VINEGAR, a solution of acetic acid, usually containing from 2 to 5 per cent. of acid, and minute proportions of vari ous ethers and other substances accord ing to the sources whence it is derived. It is a product of the oxidation of alco holic solutions, and may consequently be prepared from any body containing al cohol, or capable of being transformed into that substance. In practice it is prepared from malted barley or other grain (malt vinegar), from wine of in feriorquality (wine, French or Orleans vinegar) from dilute solution of spirit (spirit vinegar) and from cider (cider vinegar). Wood vinegar, a product of the destructive distillation of wood, is used chiefly in connection with chemical operations, and though deficient in flavor, and other qualities it is in extensive use as a table vinegar, and for the various other purposes to which common vinegar is usually applied. The circumstances which are necessary for and favor the production of vinegar are, (1) an alco holic solution (or a solution capable of developing alcohol) containing not more than 10 per cent. of spirit; (2) a suitable temperature, which may range from about 45° to 100° F.; (3) free access of atmospheric air; and, (4) the presence of substances which promote acetification or oxidation of the alcoholic solution, the chief active agency being the vinegar fungus Mycoderma aceti, which acts as a carrier of oxygen to the solution.
There are two principal processes by which ordinary vinegar is prepared, termed respectively (1) the old or slow process; and (2) the quick process. The slow process is still largely used in the preparation of French or wine vinegar, and it is also used in making British malt vinegar. In the manufacture of the latter there are a number di preliminary operations analogous to those employed in brewing. A mash of mixed malt and unmalted barley is prepared, and the wort is permitted to ferment. After com pletion of the fermentation the liquor is run into barrels. the tops of which are open but tied over with coarse canvas and stored away in darkened but mod erately-heated chambers where there is free access of air. There the acetous fermentation takes place slowly during several weeks or even months, when the contents of the barrels are emptied into two large tuns having false bottoms, over which the pressed cake from making currant wine, etc., is strewed. One of
the tanks is filled entirely, but the second is only three-fourths filled. Here the acetous fermentation proceeds vigorously, and when the vinegar is ready a portion is drawn from the second (unfilled) tun. The quantity withdrawn is made up from the full tun, and it again is filled up from the barrels. In this way the man ufacture goes on progressively. The old or slow method of vinegar making is a system requiring extensive premises and plant, and to a large extent it is now sup planted by the new or quick process.
The principle on which the various quick methods in operation depend con sists in exposing the alcoholic solution at a favorable temperature in the most in timate manner to the action of the at mosphere. The solution is made to trickle drop by drop through one or more col umns containing beech shavings or other means of fully exposing the fluid to the air, and as it descends it meets a cur rent of air ascending. In this way rapid and complete oxidation is promoted. Vin egar on domestic scale is prepared from saccharine solutions to which the vinegar fungus Illycoderma aceti is added, the solution being covered up and kept in a warm place till the acetification is com plete. The use of vinegar in the manu facture of pickles, the preparation of salads, and of acid beverages, as well as directly as a sauce with animal food, is very extensive. It is also an important substance in medicine, both for internal and external use, and its pungency com bines in a very refreshing manner with various perfumes for toilet purposes. Vinegar is a valuable aid to the digestion of the hard fibrinous and albuminous constituents of food. The qualities of vinegar depend principally on the source whence it is obtained, the best being wine vinegar, after which comes that prepared from pure malt. Inferior vine gar is frequently contaminated with sul phuric acid, of which by law one part per thousand is permitted to be present without being counted an adulteration.