Where Found (Encyclopedia of Global Resources)
Indium is widely distributed in the Earth’s crust in small amounts. It is fairly rare and is about as common as silver. Indium is never found as a free metal but only in combination with other elements. It is found as a trace component in many minerals, particularly in ores of zinc, copper, lead, and tin. The richest concentrations of indium are found in Colorado, Argentina, the United Kingdom, and Canada.
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Primary Uses (Encyclopedia of Global Resources)
Indium is used for a variety of purposes in the electronics industry, including liquid-crystal displays and transistors. It is also used in batteries, solders, coatings for glass, sealants, and alloys that melt at low temperatures.
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Technical Definition (Encyclopedia of Global Resources)
Indium (abbreviated In), atomic number 49, belongs to Group IIIA of the periodic table of the elements and resembles aluminum in its chemical and physical properties. It has two naturally occurring isotopes and an average atomic weight of 114.82. Pure indium is a soft, white metal. Its density is 7.31 grams per cubic centimeter; it has a melting point of 156.61° Celsius and a boiling point of 2,080° Celsius.
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Description, Distribution, and Forms (Encyclopedia of Global Resources)
Indium, a fairly uncommon element, occurs in the Earth’s crust with an average concentration of about one part in ten million. It is most commonly found in ores that are rich in zinc, particularly those which contain sphalerite (zinc sulfide). It is also found in ores of copper, lead, and tin.
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History (Encyclopedia of Global Resources)
Indium was discovered in 1863 by Ferdinand Reich and Hieronymous Theodor Richter. It was not produced in large amounts until 1940. Its first major industrial use was in the production of automobile and aircraft engine bearings, where it added strength, hardness, resistance to corrosion, and ability to retain a coating of oil. In the 1960’s, it was first used in transistors.
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Obtaining Indium (Encyclopedia of Global Resources)
Indium is usually obtained as a by-product of zinc production. A variety of methods exist for obtaining indium from the residue left over after most of the zinc is removed from the ore. One method involves treating the residue with dilute sulfuric acid to dissolve the remaining zinc. The undissolved material left behind is then treated with stronger acid to dissolve the indium. The indium is treated with zinc oxide to obtain indium hydroxide or with sodium sulfite or sodium bisulfite to obtain indium sulfite. Pure indium metal is then obtained by subjecting these compounds to electrolysis.
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Uses of Indium (Encyclopedia of Global Resources)
Indium is often combined with other metals such as bismuth, cadmium, lead, and tin to form alloys with a low melting point; production of indium tin oxide was the most common end use worldwide as of 2008. These alloys are used in fuses and heat-detecting sprinkler systems. It has also been mixed with lead to form solders that remain flexible over a wide range of temperatures. Molten indium has the unusual property of clinging to glass and other smooth surfaces and is often used to form seals and coatings. High-purity indium is used in combination with germanium to form transistors. The electronics industry also uses indium in liquid-crystal displays, infrared detectors, and solar cells.
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Further Reading (Encyclopedia of Global Resources)
Natural Resources Canada. Canadian Minerals Yearbook: Indium. http://www.nrcan-rncan.gc.ca/mms-smm/busi-indu/cmy-amc/content/2005/31.pdf
U.S. Geological Survey. Minerals Information: Indium Statistics and Information. http://minerals.usgs.gov/minerals/pubs/commodity/indium/
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Indium (Chemical Elements)
Indium is part of the aluminum family in Group 13 (IIIA) of the periodic table. The periodic table is a chart that shows how chemical elements are related to each other. Indium was discovered in 1863 by German chemists Ferdinand Reich (1799-1882) and Hieronymus Theodor Richter (1824-98).
Indium has a number of interesting properties. For example, it has a low melting point for metals, 156.6°C (313.9°F). When pure, it sticks very tightly to itself or to other metals. This property makes it useful as a solder. Solder is a material used to join two metals to each other. Other uses of indium are in the manufacture of batteries, electronic devices, and in research.
Discovery and naming
Between 1860 and 1863, indium, cesium, rubidium, and thallium were...
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