Y U 



plates, obliquely truncated. Their colour is amethyft-red, 

 and they are not altered by expofure to the air. 



Succinate of Tttria. — Yttria is not precipitated from its 

 folution in acids by the fuccinates, unlefs the two falts be 

 concentrated, in which cafe fmall cubic cryftals fall, which 

 are the fuccinate of yttria. 



Oxalate of Tttria. — When oxalic acid, or the oxalate of 

 ammonia, is dropped into a folution of yttria in an acid, a 

 ■white infoluble powder falls, which is the oxalate of yttria. 

 According to Vauquelin, tlus fait is compofed of 



Oxalic acid 

 Yttria 



57-5 

 42-5 



lOO 



Tartrate of Tttria — Yttria is precipitated from its folu- 

 tion in acids by the tartrate of potafti, but the precipitate 

 is diflblved by the addition of water. 



Dr. Thomfon infers, from the analyfes above-mentioned, 

 and more efpecially from the analyfis of the fulphate and 

 carbonate by Bei^zelius and Vauquelin, that the combining 

 weight or weight of the atom of yttria is 50, oxygen by 10, 

 and confequently that it is compofed of 



Yttrium 

 Oxygen 



80 

 20 



100 



and the weight of the atom of yttrium will be 40. 



With refpecl to the falts of yttria in general, it may 

 be faid, that many of them are bttle foluble ; that 

 they are capable of being precipitated from acids by the 

 phofphate of foda, the carbonate of foda, the oxalate of 

 ammonia, the tartrate of potarti, and the prufiiate of pot- 

 afh ; and laftly, that the fulphate of yttria may be dif- 

 tinguifhed from the fulphate of lime by its greater folubility, 

 and by its fweet tafte. 



YTTRIUM, the metallic bafis of yttria. See Yttria 

 fupra. 



YTTRO-TANTALITE, in Mineralogy, Tantale yttri- 

 fire, Brongniart, an ore of tantalum, combined with the 

 newly-difcovered earth called yttria, and found at Ytterby, 

 near Roflagen, in Sweden. The colour of yttro-tantalite is 

 a dark iron-black ; when pulverized it is greyifh : it occurs 

 in nodules, about the fize of a hazel-nut, and alfo cryftal- 

 lized in oblique fix-fided and four-fided prifms. It occurs 

 alfo in granular diftinA concretions. Its frafture is com- 

 paft or finely granular, and it has a (hining metallic luftre. 

 Yttro-tantalite fcratches glafs, but yields with difficulty to 

 the knife. The fpecific gravity of this mineral is 5- 13. It 

 decrepitates with the blow-pipe, but at length melts into a 

 grcenifh-yellow flag. According to Vauquelin, the confli- 

 tuent parts are, 



Oxyd of tantalum - - 45 



Oxyd of iron and yttria - ^ 



Yttro-tantalite is nearly allied to gadolinite, the other 

 mineral in which yttria is found, and occure with it at 

 Ytterby, in a bed of flefh-red felfpar in gneifs. 



YTZAIMPATLI, in the Materia Medica, a name given 

 by fome to the cevadilla, or hordeum cauflicum, the caujiic 

 Indian barley. 



YU, in Geography, a city of China, of the fecond rank, 

 Vol.. XXXIX. 



Y U C 



in Pe-tche-li; 87 miles W. of Peking. N. lat 50° r-' 

 E. long. 114° 14'.— Alfo, a city of China, of the fecond 

 rank, m Ho-nan ; 442 miles S.S.W. of Peking. N lat 

 33° 22'. E. long. 112° 38'.— Alfo, a city of China, of thb 

 lecond rank, m Ho-nan ; 377 miles S.S.W. of Peking. N. 

 lat. 34^ 16'. E. long. 113'^ i4'._Alfo, a nver of China', 

 which nfes in Ho-nan, 12 miles N. of Pi-yang, and joins 

 the Hoai, 20 miles E.S.E. of Sin-tfai.— Alfo, a river of 

 China, which rifes about 26 miles W. from Ngan-fou, in 

 Kiang-fi, and runs into the Kan-kiang, 7 miles N.N.E. of 

 liin-kiang. 



YUCATAN, a province of Mexico : it is a peninfula, 

 furrounded on the W. and N. by the gulf of Mexico, be- 

 tween the bay of Campeachy on the S.W., and that of 

 Honduras on the S.E., having the little province of Ta- 

 bafco on the S.W., and that of Vera Paz, in the audience 

 of Guatimala on the S., where it is joined on the continent 

 by an ifthmus not 12c miles broad. The climate is pretty 

 warm in fummer, which begins about April, and ends in 

 September. It rarely rains here during the winter feafon, 

 though the weather is tolerably cool, except in January and 

 February, which are almoft as hot as in the middle of 

 fummer. It is, however, very healthy, efpecially a large 

 mountainous trad, extending from Salamanca on the W., 

 to the eailcrn boundary, and where the natives live to a 

 great age. The foulh fide of this ridge is ill-peopled, and 

 worfe cultivated, for want of water ; but the north part is 

 very populous, being rendered pleafant by gentle breezes, 

 though the fun is very hot. The days and nights are nearly 

 equal all the year. The foil when properly cultivated pro- 

 duces great quantities of corn, cotton, and indigo. All 

 forts of cattle, wild-beails, honey, wax, and fowls, are 

 here in great plenty ; and on the coatts are found large 

 pieces of amber ; but as no mines were ever difcovered in 

 this country, the Spaniards are not fond of making fettie- 

 ments here, fo that it abounds moftly with Indians, fubjecl 

 to the Spaniards, who employ them in making fait, in the 

 bay of Campeachy. This peninfula has very few rivers, but 

 wells without number, and confiderable lakes ; and wherefo- 

 ever they dig up the land, abundance of fliells are found, 

 which with the lownefs of the country, and (hallownefs of 

 the fea about it, has induced many to think that the greateft 

 part of it was once under water. The capital of Yucatan 

 is Campeachy, in the bay of which, and of Honduras, the 

 former lying on the weft, and the latter on the call fide of 

 this province, the Englifh cut their logwood. 



YUCCA, in Botany, is the Tucca, Tuca, or Jucca, of 

 the original inhabitants of America. Gerarde appears firft 

 to have pubhfhed this name in England. Cafpar Bauhin 

 follows him. Linnseus, Phil. Bot. 164, lays to the charge 

 of Tournefort the introduAion of Tucca, as a fcientific 

 generic appellation, but we do not find it in his work. 

 Dillenius however adopts it in his Nova Genera, and Hor- 

 tus Elthamenjis, and Linnaeus rather overlooks than approves 

 of the barbarifm. — Linn. Gen. 170. Schreb. 226. Willd. 

 Sp. PL v. 2. 183. Mart. Mill. Did. v. 4. Ait. Hort. 

 Kew. V. 2. 291. Purfh 227. Juff. 49. Poiret in Lamarck 

 DiA. V. 8. 824. Lamarck lUuftr. t. 243. Gxrtn. t. Sj. 

 (Yuca; Dill. Nov. Gen. III. t. 5. Ponted. Anthol. 294. 

 t. 6. f. N, O. Cordyline ; Van Royen Lugd.-Bat. 22.) — 

 Clafs and order, Hexandria Monogjnia. Nat. Ord. Coro- 

 naria, Linn. Lilia, or perhaps Bromeli^, Juff. 



Gen. Ch. Cal. none. Cor. bell-fhaped, in fix deep, 

 ovate, very large, equal, -moderately fpreading fegments, 

 connefted by their claws. Neftanes none. Stam. Fila- 

 ments fix, in'ferted into the bafe of the corolla, very /hort, 

 fwelling upwards, reflexed ; anthers minute, roundi/h, Pi/2. 

 P Germen 



