382 CHEMISTRY. 



Thus in a brewery the quantity of yeast continually in- 

 creases, and it is sold largely for the raising of bread, a fer- 

 menting process to be noticed soon. There is a difference 

 of opinion as to the mode in which yeast causes fermenta- 

 tion. Some suppose that it is the yeast-plants that produce 

 this effect, while others suppose it is their decomposition. 



539. Wines, Cider, etc. In making these no addition of 

 yeast is required, for there is nitrogenous matter in the 

 juices from which they are made, which by exposure to 

 the air becomes a ferment. In making Champagne and 

 other sparkling wines, the wine is bottled before the fer- 

 mentation is finished. Of course the process goes on in 

 the bottle, and the carbonic acid produced is pent up in 

 the liquid, ready to expand and escape the moment the 

 way is opened. Sweet wines are those in which there is 

 some sugar that has not been decomposed in the fermen- 

 tation. Wines are called dry when they contain very little 

 sugar. Wines are made from other fruits as well as the 

 grape, as, for example, the currant, the gooseberry, the 

 elderberry, etc. Cider is essentially a wine made from 

 apples. Much of the so-called Champagne wine is really 

 cider, to which a peculiar flavor is given. Other wines are 

 counterfeited, and there is probably no class of men more 

 often cheated than wine-drinkers. 



540. Flavor of Wines. The flavor which distinguishes grape wines 

 as a class from other spirituous drinks is produced by a very small amount 

 of an ethereal substance called cenanthic ether. When obtained in a sep- 

 arate state it is a very fluid liquid, having a sharp, disagreeable taste, and a 

 vinous odor so powerful as to be almost intoxicating. It does not exist in 

 the grape, but is one of the products of the fermentation, and increases with 

 the age of the wine. You can have some idea of the power of this sub- 

 stance from the fact that in few wines does it constitute more than the one 

 four-thousandth part of their bulk. It is often obtained by manufacturers 

 of wines from grain spirit and cheap wines, and is used by them for produc- 

 ing imitations of wines of higher prices with such cheap articles as potato 



