214 NEGATIVE CATALYSTS 



which increase the resistance and so diminish the velocity of the 

 reaction without being changed themselves in the process. Such 

 bodies have been termed by Ostwald negative catalysts. In the 

 language of our formulae these bodies diminish the value of k, the 

 constant of reaction velocity. That these substances are truly 

 catalytic in their action is demonstrated by the extremely minute 

 quantities necessary to slow the reaction in comparison with the 

 quantities of substratum acted upon. Thus Bigelow has shown 

 that the presence of such a minimal trace of mannite as 0-000,001,4 

 grm. per cubic centimetre reduces the velocity of oxidation of 800 

 times as great an amount of sodium sulphite in solution by one-half, 

 and S. W. Young has shown that the oxidation of stannous chloride 

 or sodium sulphite is similarly reduced by mere traces of many 

 organic substances, such as nicotine, brucine, morphine, quinine, 

 aniline, mannite, and potassium cyanide. As first shown by Graham, 

 the oxidation or ignition of phosphorus is also prevented by traces of 

 organic substances, such as turpentine, alcohol, ether, and ethyl iodide. 



The number of such negative catalysts known to us is not so 

 large as that of those which increase the velocity, but this is 

 perhaps due to the fact that the interest and attention of the 

 chemist have been chiefly directed towards those substances which 

 cause or hasten reaction rather than to such as stop or retard it. 



We have already seen that the reactions caused by enzymes 

 do not proceed with a measurable velocity in the absence of the 

 enzymes, in fact, do not appear to occur at all, and hence there 

 is no necessity for the existence of negative enzymes in the body, 

 and none such have hitherto been described. 



It will be pointed out later that the existence of negative 

 catalysts, as has been urged by Ostwald, is a point of evidence 

 against the view that the mode of action of catalysts is in all cases 

 by the formation of intermediate compounds. 



ANTICATALYSTS, ANTIFERMENTS, AND ANTI-ENZYMES. 



Under the name of " Anti-catalysers," or " Paralysers," Bredig 

 has designated those substances which by their presence in small 

 quantity retard or stop the action of a catalyst. Such bodies 

 differ from the " negative catalysts " mentioned above in that 

 they do not retard the reaction by directly acting upon the sub- 

 stratum, but by acting upon a positive catalyst which is present 



