GELATINE is an animal product which is never found in the humors, but it may be obtained by boiling with water the soft and solid parts ; as the muscles, the skin, the cartilages, bones, ligaments, tendons, and membranes. Isinglass con sists almost entirely of gelatine. This substance is very soluble in boiling wa ter • the solution forms a tremulous mass of jelly when it cools. Cold water has little action upon gelatine. Alcohol and tannin (tannic acid, see GALL-NUTS) pre cipitate gelatine from its solution ; the former by abstracting the water, the lat ter by combining with the substance itself into an insoluble compound, of the nature of leather. No other acid, except the tannic, and no alkali possesses the property of precipitating gelatine. But chlorine and eerttun salts render its solu tion more or less turbid ; as the nitrate and bi-chloride of mercury, the proto chloride of tin, and a few others. Sul phuric acid converts a solution of gelatine at a boiling heat into sugar. (See LIONE ous Fnum.) Gelatine consists of carbon, 47.88; hydrogen, 7•01 ; oxygen, 27.21 (See Gum.) Gelatine brut fin, is from the skulls, blade-bones, and shank-bones of sheep, the ends cut off, the bones cut down the middle to remove the fat, steeped in mu riatic acid, then in boiling water a few minutes, wiped carefully, dried, shaken together in a bag to remove the internal pellicle, cut across, or into dice., to dis guise them, and finally dipped in a hot solution of gelatine to varnish them. It is used to make soup, keeps better than the cakes of portable soup ; and, less carefully prepared, makes carpenters' glue for fine work.
Very recently, a very beautiful spark ling gelatine has been prepared under a patent granted to Messrs. J. & G. Cox, of Edinburgh. By their process the sub stance is rendered perfectly pure, while it possesses a gelatinizing force superior even to isinglass. It makes a splendid calves' feet jelly and a milk-white blanc mange. The patentees also prepare a semi-solid gelatine, resembling jujubes, which readily dissolves in warm water, as also in the mouth, and may be employed to make an extemporaneous jelly.
The gelatine of bones may be extracted best by the combined action of steam and a current of water trickling over their crushed fragments in a properly constructed apparatus. When the gela tine is to be used as an alimentary arti cle, the bones ought to be quite fresh, well preserved in brine, or to be dried strongly by a stove. Bones are best crushed bypassing them between grooved iron rolls. The cast-iron cylinders in which they are to be steamed, should be three times greater in length than in diameter. To obtain 1,000 rations of gelatinous soup daily, a charge of four cylinders is required ; each being 31 feet long, by 14 inches wide, capable of hold ing 70 lbs. of bones. These will yield each hour about 20 gallons of a strong jelly, and will require nearly 1 gallon of water in the form of steam, and 5 gal lons of water to be passed through them in the liquid state. The 5 quarts of jelly produced hourly by each cylinder, pro ceeds from the 1 quart of steam-water and 4 quarts of percolating water.