290 VINOUS FERMENTATION. 



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 entering into combination 

 with acids. It is formed in considerable quantity 

 in fermenting liquids which are slightly alkaline, 

 under circumstances, consequently, in which it is 

 incapable of combining with an acid. 



The products of the fermentation and putrefac- 

 tion of neutral vegetable and animal matters, are 

 generally accompanied by substances of an offensive 

 odour ; but the most remarkable example of the 

 generation of a true ethereal oil is seen in the fer- 

 mentation of the Herba centaurium minorius, a 

 plant which possesses no smell. When it is ex- 

 posed in water to a slightly elevated temperature 

 it ferments, and emits an agreeable penetrating 

 odour. By the distillation 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.) 



The leaves of the tobacco plant present the same 

 phenomena ; when fresh they possess very little or 

 no smell. When they are subjected to distillation 

 with water, a weak ammoniacal liquid is obtained^ 

 upon which a white fatty crystallizable substance 

 swims, which does not contain nitrogen, and is quite 

 destitute of smell. But when the same plant, after 



