BAR 



BARYTES, or ponderous earth; terra ponderofa./ciiwr- 



trde Germ, h^tyte Yr. , • . 



The EntrliHi and French names of this earth are derived 

 from the Greek 0u.^v:, heavy, on account of the high fpccific 

 gravity of the Ponderqus Spar or native fnlphat of barytcs, 

 which' is the commoncil form in which this earth appears, 

 f I. Hiftorical notices refpefting barytes. 



It is to Scheele that Chtiniilry is indebted for the difco- 

 very of this fubllance in 1774. In his valuable eflay on 

 manganefe, he informs us that the nitric and muriatic lohi- 

 tions prepared from the native black oxyd of this metal con- 

 tain befides, an earth diflering from all thofc hitherto known 

 by its ftrong affinity for fulpluiricacid, &c. In 1775 Galhn 

 made hisanalyfis of the ponderous fpTir, and found it to cori- 

 fift of the earth newly discovered by Scheele, and lulphuiic 

 acid. Bergman repeated and confirmed the experiments of 

 thefe chemills, and named the earth terra pondorofa. Mor- 

 veau propofcd the term barote derived from the Greek, 

 which Mr. Kirwan foftened into barytes. In this appellation 

 Bergman acqniefced ; and it is now adopted by all except 

 the German chemills, w!io in conformity with their general 

 cullom prefer the term fchwererde, which is a hteral tianfla- 

 tion in their own langu:ige of tens ponderofa. Wiig'eb 

 and Afzelius contribitted to enlarge our acquaintance with 

 this fubftance ; and in 1793, Dr. Hope publiflicd his valu- 

 able experiments in the Edinburgh Tranfaftions. In 1796, 

 Klaproth augmented our knowledge by his mafterly analyfis 

 of the native fnlphats and carbonats of bai7tes ; and in 1 797 

 Pelletier and Vauquelin gave to the world their able me- 

 moirs, confirming the fafts already admitted and adding to 

 them many new ones. 



§ 2. Method of obtaining pure barytes. 



The only way of procuring this earth in a Hate of fufii- 

 cient purity for chemical experiment, is to expofe cryftal- 

 lizcd nitrat of barj-tes in a platina crucible to a moderate red 

 heat till it becomes quite dry and ha:; ceafed to give out any 

 vapours : the nitric acid will be wholly decompofed and vo- 

 latilifed, leaving the barytes behind in the form of a greyifh 

 white porous mafs more or Icfs adherent to the crucible. 

 The nitrat of bar^-tes is obtained either by diffolving the na- 

 tive carbonat of bai7tes in very dilute nitrous acid ; or by 

 heating the native fulphat of barytes in a clofe crucible with 

 charcoal, and thus converting it into fulphuret of baiytes and 

 then treating this with nitric acid, which will difTolve the 

 earth and leave the fnlpluir behind. A much more econo- 

 mical way however of preparing this earth, is mentioned by 

 Dartigues. (Ann. de Cliimie, vol.40.) Take fulphat of 

 barytes, pulverife it together with charcoal, and expofe it for 

 half an hour to a full red heat : by this means the greater 

 part will be converted into fulphuret of barytes. Pour 

 boihng water on the mafs, and a clear yellow liquor will be 

 obtained by filtrat'on : add to this, carbonat of loda ; and a 

 copious white precipitate of carbonated barytes, four times 

 the weight of the foda employed, will be depofited. This 

 being feparated from the folution of fulphuret of fcda and 

 waflied repeatedly, is to be mix'.d with charcoal and again 

 heated for about half an houi- ; the carbonic acid will be for 

 the moil part converted into gafleous oxyd of carbon, and the 

 barytes will remain in a caiidic ftate. By a (hort digeflion in 

 boiling water and inbfequcnt filtration, a clear fuperfaturated 

 folution of barytes is obtained ; from which, by evaporation 

 and gently heating in a filver crucible, the pure barytes is 

 readily procured. 



§ 3. Chemical and phyfical properties. 

 Barytes obtained by the methods mentioned in the prece-. 

 ding fcftion,is a porous mafs of a greyiQi white colour and ca- 

 I 



BAR 



fily reducible to powder : its fp. gr. in this flate cannot be 

 afceitained with much accuracy : Fourcroy Hates it at 4, 

 naffenfnitz only at 2.374. It is the mod active of the alka- 

 line earths ; and from its ready folubility, has been arranged 

 by fome modern chemills among the proper alkalies. It has 

 a har(h cau^ic talle, and afti upon the animal economy as a 

 violent poifon. It is deftitutc of fmell. It changes fyrup 

 of violets green, and the lemon yellow of turmeric to a 

 browuifli orange. 



By a llrong heat it becomes harder, denfer, and acquires 

 internally a blueilh green tinge. When ilrongly urged by 

 the blowpipe or a llream of oxygen gas upon a piece of 

 charcoal, it fufes and is partly imbibed by the charcoal and 

 partly volatilized, communicating a yellow colour to the 

 flame. 



Its affinity for water is very confidcrable. When expofed 

 to the air, it gradually imbibes moillure, fwells, and falls to 

 pieces ; attrafting at the fame time the carbonic acid of the 

 atmofphere and becomin.-j mild : hence the necifTity of keep- 

 ing it in dry well-Hopped vials. When fprinkled with a 

 little water, it exhibits the fame appearances as quicklime, but 

 with greater energy ; the mafs becomes white, is remarkably 

 increafed in bulk, and a large quantity of heat is evolved. 

 If ilirred up while hot with an additional portion of water to 

 the confiilence of a thin pafte, it afrumes,as it cools, the ilate 

 of a fold, made up of confufed needle-form cryllals ; but 

 this by cxpofure to the air becomes carbonated and falls 

 into powder. 



Water boiled upon pure bai-ytes, is capable of taking up 

 half its weiglit of this earth ; the greater jiart of which it 

 depofits by cooling, in {lender delicate cryftala implanted 

 into each other, or, by carrying on the procefs very flowly, 

 in the form of comprtlTed hexahedral prifms terminated by a 

 four-fidcd pyramid, and of a brilliant fattiny luftre. Thefe 

 cryftals appear to be conipofed cf 53 parts of water and 47 

 of barytes. By a boihng heat, they completely liquefy; and 

 at length the water being evaporated a white powder re- 

 mains behind, wliich is pure biirytes. By mere expofure to 

 the air they become efflorefccnt, and tlie earth is found to be 

 carbonated. They are foluble in ab( ut 17^ parts of v.'ater 

 5' the temperature of 60°. The fluid that reiriains after the 

 depofition of the cryftals of barytes retains ^ of the earth 

 in permanent folution, and is calledbarytic water; improperly, 

 barytic lime water. This folution is perfcdlly limpid and 

 colourlefs, lias an acrid tafle, and poiTeffes properties very ana- 

 logous to lime water. By expofure to the air it becomes 

 covered with acrufl of carbonated barytes; and this being re- 

 moved or fa'hng to the bottom, a frcfli cruft bej;irs to be 

 formed till the whole of the earth is thus feparated from tiie_ 

 water. 



Barytes, like" the other alkaline earths, combines with all 

 the known acids; and the barytic falts thus produced are for 

 the mod part readily cry.lallizable, and are diftinguiilied by 

 the ilrong mutual affinity of their elements : fulphuric acid 

 in particular is difl:dged by it from every other combina- 

 tion. 



Among the fimple inflammables, phofphorus and fulphur 

 appear to be the only ones capable of uniting with bai-ytes. 

 If alternate portions of phofphorus and pure barytes are put 

 into a ftrong glafs tube clofed at one end and expofed to a 

 red heat, the phofphorus melts, fubhmes, and combines with 

 the barytes that is in contaft with it into a brown fufible 

 mafs of a metallic luftre, the phofphuret of barytes. This 

 fubftance when breathed upon exhales a ftrong fetid odour, - 

 is luminous ia the dark, changes gradually by expofure to 

 the air into phofphat of bary^tcs, and immediately decompofes 

 water giving out phofphor?.ted hydrogen gas. 



The 



