The Tendencies of Chemistry 



by which these bodies are transformed into each 

 other. These tables of ther mo-chemical data 

 exist; they were drawn up by Berthelot from 

 his own innumerable experiments and those of 

 his pupils. The question now arises as to the 

 use to be made of them. 



The scientific value of a collection of numbers 

 depends on its usefulness for formulating laws 

 or for predicting new facts. Thus no science 

 has accumulated such quantities of numerical 

 data as meteorology; but as long as nothing 

 was deducted from them all we had the right 

 to refuse to regard meteorology as a true science. 

 If thermo-chemistry is nothing but a collection 

 of numerical constants it deserves the same 

 severe treatment. Now, according to Thomsen 

 and Berthelot, the data of thermo-chemistry 

 ought to allow the prediction of what reactions 

 are possible and what reactions are impossible. 

 They permit us to do so by means of the principle 

 of maximum work. 



Let us consider a stone placed on the de- 

 clivity of a hill; the slightest shock may cause 

 it to fall. As it falls, its energy, that is to say 

 its capacity for doing work, decreases by the 



41 



