236 THE FITNESS OF THE ENVIRONMENT 



complete. In contrast, those which are with- 

 out energy change generally proceed smoothly, 

 slowly, and without complication to a state of 

 equilibrium in which the reaction is very in- 

 complete. 1 Under the latter circumstances 

 slight changes of conditions make possible 

 a reversal of the delicately balanced process ; 

 the reaction can be made to run in either 

 direction at will. 



The absence of transformation of energy 

 accompanying hydrolysis may be illustrated 

 by a few typical cases chosen from the data 

 of simple substances. 



Such measurements of heats of reaction fall 

 well within the limits of error of the method 

 of investigation, and there can be no doubt 

 that in all such cases the heat of reaction is 

 so small that it cannot be detected by the 

 ordinary methods of measurement. 2 



1 van't Hoff, "Acht Vortrage liber Physikalische Chemie." 

 Brunswick, 1902, Lecture 6. 



2 Stohmann, Zeitschrift fur Physikalische Chemie, II, 29, 

 1888 (see also Ostwald's "Lehrbuch der Allgemeinen Che- 



