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ANALYSIS OF ORES OF IRON.

together. The mixture is pulverized, and placed in a lined cru-cible, which is to be covered. The heat of a forge-furnace isthen sufficient to effect the reduction of the metal, which is ge-nerally done in the course of half an hour.

The moist or humid way of assaying the ores of iron, is attendedwith more difficulty. The following method is the most simple :A certain quantity of iron ore is reduced to powder, and digestedwith about six parts of muriatic acid, which takes up the iron,and such earths as are soluble in that acid, and leaves the silex andthe sulphur behind; after which, the solution is to be saturatedwith potash, (or if the ore contains any copper, with ammonia)which precipitates the iron in the state of an oxid, along withthe dissolved earths; the precipitate is then well dried, andstrongly heated to redness, after which, it is pulverized, andput in digestion with diluted nitric acid, which then takes up allthe earths, together with the other heterogeneous substances,and leaves the iron behind, which, on account of its being sohighly oxidated, loses its solubility in that acid; it is then wellwashed, freed from the acid, and afterwards recovered by char-coal, or any other inflammable matter which has a strongeraffinity to the oxigen than the iron; the metal found in thebottom of the crucible, indicates the proportion of the metalcontained in a given quantity of the ore.

Arseniate of iron was analyzed by Mr. Chenevix in the fol-lowing manner: One hundred parts of it were boiled withpotash till the arsenic acid was separated. Nitrate of lead wasmixed with the solution; 100 parts of the precipitate indicated33 of arsenic acid. That portion of the ore which eluded theaction of the potash was treated with muriatic acid; the undis-solved residuum was silex. The muriatic acid was super-satu-rated with ammonia. The iron precipitated; but the copperwas dissolved by the ammonia.*

* Phil. Trans. i8oi, p. 219.