Bismuth

BISMUTH, Bi (Latin "bismuthum" * EN: bismuth; DE: Wismut; FR: bismuth; ES: bismuto; RU: висмут) is the chemical element of the group V of the Periodic System of Dmitry Mendeleev, the atomic number is 83, the atomic mass is 208.980.

The natural bismuth consists of one stable isotope 209Bi; 210Bi is the most important of the radioactive isotopes. Since the most ancient times, bismuth was considered one the types of the antimony, lead, or tin. The notion about bismuth as about the independent chemical element has been formed only during the 18th century, after the 1739, when there has been established by the German chemist J. Pott the chemical individuality of bismuth.

Bismuth is the silvery-gray metal with the pinkish tinge. Bismuth has the rhombohedral lattice with the period a = 47.364 nanometres (4.7364 Ångström), and with the angle a = 57 degrees 14 minutes 13 seconds. The density is 9800 kilograms per cubic metre, the temperature of the melting point is is 271.3 degrees Celsius, the temperature of the boiling point is 1564 degrees Celsius. During the melting, the volume of bismuth is decreased by 3.27% (the density of the liquid bismuth is 10060 kilograms per cubic metre). Bismuth is brittle at the room temperature, and is malleable at the temperature of 120-150 degrees Celsius. The hardness is 93 megapascals according to the Brinell scale, and 2.5 according to the Mohs scale. Bismuth is the least thermally conductive [the specific thermal conductivity at the temperature of 20 degrees Celsius is 8.37 watts per metre-kelvin] and the most diamagnetic (the specific magnetic susceptibility is 1.35•10^-6) metal.

Bismuth is slightly oxidized when exposed to the air. Within its subgroup, bismuth possesses the most brightly expressed basic properties; the oxidation state is +2, +3, +5, and also -3, +4, +1. Bismuth manifests the highest oxidation state +5 only within the alkaline medium during the action of the strong oxidants; within the nature, the single oxidized state of bismuth is +3. Bismuth is crystal-chemically similar to Pb2+, Sb3+, Te2-. Bismuth possesses the high affinity to electron (the redox potential Bi3+/Bi0 = +0.226). Within the nature, there are characteristic for bismuth the compounds with S, Se, and Te. Similar to the sulfide, Bi2O3 is easily soluble within the acids, and is very little soluble within the concentrated alkalies. The soluble salts of bismuth are toxic.

The content of bismuth within the Earth's crust is 1.7•10^-5% by mass. With the relatively small distribution, it manifests the brightly expressed ability to the forming of its own minerals during the endogenous and supergene processes. There are known more than 100 minerals of bismuth. There have the major industrial significance the native bismuth, bismuthine, and the sulfosalts of bismuth. Within the zone of the supergenesis, these minerals transition into the difficultly soluble hydroxides and basic carbonates of bismuth. The major form for the presence of bismuth within the erupted rocks is the own accessory mineralization. The most significant concentrations of bismuth have been noted within the acidic rocks. There are relatively beneficiated with bismuth the products of the late phases of the crystallization of the magma. The bismuth deposits proper are rare, and are usually small according to the scales. The accompanying bismuth mineralization is manifested within the ores of practically all high-temperature and medium-temperature deposits of W, Sn, Mo, Cu, Pb, Au, Co. The major types of the deposits, and the schemes for the beneficiation, see within the "Bismuth ores" article.

Depending on the composition of the impurities within the crude bismuth, which has been extracted from the concentrates, they obtain the pure bismuth using various methods: the oxidation refining under the alkaline fluxes, the segregation, the melting with sulfur, and others. The marketable bismuth contains almost 100% of the major metal. They obtain the bismuth of the high purity using the zonal recrystallization within the atmosphere of the inert gas.

Bismuth is used within the metallurgy (the obtainment of the low-melting alloys with lead, tin, cadmium; during the manufacturing of the molds for the precision casting, of the dies, of the marking, mounting, and monitoring devices; for the improvement of the processibility of the alloys of aluminium, cast iron, and steel during the production of the aeronautical and automotive motors). The significant amount of bismuth is consumed within the pharmaceutical industry (bismuth and its preparations are the disinfecting and slightly drying remedy). Within the chemical industry, bismuth is the catalyst for the production of the synthetic fibers. Bismuth is also used within the nuclear energetic industry (bismuth is the liquid heat carrier, and the cooling agent), within the electronics (the semiconductors on the basis of bismuth), within the glass (the compounds of bismuth increase the refractive index) and ceramic (the low-melting enamels) industries.