VAEIOUS PROPERTIES OF WINES. ^ 347 



into alcohol and carbonic acid. A certain quantity 

 of the sugar consequently remains mixed with the 

 wine in an undecomposed state, the condition neces- 

 sary for its further decomposition being absent. 



The azotized matters in the juice of grapes of the 

 temperate zones, on the contrary, are not completely 

 separated in the insoluble state, when the entire 

 transformation of the sugar is effected. The wine 

 of these grapes, therefore, does not contain sugar, 

 but variable quantities of undecomposed gluten in 

 solution. 



This gluten gives the wine the property of becom- 

 ing spontaneously converted into vinegar, when the 

 access of air is not prevented. For it absorbs 

 oxygen and becomes insoluble; and its oxidation is 

 communicated to the alcohol, which is converted 

 into acetic acid. 



By allowing the wine to remain at rest in casks 

 with a very limited access of air, and at the lowest 

 possible temperature, the oxidation of this azotized 

 matter is effected without the alcohol undergoing 

 the same change, a higher temperature being neces- 

 sary to enable alcohol to combine with oxygen. As 

 long as the wine in ihe stilling-casks deposites yeast, 

 it can still be caused to ferment by the addition of 

 sugar, but old well-layed wine has lost this property, 

 because the condition necessary for fermentation, 

 namely, a substance in the act of decomposition or 

 putrefaction, is no longer present in it. 



In hotels and other places where wine is drawn 

 gradually from a cask, and a proportional quantity 

 of air necessarily introduced, its eremacausis, that 

 is, its conversion into acetic acid, is prevented by 

 the addition of a small quantity of sulphurous acid. 

 This acid, by entering into combination with the 

 oxygen of the air contained in the cask, or dissolved 

 in the wine, prevents the oxidation of the organic 

 matter. 



The various kinds of beer differ from one another 

 in the same way as the wines. 



