1. Zinc Blende, from Przibram. When heated in a matrass, it falls to powder, and when this powder is heated to redness, no volatile ingredients are eliminated. If heat be applied to the powder in an open vessel, its color changes to a lighter hue, and sulphurous acid gas is evolved, which reddens moistened litmus paper. On charcoal, in the reducing flame, the color of the powder likewise assumes a lighter tinge, and traces of sulphurous acid are evolved. In the reducing flame, sinteration ensues, and the charcoal becomes coated with a yellowish sublimate, which is white when cold. When treated with a solution of cobalt, it assumes a beautiful green color-oxide of zinc. The fine powder dissolves copiously in borax and microcosmic salt; if it be heated with these fluxes on charcoal, in the oxidating flame, the glass obtained is clear, and presents the ferruginous tint only; but when the glass is over saturated, it appears turbidly streaked. The roasted, as well as the unroasted powder, dissolves with effervescence in soda on charcoal, forming an opaline mass. After continued blowing with the reducing flame, the charcoal is at first covered with a reddish-brown sublimate, the color of which is most distinct on refrigeration, and may be immediately recognized as oxide of cadmium; a large sublimate of zinc then occurs, and the soda is imbibed by the charcoal. If the unroasted substance is operated upon, a strong hepatical smell results, when the spot where the soda has been absorbed is moistened with water. From the preceding reactions, we may infer that the ingredients of Zinc Blende are Zinc, and Sulphur, with portions of Cadmium, and Iron. 2. Cupriferous Sulphide of Bismuth. It decrepitates slightly, and ultimately melts when heated in a flask, but volatile ingredients are not evolved. When heated in an open glass vessel, sulphur sublimes, and in the under part of the tube a deposit appears, which, when strongly heated, melts to brownish drops; and the substance, after cooling, is yellowish by transmitted light-oxide of bismuth. It melts readily upon charcoal, with ebullition and spirting. When the blowing is uninterrupted, nearly the whole volatilizes, and the charcoal presents an orange-yellow coating. This deposit becomes lemon-yellow on cooling, and appears to be pure oxide of bismuth. If the residuary matter be melted with borax in the oxidating flame, a beautiful green glass is obtained, which will remain unaltered when cold-iron and oxide of copper. On treating this bead with tin, the assay will be of an opalestic red color, when cold-suboxide of copper. If the roasted mineral is melted on charcoal, with bisulphate of potassa, in the oxidating flame, and the fused assay be treated according to the method given under the examination for Bismuth, the operator will not find lead. When the mineral is melted with borax, on charcoal in the reducing flame, a greenish glass is obtained, which acquires a vitriol-green tinge when treated with tin-protoxide of iron. When a small portion of the mineral is purified with proof lead, on charcoal, and submitted to the oxidating flame till the sulphur is eliminated, then melted with a little boracic acid, a button of copper remains behind, which forms about five per cent. of the quantity taken. The mineral, therefore, consists of Bismuth, Copper, and a trace of 3. Bournomite, from Kuprinz, near Freyberg. When heated per se in a flask, it decrepitates, giving off volatile ingredients. Heated in an open vessel, it evolves a large portion of sulphurous acid, and also a dense white vapor, which deposits partly on the upper, and partly on the lower side of the flask. The upper portion is volatile,-oxide of antimony,-while the under is not, and being present in large quantities, appears to consist of antimonide of lead. It melts readily on charcoal, coating it with oxide of antimony, which congeals to a black bead, possessing a rough surface. By continued blowing, the bead re-melts, and the charcoal becomes thickly coated with oxide of lead. If the globule, greatly reduced in volume, be treated with borax in the reducing flame, a colorless glass is formed,-no iron present,-but when subjected to the oxidating flame, a red cupriferous glass is obtained, suboxide of copper, and a cupreous button, which is brittle, from a small trace of sulphur, but when treated with a little soda, it becomes perfectly malleable. The cupreous globule, when cupellated with lead, gives a button of silver. This Bournonite, therefore, is composed of Sulphur, Antimony, Lead, Copper, Silver-0·1 per cent. 4. Nickel-Glance. This mineral decrepitates when heated per se in a flask, evolving a large quantity of sulphide of arsenic; as the heat augments, it melts. When heated in an open glass tube, arsenious and sulphurous acids are eliminated. Heated on charcoal, a dense arsenical vapor is evolved, part of which coats the charcoal, and is readily expelled. If the greater part of the arsenic be volatilized, the assay fuses readily to a globule, quite brittle on cooling. If this be melted with borax on charcoal in the reducing flame, the glass appears, after perfect refrigeration, greenish-blue. When the glass is separated from the metal, and heated on the ring of the platinum wire in the oxidating flame, it appears green while hot, from cobalt and oxide of iron, and after cooling only slightly blue, from oxide of cobalt. On charcoal with tin, the glass assumes a vitriol-green color, mingled with much blue. The metallic globule, separated from the borax glass, and treated again in the oxidating flame with borax on charcoal, gives the tinge from oxide of nickel only; the nickel separates in the metallic state, in the reducing flame, and the glass appears colorless. From the above reactions, we may conclude that Nickel Glance contains Arsenic, Iron, and 5. Grey Copper, from Freyberg. It decrepitates in a flask, and gives, if melted, a red sublimate of sulphide of arsenic. The powdered mineral fumes pretty strongly, in an open glass tube. This vapor deposits a white sublimate on the glass, and appears to be a mixture of arsenious acid and oxide of antimony. At the upper end of the tube, a strong smell of sulphurous acid will be recognized. The powder melts readily, per se, on charcoal, to a globule which fumes strongly. The vapor deposits partly on the charcoal, and consists of oxide of antimony. If a sufficiency has been applied, a second sublimate is obtained, nearer to the assay than the sublimate of antimony; while hot it is yellowish, on cooling white, and assumes a green color with a solution of cobalt,-oxide of zinc. On account of the large quantity of sulphur present, no arsenical smell is perceived when the assay is treated per se on charcoal; but if another portion of the mineral be treated with soda on charcoal, the sulphur separates, the arsenic volatilizes, and is distinctly perceptible from its alliaceous smell. If a portion of the mineral be gradually roasted on charcoal, and treated with borax on the same in the reducing flame, a bottle-green glass is obtained, which becomes vitriol-green after dressing with tin,iron, and leaves a somewhat liquid metallic globule, which has a light copper color, and therefore appears to consist of copper and a little antimony. If this globule be treated for some time with borax in the oxidating flame, the glass will be tinged red, from suboxide of copper, and the globule assumes a pure copper color. If the cupriferous button be cupellated with lead, a small silver globule is procured. Grey Copper, therefore, consists of Sulphur, Antimony, Arsenic, Copper, Silver, Iron, and 6. Rohstein, from the Freyberg Furnaces. Heated strongly in a matrass, it gives off no volatile particles, but assumes a blackish color. Heated in an open glass tube, it evolves sulphurous acid, recognizable by moistened litmus paper, or by its odor. On the lower side of the tube, near the assay, a thin white coating is formed, not volatile, and appearing to be antimonious acid. It melts very readily per se on charcoal; and, after a continued exposure to the reducing flame, coats the support with three different metallic oxides :-The sublimate which is at first produced, is deposited at some distance from the assay; it is white, and admits of being driven from one side to the other with the oxidating flame-oxide of antimony. That produced later, is immediately in contact with the antimonial sublimate; it is, while hot, of a lemon-yellow, and on cooling, of a sulphuryellow color-oxide of lead. The third deposit, which is near the assay, appears only in very thin white lamina; if it be moistened with a solution of cobalt, and heated strongly, but carefully, |