The Elements of Blowpipe Analysis Part 7

~Smalt.i.te~, Co(Fe, Ni) As_{2}, Co . 28, As . 72.--H = 5.5, G = 6.37-7.30.

Color, tin-white or steel-gray. l.u.s.tre, metallic. When heated to redness in an ignition tube it yields a sublimate of metallic a.r.s.enic. Before the Bp. on Ch. it fuses readily, with emission of a.r.s.enical fumes, to a grayish black magnetic globule. This globule may be examined for iron, cobalt, and nickel with the borax bead.

~Cobalt.i.te~, CoS_{2} + CoAs_{2}, Co . 36, As . 45, S . 19.--H = 5.5, G = 6.0-6.3. Color, silver-white tinged with red. Metallic l.u.s.tre. Before the Bp. on Ch. fuses easily, with emission of copious a.r.s.enical fumes, to a gray magnetic globule. Remains unchanged in the ignition tube.

~Linnaeite~, (Co, Ni)_{3}S_{4}, (Co, Ni)58, S . 42.--H = 5.5, G = 4.8-5.0.

Color, bright steel-gray, sometimes reddish. l.u.s.tre, metallic.

Crystallizes in the regular octahedron. Before the Bp. on Ch. fuses to a metallic globule which is attracted by the magnet. With borax bead gives reaction for cobalt.

~Erythrite~, Co_{3}O_{8}As_{2} + 8 H_{2}O, As_{2}S_{5} . 38.4, CoO . 37.6, H_{2}O . 24.0.--

H = 1.5-2.0, G = 2.95.

Color, crimson to peach-red. When crystallized, of pearly l.u.s.tre, but frequently dull and earthy. Heated in ignition tube gives off water, and color changes to blue or green. Before the Bp. on Ch. in R. F. it emits a.r.s.enical fumes and melts to a dark gray globule which with the borax bead reacts for cobalt.

ORES OF COPPER

~Native Copper, Cu.~--

H = 2.5-3, G = 8.5-8.9.

Color, copper-red. l.u.s.tre, metallic. Occurs usually ma.s.sive and very arborescent. Before the Bp. on Ch. it fuses, and if the heat is sufficiently high it a.s.sumes a bright bluish-green surface; on cooling it is covered with a coat of black oxide. In the borax bead it reacts for copper.

~Chalcopyrite~, CuFeS_{2}, Cu . 35, Fe . 30, S . 35.--H = 3.5-4, G = 4.1-4.3. Color, bra.s.s-yellow, often golden-yellow. l.u.s.tre, metallic.

Occurs crystallized, but is generally found ma.s.sive. Is easily scratched with a knife. Heated in an ignition tube decrepitates, and occasionally yields a faint sublimate of sulphur. Before the Bp. on Ch.

it blackens, but becomes red again on cooling. Before the Bp. on Ch.

with Na_{2}CO_{3} and KCN it is reduced, and the metals are obtained in separate ma.s.ses. It reacts with the borax bead for copper and iron.

~Copper Glance~, Cu_{2}S, Cu . 80, S . 20.--H = 2.5-3.0, G = 5.5-5.8.

Color, dark blue to steel-gray. Occurs in compact ma.s.ses, often very s.h.i.+ning. Before the Bp. on Ch. fuses to a globule which boils and emits glowing drops. Sulphur dioxide escapes abundantly, and the outer flame is colored blue. Before the Bp. on Ch. with Na_{2}CO_{3} yielding a metallic globule.

~Tetrahedrite~, 4 CuS + Sb_{2}S_{3}.--Frequently contains silver, iron, mercury, and zinc. H = 3.0-4.0, G = 4.5-5. Color, steel-gray to iron-black. Heated in an ignition tube fuses and gives a sublimate of antimonious oxide. When mercury is present this condenses in the upper part of the tube, forming the characteristic mirror. Before the Bp. on Ch. it fuses readily to a metallic globule, emitting dense white fumes; zinc and antimony coatings are deposited on the Ch. After long ignition before the Bp., if the mineral is finely powdered and mixed with Na_{2}CO_{3} and KCN, the ore is reduced to the metal.

~Cuprite~, Cu_{2}O, Cu . 89, O . 11.--

H = 3.5-4.0, G = 5.5-6.15.

Color, intense crimson-red. Before the Bp. on Ch. blackens and fuses quietly, and finally yields a metallic globule of copper. Before the Bp.

on Ch. with Na_{2}CO_{3} and KCN it is easily reduced.

~Malachite~, 2 CuO + CO_{2} + H_{2}O, CuO . 72, CO_{2} . 20, H_{2}O . 8.--

H = 3.5-4.0, G = 3.90-4.03.

Color, bright green. Occurs generally in mammillated concretions.

l.u.s.tre, s.h.i.+ning and fracture, silky. Heated in an ignition tube yields water and blackens. Before the Bp. on Ch. it fuses to a metallic globule. Before the Bp. on Ch. with Na_{2}CO_{3} and KCN it is easily reduced. With borax bead gives characteristic coloration.

~Azurite~, 3 CuO + 2 CO_{2} + H_{2}O, CuO . 69, CO_{2} . 26, H_{2}O . 5.--

H = 3.5-4.0, G = 3.77-3.83.

Color, azure-blue. Occurs usually in crystallized or globular ma.s.ses.

l.u.s.tre, earthy or vitreous. Before the Bp. and with other reagents behaves like malachite.

~Chrysocolla~, CuO + SiO_{2} + 2 H_{2}O, SiO_{2} . 34.2, CuO . 45.3, H_{2}O . 20.5.--H = 2.0-3.0, G = 2. Color, bluish-green, closely resembling malachite. Occurs usually as an incrustation, its surface being very smooth, like enamel. In an ignition tube it blackens and yields water. Before the Bp. on Ch. in O. F. it blackens, coloring the flame bright green; in the R. F. it turns red. Before the Bp. on Ch.

with Na_{2}CO_{3} yields metallic copper. In borax bead it reacts for copper.

~Atacamite~, CuCl_{2} + 3 CuO_{2}H_{2}--Cl . 16.6, O . 20.3, Cu . 50.1, H_{2}O . 13.0.--

H = 3.0-3.5, G = 3.75-3.77.

Color, green to blackish green. l.u.s.tre, adamantine to vitreous. In an ignition tube yields water. Before the Bp. on Ch. colors flame blue.

Before the Bp. on Ch. with Na_{2}CO_{3} and KCN is reduced to the metal.

In borax bead it reacts for copper.

ORES OF IRON

~Limonite~, 2 Fe_{2}O_{3} + 3 H_{2}O, Fe_{2}O_{3} . 86, H_{2}O . 14.--H = 5.0-5.5, G = 3.6-4.0. Color, brown to ochre-yellow. Earthy or semi-metallic in appearance. In an ignition tube yields water. Before the Bp. on Ch. infusible. In borax bead reacts for iron.

~Hemat.i.te~, Fe_{2}O_{3}, Fe . 70, O . 30.--

H = 5.5-6.5, G = 4.9-5.3.

Color, dark steel-gray to iron-black. l.u.s.tre, metallic. When pulverized yields a red powder. Before the Bp. on Ch. infusible. After long roasting becomes magnetic. In borax bead gives usual indications of iron.

~Magnet.i.te~, Fe_{3}O_{4}, FeO . 31, Fe_{2}O_{3} . 69.--

H = 5.5-6.5, G = 5.17-5.18.

Color, iron-black. l.u.s.tre, s.h.i.+ning and metallic. Pulverized, its powder is black. It is strongly magnetic. Fuses with difficulty before the Bp.

on Ch. In borax bead reacts for iron.

~Pyrites~, FeS_{2}, Fe . 47, S . 53.--