xvn MOLECULAR ARCHITECTURE 389 



After Fermentation : 



71.8.7 409.10.0 28.12.6 0.0.3 =510. 0.0 



Lavoisier's chapter on " Vinous Fermentation " will always 

 be remarkable for the fact that it contains one of the first 

 clear statements of the law of CONSERVATION OF MASS during 

 chemical change, sometimes described also as the INDE- 

 STRUCTIBILITY OF MATTER, and one of the first descriptions 

 and illustrations of a CHEMICAL EQUATION. The inde- 

 structibility of the atom had already been postulated by 

 Newton (p. 292). The proof that the total mass is unaltered 

 by chemical changes is closely bound up with the proof 

 that heat is imponderable ; this proof had been given by 

 Cavendish for the explosion of hydrogen and oxygen (p. 113) 

 and by Lavoisier himself for the calcination of tin in closed 

 vessels (pp. 35-38). Lavoisier was therefore able to enunciate, 

 as a guiding principle for his work on fermentation the law 

 that : 



" Nothing is created, either in the operations of art, or in 

 those of nature, and it may be set out as a principle that, in 

 every operation, there is an equal quantity of matter before 

 and after the operation ; that the quality and the quantity 

 of the principles is the same, and there are only changes, 

 only modifications." 



"On this principle is based the whole art of making ex- 

 periments in chemistry : in all of them one must suppose a 

 true equality or equation between the principles of the body 

 which one examines and those which one obtains from them 

 by analysis. Thus, since grape-juice gives carbonic acid gas 

 and alcohol, I can say that grape-juice = carbonic acid + 

 alcohol" (Works, I. 101). 



