106 Analysis of the Gray Copper Ore 



and in sortie places assumes a beautiful tempered steel taf- 

 nish. Massive and disseminated. In some specimens, it 

 exhibits the appearance of imperfect crystals. Internal 

 surface shining and metallic ; but, by exposure, it soon 

 becomes dull. Fracture small-grained, inclining to even. 

 Fragments indeterminate, and rather blunt-edged. Semi- 

 hard, the degree being almost the same as that of calcareous 

 spar ; for these two minerals reciprocally scratch each other. 

 Streak similar, opake, brittle, easily frangible; specific 

 gravity 4*878. 



1. To free the ore as completely as possible from foreign 

 matter, ic was reduced to a coarse powder, and carefully 

 picked. It was then digested in diluted muriatic acid^ 

 which dissolved a quantity of carbonate of lime, amounting 

 to 13 per cent, of the original weight of the ore. 



2. Thus purified, it was dried on the steam-bath, and 

 100 grains of it were reduced to a fine powder, and digested 

 in diluted nitric acid, till every thing soluble in that men- 

 struum was taken up. The residue was digested in the same 

 manner, in muriatic acid ; and when that acid ceased to 

 act, the residue was treated with nitro- muriatic acid till no 

 further solution could be produced. The insoluble matter 

 was of a white colour; it weighed 6*9 grains, and was al- 

 most entirely sulphate of barytes. No traces of sulphate of 

 lead, nor of oxide of antimony, could be detected in it by 

 the blow -pipe. 



3. The three acid solutions being mixed together, no 

 cloudiness appeared, nor was any change produced; a proof 

 that the ore contained no silver. 



4. The solution being evaporated nearly to dryness, was 

 diluted with water, and precipitated by muriate of barytes. 

 By this means, the sulphuric and arsenic acids, which had 

 been formed during the long-continued action of the nitric 

 acid on the ore, and the presence of which had been indi- 

 cated by re- agents, were thrown down ; for nitrate of lead, 

 added to the residual liquid, occasioned no precipitate ^ a 

 proof that no arsenic acid was present. 



5. The liquid, thus freed from arsenic acid, was mixed 

 with an excess of ammonia. It assumed a deep blue co- 

 lour, while a brown matter precipitated. It was separated 

 by the filter, and being dried, drenched in oil, and heated 

 to redness, it was totally attracted by the magnet. It 

 weighed 45*5 grains, and was iron. 



6. The ammoniacal liquid was neutralized by sulphuric 

 acid, and the copper thrown down by means of an iron 

 plate. It weighed 17*2 grains, 



7. To 



