antimony

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antimony

(ăn`tĭmō'nē) [Lat. antimoneum], semimetallic chemical element; symbol Sb [Lat. stibium,=a mark]; at. no. 51; at. wt. 121.760; m.p. 630.74°C;; b.p. 1,750°C;; sp. gr. (metallic form) 6.69 at 20°C;; valence 0, +3, −3, or +5. Antimony exists in two allotropic forms (see allotropyallotropy
[Gr.,=other form]. A chemical element is said to exhibit allotropy when it occurs in two or more forms in the same physical state; the forms are called allotropes.
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); the more common is silvery blue-white and has a rhombohedral crystalline structure. It is a poor conductor of heat and electricity and is brittle and easily powdered. It is primarily used in alloys and chemical compounds. It is a member of Group 15 of the periodic tableperiodic table,
chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled
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. Antimony rarely occurs free in nature, but its ores are widely distributed. The principal ore is stibnitestibnite
, antimony sulfide, Sb2S3, a mineral, silvery gray in color, with a metallic luster. It crystallizes in the orthorhombic system. Found in many parts of the world, it is the most important ore of antimony.
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, a sulfur compound known since early times; there are extensive deposits in China. Antimony is often found in other ores as well, e.g., silver, copper, and lead. The pure element antimony is produced from the ore by roasting it to form the oxide, then reducing the oxide with carbon or iron; often a flux of sodium sulfate or sodium carbonate is used to prevent loss of molten antimony by evaporation. Antimony does not react with air or water at room temperature; it does react with fluorine, chlorine, or bromine and is soluble in hot nitric or sulfuric acid; at higher temperatures, antimony will ignite and burn in air. It unites with hydrogen to form stibine, a poisonous gas. In combination with metals antimony forms alloys that are hard and brittle and have low melting points. The alloys of antimony include britannia metalbritannia metal,
silvery-white alloy of tin with antimony, copper, and sometimes bismuth and zinc. It is very similar in appearance to pewter, but is harder. It is used widely for the manufacture of tableware.
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, type metaltype metal,
alloy of lead with antimony, tin, and sometimes copper, so named because of its one time extensive use for making printing type. Expanding upon solidification, the alloy takes a fine and clear impression of the mold in which it hardens. It has a low melting point.
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, Babbitt metalBabbitt metal,
an antifriction metal first produced by Isaac Babbitt in 1839. In present-day usage the term is applied to a whole class of silver-white bearing metals, or "white metals.
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, and sometimes pewterpewter,
any of a number of ductile, silver-white alloys consisting principally of tin. The properties vary with the percentage of tin and the nature of the added materials.
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; these alloys expand on cooling, thereby retaining fine details of a mold. Alloys and compounds of antimony are used in bearings, storage batteries, safety matches, and as a red pigment in paint. Although antimony and many of its compounds are toxic, tartar emetictartar emetic,
poisonous, odorless, transparent rhombic crystals or white powder with a metallic, sweetish taste. Chemically, it is potassium antimony tartrate, KSbC4H4O7· 1-2H2O. It is used as a mordant in dyeing.
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 (potassium antimonyl tartrate), meglumine antimoniate, sodium stibogluconate, and other compounds are used as medicines. Small concentrations of antimony can be detected by a method similar to the Marsh testMarsh test,
method for the detection of arsenic, so sensitive that it can be used to detect minute amounts of arsenic in foods (the residue of fruit spray) or in stomach contents. The sample is placed in a flask with arsenic-free zinc and sulfuric acid.
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 for arsenic. Antimony is mixed with soot and other substances to make kohl, used for centuries by women in some countries as an eye cosmetic. A method for the extraction of antimony from stibnite was first described c.1600 by Basilius Valentinus. Although known to the ancients, the element was first adequately described by Nicolas Lémery in 1707.

Antimony

 

Sb, a chemical element in group V of Mendeleev’s periodic system. Atomic number, 51; atomic weight, 121.75. Antimony is a silvery white metal with a blue tinge. In nature, two stable isotopes are known: 121Sb (57.25 percent) and 123Sb (42.75 percent). The most important of the element’s artificial radioisotopes are 122Sb (half-life 2.8 days), 124Sb (half-life 60.2 days), and 125Sb (half-life two years).

History. Antimony has been known since antiquity. In the Orient, it was used around 3000 B.C. in making various vessels. In Egypt, as early as the 19th century B.C., powdered antimony glance (natural Sb2S3, called mesten or stem) was used for darkening eyebrows. In ancient Greece, the powder was known as stimi or stibi, hence the Latin stibium. The name antimonium came into use sometime between the 12th and 14th centuries A.D. In 1789, A. Lavoisier included antimony in his list of chemical elements, using the French name antimoine (antimonio in Spanish and Italian, Antimon in German). The Russian name for the element, sur’ma, is derived from the Turkish sürme, the term for powdered lead glance (PbS), also used for darkening eyebrows. (According to some sources, sur’ma is derived from a Persian word meaning metal.) A detailed description of the properties and methods of obtaining antimony was first given by the alchemist Basil Valentine in 1604 in Germany.

Distribution in nature. The average content of antimony in the earth’s crust (clarke) is 5 × 10–5 percent by weight. Antimony is dispersed in magma and in the biosphere. It is contained in hot groundwater, forming concentrations in hydrothermal deposits. Antimony deposits as such are known, as are antimony-mercury, antimony-lead, gold-antimony, and antimony-tungsten deposits. Of the 27 antimony minerals, antimonite (Sb2S3) has the greatest industrial importance. Because of its affinity for sulfur, antimony is often encountered as an admixture in the sulfides of arsenic, bismuth, nickel, lead, mercury, silver, and other elements.

Physical and chemical properties. Antimony is known in a crystalline form and in three amorphous forms—explosive, black, and yellow. Explosive antimony, with a density of 5.64–5.97 g/cm3, explodes upon contact; it is produced in the electrolysis of a solution of SbCl3. Black antimony, with a density of 5.3 g/cm3, is formed through the rapid cooling of antimony vapors, and yellow antimony is formed by passing oxygen through liquefied SbH3. The yellow and black forms are unstable and convert into the crystalline form at reduced temperatures. Crystalline antimony, which is the most stable form, crystallizes in the trigonal system (a = 4.5064 angstroms); this form has a density of 6.61–6.73 g/cm3 (liquid, 6.55 g/cm3), a melting point of 630.5°C, a boiling point of 1635°–1645°C, a specific heat at 20°–100°C of 0.210 kilojoule/kg· °K (0.0498 calorie/g· °C), and a thermal conductivity at 20°C of 17.6 watts/m· °K (0.042 calorie/cm· sec · °C). The linear coefficient of expansion of polycrystalline antimony is 11.5 × 10–6 at 0°–100°C; for a single crystal in the temperature range 0°–400°C, α1 = 8.1 x 10–6 and α2 = 19.5 × 10–6, and the electrical resistivity of a single crystal of antimony at 20°C is 43.045 × 10–6 ohm·cm. Antimony is diamagnetic, with a magnetic susceptibility of –0.66 × 10–6. In contrast to most metals, antimony is brittle and is easily split along cleavage planes; it can be ground into a powder. It is not forgeable and consequently is sometimes classified as a semimetal. Mechanical properties depend on the purity of the metal. The Brinell hardness of cast antimony is 325–340 meganewtons/m2 (32.5–34.0 kilograms-force/mm2), the modulus of elasticity is 285–300, and the ultimate strength is 86.0 meganewtons/m2 (8.6 kilograms-force/mm2). The configuration of the outer electrons of the antimony atom is 5s25p3. In compounds, antimony has oxidation states of +5, +3, and –3.

Antimony has relatively low chemical reactivity. It does not undergo oxidation in the air at temperatures ranging up to its melting point, and it does not react with nitrogen and hydrogen. Carbon dissolves to only a slight extent in molten antimony. The metal reacts vigorously with chlorine and other halogens to form antimony halides. It reacts with oxygen at temperatures above 630°C, forming Sb2O3. Antimony sulfides are obtained when antimony is melted in the presence of sulfur; antimony reacts similarly with phosphorus and arsenic. Antimony is stable in relation to water and dilute acids. Concentrated hydrochloric and sulfuric acids slowly dissolve antimony with the formation of the chloride SbCl3 and the sulfate Sb2(SO4)3; concentrated nitric acid oxidizes antimony to a higher oxide, which takes the form of the hydrate xSb2O5·yH2O. The difficultly soluble salts of antimonic acid have practical importance. They include antimonates (MSbO3·3H2O, where Me is Na or K) and the salts of meta-antimonous acid (not yet isolated in pure form), namely, meta-antimonates (MeSbO2·3H2O), which possess reducing properties. Antimony combines with metals to form antimonides.

Production. Antimony is obtained by the pyrometallurgical and hydrometallurgical treatment of concentrates or from ore containing 20–60 percent Sb. The pyrometallurgical methods include precipitation smelting and reduction smelting. Sulfide concentrates serve as the raw material for precipitation smelting, which is based on the replacement of antimony in the sulfide by iron: Sb2S3 + 3Fe ⇄ 2Sb + 3FeS. The iron is introduced into the charge as scrap, and the smelting is carried out in reverberatory or short rotating furnaces at 1300°–1400°C. The extraction of antimony in the form of crude metal exceeds 90 percent. The reduction smelting of antimony is based on the reduction of antimony oxides to the metal using charcoal or coal dust and on the slagging of waste rock. Reduction smelting is preceded by oxidative roasting at 550°C with an excess of air. The calcine contains the nonvolatile tetroxide of antimony. Electric furnaces can be used in both precipitation and reduction smelting. The two stages involved in the hydrometallurgical process of obtaining antimony are the treatment of the raw material with an alkaline sulfide solution, which results in the entry of antimony into solution as sul-fosalts and salts of antimonic acids, and the separation of antimony by electrolysis. Depending on the composition of the raw material and the method of production, crude antimony contains 1.5 to 15 percent impurities, for the most part Fe, As, and S.

Pyrometallurgical or electrolytic refining is used to produce pure antimony. In pyrometallurgical refining, impurities of iron and copper are removed as sulfur compounds by introducing antimonite (Sb2S3); arsenic (as sodium arsenate) and sulfur are then removed by passing air under the soda slag. In electrolytic refining with a soluble anode, crude antimony is purified of iron, copper, and other metals remaining in the electrolyte (with Cu, Ag, and Au remaining in the slurry. A solution consisting of SbF3, H2SO4, and HF serves as the electrolyte. The content of impurities in refined antimony does not exceed 0.5–0.8 percent. To obtain high-purity antimony, zone refining is carried out in an atmosphere of inert gas, or antimony is obtained from previously purified antimony trioxide or antimony trichloride.

Uses. Antimony is used mainly in lead- and tin-base alloys for battery grids, cable covering, and bearings (babbitt metal) and in alloys used in printing (type metal). These alloys have increased hardness, wear resistance, and corrosion resistance. In fluorescent lamps, calcium halophosphate is activated by antimony. Antimony is used in semiconductor materials as an alloying addition to germanium and silicon; it is also found in antimonides, for example, InSb. The radioisotope 122Sb is used as a source of gamma radiation and neutrons.

O. E. KREIN

In organisms. The content of antimony (per 100 g dry weight) is 0.006 mg in plants, 0.02 mg in marine animals, and 0.0006 mg in terrestrial animals. Antimony enters animals and humans through the respiratory organs and the gastrointestinal tract. It leaves the body mainly in the feces and, in smaller quantities, urine. The biological role of antimony is unknown. Antimony is selectively concentrated in the thyroid gland, liver, and spleen. In accumulations in red blood cells, it displays the +3 oxidation state, while accumulations in blood plasma show the +5 state. The maximum permissible concentration of antimony is 10–5–10–7g per 100 g dry tissue. At high concentrations, the element inactivates a series of enzymes involved in lipid, carbohydrate, and protein metabolism, possibly as a result of the blocking of mercapto groups.

In medicine, preparations of antimony (Solyusurmin) find use mainly in the treatment of leishmaniasis and certain forms of helminthiasis, for example, schistosomiasis.

Antimony and its compounds are toxic. Poisoning can occur during the smelting of antimony ore concentrates and production of antimony alloys. With acute poisoning, there is irritation of the mucous membrane of the upper respiratory passages and of the eyes and skin. Dermatitis and conjunctivitis may develop. Poisoning is treated with 2,3-dimercapto-1-propanol sodium sulfonate, as well as with diuretics and diaphoretics. The danger of poisoning can be reduced through adequate ventilation and the automation of certain production processes.

REFERENCES

Shiianov, A. G. Proizvodstvo sur’my. Moscow, 1961.
Osnovy metallurgii, vol. 5. Moscow, 1968.
“Issledovanie v oblasti sozdaniia novoi tekhnologn proizvodstva sur’my i ee soedinenii.” In the collection Khimiia i tekhnologiia sur’my. Frunze, 1965.

antimony

[′an·tə‚mō·nē]
(chemistry)
A chemical element, symbol Sb, atomic number 51, atomic weight 121.75.
(mineralogy)
A very brittle, tin-white, hexagonal mineral, the native form of the element.

antimony

a toxic metallic element that exists in two allotropic forms and occurs principally in stibnite. The stable form is a brittle silvery-white crystalline metal that is added to alloys to increase their strength and hardness and is used in semiconductors. Symbol: Sb; atomic no.: 51; atomic wt.: 121.757; valency: 0, --3, +3, or +5; relative density: 6.691; melting pt.: 630.76°C; boiling pt.: 1587°C