ANTIMONY 



197 



of the ore or a fragment of charcoal. The ore is then introduced ; portions of charcoal 

 about the sizo of the ore being intermixed during the charging, the fine ore placed on 

 top, a layer of charcoal afterwards added, and the crucible-cover fitted and well 

 luted down. The bottom of the pot thus charged is inserted into the mouth of tho 

 lower one. Heat is now applied ; the two pots thus arranged being placed so that 

 the lower pot is under the bars of tho furnace and the upper one surrounded with hot 

 fuel. Tho temperature should be carefully regulated, and the operation completed in 

 about 1 to 1^ hours. When cold, the liquated regulus or sulphide of antimony will 

 be found in the lower crucible, and from its weight the per-centage of pure ore con- 

 tained in the sample operated on can be calculated. The regulus should bo well 

 fused, bluish grey in colour, and the fracture bright and fibrous-crystalline. When 

 puro, sulphide of antimony contains 71'76 per cent, of metallic antimony; so that, if 

 desirable, from the weight of the regulus obtained tho quantity of metal in the sample 

 operated on can readily be calculated. The residual vein-stuff in the upper crucible 

 should be examined, to see that it is practically free from sulphide of antimony. 



(b.) Assay of Ore rich in Sulphide of Antimony, or Bcgulus obtained by Liquation () 

 or otherwise, by roasting, 3fc. 100 to 500 grains of the finely powdered ore are placed 

 in a crucible or roasting-dish, and roasted at a very low and carefully regulated 

 temperature, with frequent stirring, especially at the first part of the operation, so as 

 to prevent clogging or loss from antimony fume being given off. The roasted product, 

 which is generally grey or greyish white in colour, is then mixed with carbonate of 

 soda and charcoal powder, or tartar, or with black flux, and the assay made as for oxido 

 of antimony. 



(c.) By Cyanide of Potassium. With 100 to 200 grains of the finely powdered ore aro 

 mixed about four times its weight of coarsely powdered cyanide of potassium, tho 

 mixture transferred to a crucible, and the whole submitted to a low red heat for about 

 20 to 30 minutes. The fused contents are poured out into a mould, and when cold 

 the slag detached and the button of metallic antimony weighed. It should be bright, 

 bluish white, brittle, and break with a largely crystalline fracture. 



II. Oxides of Antimony. 



(a.) By Carbonate of Soda and Carbon. 100 to 500 grains of the finely powdered 

 ore are mixed with from 300 to 500 grains of carbonate of soda, and from 20 to 50 

 grains of charcoal powder, and the mixture submitted in a crucible to a temperature 

 gradually increasing to a red heat at the end of from 20 to 30 minutes. When the 

 fused contents are tranquil, it is poured out into a mould, and when cold the slag 

 cautiously detached, and the button of antimony cleaned and weighed. 



(b.) By Cyanide of Potassium. 100 to 200 grains of the oro are weighed and 

 mixed with about four times its weight of cyanide of potassium, and from 20 to 30 

 grains of charcoal powder, the whole exposed in a crucible to a low red heat for about 

 20 to 30 minutes, and the process completed as before described for the assay of 

 sulphide of antimony with cyanide of potassium. 



Professor Henry Eose, of Berlin, in a memoir on the natural, not oxidised, com- 

 binations of antimony and arsenic, gives tho following analyses : ' 



Browstcr's Ed!n. Jonrn. 11, 360 ; Pogg. Ann. xr, 



