316 VINOUS FERMENTATION. 



wine is owing to an ether of an organic acid, resembling one of 

 the fatty acids (cenanthic ether). 



It is only in liquids containing other very soluble acids, that 

 the fatty acids and cenanthic acid are capable of entering into 

 combination with the ether of alcohol, and of thus producing 

 compounds of a peculiar smell. This ether is found in all wines 

 containing a free acid, but is absent from those in which no acids 

 are present. This acid, therefore, is the means by which the 

 smell is produced ; since without its presence cenanthic ether 

 could not be formed. 



The greatest part of the oil of brandy made from corn con- 

 sists of a fatty acid not converted into ether; it dissolves oxide 

 of copper and metallic oxides in general, and combine* with the 

 alkalies. 



The principal constituent of this oil is an acid identical in 

 composition with cenanthic acid, but different in properties. 

 (Mulder.) It is formed in fermenting liquids, which, if they be 

 acid, contain only acetic acid, a body which has no influence in 

 causing other acids to form ethers. 



The oil of brandy made from potatoes is the hydrate of an 

 organic base analogous to ether, and capable, therefore, of enter- 

 ing into combination with acids. It is formed in considerable 

 quantity in fermenting liquids possessing an alkaline reaction ; 

 under circumstances, consequently, in which it is incapable of 

 combining with an acid. 



The products of the fermentation and putrefaction of neutral 

 vegetable and animal matters are generally accompanied by 

 substances of an offensive odor ; bui. the most remarkable exam- 

 ple of the generation of a true ethereal oil is seen in the fermen- 

 tation of the Ccntaurlum minus, a plant destitute of smell. When 

 it is exposed in water to a slightly elevated temperature it fer- 

 ments, and emits an agreeable penetrating odor. By the distil- 

 lation of the liquid, an ethereal oily substance of great volatility 

 is obtained, which excites a pricking sensation in the eyes, and 

 a flow of tears (Biichner). 



We know that most of the blossoms and vegetable substances 

 possessing a smell owe this property to a volatile oil existing in 



