UREA, one of the few organic bases of animal origin. It forms an essential constituent of the urine of all animals, and is most abundant in that of the mammalia, particularly so in the case of the carnivora. It is the principal out let of nitrogen from the system, after the materials which compose the animal tissues have experienced oxidation under the influence of inspired air. A person in good health secretes about an ounce of urea daily. Dumas made several fruitless attempts to form urea from the azotized constituents of the body, but Bechamp has recently succeeded in doing so, by subjecting albumen to the oxidizing ac tion of permanganate of potash. Urea does not appear to be formed in the kid neys, these organs appearing to act more as filters in separating it from the mass of blood in which it is formed before it reaches them; perhaps it is produced in the liver. Urea may be formed artificially in several ways, and was one of the first organic products made from inorganic materials. The easiest method of pro curing it is by heating together 56 parts of ferrocyanide of potassium with 28 of black oxide of manganese, and wash ing the residue obtained. The cyanate of potash thus formed is transformed into the ammonia salt by dissolving it in 41 parts of sulphate of ammonia. The cyanate of ammonia may be dissolved out by alcohol, and slow evaporation con verts it into urea. It crystallizes in white,
slender, straited prisms, which are slightly deliquescent. Its solution has a cool, bitterish taste, and is neutral to test paper. It is very soluble in water and hot alcohol, but sparingly so in ether. It does not appear to form a defi nite hydrate. It melts at about 270° F., and at a temperature a little above this it is decomposed into ammonia, carbon ate of ammonia, and metameric acid. A solution of urea, heated in a sealed tube, takes up four equivalents of water, and is converted into carbonate of ammonia. The same change takes place in stale urine; hence its ammoniacal odor after keeping it a few days. Though forming salts with certain of the acids, urea does not possess well-marked basic properties. With nitric and oxalic acids it forms crystallizable salts. With certain metallic oxides and salts, such as the oxides and nitrates of silver and mercury, it forms definite crystalline compounds. Urea con stitutes about one and a half per cent. of the urine of a healthy person, or about one-third of its solid constituents. The hydrogen in urea may be replaced by compound radicles, such as ethyl, phenyl, etc., giving rise to numerous com pounds, known as the compound urea. It also combines with other radicles, forming ureides.