M E T A L I, U R G V. 



71 



filtration, sulphate of soda is added, which throws down 

 the sulphate of lead: 100 gr.rsTl lead. 



the ore U first roasted, and then fiued with 

 thrice its ,. lit of black flux, and covered with salt. 

 The metallic button at the bottom of the vessel is the 

 lead, containing the other metaU present in the ore, 

 which however are in very small qua: 



flexrald the ore contain silver, the metallic button 

 Una obtained nraet be subjected to cnpejlation, or it 

 may be diasolved in nitric acid, and muriate of soda 

 added to the solution. The precipitate must then be 

 digested in weak nitric aciil, which will dissolve the 

 muriate of lead, and leave the silver, 100 of the preci- 

 pitate after tlu*. when dried =75.3 of silver. 



Arttnic. 



Amaic. Arsenic very frequently exists with other metals. 

 It U not, however, need in the metallic stale in the 

 arts. The compound of it generally employed is the 

 white oxide, or, as it ia commonly called, white arsenic, 

 which is frequently obtained in the praceain far ex- 



ia obtained by subjecting the arsenic 

 jrgecaat Iron ooxea. towhtch (foe* are 

 These are haatad by flues from a fur. 

 When red hot, abort 15 Ib. of the ore are thrown 



aaarfwhentfaewhofaofthevohu^aiarttrhassubUm- 

 anotAn* portion of otv w put in, ami loo proccw u 

 * ii 1 1 lee abort it hours, during which time, about 

 1 50 Ib. of the ore have bam employed. What ia col- 

 lected in the flaes of the boxes U broken off by ham- 

 mers, and it freed from any foreign matter adhering la 



Another preparation uf arsenic raueh Mad in the art*, 

 is yellow orpmisnt. which ia procured in the same 

 way ; the ore being previously mixed with half iu 



easily obtained from 



white 





veifht ef Mipber. 



Ml ' I < . . T 



It 



Auay of Anemic Orr. the 



ere. f y "g an ore of arsenic, ia that pointed out by 

 Chenevix, which consists in acidifying the arsenic, 

 ^pirating it by a salt of lead. For this pur. 

 ore ia triaHed with nitric acid, so as corn- 

 to acidify the anenic. Putusa is then added, 

 of lead, which throws down a 

 an to a low red heat, must 

 If it is entirely soluble iu nitric acid, 100 

 of it =" of metallic anenic 



If any of the precipitate is not soluble in nitric acid, 

 H ia sulphate of lead, the acid of which ia formed by 

 the action of the nitric acid on the sulphur of the ore. 

 The weight of what ia left, after the action of the nitric 

 acid, will indicate that of the precipitate diasvived. 



A more easy way of assaying the ore, though not 

 quite so accurate, bat sufficiently so for the purposes 

 of art, is to dissolve the on slowly in muriatic 

 to which a little nitric acid ia added. In this way the 

 meaal is dieaolvwl. and the sulphur is left. The quan- 

 tity ef this indicates that of the anenic ; loo being 

 1*8 of metal. 



Coball. 



its metallic sUtc for the 

 The preparation of it in general use 



i the oxide. Two different kind* of this are employed, Meullur- 

 zaffre and smalt : the former of which is the oxide W- 

 mixed with a quantity of verifiable earth ; the latter * "V"* 

 is the oxide which is brought to the state of glass by 

 being exposed to heat with some fusible substance. 

 These are prepared in Saxony, in Bohemia, Silesia, 

 and Lorrain. That from the former is considered the 

 beat. To prepare aaflre, the cobalt ore is exposed to 

 heat by means of the flame of wood, which is made to 

 play am it The vapour arising from the ore is convey- 

 ed through a long flue, in which it is condensed. Af. 

 ter the vapours have ceased to arise, the ore is removed 

 and reduced to powder, and a second time exposed to 

 heat. It is again reduced to fine powder, and passed 

 through sieves ; and after this U mixed with powdered 

 flints moistened. In this state it forms xaffre. Smalt 

 is prepared by mixing the oxide of cobalt, obtained in 

 the above process, with about equal parts of potashes 

 and powdered flints. The mixture is exposed to heat 

 in large pots, and frequently stirred, when in the fused 

 state, during 10 or 12 hours. It is then taken out in 

 ladles, and dropped into cold water, by which it is 

 aftuswida mere easily reduced to powder. 



The powdering of smalt ia performed by large atone 

 rollers, inclosed in cases of wood. When reduced to 

 powder, it is of a fine Una colour, and U sometimes 

 It ia employ ad not only in the arts 



to 



impart iu colour to substances with which it is fused, 

 t likewise in washing, to prevent linen from beoora- 



Coh.iit ,< 



obalt is obtained in the metallic state by deflagrat- 

 ing 4 parts of smalt, 8 of nitre, and .J of charcoal. The 

 iwidys) of the deflagration must be again subjected to 

 a similar process, and afterwards fused with 2 parts of 

 black flux. The product of thia operation, weighing 

 about one-fifth of the amah, ia mixed with one-MXth of 

 its weight of nitre, and the same quantity of black 

 oxide of manganese, and exposed to a strong heat in 

 a covered crucible for about an hour. Uy this process 

 it is freed front iron ; it still, however, retains a small 

 quantity of arsenic ; or the product of the deflagration 

 may be dissolved in nitric add, and carbonate of pot- 

 aaaa added to the solution, as long as a brownish pre- 

 cipitate ia thrown down ; when, however, the precipi. 

 tata rails of a violet colour, the addition of the salt must 

 be diaruntinated. By this means we get quit of the 

 iron, and leave the cobalt in union with nitric acid. 

 The nitrate is then exposed to heat, the acid is ex- 

 pelled, and the oxide may be reduced by fusion with 

 black flux. By these proceases cobalt is obtained suffi- 

 ciently pure for many purposes. 



Auay TheasMy of cobalt ore may be performed, I 

 though not with great accuracy, in the dry way. The 

 ore is mixed with saw-dust, and roasted to expel the or. 

 senic, and the residue afterwards exposed to an intense 

 heat for about 15 minute*, with its own weight of a 

 mixture of carbonate of potaasa and tartar. The metal- 

 lic l.utton collected below is cobalt. The scoria of this 

 operation contains a considerable quantity of metal ; 

 the whole of the cobalt ia therefore not procured, and 

 it is even doubtful if by this means the whole of the 

 arsenic U expelled. 



Mercury. 



Different methods are practised for procuring roer- 

 cury from iu ores ; they arc however ail very simple. 



