CATALYSIS AND THE ENZYMES 



very much retarded by traces of glycerin, mannitol, 

 or other organic compounds. The luminosity of 

 phosphorus is diminished or hindered by the 

 presence of turpentine, ether, or alcohol. Prob- 

 ably all such influences are based in the working 

 of these agencies on a catalysing substance. In 

 the first case which we have mentioned, traces of 

 copper contained in the common distilled water 

 of our laboratories exert a catalysing influence 

 upon the oxidation of the sulphite of sodium. 

 Organic substances, for example mannitol and 

 glycerin, are inclined to form compounds of copper 

 and so they remove the effective catalytic agent 

 from the water, and diminish the velocity of the 

 oxidation of the sulphite of sodium. 



We owe to Bredig, of Zurich, the exact knowledge 

 of the retarding influence of traces of prussic acid, 

 sulphide of hydrogen and some other substances 

 on the catalytic reaction of platinum black and 

 hydrogen peroxide. There is no doubt that 

 prussic acid or hydrogen sulphide change the 

 surface of the platinum, for they cover it with a 

 layer of platinum cyanide or sulphide. So the 

 platinum surface which exercises the catalytic 

 power is very considerably diminished. By 

 decomposition of the cyanide layer the pure plati- 

 num surface can be restored and the catalyser 

 becomes active again. There is an interesting 

 parallelism between these phenomena and the 

 poisoning of living cells by cyanide or sulphide, 

 89 



