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Global gallium market. Galium - metal or non-metal? Gallium chemical properties

The average gallium content in the earth's crust is 19 g / t. Gallium is a typical trace element with a double geochemical nature. Due to the closeness of its crystal-chemical properties with the main rock-forming elements (Al, Fe, etc.) and the wide possibility of isomorphism with them, gallium does not form large accumulations, despite the significant value of the clarke. The following minerals with a high gallium content are distinguished: sphalerite (0 - 0.1%), magnetite (0 - 0.003%), cassiterite (0 - 0.005%), garnet (0 - 0.003%), beryl (0 - 0.003%), tourmaline (0 - 0.01%), spodumene (0.001 - 0.07%), phlogopite (0.001 - 0.005%), biotite (0 - 0.1%), muscovite (0 - 0.01%), sericite ( 0 - 0.005%), lepidolite (0.001 - 0.03%), chlorite (0 - 0.001%), feldspars (0 - 0.01%), nepheline (0 - 0.1%), heckmanite (0.01 - 0.07%), natrolite (0 - 0.1%). The gallium concentration in seawater is 3 · 10−5 mg / l.

Place of Birth

Gallium deposits are known in South-West Africa, CIS countries

Gallium production

For gallium, the rare mineral gallite CuGaS2 (mixed sulfide of copper and gallium) is known. Its traces are constantly found with sphalerite, chalcopyrite and germanite. Significantly larger amounts of it (up to 1.5%) were found in the ashes of some coal. However, the main source of gallium production are solutions of alumina production in the processing of bauxite (usually containing insignificant impurities (up to 0.1%)) and nepheline. Gallium can also be obtained by processing polymetallic ores, coal. It is extracted by electrolysis of alkaline liquids, which are an intermediate product of natural bauxite processing into technical alumina. Gallium concentration in an alkaline aluminate solution after decomposition in the Bayer process: 100-150 mg / l, by the sintering method: 50-65 mg / l. In these methods, gallium is separated from most of the aluminum by carbonization, concentrating in the last fraction of the sediment. Then the enriched sludge is treated with lime, gallium goes into solution, from where the crude metal is released by electrolysis. The contaminated gallium is washed with water, then filtered through porous plates and heated under vacuum in order to remove volatile impurities. To obtain gallium of high purity, chemical (reactions between salts), electrochemical (electrolysis of solutions) and physical (decomposition) methods are used. In a very pure form (99.999%), it was obtained by electrolytic refining, as well as by the reduction of thoroughly purified GaCl3 with hydrogen.

Physical properties

Crystalline gallium has several polymorphic modifications, however, only one (I) is thermodynamically stable, having an orthorhombic (pseudotetragonal) lattice with parameters a = 4.5186 Å, b = 7.6570 Å, c = 4.5256 Å. Other gallium modifications (β, γ, δ, ε) crystallize from supercooled dispersed metal and are unstable. At elevated pressure, two more polymorphic structures of gallium II and III were observed, having, respectively, cubic and tetragonal lattices.

The density of gallium in the solid state at a temperature of 20 ° C is 5.904 g / cm³, liquid gallium (melting point = 29.8 ° C) has a density of 6.095 g / cm³, that is, when solidified, the volume of gallium increases. Gallium boils at 2230 ° C. One of the features of gallium is a wide temperature range for the existence of a liquid state (from 30 to 2230 ° C), while it has a low vapor pressure at temperatures up to 1100-1200 ° C. The specific heat of solid gallium in the temperature range T = 0-24 ° C is 376.7 J / kg · K (0.09 cal / g · deg.), In the liquid state at T = 29-100 ° C - 410 J / kg K (0.098 cal / g deg).

The specific electrical resistance in the solid and liquid states are, respectively, 53.4 · 10−6 ohm · cm (at T = 0 ° C) and 27.2 · 10−6 ohm · cm (at T = 30 ° C). The viscosity of liquid gallium at different temperatures is 1.612 poise at T = 98 ° C and 0.578 poise at T = 1100 ° C. The surface tension measured at 30 ° C in a hydrogen atmosphere is 0.735 N / m. The reflection coefficients for the 4360 Å and 5890 Å wavelengths are 75.6% and 71.3%, respectively.

Natural gallium consists of two isotopes 69Ga (61.2%) and 71Ga (38.8%). The cross section of thermal neutron capture is equal for them 2.1 · 10−28 m2 and 5.1 · 10−28 m2, respectively.

Application of gallium

Gallium arsenide GaAs is a promising material for semiconductor electronics.
Gallium nitride is used in the creation of semiconductor lasers and blue and ultraviolet light-emitting diodes. Gallium nitride has excellent chemical and mechanical properties typical of all nitride compounds.
The isotope gallium-71 is the most important material for registering neutrinos, and in this regard, the technology faces a very urgent task of separating this isotope from the natural mixture in order to increase the sensitivity of neutrino detectors. Since the content of 71Ga in the natural mixture of isotopes is about 39.9%, the isolation of a pure isotope and its use as a neutrino detector can increase the detection sensitivity by a factor of 2.5.

Gallium is expensive, in 2005 on the world market a ton of gallium cost 1.2 million US dollars, and due to the high price and at the same time with a great demand for this metal, it is very important to establish its complete extraction in aluminum production and processing of coal at liquid fuel.

Gallium has a number of alloys that are liquid at room temperature, and one of its alloys has a melting point of 3 ° C (In-Ga-Sn eutectic), but on the other hand, gallium (alloys to a lesser extent) is very aggressive to most structural materials (cracking and erosion of alloys at high temperatures). For example, in relation to aluminum and its alloys, gallium is a powerful strength reducer (see adsorption reduction in strength, Rebinder effect). This property of gallium was brilliantly demonstrated and studied in detail by P. A. Rebinder and E. D. Shchukin when aluminum comes into contact with gallium or its eutectic alloys (liquid metal embrittlement). In addition, the wetting of aluminum with a film of liquid gallium causes its rapid oxidation, similar to what happens with aluminum amalgamated with mercury. Gallium dissolves at the melting point about 1% of aluminum, which reaches the outer surface of the film, where it is instantly oxidized by air. The oxide film on the liquid surface is unstable and does not protect against further oxidation. As a result, liquid gallium alloy is not used as a thermal interface between a heat-generating component (for example, a computer's central processor) and an aluminum radiator.

As a coolant, gallium is ineffective and often simply unacceptable.
Gallium is an excellent lubricant. On the basis of gallium and nickel, gallium and scandium, metal adhesives, very important in practical terms, have been created.
Quartz thermometers (instead of mercury) are also filled with metallic gallium to measure high temperatures. This is because gallium has a significantly higher boiling point than mercury.
Gallium oxide is part of a number of strategically important laser materials of the garnet group - GHA, YAG, ISGG, etc.

The biological role and features of the circulation of gallium

Does not play a biological role.

Contact of the skin with gallium leads to the fact that ultra-small dispersed metal particles remain on it. Outwardly, it looks like a gray spot.
The clinical picture of acute poisoning: short-term excitement, then lethargy, impaired coordination of movements, weakness, areflexia, slowing of breathing, disturbance of its rhythm. Against this background, paralysis of the lower extremities is observed, then - coma, death. Inhalation exposure to gallium-containing aerosol at a concentration of 50 mg / m³ causes kidney damage in humans, as well as intravenous administration of 10-25 mg / kg of gallium salts. Proteinuria, azotemia, impaired urea clearance are noted.
Due to the low melting point, gallium ingots are recommended to be transported in bags made of polyethylene, which is poorly wetted with liquid gallium.

Gallium

GALLIUM-I; m.[from lat. Gallia - France] Chemical element (Ga), a soft fusible metal of a silvery-white color (used in the manufacture of semiconductors).

Gallium

(lat. Gallium), a chemical element of the III group of the periodic system. The name from Gallia is the Latin name for France. Silver-white fusible ( t pl 29.77ºC) metal; density (g / cm 3) solid metal 5.904, liquid 6.095; t bale 2205ºC. It is chemically stable in air. Dispersed in nature, occurs together with Al. They are mainly used (97%) in the production of semiconductor materials (GaAs, GaSb, GaP, GaN).

GALLIUM

GALLIUM (Latin Gallium, from Gallia - the Latin name for France), Ga (read "gallium"), a chemical element with atomic number 31, atomic mass 69.723.
Natural gallium consists of two isotopes 69 Ga (61.2% by mass) and 71 Ga (38.8%). Configuration of outer electron layer 4 s 2 p one . Oxidation state +3, +1 (valences I, III).
It is located in group IIIA of the periodic table of elements, in the 4th period.
The radius of the atom is 0.1245 nm, the radius of the Ga 3+ ion is 0.062 nm. The sequential ionization energies are 5.998, 20.514, 30.71, 64.2 and 89.8 eV. Pauling electronegativity (cm. POLING Linus) 1,6.
Discovery history
The existence of this element was first predicted by D.I.Mendeleev (cm. MENDELEEV Dmitry Ivanovich) in 1871 on the basis of the periodic law discovered by him. He named it eka-aluminum. In 1875 P.E. Lecoq de Boisbaudran (cm. LECOQUE DE BOUBODRAN Paul Emile) isolated gallium from zinc ores.
De Boisbaudran determined the density of gallium - 4.7 g / cm 3, which did not correspond to the value of 5.9 g / cm 3 predicted by D. I. Mendeleev. The refined value of the density of gallium (5.904 g / cm 3) coincided with Mendeleev's prediction.
Being in nature
Content in the earth's crust is 1.8 · 10 –3% by weight. Gallium is a scattered element. In nature, it occurs in the form of very rare minerals: zengeite Ga (OH) 3, gallite CuGaS 2 and others. Is a companion of aluminum (cm. ALUMINUM), zinc (cm. ZINC (chemical element)), Germany (cm. GERMANIUM), gland (cm. IRON); contained in sphalerite (cm. SPHALERITE), nepheline (cm. NEFELIN), natrolite, bauxite, (cm. BOXITS) germanite, in coals and iron ores of some deposits.
Receiving
The main source of gallium is aluminate solutions obtained during the processing of alumina. After removal of most of the Al and repeated concentration, an alkaline solution containing Ga and Al is formed. Gallium is isolated by electrolysis of this solution.
Physical and chemical properties
Gallium is a low-melting light gray metal with a bluish tint. The Ga melt can be in a liquid state at temperatures below the melting point (29.75 ° C). The boiling point is 2200 ° C, this is explained by the fact that liquid gallium has a dense packing of atoms with a coordination number of 12. It takes a lot of energy to destroy it.
The crystal lattice of the stable a-modification is formed by diatomic Ga 2 molecules interconnected by van der Waals forces (cm. INTERMOLECULAR INTERACTION), bond length 0.244 nm.
The standard electrode potential of the Ga 3+ / Ga pair is –0.53 V, Ga is in the electrochemical range up to hydrogen (cm. HYDROGEN).
In terms of chemical properties, gallium is similar to aluminum.
In air, Ga becomes covered with an oxide film, which protects it from further oxidation. With arsenic (cm. ARSENIC), phosphorus (cm. PHOSPHORUS), antimony (cm. ANTIMONY) forms gallium arsenide, phosphide and antimonide, with sulfur (cm. SULFUR), selenium (cm. SELENIUM), tellurium (cm. TELLURIUM)- chalcogenides. When heated, Ga reacts with oxygen (cm. OXYGEN)... With chlorine (cm. CHLORINE) and bromine (cm. BROMINE) gallium reacts at room temperature with iodine (cm. IOD)- when heated. Gallium halides form Ge 2 X 6 dimers.
Gallium forms polymer hydrides:
4LiH + GaCl 3 = Li + 3LiCl.
The stability of ions decreases in the series BH 4 - - AlH 4 - - GaH 4 -. Ion BH 4 is stable in aqueous solution, AlH 4 - and GaH 4 - are rapidly hydrolyzed:
GaH 4 - + 4H 2 O = Ga (OH) 3 + OH - + 4H 2
When heated under pressure, Ga reacts with water:
2Ga + 4H 2 O = 2GaOOH + 3H 2
With mineral acids, Ga slowly reacts with the evolution of hydrogen:
2Ga + 6HCl = 2GaCl 3 + 3H 2
Gallium dissolves in alkalis with the formation of hydroxogallates:
2Ga + 6H 2 O + 2NaOH = 2Na + 3H 2
Gallium oxide and hydroxide exhibit amphoteric properties, although their main properties are enhanced in comparison with Al:
Ga 2 O 3 + 6HCl = 2GaCl 2,
Ga 2 O 3 + 2NaOH + 3H 2 O = 2Na
Ga 2 O 3 + Na 2 CO 3 = 2NaGaO 2 + CO 2
When a solution of any gallium salt is made alkaline, gallium hydroxide of variable composition Ge 2 O 3 · x H 2 O:
Ga (NO 3) 2 + 3NaOH = Ga (OH) 3 Ї + 3NaNO 3
When Ga (OH) 3 and Ga 2 O 3 are dissolved in acids, aqua complexes 3+ are formed, therefore, gallium salts are released from aqueous solutions in the form of crystalline hydrates, for example, gallium chloride GaCl 3 6H 2 O, gallium potassium alum KGa (SO 4) 2 12H 2 O. Gallium aqua complexes in solutions are colorless.
Application
About 97% of the gallium produced by industry is used to obtain compounds with semiconducting properties, for example, gallium arsenide GaAs. Metallic gallium is used in radio electronics for "cold soldering" of ceramic and metal parts, for doping Ge and Si, and for obtaining optical mirrors. Ga can replace Hg in electric rectifiers. The eutectic alloy of gallium with indium is used in the radiation circuits of reactors.
Features of treatment
Gallium is a low-toxic element. Due to the low melting point, Ga ingots are recommended to be transported in bags made of polyethylene, which is poorly wetted with liquid gallium.

encyclopedic Dictionary. 2009 .

Synonyms:

See what "Gallium" is in other dictionaries:

Metal, a simple body, the existence of which Mendeleev foresaw and which was discovered by Lecoq de Buobodran. Dictionary of foreign words included in the Russian language. Chudinov AN, 1910. GALLIUM, an undecomposable mineral, blue-white; solid,… … Dictionary of foreign words of the Russian language

- (Gallium), Ga, chemical element of the III group of the periodic system, atomic number 31, atomic mass 69.72; metal. Gallium was discovered by the French chemist P. Lecoq de Boisbaudran in 1875 ... Modern encyclopedia

Ga (lat.Gallium * a. Gallium; N. Gallium; F. gallium; I. galio), chem. element of the III group periodic. Mendeleev systems, at. n. 31, at. m. 69.73. Consists of two stable isotopes 69Ga (61.2%) and 71Ga (38.8%). Predicted in 1870 by D.I. ... ... Geological encyclopedia

gallium- I, m. gallium m. From lat. the name of France, where it was discovered in 1875 by the chemist Lecoq de Boidbaudran. ES. Chemical element, soft hot melt silvery white metal; is used instead of mercury for the manufacture of manometers and high-temperature ... ... Historical Dictionary of Russian Gallicisms

Gallium- (Gallium), Ga, chemical element of the III group of the periodic system, atomic number 31, atomic mass 69.72; metal. Gallium was discovered by the French chemist P. Lecoq de Boisbaudran in 1875. ... Illustrated Encyclopedic Dictionary

GALLIUM- chem. element, symbol Ga (Latin Gallium), at. n. 31, at. m. 69.72; silvery white metal; density 5904 kg / m3, tm = 29.8 ° С, tboil = 2230 ° С. Gallium as a liquid exists in a very wide temperature range, therefore it is used in ... ... Big Polytechnic Encyclopedia Dictionary of Synonyms

- (chem.). The properties of this elementary body, Ga = 69, 86, were predicted (D. I. Mendeleev) periodic system elements, such as ecoaluminum, in 1871. In 1875 Lecoq de Boisbaudran discovered G. in zinc debris from Pierrefit (in the Pyrenees) with the help of ... ... Encyclopedia of Brockhaus and Efron

gallium- Ga Element of III group Periodic. systems, at. n. 31, at. m. 69.72; silvery white light metal. Consists of two stable isotopes with mass numbers 69 (60.5%) and 71 (39.5%). The existence of Ga ("eka-aluminum") and DOS. his holy va ... ... Technical translator's guide

In nature, it will not be possible to find large deposits, since he simply does not form them. In most cases, it can be found in ore minerals or germanite, where there is a chance of finding from 0.5 to 0.7% of this metal. It is also worth mentioning that gallium can be obtained during the processing of nepheline, bauxite, polymetallic ores or coal. First, a metal is obtained, which undergoes processing: washing with water, filtration and heating. And in order to obtain high quality this metal, special chemical reactions are used. A large level of gallium production can be observed in African countries, namely in the southeast, Russia and other regions.

As for the properties of this metal, its color is silver, and at low temperature conditions it can remain in a solid state, but it will not be difficult for it to melt if the temperature even slightly exceeds room temperature. Since this metal is close to aluminum in its properties, it is transported in special packages.

The use of gallium

Gallium has been used relatively recently in the production of low-melting alloys. But today it can be found in microelectronics, where it is used with semiconductors. Also, this material is good as a lubricant. If gallium is used together or scandium, then excellent quality metal adhesives can be obtained. In addition, gallium metal itself can be used as a filler in quartz thermometers, since it has a higher boiling point than mercury.

In addition, it is known that gallium is used in the manufacture of electric lamps, the creation of signaling systems for and fuses. Also, this metal can be found in optical devices, in particular, to improve their reflective properties. Gallium is also used in pharmaceuticals or radiopharmaceuticals.

But at the same time, this metal is one of the most expensive, and it is very important to establish its high-quality extraction in the production of aluminum and the processing of coal for fuel, because the unique natural gallium is widely used today due to its unique properties.

The element has not yet been synthesized, although nanotechnology gives hope to scientists working with gallium.

Gallium is an element of the main subgroup of the third group of the fourth period of the periodic system chemical elements DI Mendeleev, with atomic number 31. It is designated by the symbol Ga (lat. Gallium). Belongs to the group of light metals. The simple substance gallium is a soft plastic metal of a silvery-white color with a bluish tint.

Atomic number - 31

Atomic mass - 69.723

Density, kg / m³ - 5910

Melting point, ° С - 29.8

Heat capacity, kJ / (kg ° C) - 0.331

Electronegativity - 1.8

Covalent radius, Å - 1.26

1st ionization potential, eV - 6.00

The history of the discovery of gallium

French chemist Paul Émile Lecoq de Boisbaudran went down in history as the discoverer of three new elements: gallium (1875), samarium (1879) and dysprosium (1886). The first of these discoveries brought him fame.

At that time, he was little known outside of France. He was 38 years old, he was mainly engaged in spectroscopic research. Lecoq de Boisbaudran was a good spectroscopist, and this ultimately led to success: he discovered all three of his elements by the method of spectral analysis.

In 1875, Lecoq de Boisbaudran investigated the spectrum of zinc blende brought from Pierrefit (Pyrenees). In this spectrum, a new violet line was discovered. The new line indicated the presence of an unknown element in the mineral, and, quite naturally, Lecoq de Boisbaudran made every effort to isolate this element. This was not easy to do: the content of the new element in the ore was less than 0.1%, and in many ways it was similar to zinc *. After lengthy experiments, the scientist managed to get a new element, but in very small quantities. So small (less than 0.1 g) that Lecoq de Boisbaudran was far from fully able to study its physical and chemical properties.

The message about the discovery of gallium - this is how a new element was named in honor of France (Gaul is its Latin name) - appeared in the reports of the Paris Academy of Sciences.

This message was read by D.I. Mendeleev and recognized in gallium the eka-aluminum predicted by him five years earlier. Mendeleev immediately wrote to Paris. "The method of discovery and isolation, as well as the few properties described, make it possible to assume that the new metal is nothing more than eka-aluminum," - said in his letter. Then he repeated the properties predicted for that element. Moreover, never holding grains of gallium in his hands, without seeing it in the eye, the Russian chemist argued that the discoverer of the element was mistaken, that the density of the new metal could not be 4.7, as Lecoq de Boisbaudran wrote - it must be greater. about 5.9 ... 6.0 g / cm 3! But experience has shown the opposite: the discoverer was mistaken. The discovery of the first of the elements predicted by Mendeleev significantly strengthened the position of the periodic law.

Finding Gaulin nature

The average gallium content in the earth's crust is 19 g / t. Gallium is a typical trace element with a double geochemical nature. The only gallium mineral, gallite CuGaS 2, is very rare. The geochemistry of Gallium is closely related to the geochemistry of aluminum, which is due to the similarity of their physicochemical properties. The bulk of gallium in the lithosphere is contained in aluminum minerals. Due to the closeness of its crystal-chemical properties with the main rock-forming elements (Al, Fe, etc.) and the wide possibility of isomorphism with them, gallium does not form large accumulations, despite the significant value of the clarke. The following minerals with a high gallium content are distinguished: sphalerite (0 - 0.1%), magnetite (0 - 0.003%), cassiterite (0 - 0.005%), garnet (0 - 0.003%), beryl (0 - 0.003%), tourmaline (0 - 0.01%), spodumene (0.001 - 0.07%), phlogopite (0.001 - 0.005%), biotite (0 - 0.1%), muscovite (0 - 0.01%), sericite ( 0 - 0.005%), lepidolite (0.001 - 0.03%), chlorite (0 - 0.001%), feldspars (0 - 0.01%), nepheline (0 - 0.1%), heckmanite (0.01 - 0.07%), natrolite (0 - 0.1%).

Physical properties Gaul

Perhaps the most famous property of gallium is its melting point, which is 29.76 ° C. It is the second most fusible metal in the periodic table (after mercury). This allows you to melt the metal while holding it in your hand. Gallium is one of the few metals that expands when the melt solidifies (others are Bi, Ge).

The density of gallium in the solid state at a temperature of T = 20 ° C is 5.904 g / cm³.

One of the features of gallium is a wide temperature range for the existence of a liquid state (from 30 to 2230 ° C), while it has a low vapor pressure at temperatures up to 1100 ÷ 1200 ° C. The specific heat capacity of solid gallium in the temperature range T = 0-24 ° C is 376.7 J / kg K (0.09 cal / g deg.), In the liquid state at T = 29-100 ° C - 410 J / kg K (0.098 cal / g deg).

The resistivity in the solid and liquid state is, respectively, 53.4 · 10 −6 ohm · cm (at T = 0 ° C) and 27.2 · 10 −6 ohm · cm (at T = 30 ° C). The viscosity of liquid gallium at different temperatures is 1.612 poise at T = 98 ° C and 0.578 poise at T = 1100 ° C. The surface tension measured at 30 ° C in a hydrogen atmosphere is 0.735 N / m. The reflection coefficients for the 4360 Å and 5890 Å wavelengths are 75.6% and 71.3%, respectively.

Natural gallium consists of two isotopes 69 Ga (61.2%) and 71 Ga (38.8%). The cross-section of thermal neutron capture is 2.1 · 10 −28 m² and 5.1 · 10 −28 m² for them, respectively.

Gallium is a low-toxic element. Due to the low melting temperature, gallium ingots are recommended to be transported in polyethylene bags, which are poorly wetted by the gallium melt. At one time, the metal was even used to make fillings (instead of amalgam ones). This application is based on the fact that when mixing copper powder with molten gallium, a paste is obtained, which hardens after a few hours (due to the formation of an intermetallic compound) and then can withstand heating up to 600 degrees without melting.

At high temperatures, gallium is very corrosive. At temperatures above 500 ° C, it corrodes almost all metals except tungsten, as well as many other materials. Quartz is resistant to molten gallium up to 1100 ° C, but a problem can arise due to the fact that quartz (and most other glasses) is well wetted by this metal. That is, gallium will simply stick to the walls of the quartz.

Chemical properties Gaul

The chemical properties of gallium are close to those of aluminum. An oxide film formed on the metal surface in air protects gallium from further oxidation. When heated under pressure, gallium reacts with water, forming a compound GaOOH according to the reaction:

2Ga + 4H 2 O = 2GaOOH + 3H 2.

Gallium interacts with mineral acids with the release of hydrogen and the formation of salts, and the reaction proceeds even below room temperature:

2Ga + 6HCl = 2GaCl 3 + 3H 2

The products of the reaction with alkalis and potassium and sodium carbonates are hydroxogallates containing ions Ga (OH) 4 - and, possibly, Ga (OH) 6 3- and Ga (OH) 2 -:

2Ga + 6H 2 O + 2NaOH = 2Na + 3H 2

Gallium reacts with halogens: the reaction with chlorine and fluorine occurs at room temperature, with bromine - already at −35 ° C (about 20 ° C - with ignition), interaction with iodine begins when heated.

Gallium does not interact with hydrogen, carbon, nitrogen, silicon and boron.

At high temperatures, gallium is capable of destroying various materials and its effect is stronger than the melt of any other metal. So, graphite and tungsten are resistant to the action of gallium melt up to 800 ° C, alundum and beryllium oxide BeO - up to 1000 ° C, tantalum, molybdenum and niobium are stable up to 400 ÷ 450 ° C.

With most metals, gallium forms gallides, with the exception of bismuth, as well as metals of the zinc, scandium, and titanium subgroups. One of the V 3 Ga gallides has a rather high superconducting transition temperature of 16.8 K.

Gallium forms polymer hydrides:

4LiH + GaCl 3 = Li + 3LiCl.

The stability of ions decreases in the order BH 4 - → AlH 4 - → GaH 4 -. Ion BH 4 is stable in aqueous solution, AlH 4 - and GaH 4 - are rapidly hydrolyzed:

GaH 4 - + 4H 2 O = Ga (OH) 3 + OH - + 4H 2 -

When Ga (OH) 3 and Ga 2 O 3 are dissolved in acids, aqua complexes 3+ are formed, therefore, gallium salts are released from aqueous solutions in the form of crystalline hydrates, for example, gallium chloride GaCl 3 * 6H 2 O, gallium potassium alum KGa (SO 4) 2 * 12H 2 O.

The interaction of gallium with sulfuric acid takes place in an interesting way. It is accompanied by the release of elemental sulfur. In this case, sulfur envelops the surface of the metal and prevents its further dissolution. If you wash the metal with hot water, the reaction will resume, and will continue until a new "skin" of sulfur grows on the gallium.

Basic connections Gaul

Ga 2 H 6- volatile liquid, melting point −21.4 ° C, boiling point 139 ° C. In an ether suspension with lithium or thallium hydrate, it forms the compounds LiGaH 4 and TlGaH 4. Formed by treating tetramethyldigallane with triethylamine. Has banana connections, just like diborane

Ga 2 O 3- white or yellow powder, melting point 1795 ° C. There are two modifications. α- Ga 2 O 3 - colorless trigonal crystals with a density of 6.48 g / cm³, slightly soluble in water, soluble in acids. β- Ga 2 O 3 - colorless monoclinic crystals with a density of 5.88 g / cm³, slightly soluble in water, acids and alkalis. It is obtained by heating metallic gallium in air at 260 ° C or in an oxygen atmosphere, or by calcining gallium nitrate or sulfate. ΔH ° 298 (sample) −1089.10 kJ / mol; ΔG ° 298 (sample) −998.24 kJ / mol; S ° 298 84.98 J / mol * K. They exhibit amphoteric properties, although the main properties, in comparison with aluminum, are enhanced:

Ga 2 O 3 + 6HCl = 2GaCl 2 Ga 2 O 3 + 2NaOH + 3H 2 O = 2Na Ga 2 O 3 + Na 2 CO 3 = 2NaGaO 2 + CO 2

Ga (OH) 3- falls out in the form of a jelly-like precipitate during the treatment of solutions of salts of trivalent gallium with hydroxides and carbonates of alkali metals (pH 9.7). It dissolves in concentrated ammonia and a concentrated solution of ammonium carbonate, precipitates upon boiling. By heating, gallium hydroxide can be converted to GaOOH, then to Ga 2 O 3 * H 2 O, and finally to Ga 2 O 3. Can be obtained by hydrolysis of trivalent gallium salts.

GaF 3- White powder. t pl> 1000 ° C, t bp 950 ° C, density - 4.47 g / cm³. Slightly soluble in water. Known crystalline hydrate GaF 3 · 3H 2 O. Obtained by heating gallium oxide in a fluorine atmosphere.

GaCl 3- colorless hygroscopic crystals. t pl 78 ° C, t bp 215 ° C, density - 2.47 g / cm³. Let's well dissolve in water. It hydrolyzes in aqueous solutions. Obtained directly from elements. It is used as a catalyst in organic syntheses.

GaBr 3- colorless hygroscopic crystals. t pl 122 ° C, t bp 279 ° C density - 3.69 g / cm³. It dissolves in water. It hydrolyzes in aqueous solutions. Slightly soluble in ammonia. Obtained directly from elements.

GaI 3- hygroscopic light yellow needles. melting point 212 ° C, boiling point 346 ° C, density - 4.15 g / cm³. It is hydrolyzed with warm water. Obtained directly from elements.

GaS 3- yellow crystals or white amorphous powder with a melting point of 1250 ° C and a density of 3.65 g / cm³. It interacts with water and is completely hydrolyzed. Obtained by the interaction of gallium with sulfur or hydrogen sulfide.

Ga 2 (SO 4) 3 18H 2 O- a colorless substance, readily soluble in water. It is obtained by the interaction of gallium, its oxide and hydroxide with sulfuric acid. With alkali metal and ammonium sulfates, it readily forms alum, for example, KGa (SO 4) 2 · 12H 2 O.

Ga (NO 3) 3 8H 2 O- colorless crystals, soluble in water and ethanol. Decomposes on heating to form gallium (III) oxide. It is obtained by the action of nitric acid on gallium hydroxide.

Gallium production

The main source of gallium production is aluminum production. Gallium in the processing of bauxite by the Bayer method is concentrated in the circulating mother liquors after the separation of Al (OH) 3. Gallium is isolated from such solutions by electrolysis on a mercury cathode. Ga (OH) 3 is precipitated from the alkaline solution obtained after treating the amalgam with water, which is dissolved in alkali and gallium is isolated by electrolysis.

In the soda-lime method of processing bauxite or nepheline ore, Gallium is concentrated in the last fractions of sediments released during carbonization. For additional enrichment, the hydroxide sediment is treated with milk of lime. In this case, most of the Al remains in the precipitate, and the Gallium goes into solution, from which the gallium concentrate (6-8% Ga 2 O 3) is separated by passing CO 2; the latter is dissolved in alkali and gallium is isolated electrolytically.

The source of gallium can also be the residual anode alloy of the process of refining Al by the method of three-layer electrolysis. In zinc production, sources of gallium are sublimates (Waelz oxides) generated during the processing of zinc cinder leaching tailings.

Liquid Gallium obtained by electrolysis of an alkaline solution, washed with water and acids (HCl, HNO 3), contains 99.9-99.95% Ga. A more pure metal is obtained by vacuum melting, zone melting, or by pulling a single crystal from the melt.

Application of gallium

Gallium arsenide GaAs is a promising material for semiconductor electronics.

Gallium nitride is used in the creation of semiconductor lasers and blue and ultraviolet light-emitting diodes. Gallium nitride has excellent chemical and mechanical properties typical of all nitride compounds.

As an element of the III group, contributing to the enhancement of "hole" conductivity in a semiconductor, gallium (with a purity of not less than 99.999%) is used as an additive to germanium and silicon. Intermetallic compounds of gallium with Group V elements - antimony and arsenic - themselves have semiconducting properties.

The isotope gallium-71 is the most important material for detecting neutrinos, and in this regard, the technology faces a very urgent task of separating this isotope from the natural mixture in order to increase the sensitivity of neutrino detectors. Since the content of 71 Ga in the natural mixture of isotopes is about 39.9%, the isolation of a pure isotope and its use as a neutrino detector can increase the detection sensitivity by 2.5 times.

The addition of gallium to the glass mass makes it possible to obtain glasses with a high refractive index of light rays, and glasses based on Ga 2 O 3 transmit infrared rays well.

Liquid gallium reflects 88% of the incident light, while solid gallium reflects slightly less. Therefore, gallium mirrors are made very easy to manufacture - a gallium coating can even be applied with a brush.

Gallium has a number of alloys that are liquid at room temperature, and one of its alloys has a melting point of 3 ° C, but on the other hand, gallium (alloys to a lesser extent) is highly corrosive to most structural materials (cracking and erosion of alloys at high temperatures), and as a coolant, it is ineffective, and often simply unacceptable.

Attempts have been made to use gallium in nuclear reactors, but the results of these attempts can hardly be considered successful. Not only does gallium quite actively capture neutrons (capture cross section 2.71 barn), it also reacts at elevated temperatures with most metals.

Gallium has not become an atomic material. True, its artificial radioactive isotope 72 Ga (with a half-life of 14.2 hours) is used to diagnose bone cancer. Gallium-72 chloride and nitrate are adsorbed by the tumor, and by fixing the radiation characteristic of this isotope, doctors almost accurately determine the size of foreign formations.

Gallium is an excellent lubricant. On the basis of gallium and nickel, gallium and scandium, practically very important metal adhesives have been created.

Quartz thermometers (instead of mercury) are also filled with metallic gallium to measure high temperatures. This is because gallium has a significantly higher boiling point than mercury.

Gallium oxide is a component of a number of strategically important laser materials.

Gallium production in the world

Its world production does not exceed two hundred tons per year. With the exception of two recently discovered deposits - in 2001 in Gold Canion, Nevada, USA, and in 2005 in Inner Mongolia, China - gallium is nowhere found in commercial concentrations anywhere in the world. (In the last deposit, the presence of 958 thousand tons of gallium in coal was established - this is a doubling of the world's gallium resources).

The world's gallium resources in bauxite alone are estimated to exceed 1 million tons, and in the aforementioned deposit in China, 958 thousand tons of gallium in coal is a doubling of the world's gallium resources).

There are not many gallium producers. One of the leaders in the gallium market is GEO Gallium. Its main capacities until 2006 consisted of an enterprise in Stade (Germany), where about 33 tons per year are mined, a plant in Salindres, which processes 20 tons / year (France) and in Pinjarra (Western Australia) - potential (but not introduced into system) capacity up to 50 tons / year.

In 2006, the position of manufacturer # 1 weakened - the Stade plant was bought by the English MCP and the American Recapture Metals.

The Japanese company Dowa Mining is the world's only producer of primary gallium from zinc concentrates along the way in the production of zinc. The full capacity for Dowa Mining raw material is estimated to be up to 20 tons / year. In Kazakhstan, the Aluminum of Kazakhstan enterprise in Pavlodar - the full capacity is up to 20 tons / year.

China has become a very important supplier of gallium. There are 3 major primary gallium producers in China - Geatwall Aluminum Co. (up to 15 tons / year), Shandong Aluminum Plant (about 6 tons / year) and Guizhou Aluminum Plant (up to 6 tons / year). There are also a number of joint ventures. Sumitomo Chemical has set up a joint venture in China with a capacity of up to 40 tons / year. The American company AHT has established a joint venture Beijing JiYa semiconductor Material Co. with the largest Chinese aluminum enterprise Shanxi Aluminum Factory. with a capacity of up to 20 tons / year.

Gallium production in Russia

In Russia, the structure of gallium production is determined by the formation of the aluminum industry. The two leading groups that announced the merger, Russian Aluminum and SUAL, are the owners of gallium plots created at the alumina refineries.

Russian Aluminum: Nikolaev Alumina Refinery in Ukraine (classical Bayer hydrochemical method of tropical bauxite processing, site capacity - up to 12 tons of gallium / year) and Achinsk Alumina Refinery in Russia (processing by sintering nepheline raw materials - urtites from the Kiya-Shaltyrsky deposit of the Krasnoyarsk Territory, site capacity - 1.5 tons of gallium / year).

SUAL: Capacities in Kamensk-Uralsky (Bayer-sintering technology of bauxites of the Severo-Uralsky bauxite ore region, site capacity - up to 2 tons of gallium / year), at Boksitogorsk alumina refinery (processes bauxites of the Leningrad region by sintering, capacity - 5 tons of gallium / year, currently mothballed) and Pikalevsky Alumina (processes nepheline concentrates from apatite-nepheline ores of the Murmansk region by sintering, the site capacity is 9 tons of gallium / year). In total, all Rusal and SUAL enterprises can produce over 20 tons / year.

Real production is lower - for example, in 2005, 8.3 tons of gallium were exported from Russia and 13.9 tons of gallium from the Nikolaev Alumina Refinery were exported from Ukraine.

In preparing the material, information from the "Kvar" company was used.

The existence of gallium ("ekaaluminium") and its main properties were predicted in 1870 by D. I. Mendeleev. The element was discovered by spectral analysis in Pyrenean zinc blende and isolated in 1875 by the French chemist P.E. Lecoque de Boisbaudran; named after France (lat. Gallia). The exact coincidence of the properties of gallium with those predicted was the first triumph of the periodic table.

Being in nature, getting:

Consists of two stable isotopes with mass numbers 69 (60.5%) and 71 (39.5%). The average gallium content in the earth's crust is relatively high, 1.5 · 10 -3% by weight, which is equal to the content of lead and molybdenum. Gallium is a typical trace element. The only gallium mineral, gallite CuGaS 2, is very rare. The geochemistry of gallium is closely related to the geochemistry of aluminum, which is due to the similarity of their physicochemical properties. The bulk of gallium in the lithosphere is contained in aluminum minerals. The gallium content in bauxite and nepheline ranges from 0.002 to 0.01%. Increased gallium concentrations are also observed in sphalerites (0.01-0.02%), in coal (together with germanium), and also in some iron ores. China, the USA, Russia, Ukraine, and Kazakhstan have significant reserves of gallium.
The main source of gallium production is aluminum production. In the processing of bauxite, gallium is concentrated in mother liquors after the separation of Al (OH) 3. Gallium is isolated from such solutions by electrolysis on a mercury cathode. Ga (OH) 3 is precipitated from the alkaline solution obtained after treating the amalgam with water, which is dissolved in alkali and gallium is isolated by electrolysis.
Liquid gallium obtained by electrolysis of an alkaline solution, washed with water and acids (HCl, HNO 3), contains 99.9-99.95% Ga. A more pure metal is obtained by vacuum melting, zone melting, or by pulling a single crystal from the melt.

Physical properties:

The metal is silvery white, soft and heavy. A distinctive feature of gallium is a large interval of the liquid state (melting point 29.8 ° C, boiling point 2230 ° C) and low vapor pressure at temperatures up to 1100-1200 ° C. The density of the solid metal is 5.904 g / cm 3 (20 ° C), which is lower than that of the liquid metal; therefore, crystallizing gallium, like ice, can rupture a glass ampoule. The specific heat capacity of solid gallium is 376.7 J / (kg K).

Chemical properties:

Gallium is stable in air at ordinary temperatures. Above 260 ° C, slow oxidation is observed in dry oxygen (the oxide film protects the metal). Chlorine and bromine react with gallium in the cold, iodine - when heated. Molten gallium at temperatures above 300 ° C interacts with all structural metals and alloys (except W), forming intermetallic compounds.
When heated under pressure, gallium reacts with water: 2Ga + 4H 2 O = 2GaOOH + 3H 2
Ga slowly reacts with mineral acids with the evolution of hydrogen: 2Ga + 6HCl = 2GaCl 3 + 3H 2
At the same time, gallium dissolves slowly in sulfuric and hydrochloric acids, quickly in hydrofluoric acids, and gallium is stable in nitric acid in the cold.
In hot solutions of alkalis, gallium slowly dissolves. 2Ga + 6H 2 O + 2NaOH = 2Na + 3H 2

The most important connections:

Gallium oxide, Ga 2 O 3 - white or yellow powder, m.p. 1795 ° C. It is obtained by heating metallic gallium in air at 260 ° C or in an oxygen atmosphere, or by calcining gallium nitrate or sulfate. There are two modifications. Reacts slowly with acids and alkalis in solution, exhibiting amphoteric properties:
Gallium hydroxide, Ga (OH) 3 - precipitates as a jelly-like precipitate during the treatment of solutions of trivalent gallium salts with alkali metal hydroxides and carbonates (pH 9.7). Can be obtained by hydrolysis of trivalent gallium salts.
Shows amphoteric, with some predominance of acidic, properties, when dissolved in alkalis forms gallats(for example Na). It dissolves in concentrated ammonia and a concentrated solution of ammonium carbonate, precipitates upon boiling. By heating, gallium hydroxide can be converted to GaOOH, then to Ga 2 O 3 * H 2 O, and finally to Ga 2 O 3.
Gallium salts... GaCl 3 - colorless hygroscopic crystals. tp 78 ° C, tboil 215 ° C Ga 2 (SO 4) 3 * 18H 2 O - a colorless substance, readily soluble in water, forms double salts such as alum. Ga (NO 3) 3 * 8H 2 O - colorless crystals soluble in water and ethanol
Gallium sulphide, Ga 2 S 3 - yellow crystals or white amorphous powder with m.p. 1250 ° C, decomposes with water.
Gallium hydrides is obtained from organo-gallium compounds. They are similar to boron and aluminum hydrides: Ga 2 H 6 - digallan, a volatile liquid, melting point - 21.4 ° C, boiling point 139 ° C. x is polygallan, a white solid. Hydrides are unstable, decompose with the release of hydrogen.
Lithium galanate, Li is obtained in ether solution by the reaction 4LiH + GaCl 3 = Li + 3LiCl
Colorless crystals, unstable, hydrolyzed by water with the evolution of hydrogen.

Application:

Gallium can be used to make highly reflective optical mirrors.
Gallium is an excellent lubricant. On the basis of gallium and nickel, gallium and scandium, practically very important metal adhesives have been created.
Gallium arsenide GaAs, as well as GaP, GaSb with semiconducting properties are promising materials for semiconductor electronics. They can be used in high-temperature rectifiers and transistors, solar batteries and infrared receivers.
Gallium oxide is a component of important laser materials of the garnet group - GSGG, YAG, ISGG, etc.
Gallium is expensive, in 2005 on the world market a ton of gallium cost 1.2 million US dollars, and due to the high price and at the same time with a great demand for this metal, it is very important to establish its complete extraction in aluminum production and processing of coal at liquid fuel.

Alexey Ivanov
KhF Tyumen State University, group 561.