FERMENTATION. 387 



C 2 H 5 (HO), ether is (C 2 H 5 ) 2 O. As stated in 423, if we re- 

 gard alcohol as a hydrate of the radical ethyl C 2 H 5 , ether 

 may be regarded as the oxide of this radical. Ether is a 

 very light liquid. If exposed to a heat of 35.6, two de- 

 grees less than blood heat, it boils, and it has never yet 

 been frozen. It is exceedingly volatile. On account of its 

 volatility and the effect of heat upon it, it must be kept in 

 a cool place and in tightly closed bottles. If the hand be 

 moistened with it, there ensues a sensation of great cold, 

 owing to the rapid evaporation. It is very combustible, and 

 its vapor mingled with the air forms an explosive mixture. 

 The inhalation of it in considerable amount produces in- 

 sensibility, and it is therefore much used in surgery to pre- 

 vent the patient from suffering while undergoing an oper- 

 ation, and also to some extent in medicine to relieve the 

 pain of disease. It is also used to dissolve gun-cotton, or 

 pyroxyline ; the solution is largely employed by photog- 

 raphers to form the collodion films of the glass plates on 

 which the negative pictures are produced. 



548. Compound Ethers. As ether is an oxide it unites 

 with acids to form compounds which may properly be 

 termed salts. That very common medicine, the sweet 

 spirits of nitre, is one of these salts diluted with alcohol. 

 The essences used in flavoring wines, cordials, and in cook- 

 ing food, are really compound ethers, artificially prepared 

 on a large scale. In the following table (p. 388) you have 

 a list of some of these perfume ethers, their formulaa, and 

 the flavors they imitate. By mixing these ethers with each 

 other, and with essential oils in various proportions, the 

 odor and flavor of nearly every fruit may be imitated. 

 Dilution with alcohol best develops the flavor. 



Salicylol is not an ether, but finds a place in this table 

 for obvious reasons. 



549. How Ether is Obtained. It is by the action of sul- 



