THE EQUATION OF ACETIC FERMENTATION 303 



but the reasons for these phenomena could not be given. The ABBE KOZIER (I.) 

 concluded from his experiments that air is absorbed by the wine in process of 

 turning sour, but LAVOISIER (I.) afterwards shewed that this is only true of one 

 of the constituents of the atmosphere, viz., oxygen. He stated that "acetic 

 fermentation is nothing more than the souring of wine, effected in the open air 

 by absorption of oxygen." In 1821 Edmund Davy discovered platinum-black, a 

 substance which, when moistened with spirits of wine, becomes white-hot, the 

 formation of acetic acid being evidenced by the odour evolved. This observation 

 was followed up by DOBEREINER (I.), who found that, in this reaction, the alcohol 



FIG. 89. Bacterium aceti. 



Long threads. Culture twenty -four hours old in " doppel-bier " at 4o-4o.5 C. In several places the 

 breadth of the threads is exaggerated. Magn. 1000. (After Unmcn.) 



takes up oxygen water and acetic acid, but no carbon dioxide, being formed. 

 By observing the volume of oxygen consumed by a weighed quantity of alcohol, 

 he arrived at the following equation for this oxidation process : 



C 4 H 6 2 + 40 = C 4 H 4 4 -I- 2HO 



which, translated from the symbolical language of equivalent formulae to that of 

 atomic formula?, reads as follows : 



C 2 H 6 + 2 = C 2 H 4 Oo + H 2 0< 



Hence, Dobereiner concluded that, for the production of acetic acid, only three 

 substances are required : alcohol, oxygen, and a body capable of absorbing and 

 condensing the latter, and thus bringing it into more intimate contact with the 

 first named, whereupon the reaction ensues. 



The above experiment of Dobereiner's was taken by chemists as a starting- 

 point in attempts at elucidating the phenomenon of acetic fermentation. The 

 intermediary part played by the " mother of vinegar " in the souring of wine 

 was obvious, since it was well known that without this " mother" no conversion 



