CHAPTER V 



CHEMICAL EQUILIBRIA 



WE have now to investigate the equilibria of enzy- 

 matic processes and to compare them with the 

 equilibria in physical chemistry. VAN 'T HOFF ex- 

 pressed in 1898 the opinion that it might be possible 

 by the aid of enzymes, which decompose certain 

 substances, to synthesise these substances from 

 their products of decomposition. This opinion pre- 

 supposes that an equilibrium exists between these 

 products and their compound just as between an 

 ester (with water) and its products of decomposition, 

 acid and alcohol ; in this case the equilibrium is 

 reached when about f of the ester are decomposed. 

 On the other hand, if we invert cane-sugar by the 

 aid of an acid, the equilibrium lies so very near to 

 the end, where the sugar is totally decomposed, that 

 we have no hope of synthesising the sugar from its 

 products, dextrose and laevulose. As a matter of 

 fact it has been repeatedly maintained that this 

 synthesis has met with success, both by means of 

 acids and by means of invertase, but HUDSON has 

 proved that these assertions depend upon errors of 

 observation. 



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