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wfed, thefe impurities difiblve in the flux (whichis one of the great ufes of thefe fubftances) andone or at moft two operations, will fuffice.

. When copper is pure (that is, of a faleablepurity, for it is very rarely found abfolutely pure)it is foft, malleable, and of a beautiful brilliantyellow-red where recently cut or filed. On thecontrary, when containing fulphur, arfenic, oriron, it is black, denfe, fonorous, brittle, and moreof a vitreous than a truly metallic appearance.In this ftate it is called copper-matt, or blacktopper by metallurgifts. Subfequent melting incontact with air, or with fluxes, removes thefeimpurities, and if the operation be judiciouflyperformed, the lofs fuftained by the matt, inbeing converted into pure copper is principallythat of the impurities; for it is a valuable pro-perty of this metal to be much lefs eafily oxi-dated, fcorified, and diflolved by fulphurets,than any of the metals with which.it is ufuallyfound mixed, and particularly than iron.

After all, however, the analyfis of copperores in the dry way can only give an approxi-mation to accuracy in the refult, except in thetreatment of the pure native oxyds or carbonats,which are indeed among the moft valuable ores,but are thofe which the feldomeft come underthe notice of the practical metallurgift.

The analyfis of copper ores in the moift wayis performed in a tolerably uniform manner,the ore being firft treated with an acid whichdiJTolves all the metallic part, leaving the ful-phur and filex -, after which the different metalsare feparately precipitated from the folution,either in the metallic ftate, or in certain knownforms of combination, from which the metallicportion can be accurately inferred.

The particular fteps of many of thefe ana-lyfes will be prefently given; the general modeof feparating copper from the metals withwhich it is alloyed is as follows: from fiver,by adding to the nitrous folution of the mixedmetals muriat of foda, which feparates tire fil-ver, as luna cornea, and leaves the copper :—from lead, by adding to the folution fulphat offoda, which precipitates an infoluble fulphat oflead, and leaves the copper :—from antimony,by digefting the mixed oxyds of copper and an-timony with nitric acid, which diflolves thecopper and leaves the antimony :—-from iron,by iuperfaturating the mixed folution with am-monia, which redifiolves the copper and leavesthe oxyd of iron ; or elfe by immerfing a pieceof polifhed iron in the folution, which will fepa-rate the copper and leave the iron in folution,(a precaution to be obferved here, however, willVOL. I.

be prefently mentioned 1 ) •.—from tin , by im-merfing a piece of metallic tin in the folution,which will precipitate the copper only ‘.—fromarfenic , by diflblving in nitrous acid and addingacetite or nitrat of lead which will feparate thearfenic in the form of an infoluble arfeniat oflead, and leave the copper. If an excels oflead remain, add fulphat of foda, as above men-tioned :—from Nickel in the following way:when this metal is found it is generally in con-junction with iron j and ammonia, which pre-cipitates all the three metals from their acid fo-lution, redifiolves, when in excefs, both thenickel and copper; but to obtain the copperfingly, again fuperfaturate with muriatic acid,and immerfe a piece of iron, which will fepa-rate the copper, and leave the nickel diffolved.

Copper is obtained feparate, in wet analyfis,in three ftates, in each of which the weight maybe taken, either in the metallic ftate, or as thegreen carbonat, or as the black oxyd. If apiece of polilhed iron is immerfed in an acidfolution of copper it is almoft inftantly coveredwith a brilliant coating of metallic copper,owing to an exchange having taken place, aportion of the iron being diflolved, and fepa-rating an equivalent quantity of copper fromthe folution. As this proceeds, the precipitateof metallic copper increafes, and incrufts tireremaining iron, forming a bundle of raggedfilaments which the flighted: force will detachif the folution is fufficiently diluted. At ladthe folution contains only iron, and the wholeof the copper is thus obtained in the metallicftate, which only requires waffling and drying.This precipitation is much afiifted by boilingfor a fliort time, efpecially at laft, withoutwhich indeed the laft portions of copper willhardly feparate. The folution when purely cu-preous is of a fine azure blue, but when con-verted to a folution of iron becomes green. Itftiould be remembered, however, that for a per-fect feparation of copper from iron by thismethod, the folution fhould be in the fulphuricor muriatic acids and not the nitrous, forthough iron will equally difplace copper fromthe nitrous as from the other acids, the nitratof iron is itfelf largely decompofed by mereheat or expofure to air, and lets fall a fullyoxidated iron, which in this cafe mixes withthe fine filaments of the reduced copper, andvitiates the refult of the analyfis. When, there-fore, it has been neceffary to employ this acidin the previous part of the analyfis, the metallic-contents fhould either be firft precipitated by analkali and rediffolved in muriatic acid, or the2 T