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VINEGAR

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Originally appearing in Volume V28, Page 96 of the 1911 Encyclopedia Britannica.
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VINEGAR , a dilute See also:

solution of impure acetic See also:acid, prepared by the acetous See also:fermentation of See also:alcohol or of substances which yield alcohol when suitably decomposed (See also:ordinary vinegar), or obtained from the products resulting on the dry See also:distillation of See also:wood (wood vinegar). Ordinary or table vinegars, which contain, in addition to acetic acid, small quantities of alcohol, higher acids such as tartaric and succinic, various See also:esters, albuminous substances, &c., are produced solely by acetous fermentation, wood vinegar being only employed in certain arts. Ordinary vinegar has been known from the earliest times, and its See also:power of combining with or dissolving See also:mineral substances caused the alchemists to investigate its preparation and properties. They failed, however, to obtain pure acetic acid, although by distillation they prepared more concentrated solutions (spiritus Veneris). In 1697 See also:Stahl showed that vinegar could be concentrated by freezing out See also:part of the See also:water, and, better, in 1702, by neutralizing the acid with an See also:alkali and distilling the See also:salt with oil of See also:vitriol. A notable improvement was made in 1789 by LOwitz, who showed that the dilute acid could be concentrated by repeatedly passing it over See also:charcoal See also:powder, and by cooling he obtained a crystalline substance named in 1777 by Durande, " glacial acetic acid." The presence of an acid substance in the products of the dry distillation of wood was mentioned by See also:Glauber in 1648 and received the name of pyroligneous acid. Its identity with acetic acid was demonstrated by See also:Vauquelin in 1800. The mechanism of acetous fermentation is described under FERMENTATION; here we only treat of the actual processes. There are two methods in use: the " See also:quick " See also:process, proposed in 1720 by See also:Boerhaave and introduced by Schiitzenbach in 1823 (analogous processes were proposed at about the same See also:time by Wagmann in See also:Germany and by See also:Ham in See also:England), and the older or " slow " process. In the " quick " process See also:advantage is taken of the fact that the fermentation proceeds more quickly when a large See also:surface of the liquid is exposed to See also:air. Any alcoholic liquid can be treated. The apparatus consists essentially of a vat divided into three portions: the lowest, which is separated from the one above by a grid or false bottom, serves for the collection of the vinegar; the central portion, which is by far the largest, is the chamber wherein the fermentation is effected; and it is separated from the topmost See also:section by a disk perforated with holes about the See also:size of quills through which thin strings See also:lead into the upper part of the central section.

The purpose of this disk is to subdivide the liquid placed upon it into drops so as to increase the surface of the liquid. The sides of the vat enclosing the lowest portion are provided with a See also:

ring of holes to admit air to the tub; and the vat is enclosed with a tightly fitting lid perforated by a hole through which the liquor to be fermented is admitted and the air See also:drawn upwards from the See also:base escapes. The central chamber is filled with some material of large surface. The commonest are See also:beech-wood shavings, which, before use, must be carefully freedfrom all extractives by washing and steaming, then dried, and finally soured by See also:immersion in hot vinegar for twenty-four See also:hours. The fermented wort, prepared in various ways and of varying See also:composition, or See also:wine, is warmed to about 38° C. and then fed into the upper chamber. Falling on to the shavings, the surface is largely in-creased, and the fermentation which ensues maintains the temperature at about 37°, and draws a current of air upwards through the shavings, which after a time become covered with the so-called See also:mother of vinegar. If the liquid contains only 4% of alcohol, it is completely converted into acetic acid, but stronger liquors require to be passed through the vat three or four times. Some of the alcohol (and consequently some acetic acid) is carried away by the air which escapes to the See also:top of the vat; this is avoided in some factories by leading the air over or into water, whereby the alcohol and aldehyde are recovered. The same is effected in See also:Singer's generators, which are coupled together in tiers. For making wine-vinegar by the slow process, full-bodied wines about one See also:year old and containing To % of alcohol (this amount being obtained, when necessary, by blending) are preferred; and they are clarified by See also:standing with beech shavings upon which the lees See also:deposit. The fermentation is carried out in casks holding from 5o to Too gallons; these casks are repeatedly extracted with water in See also:order to prevent any impurity finding its way into the vinegar; also it is found that the casks foul after about six years' use, when it is necessary to remove the deposits of See also:argol, yeast sediments, &c., and re-See also:extract with water, after which they are again See also:fit for use. In conducting the fermentation the cask is one-third filled with boiling strong vinegar and allowed to stand for eight days.

Nine pints of the wine are now added every See also:

day until the cask is two-thirds full, and the mixture is allowed to stand for fourteen days. After this See also:interval from so gallons to See also:half the contents of the cask are drawn off, and .more wine added. The working temperature is about 25°. The progress of the operation is shown by the See also:white froth which appears on a spatula after immersion in the liquid; if it be reddish, more wine must be added. In certain parts of See also:France, See also:Holland and of the See also:Rhine See also:district a different See also:procedure is adopted. Two casks, fitted with false bottoms on which are placed See also:vine cuttings, are taken; one cask is completely filled with the wine, whilst the other is only half filled. The acetification proceeds more rapidly in the second cask, and after twenty-four hours half the contents of the first cask are transferred to it, and the process repeated. The product is settled in casks containing See also:birch wood, and after fourteen days it is put upon the See also:market. In preparing See also:malt vinegar, an infusion of malt is prepared by extracting it with water at 72°, then at a higher temperature and finally at the boiling-point. After cooling the extracts are fermented with yeast, and the product kept for some months before acetification. This step can be effected by the quick process as described above, or by the slow process. In the latter the liquid at 25° is transferred to barrels lying on their sides and the fermentation allowed to proceed.

When the process is See also:

complete the product is filtered through rapes in a fining See also:tun. This is a cask fitted with a false bottom in which are placed spent See also:tanner's wood, shavings, or, better, the pressed stalks and skins of grapes and raisins from wine manufacture. See also:Household vinegar is made in upright casks; after twenty-four hours it is transferred to a similar cask, and the process repeated in a third and See also:fourth cask. Malt vinegar is sold in four strengths designated 18, 20, 22, 24, the last being " See also:proof " vinegar, containing 6% of acetic acid and having a specific gravity of 1.019. These See also:numbers represent the grains of dry pure See also:sodium carbonate, which are neutralized by one fluid See also:ounce of the vinegar. Several other vinegars are made. Crystal vinegar is ordinary vinegar decolorized by treatment with See also:animal charcoal. See also:Ale vinegar is prepared from strong sour See also:pale ale; it has a tendency to putrefy. See also:Glucose or See also:sugar vinegar is made by first fermenting amylaceous substances to alcohol, and then acetifying the alcohol. See also:Compound table vinegars are made by digesting ordinary vinegar with condiments such as See also:pepper, See also:garlic, See also:capers, &c.; whilst aromatic vinegars popularly used in vinaigrettes on See also:account of their refreshing, stimulating pungency are obtained by distilling ordinary vinegar with See also:plants, perfumes and aromatic substances. Medicinal vinegars are prepared either by digestion or distillation of vinegar with various drugs. Vinegar, however, is not now much used in See also:medicine, although occasionally taken, under a false impression, in order to reduce obesity.

Wood vinegar is not used in cooking, as it lacks those substances which render ordinary vinegar palatable. It is largely manufactured for See also:

conversion into pure acetic acid and acetom; and also for use as an antiseptic and wood preservative.

End of Article: VINEGAR

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