282 VINOUS FERMENTATION. 



ON VINOUS FERMENTATION : WINE AND BEER. 



It has already been mentioned, that fermenta- 

 tion is excited in the juice of grapes by the access 

 of air ; alcohol and carbonic acid being formed by 

 the decomposition of the sugar contained in the 

 fluid. But it was also stated, that the process once 

 commenced, continues until all the sugar is com- 

 pletely decomposed, quite independently of any 

 further influence of the air. 



In addition to the alcohol and carbonic acid 

 formed by the fermentation of the juice, there is 

 also produced a yellow or grey insoluble substance, 

 which contains a large quantity of nitrogen. It is 

 this body which possesses the power of inducing 

 fermentation in a new solution of sugar, and which 

 has in consequence received the name si ferment. 



The alcohol and carbonic acid are produced from 

 the elements of the sugar, and the ferment from 

 those azotised constituents of the grape juice, which 

 have been termed gluten, or vegetable albumen. 



According to the experiments of De Saussure, 

 fresh impure gluten evolved, in five weeks, twenty- 

 eight times its volume of a gas of which f consisted 

 of carbonic acid, and of pure hydrogen gas ; 

 ammoniacal salts of several organic acids were 

 formed at the same time. Water must, therefore, 

 be decomposed during the putrefaction of gluten ; 

 the oxygen of this water must enter into combina- 

 tion with some of its constituents, whilst hydrogen 



