BISMUTH

Bi. Bismuth , Etain de glace , Fr.; Bismuth , Wismuth , W.-metall , Ger. One of the metals. IMG:596405606043057898_i309.png: Bismuth furnace in section.   a , Eliquation-tube. [182] b , End at which it is charged. c , End from which the metal flows. d , Receiving-pan. e , Water-trough. f , Grate, . [183] g, g , Draught-holes. [182] Several of these tubes are usually set side by side together. [183] Usually one to each eliquation-tube. Sources. Bismuth occurs in the mineral kingdom in the metallic state ( NA′TIVE BISMUTH ), and in combination with sulphur ( BIS′MŬTHĬNE ), and with oxygen ( B. O′CHRE , .). That of commerce is mostly imported from Saxony, where it is chiefly obtained from native bismuth by the simple proce of eliquation. The ore, sorted by hand from the gangue, and broken into pieces of about the size of nuts, is introduced into the ignited iron pipes of the furnace (see engr. ) until these latter are filled to about one half their diameter and to three fourths of their length. From these the liquefied metal is allowed to flow into iron pans containing some coal-dust, and from these into a trough of water, in which it is granulated and cooled. It is subsequently remelted and cast into moulds so as to form ‘bars’ varying in weight from 25 to 56 lbs. each. In this state it usually contains a small admixture of arsenic, iron, lead, and sulphur; from the first of which it may be freed by exposure for some time, under charcoal, at a dull red heat. It is best obtained in a pure condition by heating to redne , in a covered crucible, a mixture of oxide, or sub nitrate of bismuth, with half its weight of charcoal. Prop. Colour greyish-white with a reddish tint; crystalline; very brittle (may be powdered); melts at about 480° Fahr., and does not re-solidify until cooled to 6 or 7° below this point; it volatilises at a strong heat, and, in close ve els, the fumes condense unchanged in crystalline lam inæ; little acted on by the air, but when exposed to it at a high temperature burns with a faint blue flame, emitting yellow fumes which condense into a yellow pulverulent oxide; when slowly cooled, in large ma es, it forms large cubic crystals or octahedrons of great beauty; nitric acid, somewhat dilute, di olves it freely. It is highly diamagnetic. Sp. gr. 9·8 to 9·83, which, by careful hammering, may be increased to 9·8827. A bar of bismuth, when heated from 32° to 212°, expands exactly 1 ⁄ 710 in length. Uses, . Bismuth enters into the composition of STEREOTYPE-METAL , SOLDER , PEWTER , FUSIBLE METALS , and several other alloys. Added to other metals it renders them more fusible. An alloy of tin, nickel, bismuth, and silver is said to hinder iron from rusting. A mixture of bismuth, lead, and tin is much employed for taking impre ions from dies, forming moulds, and for other purposes. Bismuth salts are usually insoluble, or decomposed by any quantity of water into free acid and a basic salt. They are nearly all colourle , and, except the chloride, more volatile. They are easily recognised by the following reactions:— Their saturated or concentrated solutions giving a white precipitate on dilution with water:—Sulphuretted hydrogen blackens them, or gives a black precipitate:—The nitric solution is unaffected by the addition of sulphuric acid:—Chromate of pota ium gives a yellow precipitate, which differs from that from lead, by being soluble in nitric acid, and insoluble in pota a. Von Kobbell takes a mixture of pota ium iodide and flowers of sulphur in equal proportions, and heats the whole on charcoal before the blowpipe; the production of bright scarlet, very volatile bismuth iodide ensues, even when only traces of bismuth are present. For a method of volumetrically estimating bismuth, consult a paper by Mr Pattison Muir, in the ‘Journal of the Chemical Society,’ April, 1876.