FERMENTATION OF VINEGAR. 161 



of water, and forms one equivalent of sugar: it 

 follows from this fact, that the quantity of sugar 

 formed always weighs considerably more than the 

 starch from which it is obtained. 



374. One equivalent of starch contains 12 equiv. 

 carbon, 10 equiv. oxygen, 10 equiv. hydrogen ; when 

 acted on by diastase, or boiled with a dilute acid, 

 it takes* up in addition the elements of 4 equiv. of 

 water, or 4 equiv. of oxygen, and 4 equiv. hydrogen, 

 and is converted into 1 equiv. of grape sugar, con- 

 sisting of 12 equiv. carbon, 14 equiv. oxygen, 14 

 equiv. hydrogen. 



Carbon. Oxygen. Hydrogen. 

 1 equiv. Starch, containing 12 10 10 



and 4 equiv. Water "0 4 4 



forms — — — 



1 equiv. Grape Sugar " 12 14 14 



375. A liquid which has already undergone the 

 vinous or alcoholic fermentation, is still able to 

 undergo another change, namely, the acetic ferment- 

 ation ; which occurs where weak spirit of wine, in 

 contact with some ferment, is exposed to the air. 

 Alcohol and water together, whether exposed to the 

 air or not, undergoes no change whatever ; when a 

 small quantity of decomposing azotized matter is 

 added, then the acetic fermentation commences, and 

 vinegar is formed (476). 



376. In the formation of vinegar from spirit, the 

 presence of air or oxygen is necessary. One equiv- 

 alent of alcohol consists of 4 equiv. carbon, 2 equiv. 



14* 



