SECTION X 



ENZYMES. 



It has long been known to chemists that the velocity of 

 chemical reactions could, in many cases, be increased by the 

 presence of relatively small quantities of certain substances 

 which do not appear to take any immediate part in the 

 reaction. 



This is well illustrated by the familiar example of the 

 effect of a small quantity of manganese dioxide in bringing 

 about the liberation of oxygen from potassium chlorate at a 

 temperature much lower than would be possible by heating 

 this substance alone. 



Other examples of the accelerating influence of foreign 

 substances on the velocity of reactions are to be found in the 

 use of cuprous chloride in Deacon's chlorine process, and of 

 spongy platinum, either in the manufacture of sulphuric acid by 

 the contact process, or for effecting the explosive combination 

 of hydrogen and oxygen. 



Similarly, the hydrolysis of cane sugar according to the 

 equation — 



Ci.HooOji + H,0 = aQH.jOg 



takes place very slowly in neutral aqueous solutions, but 

 may be greatly accelerated by warming the solution with a 

 little mineral acid. 



A feature common to all the above reactions is the fact that 

 the substance which produces the accelerating influence is un- 

 altered by the reaction, and can usually be recovered from the 

 reaction-product unchanged in quality and quantity. 



Substances which have this remarkable property of being 

 able in some way to influence the velocity of a reaction, 

 without apparently undergoing any change themselves, and 



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