762 



URANITEURI. 



chimsthal, in Bohemia. In Cornwall, it has been 

 found in the tin mines of Tincroft, near Redruth. 



i'. Uranite. This beautiful species is found in 

 small, but very perfect crystals, of the form of the 

 right square prism, which is usually so low as to 

 appear tabular. The terminal and lateral edges 

 are often replaced. Cleavage takes place parallel 

 to the sides of the primary form, and with great 

 ease parallel to the terminal planes ; lustre pearly 

 or adamantine; colour emerald-green, leek-green 

 or siskin-green ; streak corresponding to the colour ; 

 transparent to translucent on the edges; sectile; 

 hardness a little above that of gypsum ; specific 

 gravity 3-115. It also occurs massive, having a 

 granular composition. It consists of 



Oxide of uranium, 60-00 



Phosphoric acid 16-00 



Oxide of copper 9-00 



Silex, 050 



Water 14-50 



Alone, it becomes yellow before the blow-pipe, and 

 loses its transparency. Upon charcoal, it intumes- 

 ces a little, and melts into a black globule. It oc- 

 curs in veins of copper, silver, tin and iron. 

 Beautiful varieties have been found in the Gunnis 

 lake mine, in Cornwall. It also occurs in the 

 Saxon and Bohemian mining districts. It is like- 

 wise met with at Bodenmais, in Bavaria, and at 

 Limoges, in France. 



History of the Metal and its Compounds. The 

 easiest method of procuring the metal from the ore 

 is the following : The pitchblende is reduced to 

 a fine powder, and digested in nitric acid till every 

 thing soluble is taken up. The solution is then 

 rendered as neutral as possible by evaporation, and 

 a current of sulphureted hydrogen gas passed 

 through it as long as any precipitate continues to 

 fall. The liquid is filtered and heated, to drive off 

 all traces of sulphureted hydrogen. It is now pre- 

 cipitated by caustic ammonia ; and the precipitate, 

 after being well washed, is digested, while still 

 moist, in a pretty strong solution of carbonate of 

 ammonia. A fine lemon-yellow liquid is obtained, 

 which, being set aside for a few days, deposits an 

 abundance of fine yellow crystals, in right rectan- 

 gular prisms. These crystals, being exposed to a 

 red heat, give out water, carbonate of ammonia, 

 and oxygen gas, and leave a black oxide of uranium, 

 which is easily reduced to the metallic state by 

 passing a current of dry hydrogen gas over it, placed 

 in a glass tube, and heated by a spirit lamp. The 

 metal presents a liver-brown colour, and remains in 

 the state of a powder. No heat that we can raise 

 is sufficient to melt it into a mass : of course its 

 malleability and ductility are unknown. It has con- 

 siderable lustre, and is soft enough to yield to the 

 file. Its specific gravity is 8-10. It undergoes no 

 change in the ordinary temperature of the atmos- 

 phere ; but when heated to redness, it takes fire, 

 swells, and is converted into green oxide. It is 

 insoluble in sulphuric and muriatic acids, whether 

 concentrated or diluted ; but nitric acid dissolves it 

 with facility. Uranium combines with two differ- 

 ent proportions of oxygen, and forms two oxides. 

 The protoxide is green, and the peroxide, or acid o: 

 uranium, is yellow. The former of these is obtainet 

 by exposing metallic uranium to a red heat. Its colour 

 while in grains, is black; but when in powder, it is 

 dark green. It is soluble in sulphuric and muriatic 

 acids. The solutions are green. When dissolved in 

 nitric acid, it is converted into the peroxide. Pro- 

 toxide of uranium is tasteless, and, when anhydrous, 



is not altered by exposure to the air. Peroxide of 

 uranium, or uranic acid, is obtained by dissolving the 

 protoxide in nitric acid, and precipitating by caus- 

 tic ammonia. A beautiful yellow powder is ob- 

 ained, which is a combination of peroxide of uiu- 

 iuiii and ammonia. Such is its tendency to <-<>m- 

 ine with other bodies, that it cannot be obtained 

 n a separate state. If we attempt to drive off tin: 

 immonia and water, with which it is united, it loses 

 ixygen at the same time, and is converted into |>i<>- 

 oxide. The same change takes place when we 

 icat pernitrate of uranium. Nothing is known res- 

 ecting the combinations which this metal is capa- 

 >le of forming with chlorine, bromine, and iodine, 

 or with azote, carbon, boron, silicon, and phospho- 

 us. A sulphuret of uranium has been formed, 

 which has a black colour, and, when rubbed, a me- 

 al lie lustre. Its capacity for forming alloys with 

 he other metals remains, in consequence of the 

 scarcity of the metal, uninvestigated. The oxides 

 of uranium are used in painting upon porcelain, 

 ielding a fine orange colour in the enamelling fire, 

 and a black one in that in which the porcelain itself 

 s baked. 



URANUS. According to the cosmo-theogony 

 of the Greeks, Gaea (Earth) proceeded from chaos 

 (the infinite void of space). The earth produced 

 Uranus (in remote antiquity, the personification of 

 ;he sphere of light, the heavenly vault), and by him 

 became the mother of the Titans, the youngest of 

 whom was called Kronos (Time). All the further 

 productions of nature proceeded from the embraces 

 of the Titans and Titanides. This was expressed 

 in the plastic language of the ancient poets, thus : 

 Time (.Kronos) put an end to the productive power 

 of Uranus, and emasculated him with his sickle. 



Uranus is also a name given by the continental 

 astronomers to the planet which we commonly 

 call Herschel. 



URBANISTS. See .Franciscan*. 



UREA. See Urine. 



URI ; a Swiss canton, bounded north by Schweitz 

 east by Glarus and Orisons, south by Tessin, and 

 west by Berne and Unterwalden ; square miles, 

 508; population, 14,000. The inhabitants are 

 Germans by descent and language ; of the Catholic 

 religion ; the government democratic. The canton 

 is divided into two districts, Uri and Urseren ; the 

 chief town is Altorf. The country is extremely 

 rugged, composed of barren and bleak mountains 

 and deep valleys. Here are the elevated summits 

 of St Gothard, which are covered with perpetual 

 snow. The canton is traversed from north to 

 south by the Reuss, and contains a number of lakes 

 and mountain streams. Of the valleys, the two 

 largest are those of the Reuss and of Urseren, each 

 of which admits of a small extent of tillage ; but 

 pasturage is the principal source of subsistence ; 

 and cattle, cheese, wool, leather, and timber, the 

 articles of export. Not far from Altorf is the vil- 

 lage of Burgelen, the birth-place of William Tell. 

 Uri concluded, in 1308, a league for ten years, with 

 Schweitz and Unterwalden, which, in 1315, was 

 changed into the perpetual league. The whole canton 

 consists of mountains and valleys, and is surrounded 

 by mountains always covered with snow. On the 

 south is mount St Gothard, 9944 feet high. Little 

 grain is raised ; orchard fruits succeed well. The 

 chief occupation of the people is raising cattle (Uri 

 has 10,000 head of cattle) and making cheese. The 

 road over the St Gothard yields them much profit; 

 . formerly above 15,000 people passed over it an- 



