ACETIC FERMENTATION. 195 



vats provided with false bottoms pierced full of holes, 

 a layer of vine-stalks and mark is first placed in the 

 vat, covering the false bottom, and the vats are then 

 nearly filled with wine. The vine-stalks and mark act 

 as a ferment, and soon bring the wine into a state of 

 active fermentation: air is absorbed, heat given out, 

 and vinegar is formed (383). 



480. Care is always taken to check the rapidity 

 of this fermentation, or to prevent the liquor from 

 becoming too warm ; if this were permitted, the spirit 

 of the wine, as well as the vinegar formed, being both 

 volatile, would be driven off, or at least a consider- 

 able portion of them would be lost. 



481. Any liquid containing spirit may be fermented 

 into vinegar; and, consequently, as starch and sugar 

 may be converted into spirit, so, solutions containing 

 those substances may readily be turned into vinegar, 

 by being fermented : when this is the case, the pro- 

 cess is not stopped when the alcoholic fermentation 

 is complete, but is allowed to proceed as long as 

 possible. 



482. In countries where wine is made, vinegar is 

 chiefly made from the grape ; in other places malt is 

 usually employed. A similar form of vat is used for 

 that purpose as in the manufacture of wine-vinegar, 

 the only difference being, that a sweet-wort is substi- 

 tuted for the wine. Grape-mark, which is commonly 

 called rape by the vinegar-makers, is generally used 

 as a ferment. 



483. As soon as the wort has acquired a certain 



