THE MANUFACTURE OF VINEGAR. 451 



cent of alcohol, the bacteria attack these ethers, and finally the acetic 

 acid itself causing complete oxidation according to the equation: 



C 2 H 4 O 2 + 4O= 2CO 2 + 2H 2 O. 



The addition of a new supply of alcohol, however, immediately 

 arrests this reaction. In practice the acetification should be stopped 

 when the alcohol has fallen to i or 2 per cent, otherwise there is a loss 

 of flavor and of acetic acid, which may continue until all the acid is 

 destroyed. 



The length of time during which the acetic bacteria retain their 

 vitality varies with the moisture and the temperature. In nutrient 

 solutions, they live from one to as many as ten years; in the dry state, 

 from three months at ordinary temperatures, to twelve months at 2. 



PROCESSES OF MANUFACTURE. 



RAW MATERIALS. Originally vinegar was made from wine, as indicated 

 by the etymology of the word which means "acetified wine." Later, 

 other alcoholic beverages such as cider and beer were used for the same 

 purpose. In these liquids, the acetic bacteria find all the mineral and 

 organic matters necessary for their development, together with alcohol 

 in amounts favorable for acetic fermentation. At present, a large 

 number of materials containing alcohol, or starchy and sugary matters, 

 which, by preliminary yeast fermentation, can be changed into alcohol 

 are used as sources of vinegar. The most important of these are honey, 

 molasses, and various fruit juices. 



All these materials make wholesome vinegar of varying degrees of 

 quality. Those of wine and cider are usually classed as the best, and 

 those of malt and honey next. The great bulk of the vinegar of commerce, 

 however, at present is made by the acetification of distilled alcohol. 

 This is not vinegar strictly speaking but an imitation, consisting of a 

 dilute solution of acetic acid without the various flavors which are an 

 essential part of pure vinegar. In order to give it a semblance of the 

 latter, it is often colored with caramel and flavored with various sub- 

 stances. 



Other imitations of vinegar sometimes appear on the market, con- 

 taining wood vinegar, or even mineral acids. These, however, are 

 more or less poisonous and their sale is usually forbidden by law. 



