Page:Collier's New Encyclopedia v. 10.djvu/165

LEFT UBENA 137 URIC ACID 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. URENA, in botany, the typical genus of Urenese. Involucre and calyx five-cleft; style divided above into 10 portions; carpels, five, prickly at the top. tf. labata, a shrub commonly occurring with the mango and bamboo in Bengal and throughout India, and U. simiata, a small Indian shrub, have strong fibers, prob- ably well adapted for the manufacture of sacking and twine. In Brazil a de- coction of the root and stem of U. labata is employed as a remedy in windy colic, and the flowers are given as an expec- torant in dry and inveterate cough. XJIIETHRA, in anatomy, a membra- nous tube running from the bladder first directly downward and then forward be- neath the arch of the pubes. It is the excretory passage for the urine, serving also in the male for the ejaculation of the semen. URFE, HONORE D', a French ro- mance-writer ; born in Marseilles, France, Feb. 11, 1568. He is celebrated for his immensely popular bucolic and allegori- cal romance "Astree" (1st part, 1610). It introduces us to a sort of ideal world, in which elegant ladies and gentlemen appear clad as shepherds and shepherd- esses, and make pretty observations on topics of the period. He left it unfinished, and the conclusion was supplied by his secretary. He died in Villefranche, France, June 1, 1625. URGA, a town of Mongolia; on the Tola river; in a valley in the great Asiatic plateau; 180 miies S. E. of Ki- achta, on the trade route to Peking. It is the religious center for northern Mon- golia, has considerable trade, and a popu- lation (partly living in tents outside the city proper) of about 30,000, mostly Chinese. In and about the town, which is the seat of the Bogdan or chief Lama of the Mongols, there are about 14,000 Mongolian Lamas. URI, one of the "Forest Cantons" of Switzerland; forms part of the hill country which surrounds the Lake of Lucerne; area, 415 square miles; pop. about 25,000. It consists of one valley, that of the Reuss, through which runs the great road, and also the railway, into Italy by the St. Gothard Pass. Uri is almost entirely pastoral; and the con- stitution is a pure democracy. URIC ACID, a very important ex- crementitious product, which occurs in small quantities in human urine, to the extent of rather less than 1 per cent, of the solid matter contained in it. It is met with in much greater abundance in the excrement of birds and reptiles, that of the boa consisting almost entirely of urate of ammonia. Guano also contains large quantities of it, and has been most extensively employed as its source in the now almost extinct manufacture of murexide dyes. When excess of uric acid is secreted in the system, it deposits hard crystallizing grains in the bladder, which, if retained, gradually form con- cretionary calculi, and grow into the disease known as gravel or stones. In gouty patients, uric acid accumulates around the joints, forming white friable concretions, known improperly as chalk- stones. Uric acid is generally prepared by dissolving the dried excrement of the boa in water, and converting the urate of ammonia into nitrate of potash by adding excess of potash, and boiling till the whole of the ammonia has been set free. Hydrochloric acid is then added, and the acid separates in minute crystals, which are thoroughly washed and dried. Pure uric acid is a white crystalline powder, requiring 10,000 parts of water