate, m/40 '0070 



m/80 '0135 



m/200 .... "0194 

 Control experiment '0180 



* Bredig, ' Anorg. Fermente/ p. 84. 



f Oppenheimer, loc. cit., p. 41. 



J Pavy, ' Journ. of Physiology,' vol. 22, p. 391 (1898). 



