Antimony (Sb)
Antimony (Sb) is a metalloid with the atomic number 51, known for its unique properties and diverse applications. It primarily occurs as stibnite (Sb2S3), a sulfide mineral that is the most commercially important antimony ore, mainly sourced from countries like China, Germany, Peru, and Japan. With a silvery blue-white appearance, pure antimony is brittle and poor in electrical and thermal conductivity. This element is integral in the production of various alloys, enhancing hardness and melting characteristics.
Antimony's uses extend into numerous industries, including the manufacture of ceramics, glass, batteries, paints, and flame retardants, as well as in military applications. Historically, it has been utilized since ancient times for medicinal purposes and cosmetics. Environmental concerns arise from antimony's potential health risks, as it can contaminate water sources and is associated with respiratory and skin disorders. The element's strategic importance is underscored by its role in essential products, making it a crucial resource in modern manufacturing and technology.
Antimony (Sb)
Where Found
While antimony does not often occur free in nature, its ores are widely distributed. The antimony ore of greatest commercial importance is stibnite (Sb2S3), most of which is supplied by China, Germany, Peru, and Japan, among other countries.
Primary Uses
Antimony is a strategic resource with many uses. It is a key component in many alloys, and its compounds are employed in the manufacture of such products as ceramics and glass, batteries, paints and pigments, chemicals, matches, explosives, fireworks, flame retardants, and medicines.
Technical Definition
Antimony (abbreviated Sb), atomic number 51, is a metalloid belonging to Group VA of the periodic table of the elements. It has two naturally occurring isotopes and an average molecular weight of 121.75. Pure antimony has rhombohedral crystals and is silvery blue-white in color. It is brittle, can be easily powdered, and conducts heat and electricity poorly. Its specific gravity is 6.69 at 20° Celsius; its melting point is 630.5° Celsius, and its boiling point is 1,380° Celsius.
Description, Distribution, and Forms
Antimony is a metalloid with a lithospheric concentration of 0.2 gram per metric ton. When used in metallurgical combinations antimony forms hard, brittle materials that melt at relatively low temperatures, characteristics that make this element an important component in many alloys.
The most economically important antimony ore is antimony sulfide, or stibnite. In the United States the element is usually obtained only as a by-product of smelting the copper ore tetrahedrite, (Cu, Fe)12Sb4S13, or other sulfide ores of base metals. While recycling scrap metal and storage batteries was once a significant secondary source of antimony for the United States, the development of low-maintenance lead-acid automobile batteries that use lead alloys with less or no antimony has decreased this supply. In 2007, for example, the United States consumed 9,590 metric tons of antimony, and total world production was estimated at 170,000 metric tons.
Antimony ores are widely distributed; China, Bolivia, South Africa, Russia, Tajikistan, and Australia are the chief producers. China is believed to have the world’s greatest reserves of the element; extensive deposits of stibnite are found in the southern province of Hunan. Antimony-bearing rocks can be found in soils, groundwater, and surface waters. Most antimony deposits are associated with igneous activity and are believed to have been precipitated from watery fluids at relatively shallow depths and low temperatures.
Antimony is rarely found free in nature. Stibnite, the predominant antimony ore, is a silvery gray sulfide mineral that occurs in masses or prismatic crystals. Frequently it is found in association with quartz and economic minerals such as ores of mercury, tungsten, tin, lead, copper, silver, and gold. Stibnite deposits are often in the form of veins, seams, pockets, or lenses.
Antimony can enter groundwater and surface water through the naturalweathering of rock or through industrial pollution. It can cause disorders of the human respiratory and cardiovascular systems, skin, and eyes, and it is a suspected cancer-causing agent. The 1974 Safe Drinking Water Act set the maximum allowable concentration for total antimony in drinking water in the United States at 6 micrograms per liter.
History
Antimony has been used since biblical times as an ingredient in medicines and in kohl, an eye cosmetic made up of powdered stibnite mixed with soot and other materials. In Tello, Chaldea, a vase from approximately 4000 b.c.e. was found that had been cast in elemental antimony; antimony was also reportedly used by the early Egyptians to coat copper items. By the sixteenth century, the element was recognized as an alloy ingredient that could improve the tone of bell metal; as a source of yellow pigment for painting earthenware, enamels, and glass; and as an ulcer medicine. The earliest known description of the extraction of antimony from stibnite was written by Basilius Valentinus around 1600. The increasing industrialization of the late nineteenth and early twentieth centuries was accompanied by a rapid rise in antimony consumption. The need for ammunition, arms, and flame-retardant items during World Wars I and II further increased the demand for antimony. In the 1930’s, consumption of the element also rose with the expansion of the automobile industry, which used lead-antimony alloys in storage batteries.
Obtaining Antimony
Antimony ore is roasted with iron in a blast furnace; the roasting produces antimony oxide, from which the iron removes the oxygen to free the antimony. A flux of sodium sulfate or sodium carbonate may be used to prevent the loss of molten antimony through evaporation. Complex ores, those with base metals present, are treated by leaching and electrolysis.
Uses of Antimony
Antimony is an important element in many alloys. Britannia metal, an alloy of tin with antimony, copper, and sometimes bismuth and zinc, resembles pewter in appearance and is used in the manufacture of tableware. Antimony is sometimes added to pewter, an alloy composed largely of tin, to increase whiteness and hardness. Babbitt metal, an antifriction alloy used in bearings, is composed chiefly of tin, copper, and antimony. Type metal, named for its use in the manufacture of printing type, is an alloy of lead with antimony, tin, and sometimes copper; this alloy is also used in metal parts for some musical instruments. Various alloys of antimony and lead are used in solder, starting-lighting-ignition batteries (particularly plates, terminals, and connectors), ammunition, communication equipment, corrosion-resistant pumps and pipes, tank linings, and roofing sheets.
Antimony is used as a decolorizing and refining agent in television screens, fluorescent tubes, and optical glass. Small amounts of the element are used in some medicines. Antimony oxides serve as stabilizers and flame retardants in plastics. They are also used to make adhesives, rubber, textiles, paints, and other combustibles flame resistant. Antimony sulfides are employed as a component of fireworks and ammunition. Antimony compounds are used in the manufacture of matches, explosives, vulcanized rubber, paints and pigments, chemicals, semiconductors, batteries, glass, and ceramics. Its military applications make antimony a strategic mineral.
Bibliography
Greenwood, N. N., and A. Earnshaw. “Arsenic, Antimony, and Bismuth.” In Chemistry of the Elements. 2d ed. Boston: Butterworth-Heinemann, 1997.
Henderson, William. “The Group 15 (Pnictogen) Elements: Nitrogen, Phosphorus, Arsenic, Antimony, and Bismuth.” In Main Group Chemistry. Cambridge, England: Royal Society of Chemistry, 2000.
Krebs, Robert E. The History and Use of Our Earth’s Chemical Elements: A Reference Guide. Illustrations by Rae Déjur. 2d ed. Westport, Conn.: Greenwood Press, 2006.
Massey, A. G. “Group 15: The Pnictides—Nitrogen, Phosphorus, Arsenic, Antimony, and Bismuth.” In Main Group Chemistry. 2d ed. New York: Wiley, 2000.
Natural Resources Canada.
U.S. Geological Survey.