Lond. Edin. Acetum Vini, Dub. Vinegar.

Syn. Vinaigre (F.), Essig(G.), Aceto (I.), Vinagre (S.), Viinacdike (Danish), Winattika (Swed.), Canchiea (Sans.), Khull (Arab.), Chooca Wynazin (Malay), Kadi (Tarn.), Cirka (Pers.), Kudidia (Cyng), (Bely.).

This is a well known acid liquor, produced by exciting the acetous fermentation in substances which have undergone, or are susceptible of, the vinous fermentation. Sugar and water, the saccharine vegetable juices, infusions of malt, malt liquors, cider, and wine1, may be converted into vinegar, by adding to them yeast or any other ferment, and exposing them in vessels to which the air has access, in a temperature between 75° and 90°. In wine countries, as France and Italy, vinegar is made from the lees of wine, which are worked up with new wine, then strained and exposed to the heat of the sun, or placed in stoved rooms, in casks set upright, with a hole cut through the heading, and left open until the whole of the liquor is thoroughly acidified. In this country it is prepared chiefly from malt. An infusion of malt is made, then properly cooled, and put into large and deep fermenting tuns; "where it is mixed with yeast, and kept in fermentation for four or five days." The liquor is now distributed into smaller vessels, placed in a chamber heated by means of a stove; and kept there for about six weeks, or until the whole is soured.

This is emptied into common barrels, which are placed in the open air, the bung-hole of each being simply covered with a tile to keep out the wet: and in this situation such a gentle fermentation goes on, that in four or five months, according to the heat of the weather, perfect vinegar is formed. The process is then completed in the following manner : "Large tuns are employed with a false bottom, on which is put a quantity of the refuse of raisins and other fruit, left by makers of homemade wines, called, technically, rape. These rape tuns are worked by pairs: one of them is quite filled with the vinegar from the barrels, and the other only three quarters full, so that the fermentation is excited more easily in the latter than the former, and every day a portion of the vinegar is laded from one to the other till the process is finished."1

1 New wines are better for this purpose than old, as they contain more extractive matter.

The theory of the acetous fermentation is not yet fully understood. Air and a moderate temperature are necessary for exciting and keeping it up. The former affinities between the components of the ingredients are broken, and new ones formed; while a quantity of carbon is thrown off, and uniting with the oxygen of the air, produces the carbonic acid gas, which appears during the process: but the production of carbonic acid is not essential to the formation of acetous acid. Although alcohol alone cannot easily be converted into vinegar, yet the strongest wine produces the best vinegar; and hence that made from malt is weaker, less pure, and more liable to spoil, than wine vinegar. The essential part of vinegar is acetic acid and water; in the proportion of five parts to ninety-five of water2 : but it also contains colouring matter, some un-decomposed alcohol, gluten, mucilage, sugar, extractive matter, a small proportion (1/1000) of its weight of sulphuric acid, and often some malic and tartaric acids.

Qualities.-Vinegar, when well made, is clear and limpid; has an agreeable penetrating odour, and a pleasant acid taste. The colour varies from a pale yellow to a deep red : and as it is derived from the extractive matter, malt vinegar is always higher coloured than wine vinegar. When long kept, particularly if it be exposed to the air, vinegar, becomes muddy and ropy, acquires an unpleasant smell, loses its acidity, and putrefies. It, however, may be kept good for a much longer time if it be boiled for a few minutes, so as to coagulate and separate the gluten, on the presence of which the above changes depend; and be preserved in well corked bottles.3 It is often adulterated with sulphuric acid, which is allowed to a certain extent by the Excise laws: it may be detected by a solution of acetate of baryta, forming, when dropped into the suspected vinegar, a white precipitate, which is insoluble in nitric acid, after being exposed to a strong heat. If 1000 parts yield more than 2.5 of sulphate of baryta, the vinegar contains too much sulphuric acid.

If water of baryta be employed, sulphate of potassa or of lime will also produce a precipitate, if present in the vinegar, in which case a preferable test is chalk short of the quantity necessary to saturate the portion of vinegar: for by throwing the whole on a filter, and adding distilled water, the acetate of lime is dissolved, but the sulphate which is formed, if sulphuric acid be present, remains undissolved on the filter. Muriatic acid is detected by nitrate of silver forming a precipitate, which is insoluble in nitric acid; but soluble whilst it is still moist in liquid ammonia. Nitric acid is detected by first mixing some common salt in the vinegar, then saturating with potassa, and evaporating to dryness : if gold leaf be then diffused through equal parts of sulphuric acid and water, and the mixture added to the dry residue and boiled, if the vinegar contains nitric acid, the gold leaf will be dissolved.1 If grains of paradise, spurge flax, capsicum, or pellitory of Spain, which are sometimes used to adulterate vinegar, be present, they can only be detected by the taste.

1 Aikiri's Dictionary of Chymistry, art. Vinegar. 2 Journal of Science and the Arts, vol. vi. p. 259.

3 Vinegar termed No. 21. is estimated to contain 5 per cent, of real acid.

The use of vinegar as a condiment, and an antiseptic, for pickling and preserving animal and vegetable matter, is well known.

Medical properties and uses.-Vinegar, when taken into the stomach, acts as a tonic and a refrigerant, promotes diaphoresis and the discharge of urine : and when externally applied is moderately stimulant and astringent.

In inflammatory fevers it may be used to acidulate the ordinary beverage. It is given as a remedy in putrid diseases and in scurvy : and it is the most easily procured, and the best means of counteracting the effects of over doses of narcotic poisons, after the poisons have been removed from the stomach; for which purpose it should be administered in doses of a table spoonful, frequently repeated, after the stomach has been freely emptied by a proper emetic. It acts as a conservative agent when given with acetate of lead, and prevents any colic occurring. It is employed as a glyster in obstinate costiveness; and externally in the form of fomentation, or of lotion, in burns, bruises, sprains, and chronic ophthalmia; and, diluted with water, it is the best lotion for clearing the eye of small particles of lime, when they adhere to any part of the ball or the lids. Its vapour is inhaled in putrid sore throat; and it is diffused through sick rooms with the view of neutralising pestilential effluvia: but as a fumigation it has little efficacy.

The dose of vinegar is f 3 ss. to f 3 iv. in any bland vehicle; and the quantity given in glysters f j. to f ij.

Officinal preparations. Acidum aceticum dilutum, E. Acetum destillatum, L. D. Syrupus Aceti, E. Syr. Colchici autumnalis, E. Cataplasma sinapis, L. D. Ceratum Saponis, L. Linimentum Aeruginis, L.