GAY-LUSSAC'S OPINION 1 1 



age. The discovery by Lavoisier that combustion is a process of oxidation, a 

 combination of oxygen with the combustible substance, was an event the 

 influence whereof extended over the entire domain of chemistry. The assign- 

 ment to oxygen of a part in the process of fermentation was therefore opportune ; 

 but Gay-Lussac was especially prompted by another circumstance. 



A Parisian confectioner and cook, named Appert, had made practical use of 

 the experiment devised by his contemporary Spallanzani for the refutation of 

 the heterogenists and, after some preliminary trials, perfected his process for 

 preserving meats, vegetables, spirituous liquors, &c. To this end he exposed 

 them, in hermetically closed vessels, to the temperature of boiling water for 

 some time a process which had somewhat earlier (1782) been recommended by 

 the Swedish chemist SCHEELE (I.) for the conservation of vinegar. In this way 

 APPERT founded a new branch of industry the manufacture of conserves 

 which brought him both wealth and fame. He published a volume (I.) which 

 comprised the results of his experience. It was widely circulated and ran into 

 several editions, the first of which appeared in 1810, and the fourth in 1831. 



It is therefore little matter for surprise that the attention of the Parisian 

 chemist was directed (whether from the culinary or the literary side) to the 

 productions of his enterprising fellow-citizen. GAY-LUSSAC (I.) now examined 

 conserves prepared according to Appert's process, and found them to be free 

 from gaseous oxygen. This incited him to make fermentation experiments 

 with wine-must, <kc., the results of which led him to assert that the presence 

 of oxygen is necessary to the inception of fermentation. A number of over- 

 zealous colleagues, in expounding their master's opinion, added new features to 

 it, and subsequently credited him with the assertion that oxygen is the actual 

 ferment a statement as unfounded as it is inaccurate. Gay-Lussac only claimed 

 for the gas'a single function, the inception of fermentation ; once the process was 

 in operation the stimulus was no longer required. With regard to the nature 

 of this stimulating action he was, however, unable to report more definitely. 



Among the observations which led Gay-Lussac to adopt this view, mention 

 may be made of one which appeared to him particularly conclusive, namely, the 

 sterilisation of wine-must by sulphuring. When wine-casks, before filling, are 

 thoroughly sulphured i.e. the internal air contained in them is heavily charged 

 with sulphur dioxide by burning sulphur in the casks the grape juice thereafter 

 introduced remains quiet and passive, without fermenting. This circumstance 

 is now unanimously ascribed to the vitality of the yeast cells in the must being 

 destroyed by the sulphurous acid. Gay-Lussac, on the other hand, viewing the 

 matter differently from his standpoint, held the opinion that as the sulphurous 

 acid had a strong affinity for the oxygen, the two combined, and as no oxygen 

 was available for starting the fermentation, the must necessarily remained inert. 



The experiments made by Schwann in 1838, and described in 13, refuted 

 the opinion of Gay-Lussac, by demonstrating that the role of exciting fermentation 

 is set up by certain microscopic living creatures which perform their functions 

 in the absence of oxygen. Subsequent research proved that the presence of this 

 gas is altogether superfluous, so far as the progress of alcoholic fermentation is 

 concerned, although it is not without influence thereon. PASTEUR (II.) in 1861 

 established it as a fact that this progress is more satisfactorily effected when 

 the fermenting liquid is subjected to brisk aeration. 



12. Cagniard-Latour's Vitalistic Theory of Fermentation. 



The French apothecary ASTIER (I. and II.) has generally been credited with 

 being the next individual, after Leeuwenhoek, who gave his attention to the 

 nature of yeast. An examination of his published works shows, however, that 



