No. 606] 



BIOLOGICAL ENIGMAS 



335 



of water does not appear to depend merely upon the 

 chemical instability of the solute. 



The increase in reaction velocity which characterizes 

 catalysis is to be attributed to three more or less sep- 

 arable influences exerted by the catalytic surface, (1) the 

 local increase in the concentrations of the reacting sub- 

 stances at the surface, (2) the impressment upon the 

 attached molecules, of a relative orientation which is 

 favorable to chemical union, or which in part constitutes 

 such union, and (3) the spreading and weakening of the 

 fields of force of the molecules, due to their interaction 

 with the surface fields. The first factor, alone, would be 

 of primary importance for the combination of free atoms 

 —a relatively rare process— while the last factor, alone, 

 would be responsible for the acceleration of simple de- 

 compositions. Eeactions between two or more molecular 

 groups, whether synthetic or metathetic, should be influ- 

 enced by all three factors. Strutt^' has shown that in 

 certain typical chemical reactions, only one out of many 

 millions of collisions between potentially readable mole- 

 cules results in chemical interaction. The active collisions 

 probably coincide with the presence in the colliding sys- 

 tem of favorable relative orientations and states of the 

 molecular fields, which in the absence of a catalyzer de- 

 pend upon chance, l)ut wiiicli in the ]>resence of a catalyzer 

 are encouraged by tlu' naturr of the catalytic surface. 



It is of course not ])ossi1ile in a paper of this sort to 

 enter into the matheniatLcs of the theory of catalysis which 

 is outlined above.^'-* Catalytic influence is obviously only 

 one among many factors which affect a chemical reaction. 

 Catalysis is possible only when the appropriate raw ma- 

 terials are provided, and when the energ\' relations of the 

 system are such as to make the reaction thermodynam- 

 ically conceivable. The heterocatalytic effect of a given 

 substance may far outweigh its autocatalytic effect either 



27Strutt, R. J., "Molecular Statistics of Some Chemical Actions," Pro- 

 ceedings of the Eoyal Society (1912), A, 87, 302^309. 



28 Cf. Mellor, loc cit., 250-254. Also Bayliss, loc. cit., 49-71. 



29 For a development of the mass action relationships involved, see Lang- 



