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VITRIOL (OIL OF), OR SULPHURIC ACID.

A combination of oxygen, sulphur, and water, made by submitting the native sulphuret of iron, called pyrites, in powder, to a red heat: this is the simplest and newest method by wbich it is manufactured on

a large scale. Before the above invention it was only obtained by the much more expensive process—the combustion of sulphur and nitre. The vapour exhaled in both these processes, is received in leaden chambers, covered at the bottom with a thin stratum of water, wbich becomes strongly acidified; it is then boiled in leaden boilers, and the water being converted into steam, flies off, leaving the strong acid to volatilize, which requires a much bigher degree of heat than water. It is a dense unctuous, and colourless fluid, caustic, and intensely sour, even when very largely diluted—as a medicine it is tonic, and generally considered astringent. It is an extremely valuable agent to the scientific chemist ; it is also of great importance in pharmacy, in the formation of the salts called sulphates, and other products. The well-known Epsom salt, properly called sulpbate of magnesia, is a combination of sulphuric acid, magnesia, and water. Glauber salt is likewise a sulphate of soda. Excepting the acetic, the arts and manufactures are more indebted to this than any other acid. It is used in metallurgy, bleaching, dyeing, &c. (See Copperas.) In domestic uses, for cleaning coppers, the diluted acid, called spirit of vitriol, is made use of, and sometimes the strong; this has frequently been swallowed by mistake, and in many cases bas proved fatal : the best antidote is magnesia and water, and in its absence a copious draught of chalk and water.

VINEGAR.

A very dilute acetic acid (63), which is its base, in combination with mucilaginous, saccharine, and other vegetable matter; it varies in colour from a pale yellow to a deep red, should be perfectly transparent, of an agreeable penetrating odour, and a pleasant acid taste. In wine countries, it is produced by the exposure of wine to the action of air and a due temperature ; it is sometimes made from solutions of sugar and saccharine fruits; in this country it is cbiefly prepared from malt. An infusion of malt is made, then properly cooled, and put into large and deep fermenting tuns, with a portion of yeast, and the fermentation kept up for four or five days, after which the liquor is distributed into smaller vessels, placed in a chamber beated by means of a stove, and kept there for about six weeks or until the whole is soured; it is then emptied into common barrels, wbich are placed

in the open air, the bungbole 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 false bottoms, on which is put a quantity of the refuse of raisins and other fruit, left by makers of home-made wine, technically

These rape tuns are worked by pairs, one of which 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 completed; the theory of the acetous fermentation is not yet fully understood.

called rape.

WAX.

A firm and solid substance, rather heavy, and of a yellow colour, extracted by the bees from the pollen (64) of flowers. When new, it is rather tough, but becomes brittle by age.

In the nice bee, what sense so subtly true!

From poisonous herbs extracts the healing dew. By repeated distillation a volatile oil is extracted from wax; it is easily dissolved with fixed alkalies, and is soluble in water. The white wax is formed from the common yellow by bleaching, and is manufactured into candles, and employed for mary of the better purposes of the arts where wax is required. Both kinds are used in medicine. Artists have employed this substance in the formation of models of the human frame, and exbibitions of this pature are of frequent occurrence.

WAFERS.

A mixture of flour, white of egg, isipglass, and yeast, thinned with gum water, coloured, and well beaten together; they are then rolled out to a proper thickness, dried in a stove and stamped out to any shape, generally round. They are used for sealing letters, &c.

WOOL.

A kind of long soft hair, which covers the skins of several animals, particularly the sheep and goat. That of the sheep is used in manufacturing cloths, stuffs, flannels, &c. The most beautiful European wools are brought from Spain and Saxony; the former being celebrated for its fine breed of Merino sheep, which have been introduced into this country, and are here found to maintain the excellent qualities of the fleece. The Highland Wool and that from the Shetland Isles is nearly equal in quality, as also that from New South Wales. The hair of the goat, an animal common in some parts of England, but particularly in the mountainous districts of Wales, is made into various articles, such as coarse hair clotbs, &c. From the goats of Angora, a town of Natolia, a beautiful wool is obtained, which is very valuable, and manufactured into shawls, much esteemed in this country; and those called casbmerian, manufactured from the best of this species, are particularly elegant. Mohair is also obtained from a goat found in or near Angora, and is converted into a variety of similar articles.

WHALEBONE.

The upper jaw of the Balæna or Whale furnishes this bone. It is formed of thin parallel lamina, some four yards in length; of these there are generally 350 on each side. They are surrounded with long hair to prevent the tongue being injured by them, and they also act as strainers in preventing the return of the food when they discharge the water out of their mouths. The other bones of the whale are hard, porous, and full of marrow. There are two very strong bones which sustain the upper lip, lying against each other in the shape of a half-moon. Wbalebone was formerly an article of great value in commerce, and sold for £600 the ton. Its price,

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