Indium
Indium | ||||||||||||||||||||||||||
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Pronunciation | /ˈɪndiəm/ | |||||||||||||||||||||||||
Appearance | silvery lustrous gray | |||||||||||||||||||||||||
Standard atomic weight Ar°(In) | ||||||||||||||||||||||||||
Indium in the periodic table | ||||||||||||||||||||||||||
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kJ/mol | ||||||||||||||||||||||||||
Heat of vaporization | 231.8 kJ/mol | |||||||||||||||||||||||||
Molar heat capacity | 26.74 J/(mol·K) | |||||||||||||||||||||||||
Vapor pressure
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Atomic properties | ||||||||||||||||||||||||||
Discovery | Ferdinand Reich and Hieronymous Theodor Richter (1863) | |||||||||||||||||||||||||
First isolation | Hieronymous Theodor Richter (1864) | |||||||||||||||||||||||||
Isotopes of indium | ||||||||||||||||||||||||||
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Indium is a
Indium is a
Indium has no biological role and its compounds are toxic when inhaled or injected into the bloodstream, although they are poorly absorbed following ingestion.[17][18]
Etymology
The name comes from the Latin word indicium meaning violet or indigo.[19]
Properties
Physical
Indium is a shiny silvery-white, highly
The density of indium, 7.31 g/cm3, is also greater than gallium, but lower than thallium. Below the
Chemical
Indium has 49 electrons, with an electronic configuration of [
A number of standard electrode potentials, depending on the reaction under study,[30] are reported for indium, reflecting the decreased stability of the +3 oxidation state:[24]
In2+ + e− ⇌ In+ E0 = −0.40 V In3+ + e− ⇌ In2+ E0 = −0.49 V In3+ + 2 e− ⇌ In+ E0 = −0.443 V In3+ + 3 e− ⇌ In E0 = −0.3382 V In+ + e− ⇌ In E0 = −0.14 V
Indium metal does not react with water, but it is oxidized by stronger oxidizing agents such as
Isotopes
Indium has 39 known
The stablest
Compounds
Indium(III)
- In(OH)3 + 3 HCl → InCl3 + 3 H2O
The analogous sesqui-chalcogenides with
Direct reaction of indium with the pnictogens produces the gray or semimetallic III–V semiconductors. Many of them slowly decompose in moist air, necessitating careful storage of semiconductor compounds to prevent contact with the atmosphere. Indium nitride is readily attacked by acids and alkalis.[38]
Indium(I)
Indium(I) compounds are not common. The chloride, bromide, and iodide are deeply colored, unlike the parent trihalides from which they are prepared. The fluoride is known only as an unstable gaseous compound.[39] Indium(I) oxide black powder is produced when indium(III) oxide decomposes upon heating to 700 °C.[35]
Other oxidation states
Less frequently, indium forms compounds in oxidation state +2 and even fractional oxidation states. Usually such materials feature In–In bonding, most notably in the halides In2X4 and [In2X6]2−,[40] and various subchalcogenides such as In4Se3.[41] Several other compounds are known to combine indium(I) and indium(III), such as InI6(InIIICl6)Cl3,[42] InI5(InIIIBr4)2(InIIIBr6),[43] and InIInIIIBr4.[40]
Organoindium compounds
Organoindium compounds feature In–C bonds. Most are In(III) derivatives, but cyclopentadienylindium(I) is an exception. It was the first known organoindium(I) compound,[44] and is polymeric, consisting of zigzag chains of alternating indium atoms and cyclopentadienyl complexes.[45] Perhaps the best-known organoindium compound is trimethylindium, In(CH3)3, used to prepare certain semiconducting materials.[46][47]
History
In 1863, the German chemists
Richter went on to isolate the metal in 1864.[51] An ingot of 0.5 kg (1.1 lb) was presented at the World Fair 1867.[52] Reich and Richter later fell out when the latter claimed to be the sole discoverer.[50]
Occurrence
Indium is created by the long-lasting (up to thousands of years)
Indium is the
Different estimates exist of the amounts of indium contained within the ores of other metals.[59][60] However, these amounts are not extractable without mining of the host materials (see Production and availability). Thus, the availability of indium is fundamentally determined by the rate at which these ores are extracted, and not their absolute amount. This is an aspect that is often forgotten in the current debate, e.g. by the Graedel group at Yale in their criticality assessments,[61] explaining the paradoxically low depletion times some studies cite.[62][16]
Production and availability
Indium is produced exclusively as a by-product during the processing of the ores of other metals. Its main source material are sulfidic zinc ores, where it is mostly hosted by sphalerite.[16] Minor amounts are also extracted from sulfidic copper ores. During the roast-leach-electrowinning process of zinc smelting, indium accumulates in the iron-rich residues. From these, it can be extracted in different ways. It may also be recovered directly from the process solutions. Further purification is done by electrolysis.[64] The exact process varies with the mode of operation of the smelter.[20][16]
Its by-product status means that indium production is constrained by the amount of sulfidic zinc (and copper) ores extracted each year. Therefore, its availability needs to be discussed in terms of supply potential. The supply potential of a by-product is defined as that amount which is economically extractable from its host materials per year under current market conditions (i.e. technology and price).[65] Reserves and resources are not relevant for by-products, since they cannot be extracted independently from the main-products.[16] Recent estimates put the supply potential of indium at a minimum of 1,300 t/yr from sulfidic zinc ores and 20 t/yr from sulfidic copper ores.[16] These figures are significantly greater than current production (655 t in 2016).[66] Thus, major future increases in the by-product production of indium will be possible without significant increases in production costs or price. The average indium price in 2016 was US$240/kg, down from US$705/kg in 2014.[67]
China is a leading producer of indium (290 tonnes in 2016), followed by South Korea (195 t), Japan (70 t) and Canada (65 t).[66] The Teck Resources refinery in Trail, British Columbia, is a large single-source indium producer, with an output of 32.5 tonnes in 2005, 41.8 tonnes in 2004 and 36.1 tonnes in 2003.
The primary consumption of indium worldwide is
Applications
In 1924, indium was found to have a valued property of stabilizing
Indium(III) oxide and
Indium has many
Indium wire is used as a vacuum seal and a thermal conductor in cryogenics and ultra-high-vacuum applications, in such manufacturing applications as gaskets that deform to fill gaps.[77] Owing to its great plasticity and adhesion to metals, Indium sheets are sometimes used for cold-soldering in microwave circuits and waveguide joints, where direct soldering is complicated. Indium is an ingredient in the gallium–indium–tin alloy galinstan, which is liquid at room temperature and replaces mercury in some thermometers.[78] Other alloys of indium with bismuth, cadmium, lead, and tin, which have higher but still low melting points (between 50 and 100 °C), are used in fire sprinkler systems and heat regulators.[64]
Indium is one of many substitutes for mercury in
Indium's high neutron-capture cross-section for thermal neutrons makes it suitable for use in
In 2009, Professor
Biological role and precautions
Hazards | |
---|---|
GHS labelling: | |
Warning | |
H302, H312, H315, H319, H332, H335 | |
P261, P280, P305+P351+P338[84] | |
NFPA 704 (fire diamond) |
Indium has no
People can be exposed to indium in the workplace by inhalation, ingestion, skin contact, and eye contact. Indium lung is a lung disease characterized by pulmonary alveolar proteinosis and pulmonary fibrosis, first described by Japanese researchers in 2003. As of 2010[update], 10 cases had been described, though more than 100 indium workers had documented respiratory abnormalities.[17] The National Institute for Occupational Safety and Health has set a recommended exposure limit (REL) of 0.1 mg/m3 over an eight-hour workday.[89]
See also
Notes
- ^ The thermal expansion is anisotropic: the parameters (at 20 °C) for each crystal axis are αa = 53.2×10−6/K, αc = −9.75×10−6/K, and αaverage = αV/3 = 32.2×10−6/K.[3]
References
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Sources
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External links
- Indium at The Periodic Table of Videos(University of Nottingham)
- Reducing Agents > Indium low valent
- NIOSH Pocket Guide to Chemical Hazards (Centers for Disease Control and Prevention)