bismuth

—bismuthal, adj.

/biz"meuhth/, n. Chem.

a brittle, grayish-white, red-tinged, metallic element used in the manufacture of fusible alloys and in medicine. Symbol: Bi; at. wt.: 208.980; at. no.: 83.

[1660-70; earlier bismutum < NL bisemutum, Latinized form of G Wissmuth (now Wismut) < ?]

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Semimetallic to metallic chemical element, chemical symbol Bi, atomic number 83.

Hard, brittle, and lustrous, it has a distinctive gray-white colour with a reddish tinge. It is often found free in nature and also occurs in compounds and in mixed ores. Bismuth alloys are used (because of their low melting points) in making metal castings, special solders, automatic sprinkler heads, fuses, and many fire-detection devices. Bismuth phosphomolybdate is a catalyst in the production of acrylonitrile, an important raw material for fibres and plastics. Salts of bismuth are used in making soothing agents for digestive disorders (especially bismuth subsalicylate), in treating skin infections and injuries, and in lipstick, nail polish, and eye shadow, to which they impart a pearlescent quality.

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▪ chemical element

 the most metallic and the least abundant of the elements in the nitrogen family (Group Va of the periodic table).

      Bismuth is the most diamagnetic of all metals (i.e., it exhibits the greatest opposition to being magnetized) and has the lowest thermal conductivity of all metals except mercury. It is hard, brittle, lustrous, and coarsely crystalline. It can be distinguished from all other metals by its colour—gray-white with a reddish tinge. Bismuth was first described in 1450 by Basil Valentine, a German monk.

      Bismuth is often found free in nature. It also occurs in compounds: as the sulfide bismuthinite, or bismuth glance (Bi₂S₃); the oxide bismite (Bi₂O₃); and the carbonate bismutite (BiO)₂CO₃. Bismuth is frequently associated with ores of tin, lead, or copper, from which it is separated as a by-product during their refining. Pure bismuth can also be obtained by reducing the oxide with carbon or by roasting the sulfide in the presence of charcoal and metallic iron to remove the sulfur.

      Although it does not tarnish in air at ordinary temperatures, bismuth forms an oxide coating when heated. The yellow colour of this oxide distinguishes it from those formed by other metals. At red heat, bismuth reacts with steam, but it is not affected by cold, air-free water; it combines directly with sulfur and with the halogens (fluorine, chlorine, bromine, iodine). The element is not attacked by hydrochloric acid, and only slightly by hot sulfuric acid, but it is rapidly dissolved by either dilute or concentrated nitric acid.

      Like antimony and water, bismuth expands slightly upon solidifying, a property that renders bismuth alloys particularly suited to the manufacture of sharply detailed metal castings. Because the alloys have low melting points, they are used in special solders as well as in automatic sprinkler heads, fire-door release lines, fuses, safety plugs for compressed-gas cylinders, and many other fire-detection devices. Thermoelectric equipment for refrigeration uses bismuth telluride (Bi₂Te₃) and bismuth selenide (Bi₂Se₃). The principal chemical application of the element is in the form of bismuth phosphomolybdate (BiPMo₁₂O₄₀), a highly effective catalyst for the air oxidation of propylene and ammonia to acrylonitrile, which is used to manufacture acrylic fibres, plastics, and paints. Salts of bismuth frequently are used in soothing agents for the treatment of digestive disorders, in outlining the alimentary tract during X-ray examination, and in treating injuries and infections of the skin. The oxychloride BiOCl has been used to impart a pearlescent quality to lipstick, nail polish, and eye shadow. For comparative statistical data on bismuth production and reserves, see mining (table).

atomic number

83

atomic weight

208.980

melting point

271.3 °C (520.3 °F)

boiling point

1,560 °C (2,840 °F)

density

9.747 g/cm³ at 20 °C (68 °F)

oxidation states

+3, +5

electron config.

1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰4f ¹⁴5s²5p⁶5d¹⁰6s²6p³

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