The Evolution of the Sciences 



tific knowledge can be discovered. If, however, 

 violent reactions are unsuited for experiment, 

 it is quite different with slow and weak reactions, 

 and especially with these reversible reactions 

 which occur on the border of states of equilibrium. 

 The chemist can then bring into action, separ- 

 ately, each of the variables defining the system: 

 the masses of the bodies under consideration, 

 their degree of dilution and temperature, the 

 duration of the reaction, and he can determine 

 the direction and the magnitude of the resulting 

 action. Thus, whereas the early chemists were 

 attracted by the intensity of violent reactions, 

 modern chemistry is chiefly interested in slow 

 reactions, in which it is easier to take the mechan- 

 ism to pieces and expose the springs to view. 

 The great chemist, J. B. Dumas, expressed this 

 idea with the prescience of genius when he 

 wrote: 1 " We may predict that if some day 

 accurate views are obtained regarding the 

 nature of chemical affinity they will be due 

 far more probably to the study of the weakest 

 than of the most energetic chemical actions/' 



1 Lemons de Philosophic chimique, delivered at the College 

 de France in 1836, p. 195. 



52 



