"The law of conservation of mass was first put into definite form by Lavoisier, in the eighties of the eighteenth century. In considering the fermentation of fruit-juices, wherein carbonic acid gas and alcohol are produced, Lavoisier said:—"We must evidently have a complete knowledge of the analyses and the nature of the substances which can be fermented; for nothing is created, either in the operations of art, or in those of nature, and it may be laid down as a principle that, in every operation there is an equal quantity of matter before and after the operation; ...there is nothing but certain changes, certain modifications. The whole art of experimenting in chemistry rests on this principle; in all experiments one is obliged to assume an actual equality between the principles [that is, elements] of the substances examined and those obtained by the analysis of these substances. Thus, inasmuch as grape-juice yields carbonic acid gas and alcohol, I can affirm that grape juice=carbonic acid gas+alcohol.""