The Frontiers of the Sciences 



chemical and organoleptic properties/* This 

 definition clearly separates chemistry from 

 physics, which studies one by one the different 

 properties of matter, and whose aim is conse- 

 quently abstract, whilst chemistry deals with a 

 concrete object. Chemistry was too busy with de- 

 scriptions to be able to recognise reactions as any- 

 thing but disturbed periods separating two states 

 of equilibrium, and satisfied itself with vague 

 hypotheses regarding affinities. The classical 

 treatises, with their succession of portraits of 

 chlorine, hydrogen, oxygen and their com- 

 pounds, recall some of the old histories devoted 

 to the description of our kings and their august 

 alliances, which passed over in a line, as un- 

 worthy of the notice of posterity, the disturbed 

 periods called either revolts or revolutions, ac- 

 cording to their importance. 



But in the end molecular revolutions came 

 in for more attention. The investigation of the 

 formation of ethers and of dissociation showed 

 that chemical reactions, like other phenomena, 

 obey laws. Later, Berthelot attempted to solve 

 the problem of chemical mechanics by investi- 

 gating the heat developed by reactions. The 



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