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A patent has recently been obtained by Mr. Henderson, of Bristol, for a method of obtaining copper and other metals associated with it in quartzose copper ores in the wet way. This method appears likely to be of considerable value for working ores containing a large admixture of gangue. In the case of ores containing only oxyds, carbonates, arseniates, phosphates, and similar compound, no preliminary treatment is requisite ; but ores containing chiefly sulphides must be first roasted, for the purpose of driving off the sulphur, and converting the metal into the state of oxyds. The crushed ore is introduced into vats, with perforated false bottoms, raised some inches from the true bottoms, and covered with a layer of brushwood or straw, to prevent the ore falling through. When the vats are filled, hydrochloric acid is poured on the top of the ore, so as gradually to filter downwards through it, dissolving out the metallic oxyds meanwhile. The liquid that accumulates at the bottom of the vats is pumped up, and made to pass several times through the ore, so as to saturate the acid as much as possible; or a series of vats may be used, through which the liquid is passed successively. When the metallic oxyd, c, is dissolved out of the ore, the residue is washed with water, removed, and a fresh charge of ore put into the vats. The strength of the acid to be used varies according to the nature of the ore operated upon. A loose, porous, and poor ore requires a weaker acid than a more compact, richer ore. The liquid thus obtained contains the metals—copper, iron, lead, c.—in the state of chlorides. If it contains any iron in the state of protochloride, enough chlorine is added to convert it into perchloride of iron; and, after this has been effected, finely powdered carbonate of lime is added in slight excess, for the purpose of precipitating oxyd of iron. Lead and some other metals are also separated from the liquid by this means. The clear liquid from which the precipitate has been separated will then contain copper, which is precipitated as oxyd by means of quicklime. This is effected best at a boiling temperature. The precipitation may also be effected at the boiling point by carbonates of lime, baryta, magnesia, c, sulphides of barium, calcium, c, or the lime waste from soda works. In this way an oxyd, carbonate, together with, in all cases, a solution of chloride of calcium, is produced. The precipitate is washed, dried, and smelted in the ordinary way.—Mining Chronicle.
