Page:Popular Science Monthly Volume 23.djvu/644

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which has a faint smell of roast meat, is very good, and can be used in the preparation of soups and broths.

The meat-biscuit of Gail Borden is prepared by seething freshly killed beef with hot water till all the nourishing constituents are extracted. The solution of these constituents is then dried to the consistency of an extract, and this is mixed with flour into a dough which is made into cakes and baked in a moderately hot oven. According to Mr. Borden, five hundred grammes of the biscuit contain as much nutritive matter as two and a half kilogrammes of fresh meat. In a similar way, turnips, celery, spinach, and other vegetables, are dried and compressed in square cakes, which, enveloped in tin-foil, will keep fresh in the market for a very long time.

Other methods of preservation depend on the use of antiseptics. Besides carbolic and salicylic acids, borax, boric acid, boroglycerine, and xanthogenate of potash, may be used in preserving. Aqueous solutions of boric acid and borax are very effective preservatives, for many months, of meats, fish, vegetables, or fruits, which are immersed in them. Pulverized borax is also effective, whether by itself or mixed with pulverized alum and gypsum.

The substance called boroglycerine has recently attracted considerable attention. With it Professor Barff has prepared meat for preservation during long voyages, and has shipped experimental packages of beef across the Atlantic Ocean and back without their undergoing any change. Mr. Russell, President of the English Society of Arts, has also, independently of Professor Barff, found it excellent for the preservation of meat and milk. It promises to come into general use, for its application is without the slightest danger to the healthful or other qualities of the food, and it is very cheap. The "Deutschen Industrie Zeitung" gives the following directions for its preparation: Glycerine is heated to as high a temperature as it will bear without decomposition, and as much crystallized boric acid is added to it as it will dissolve. The usual proportion is 92 parts of glycerine to 62 parts of boric acid. The mixture is then heated to a temperature of about 400°, till after four or five hours the vapor of water ceases to pass from it. The resultant product, after cooling, is boroglycerine, in the form of a yellow, transparent mass, soluble in water and alcohol. It is applied to organic substances in solutions of one part to forty parts of water.

With xanthic acid, Professor Zöllner, of Vienna, has preserved beef and veal, poultry, pigeons, and over-ripe plums. Its operation is the more effective because it is volatile at ordinary temperatures, and a very small proportion of its vapor in the air of a chamber is efficient to prevent all decay.

A preservative salt, patented by a German manufacturer, consists of crystallized boric acid and phosphate of soda, to which a mixture of common salt and saltpeter is added.