The discovery of indium metal happened by chance in 1863 in Germany. Chemists Ferdinand Reich and Theodor Richter tried to detect thallium in zinc minerals mined in Saxony. They resorted to the method of spectroscopic research. But instead of the green line characteristic of thallium, Theodor Richter saw a blue line in the spectrum of the zinc mineral. None of the elements known at that time could give such a spectrum. It was decided to name the discovered element indium, by resemblance to the indigo dye. Later, they obtained pure metal, but in very small quantities, and presented it to the scientific community. Here it is necessary to note the contribution of D.I. Mendeleev, who corrected the discoverers about valency and atomic mass.

Indium is a trivalent element with an atomic mass of 114.82. In the periodic table, it is in the main subgroup of the third group of the fifth period and is denoted by the symbol In. Indium is a light metal. It has a silvery-white color, malleable, very soft (can be cut with a knife). In chemical properties, indium is closer to gallium and aluminum. The melting point is 156.5 °C. Indium is a by-product of the processing of ores of zinc, tin, lead or copper. It is extremely rare in the form of nuggets. The main indium minerals are jalinide, roquesite, and indite. Indium metal is a bright representative of scattered elements.

With the development of the electrical industry, indium is becoming increasingly popular and becoming a scarce material. Its use has been actively developed in the production of bearings. The addition of indium improves the corrosion resistance and wettability of the bearing. This property is used in mechanisms with rubbing metals. Indium acts as a lubricant here. Later, with the development of semiconductor technology, indium metal received a new round of its application. It is used as an additive in the production of touch screens, solar panels, batteries. Indium acts as a component in a number of low-melting solders. It is used in the nuclear industry. It is indispensable in the production of special mirrors and many other reflective elements.

At the moment, indium metal is increasingly included in the industrial production of many technically complex products. Its use is limited only by its small proportion in nature. Despite this, interest in India is only growing every year.

Indium is a typical trace element, its average content in the lithosphere is 1.4·10-5% by weight. During magmatic processes, India is slightly accumulated in granites and other acidic rocks. The main processes of concentration of India in the earth's crust are associated with hot aqueous solutions that form hydrothermal deposits. Indium is bound in them with Zn, Sn, Cd, and Pb. Sphalerites, chalcopyrites and cassiterites are enriched in Indium by an average of 100 times (the content is about 1.4 10-3%). Three minerals of India are known - native Indium, roquesite CuInS2 and indite In2S4, but all of them are extremely rare. Of practical importance is the accumulation of India in sphalerites (up to 0.1%, sometimes 1%). Enrichment in India is typical for deposits of the Pacific ore belt.

Physical properties India.

The crystal lattice of India is tetragonal face-centered with parameters a = 4.583Å and c= 4.936Å. Atomic radius 1.66Å; ionic radii In3+ 0.92Å, In+ 1.30Å; density 7.362 g/cm3. Indium is fusible, its melting point is 156.2 ° C; bp 2075 °C. Temperature coefficient of linear expansion 33 10-6 (20 °С); specific heat at 0-150°C 234.461 J/(kg K), or 0.056 cal/(g°C); electrical resistivity at 0°C 8.2 10-8 ohm m, or 8.2 10-6 ohm cm; modulus of elasticity 11 n/m2, or 1100 kgf/mm2; Brinell hardness 9 MN/m2, or 0.9 kgf/mm2.

Chemical properties of India.

In accordance with the electronic configuration of the 4d105s25p1 atom, indium in compounds exhibits valences of 1, 2, and 3 (predominantly). In air in a solid compact state, indium is stable, but oxidizes at high temperatures, and above 800 ° C it burns with a violet-blue flame, giving In2O3 oxide - yellow crystals, readily soluble in acids. When heated, indium easily combines with halogens, forming soluble halides InCl3, InBr3, InI3. Indium is heated in a flow of HCl to obtain InCl2 chloride, and when InCl2 vapor is passed over heated In, InCl is formed. With sulfur, indium forms sulfides In2S3, InS; they give compounds InS In2S3 and 3InS In2S3. In water in the presence of oxidants, indium slowly corrodes from the surface: 4In + 3O2+6H2O = 4In(OH)3. In acids, Indium is soluble, its normal electrode potential is -0.34 V, and practically insoluble in alkalis. Salts of India are easily hydrolyzed; hydrolysis product - basic salts or hydroxide In(OH)3. The latter is highly soluble in acids and poorly soluble in alkali solutions (with the formation of salts - indates): In (OH) 3 + 3KOH = K3. Indium compounds of lower oxidation states are rather unstable; halides InHal and black oxide In2O are very strong reducing agents.

Getting India.

Indium is obtained from waste and intermediate products of zinc, lead and tin production. This raw material contains from thousandths to tenths of a percent India. The extraction of India consists of three main stages: obtaining an enriched product - India concentrate; processing of concentrate to crude metal; refining. In most cases, the feedstock is treated with sulfuric acid and indium is transferred into a solution, from which a concentrate is isolated by hydrolytic precipitation. Rough Indium is isolated mainly by carburizing on zinc or aluminum. Refining is carried out by chemical, electrochemical, distillation and crystal-physical methods.

Application India.

Indium and its compounds (for example, InN nitride, InP phosphide, InSb antimonide) are most widely used in semiconductor technology. Indium is used for various anti-corrosion coatings (including bearing coatings). Indium coatings are highly reflective, which is used to make mirrors and reflectors. Certain alloys of indium are of industrial importance, including fusible alloys, solders for gluing glass to metal, and others.

Indium is an element of the main subgroup of the third group of the fifth period of the periodic system of chemical elements of D. I. Mendeleev, atomic number 49. It is designated by the symbol In (lat. India). Belongs to the group of light metals. Malleable, low-melting, very soft metal of silver-white color. Similar in chemical properties to aluminum and gallium, in appearance to zinc.

Discovery of India

In the middle of the last century, two prominent German scientists Gustav Robert Kirchhoff and Robert Wilhelm Bunsen came to the conclusion about the individuality of the line spectra of chemical elements and developed the fundamentals of spectral analysis. It was one of the first methods of studying chemical objects by physical means.

By this method, Bunsen and Kirchhoff in 1860 ... 1861. discovered rubidium and cesium. Other researchers have adopted it as well. In 1862, the Englishman William Crookes, in the course of a spectroscopic study of sludge sent from one of the German sulfuric acid plants, discovered lines of a new element - thallium. And a year later, indium was discovered, and the youngest method of analysis at that time and the youngest element played important roles in this discovery.

In 1863, German chemists Reich and Richter subjected zinc blende from the vicinity of Freiberg to spectroscopic analysis. From this mineral, scientists obtained zinc chloride and placed it in a spectrograph, hoping to detect a bright green line characteristic of thallium. Hopes were justified, but it was not this line that brought Reich and Richter world fame.

The spectrum also included a blue line (wavelength 4511 Ǻ), approximately the same as that produced by the well-known indigo dye. None of the known elements had such a line.

This is how indium was discovered - an element named after the color of its characteristic indigo line in the spectrum.

Until 1870, indium was considered a divalent element with an atomic weight of 75.6. In 1870 D.I. Mendeleev established that this element is trivalent, and its atomic weight is 113: this was obtained from the patterns of periodic changes in the properties of elements. This assumption was also supported by new data on the heat capacity of indium. What reasoning led to this conclusion is said in an excerpt from the article by D.I. Mendeleev (see below "Mendeleev about India").

Later it was found that natural indium consists of two isotopes with mass numbers 113 and 115. The heavier isotope predominates - it accounts for 95.7%.

Until 1950, both of these isotopes were thought to be stable. But in 1951 it turned out that indium-115 is subject to beta decay and gradually turns into tin-115. This process is very slow: the half-life of indium-115 nuclei is very long - 6·10 14 years. Because of this, it was not possible to detect the radioactivity of indium earlier.

In recent decades, about 20 radioactive isotopes of indium have been artificially obtained. The longest-lived of these, 114 In, has a half-life of 49 days.

Geochemistry and mineralogy of indium

From the nature of the arrangement of electrons in the atom, it follows that indium should be classified as a chalcophile element (18 electrons in the penultimate layer). Currently, 4 indium minerals are known: native indium, roquesite CuInS 2 , indite FeIn 2 S 4 , jalindite In(OH) 3 . In general, indium occurs as an isomorphic admixture in early high-iron sphalerite, where its content reaches tenths of a percent. In some varieties of chalcopyrite and bed, the content of indium is hundredths - tenths of a percent, and in cassiterite and pyrrhotite - thousandths of a percent. In pyrite, arsenopyrite, wolframite and some other minerals, the concentration of indium is grams per ton. Sphalerite and other minerals containing at least 0.1% indium are still of industrial importance for indium. Indium does not form independent deposits, but is included in the composition of ores of deposits of other metals. The highest content of indium was found in ores of cassiterite-bearing skarns and sulfide-cassiterite deposits of various types.

Physical properties of indium

The crystal lattice of India is tetragonal face-centered with parameters a = 4.583Å and c= 4.936Å. Atomic radius 1.66Å; ionic radii In 3+ 0.92Å, In + 1.30Å; density 7.362 g/cm 3 . Indium is fusible, its t pl is 156.2 ° C; t bale 2075 °C. Temperature coefficient of linear expansion 33 10 -6 (20 °C); specific heat at 0-150°C 234.461 J/(kg K), or 0.056 cal/(g°C); electrical resistivity at 0°C 8.2·10 -8 ohm·m, or 8.2·10 -6 ohm·cm; modulus of elasticity 11 N/m 2 , or 1100 kgf/mm 2 ; Brinell hardness 9 MN / m 2, or 0.9 kgf / mm 2.

Getting indium

Extracting indium from minerals is quite difficult. This is one of the scattered elements. Contained in minerals: sphalerite, marmatite, franklinite, alunite, calamine, rhodonite, phlogopite, mangantantalite, siderite, cassiterite, wolframite, samarskite. In none of the listed minerals does the average content of the element exceed tenths of a percent. Indium minerals proper—roquesite CuInS 2 , indite FeIn 2 S 4 , and jalindite In(OH) 3—are very rare. Native indium is also extremely rare, although under normal conditions this metal is not oxidized by atmospheric oxygen and, in general, it has significant chemical resistance.

Obtained from waste and intermediate products of the production of zinc, lead and tin. This raw material contains from 0.001% to 0.1% indium.

The technology for extracting indium, like many other metals, usually consists of two stages: first, a concentrate is obtained, and then a crude metal.

In the first concentration step, indium is separated from zinc, copper, and cadmium. This is achieved by simply adjusting the acidity of the solution, or more specifically, the pH value. Cadmium hydroxide precipitates from aqueous solutions at a pH of 8, copper and zinc hydroxides at 6. In order to “precipitate” indium hydroxide, the pH of the solution must be brought to 4.

Although technological processes based on precipitation and filtration have been known for a long time and are considered well developed, they do not allow all indium to be extracted from the raw material. In addition, they require rather bulky equipment.

The method of liquid extraction is considered more promising. This is the process of selective transition of one or more components of a mixture from an aqueous solution into a layer of an organic liquid immiscible with it. Unfortunately, in most cases, not one element, but several, passes into the “organic”. You have to extract and re-extract the elements several times - transfer the desired element from water to a solvent, from a solvent back to water, from there to another solvent, and so on, until complete separation.

For some elements, including indium, extractant reagents with high selectivity have been found. This makes it possible to increase the concentration of rare and trace elements hundreds and thousands of times. Extraction processes are easy to automate, this is one of their most important advantages.

Of the complex sulfuric acid solutions, in which there was much less indium than Zn, Cu, Cd, Fe, As, Sb, Co, Mn, Tl, Ge and Se, indium is well, selectively, extracted with alkyl phosphoric acids. Together with indium, mainly ferric and antimony ions pass into them.

It is not difficult to get rid of iron: before extraction, the solution must be treated in such a way that all Fe 3+ ions are reduced to Fe 2+, and these indium ions are not fellow travelers. It is more difficult with antimony: it has to be separated by re-extraction or at later stages of obtaining metallic indium.

The method of liquid extraction of indium with alkylphosphoric acids (of which di-2-ethylhexylphosphoric acid turned out to be especially effective) made it possible to significantly reduce the time for obtaining this rare metal, reduce its cost and, most importantly, extract indium more completely. Raw indium is refined by electrochemical or chemical methods. Ultra-pure indium is obtained by zone melting and by the Czochralski method - by pulling single crystals from crucibles.

The cost of indium in 2010 ranged from 25 to 30 thousand rubles per kg.

Application of indium

In recent years, world consumption of indium has grown rapidly and in 2005 reached 850 tons. The indium-mercury oxide electrochemical system is used to create extremely time-stable current sources (accumulators) with a high specific energy intensity for special purposes. An important area of ​​application for indium is high vacuum technology, where it is used as a sealant (gaskets, coatings); in particular, when sealing spacecraft and powerful elementary particle accelerators.

Previously, indium was used mainly for the manufacture of bearings. The addition of indium improves the mechanical properties of bearing alloys, increases their corrosion resistance and wettability.

Lead-silver bearings with an indium surface layer are widely used.

Indium has also found application in the production of certain alloys, especially fusible ones. Known, for example, is an alloy of indium with gallium (24 and 76%, respectively), which is in a liquid state at room temperature. Its melting point is only 16°C. Another alloy, which together with indium includes bismuth, lead, tin and cadmium, melts at 46.5°C and is used for fire alarms.

Sometimes indium and its alloys are used as solder. Being molten, they adhere well to many metals, ceramics, glass, and after cooling they “seize” with them firmly. Such solders are used in the production of semiconductor devices and in other branches of technology. The semiconductor industry has generally become the main consumer of indium.

Indium-silver alloys are insensitive to hydrogen sulfide and serve to create high-quality reflective surfaces. A number of alloys of indium with gallium, tin and zinc are liquids at room temperature (one of the alloys melts at +3 °C) and can be used as a liquid metal coolant.

Indium has a high thermal neutron capture cross section and can be used to control a nuclear reactor, although it is more convenient to use its compounds in combination with other elements that capture neutrons well. Thus, indium oxide is used in nuclear technology for the manufacture of glass used to absorb thermal neutrons.

Due to its softness, indium cannot be used in jewelry or construction. In indium, the tensile strength is 6 times less than that of lead. The metal is 20 times softer than pure gold and easily scratched with a fingernail. But the addition of indium increases the hardness of lead and especially tin.

Low-melting indium could serve as an excellent lubricant for rubbing parts operating at temperatures above 160, but below 2000 ° C - such temperatures often develop in modern machines and mechanisms.

Indium salts are used as additives to some luminescent compositions. They destroy the phosphorescence of the composition after the excitation is removed. If a conventional fluorescent lamp continues to shine for some time after being switched off, then a lamp with a composition containing indium salts goes out immediately after being switched off.

(Indium) In is a chemical element of the 13th (IIIa) group of the periodic system, atomic number 49, atomic mass 114.82. The structure of the outer electron shell 5s 2 5p 1 . There are 37 known isotopes of indium from 98 In to 134 In. Among them, only one stable 113 In. There are two isotopes in nature: 113 In (4.29%) and 115 In (95.71%) with a half-life of 4.41 10 14 years. The most stable oxidation state in compounds: +3.

The discovery of indium took place in an era of rapid development of spectral analysis, a fundamentally new (at that time) research method discovered by Kirchhoff and Bunsen. The French philosopher O. Comte wrote that mankind has no hope of knowing what the Sun and stars are made of. Several years passed, and in 1860 the Kirchhoff spectroscope refuted this pessimistic prediction. The next fifty years were the time of the greatest successes of the new method. After it was established that each chemical element has its own spectrum, which is as characteristic of its property as a fingerprint is a sign of a person, the “chase” for the spectra began. In addition to Kirchhoff's outstanding studies (which almost led him to complete blindness) of the elemental composition of the Sun, observations of the spectra of terrestrial objects were no less triumphant: in 1861, cesium, rubidium and thallium were discovered.

In 1863 Ferdinand Reich (1799–1882), professor at the Freiberg Mineralogical School (Germany) and his assistant Theodor Richter (1824–1898), examined samples of zinc blende (sphalerite mineral, ZnS) spectroscopically to detect thallium in them. Reich and Richter isolated zinc chloride from a sphalerite sample by the action of hydrochloric acid and placed it in a spectrograph with the hope of registering the appearance of a bright green line characteristic of thallium. Professor F. Reich suffered from color blindness and could not distinguish the colors of the spectral lines, so all observations were recorded by his assistant Richter. It was not possible to detect the presence of thallium in sphalerite samples, but what was Reich's surprise when Richter informed him of the appearance of a bright blue line (4511 Å) in the spectrum. It was found that the line did not belong to any of the previously known elements and differed even from the bright blue line of the cesium spectrum. Due to the similarity of the color of the characteristic band in the emission spectrum with the color of indigo dye (Latin "indicum" - Indian dye), the discovered element was named indium.

Since the new element was discovered in sphalerite, the discoverers considered it to be an analogue of zinc and assigned it an incorrect valency of two. They also determined the atomic weight of the equivalent of indium, which turned out to be 37.8. Based on the valence of 2, the atomic weight of the element was incorrectly set (37.8 × 2 = 75.6). Only in 1870, D.I. Mendeleev, on the basis of the periodic law, established that indium has a valency of three, and is, therefore, an analogue of aluminum, and not zinc.

Thus, in 1871, indium became the 49th element of the periodic table.

Bleshinsky S.V., Abramova V.F. Chemistry indium. Frunze, 1958
Figurovsky N.A. The discovery of the elements and the origin of their names. M., Science, 1970
Chemistry and technology of rare and trace elements, v.1. Under. ed. K.A. Bolshakov. M., 1976
Popular library of chemical elements. Under. ed. Petryanova-Sokolova I.V. M., 1983
Fedorov P.I., Akchurin R.Kh. Indium. M., 2000

To find " INDIUM" on

Indium is a silvery-white metal with a strong luster, similar in appearance to zinc. It is close to lithium in hardness and can be easily cut with a knife. The density of indium is 7.31 g/cm3, it melts at 156.5°C. At the same time, like gallium, the boiling point is a couple of thousand degrees higher than the melting point - 2080 ° C.

It is similar in chemical properties to aluminum and gallium, since these metals are in the same group of the periodic system of chemical elements, but in general it is less active in reactions. Stable in a humid atmosphere, does not dissolve in alkalis. Reacts with almost all acids, dissolves slowly even in weak organic acids.

Indium is a rare and trace element, it does not form its own deposits and is mined as a by-product during the processing of ores of other metals. For the production of indium, only those minerals in which it contains no less than 0.1% are of industrial importance. As a rule, most of it is in sphalerite (zinc sulfide), but even there its amount does not exceed 0.5%. Thus, the production of indium always accompanies the production of zinc, and to a lesser extent, tin and lead. The scheme for extracting indium is rather complicated, since the metal does not have distinctive chemical properties that could help in isolating it separately from other metals; at the same time, such methods as ion exchange, extraction, as well as hydrolytic precipitation and cementation are consistently applied, using small differences in the degree of hydrolysis of salts and standard potentials of different metals. The crude metal formed at the last stage is purified by various methods, in particular zone melting, which makes it possible to obtain indium with a purity of up to 99.99999%.

Indium and its compounds are most widely used in technology: the manufacture of liquid crystal screens (a thin film of indium-tin oxide), microelectronics (an admixture to germanium and silicon), a sealant in high vacuum technology (in particular, spacecraft), coating mirrors (in particular astronomical, where the constancy of the reflection coefficient in the visible part of the spectrum is important), thermoelectric materials based on indium arsenide, the production of very stable batteries with a high specific energy intensity for special purposes (mercury and indium oxide system), coating of some engine elements to reduce wear. In addition, indium is an important component of solders (due to the high adhesion of indium, this additive makes it possible to solder metals to glass and other materials), radiopharmaceutical preparations are made from its isotopes, its orthophosphate is added to dental cements, and a number of indium compounds have luminescent properties, which is used in different areas. Also, an alloy of indium (5%) with gold and silver is used as a decorative metal (the so-called green gold)

Thus, with the development of technology, the consumption of indium also grows. At the same time, the production of LCD screens consumes at least half of all mined metal. The production of primary indium (from 500 to 800 tons per year) from time to time catches up with demand, which causes price volatility. According to some estimates, the reserves of natural indium will be exhausted by 2030, unless the rate of its recycling and reuse increases.