U R A 



sfenus, that we (liould not wonder if they prove the fame. 

 vVc have been fhewn at fir J. Banks's, a native capfule and 

 feeds of a Strelit'i.la from the Cape, which anfv/er exadlly to 

 tke charadlers of Urania, though no tunic is dcfcribed in 

 STRfei.;TZlA ; fee that article. 



UraNia, or Calejlis, in Mythology, one of the nine Mufes 

 that prcfidcd over aftronomy : ilie is reprefented as clothed 

 with an a/.ure-oolouicd robe, crowned with Ravs, holding a 

 globe in iicr hand, or fometimcs with the globe at her feet, 

 and furroundcd with levcral mathematical inflruments. On 

 medals the globe ftands upon a tripod. 



Ukania, a goddefs of the Arabians, and of the Moors 

 of Africa, called alfo yHilat and Ccelejiis. The Urania of 

 the Arabs is fuppofed to have been the Moon, as Bacchus 

 was the Sun ; and thcfe two luminaries were among them 

 objfds of worfliip. The Coeleftis of the Moorf, mentioned 

 by TertuUian, was the Venus Urania, fo well known in 

 Syria, that is, the planet of that name ; for it is certain that 

 almoll all nations wordiipped the ftars, and had gods natural 

 and gods animated. 



URANIBURGH, q. d. thi City of the Heavens, a term 

 often heard among allronomers, being the name of a cele- 

 brated obfervatory, in a callle in the little illand Weenen, 

 or Huen, in the Sound ; built by that noble Dane, Tycho 

 Brahe ; and furnilhed with inflruments for obferving the 

 courfe and motions of the heavenly bodies. 



This famed obfervator}-, finifhed about the year 1580, 

 did not fubfill above feventeen years ; when Tycho, who 

 little thought to have erected an edifice of fo fhort a dura- 

 tion, and who had even publifhed the figure and pofition of 

 the heavens, which he had chofen for the moment to lay the 

 iirft Hone in, was obliged to abandon his country. 



Soon after this, thofe to whom the property of the ifland 

 was given, made it their bufinefs to demohfli Uraniburgh : 

 part of the ruins was difperfed into divers places ; the refl 

 ferved to build Tycho a handfome feat upon his ancient 

 eftate, which to this day bears the name of Uraniburgh. 

 For as to the ancient Uraniburgh, there is now no footftep 

 of it remaining. It was here Tycho compofed his cata- 

 logue of the Hars. 



M. Picart, making a voyage to Uraniburgh, found Ty- 

 cho's meridian line, drawn thereon, to deviate from the 

 meridian of the world : which confirms tlie conjefture of 

 ■fome, that the pofition of the meridian line may vary. See 

 TvcHO Brahb. 



URANIUM, in Mineralogy and Metallurgy, a metal fo 

 called from the planet Uranus or Herfchel, by the cele- 

 brated chemill Klaproth, who difcovered it in 1789, in an 

 ore which had been formerly fuppofed to contain zinc or 

 iron. Uranium is of an iron-grey colour ; it poflefTcs con- 

 fiderable metallic luftre ; it is brittle and hard, but yields to 

 the tile. It has hitherto only been obtained in grains, or in 

 fmall quantities as a porous cohering mafs. The fpecific 

 gravity of uranium, according to Klaproth, is 8.01 ; but 

 according to Bucholz, 9. Uranium melts with great diffi- 

 culty ; but when heated to rednefs in an open vefTel, it un- 

 dergoes a fpecies of combullion, glowing like a coal, and 

 is converted into a black powder, gaining in weight about 

 five parts in the hundred. This powder is the black oxyd. 

 The yellow oxyd is obtained by precipitating uranium from 

 its foiution in nitric acid by an alkali. The yellow oxyd of 

 uranium is Infoluble in p\irc alkalies, but is foluble by the 

 alkaline carbonates ; the former property dillinguillies it 

 from the oxyd of tungllen. The yellow oxyd confifls of 

 eight parts metal, and twenty of oxygen. The combina- 

 tions of uranium with the other metals are unknown. With 

 fulphur the yellow oxyd of uranium may be combined, by 



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mixing two parts of fulphur and one of oxyd, and expofing 

 the mixture to heat in a crucible. Mott of the fulphur is 

 driven off; the reliduum is a blackiHi-brown mafs, being a 

 fulphuret of uranium. If the heat be increafed, the whole 

 of the fulphur is fublimed, and the uranium remains in a 

 metallic ftate, in tfie form of a black coarfe powder. Me- 

 tallic uranium is only perfcftly foluble in nitric acid. 

 Bucholz fuppofes that there are feveral oxyds of this metal, 

 diftinguifhed by their different colours, as under : 



Protoxyd, - Grcyifli-black. 



Second oxyd, - Dark grey, inclining to violet. 



Third oxyd, - Greenifh-brown. 



Fourth oxyd, - Grcyifh-green. 



Fifth oxyd, - Orange. 



Peroxyd, - Lemon-yellow. 



To obtain uranium from its ores, in which it exifts in the 

 flate of oxyd, the are mull be diflolved in dilute nitric 

 acid. The foiution may cor.tai.T iron, copper, and lime. 

 By evaporating it to drynefs, and expofing the dry mafs to 

 a moderately flrong heat, the iron is rendered infoluble, but 

 the other ingredients will be taken up by dillilled water. 

 Ammonia poured into this foiution, and digefled in it for 

 fome time, retains the copper, but throws down the 

 uranium. 



The precipitate is to be waili-'d with ammonia till the 

 liquid comes off colourlefs ; it is then to be dilTolved in 

 nitric acid, and to be concentrated by evaporation, and fct 

 by to cryllallize. The green-coloured cryllals that form, 

 may be picked out and dried on blotting-paper, then dif- 

 folved in water, and the liquid partly evaporated and left to 

 cryflallize. By this means the whole of the lime will re- 

 main behind. The cryllals will confift of pure oxyd of 

 uranium united to nitric acid ; they are to be expofed to a 

 red heat ; a yellow powder remains, which is the oxyd of 

 uranium. This powder is to be mixed with a fmall quan- 

 tity of charcoal powder, and expofed to a violent heat, by 

 which it is reduced to a metalhc flate. The experiment 

 fucceeds befl when the oxyd is mixed with only the one- 

 twentieth part of charcoal, and inclofed in a charcoal cru- 

 cible to exclude the air. Klaproth employed a heat equal 

 to 170^ Wedgwood, to obtain this metal. No flux has 

 hitherto been found of any fervice in facilitating the reduc- 

 tion of uranium. 



Uranium has not hitherto been applied to any ufeful pur- 

 pofe in the arts, eitiier in its metallic flate, or in combina- 

 tion with acids as a metalline fait. 



With nitric acid, oxyd of uranium unites in two propor- 

 tions. The nitrate is an extremely foluble fait, of a lemon- 

 yellow colour. The cryllals have generally tiie form of 

 hexagonal tables, more or lefs perfeft ; but by careful ma- 

 nagement, they may be obtained in large four-fidcd reftan- 

 gular flat prifms. At the temperature of 100", they fall 

 into a white powder. In a damp .itmofpherc, they loon 

 deliquefce. 



They confift, according to Buch<dz, of 



Oxyd of uranium - - f>i 



Acid 2J 



Water .... 14 



When nitrate of uranium is heated till its colour becomes 

 orange-red, it does not diffolve completely in water, but 

 leaves a yellow powder, which lias been lliewn by Bucholz 

 to be a fnbnitrate. 



The oxyd of uranium combines with the muriatic and 

 3 R 2 fiilphnnc 



