URE, ANDREW ( 1778-1857 ). A Scotch chemist. born at Glasgow. Ile studied at Glasgow and Edinburgh. In 1802 he became professor of chemistry and natural philosophy in the Ander sonian Institution at Glasgow; took an active part in the establishment (1809) of the Glasgow Observatory, and was appointed its first di rector. In 1830 he removed to London, and in 1834 he was appointed analytical chemist to the Board of Customs. Be published a number of valuable works, his two dictionaries remaining for many years the standard books of reference: viz. his Dictionary of Chemistry (2 vols. 1821), and A Dictionary of. Arts, Jhrnufactures, and Mines (1837 and several later editions). Among his other works may he mentioned the Rystenzatie Table of the Materia Medica (1813) ; A New System of Geology (1829) ; the Philosophy of Manufactures (1835) ; and The Cotton Manu facture of Great Britain Compared with That of Other Countries (1836 and 1861).
UREA (Neo-Lat., from Gk. otpov, o-uron, urine), or CARRAMIDE, An organic substance which derives its name from its hav ing been originally discovered in urine, of which it forms the most important and characteristic ingredient. Pure urea, which has been allowed to crystallize slowly, occurs in white, glistening, streaked, four-sided prisms; hut when the crys tallization is rapid or disturbed, it separates in small white silky needles. It is devoid of smell,
has a coolish, bitter taste, like that of salt petre (which it closely resembles in its external form), and is very slightly deliquescent. It is readily soluble in water and alcohol, but only slightly in ether. Pure urea melts at 132° C.; dry circa may be sublimed without decomposition by heating in vacua between 120° and 130° C. If heated, under ordinary pres sure, above these temperatures, it is decomposed with formation of ammonia, cyanuric acid, biuret, and carbonic acid; the formation of biuret is represented by the following chemical equation: 2C0 = Urea Binret Ammonia. The formation of ctanuric acid takes place indirectly, probably through the combina tion of biuret with cyanic acid. If heated with water at 120°, or if boiled with dilute mineral acids, urea combines with water, yielding am monia and carbonic acid according to the follow ing equation: