CHEMICAL PHENOMENA IN LIFE 



which made Bredig call such retarding substances 

 Poisons for catalytic and enzyme effects. 



A very interesting result in chemical reactions 

 is often given by the phenomenon that the cata- 

 lysing substance is formed by the reaction itself. 

 Pure copper metal is very much less soluble in 

 quite pure nitric acid than in nitric acid which 

 contains a little nitrous acid. The latter acid has 

 a catalytic influence on the process of the dissolving 

 of copper. Now some small quantity of nitrous 

 acid is always formed by the reduction of the 

 nitric acid during the process of dissolving copper. 

 We therefore see that, after a certain time, the 

 copper dissolves much more quickly than in the 

 beginning. Such a catalysis is called A utocatalysis. 

 We may compare it to the influence of heat on the 

 dissolution of sodium hydroxide, during which 

 process heat can be produced by the process itself. 



Catalytic substances sometimes, in the same way 

 as platinum black or acids, may influence a large 

 number of reactions. Acids particularly are quite 

 usual catalytic substances which affect nearly 

 every kind of reaction. 



It is a very important fact that the final equi- 

 librium in the reaction is as little altered by the 

 presence of the catalysing substance as that the 

 order of- the reaction is changed. Consequently 

 the catalytic influence does not extend but to the 

 reaction velocity. Catalytic reactions are of the 

 greatest importance for chemical phenomena in 

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