Application of gallium. Is gallium a metal or a non-metal? How to obtain gallium

Gallium

GALLIUM-I; m.[from lat. Gallia - France] Chemical element (Ga), a soft, fusible silvery metal white(used in semiconductor production).

Gallium

(lat. Gallium), chemical element Group III periodic table. The name from Gallia is the Latin name for France. Silver-white fusible ( t pl 29.77ºC) metal; density (g/cm 3) of solid metal 5.904, liquid 6.095; t kip 2205ºC. Chemically resistant in air. Disseminated in nature, found together with Al. They are mainly used (97%) in the production of semiconductor materials (GaAs, GaSb, GaP, GaN).

GALLIUM

GALLIUM (lat. Gallium, from Gallia - the Latin name of 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%). Outer electron layer 4 configuration s 2 p 1 . Oxidation state +3, +1 (valency I, III).
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. Electronegativity according to Pauling (cm. PAULING Linus) 1,6.
History of discovery
For the first time the existence of this element was predicted by D. I. Mendeleev (cm. MENDELEEV Dmitry Ivanovich) in 1871 on the basis of the periodic law he discovered. He called it ekaaluminum. In 1875 P. E. Lecoq de Boisbaudran (cm. LECOQ DE BOISBAUDRAN (Paul Emile) isolated gallium from zinc ores.
De Boisbaudran determined the density of gallium to be 4.7 g/cm3, which did not correspond to the value predicted by D.I. Mendeleev of 5.9 g/cm3. The refined value of gallium density (5.904 g/cm3) coincided with Mendeleev’s prediction.
Being in nature
Contents in earth's crust 1.8·10–3% by mass. Gallium is a trace element. It occurs in nature in the form of very rare minerals: zengeite Ga(OH) 3, gallite CuGaS 2 and others. Is a satellite of aluminum (cm. ALUMINUM), zinc (cm. ZINC (chemical element)), Germany (cm. GERMANIUM), gland (cm. IRON); found in sphalerites (cm. SPHALERITE), nepheline (cm. NEPHELIN), natrolite, bauxite, (cm. BOXITE) germanite, in coals and iron ores of some deposits.
Receipt
The main source of gallium is aluminate solutions obtained during the processing of alumina. After removing 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. Molten Ga can be in a liquid state at a temperature below the melting point (29.75 °C). The boiling point is 2200 °C, this is explained by the fact that in liquid gallium there is a dense packing of atoms with a coordination number of 12. To destroy it, a lot of energy must be spent.
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 series before hydrogen (cm. HYDROGEN).
By chemical properties gallium is similar to aluminum.
In air, Ga is 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 –. The BH 4 ion is stable in aqueous solution, AlH 4 and GaH 4 are quickly 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
Ga reacts slowly with mineral acids, releasing hydrogen:
2Ga + 6HCl = 2GaCl3 + 3H2
Gallium dissolves in alkalis to form hydroxogallates:
2Ga + 6H 2 O + 2NaOH = 2Na + 3H 2
Gallium oxide and hydroxide exhibit amphoteric properties, although their basic properties are enhanced compared to 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 alkalized, gallium hydroxide of variable composition Ge 2 O 3 is released x H2O:
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 isolated 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 industrially produced gallium is used to produce compounds with semiconductor properties, for example, gallium arsenide GaAs. Gallium metal is used in radio electronics for “cold soldering” of ceramic and metal parts, for doping Ge and Si, and producing optical mirrors. Ga can replace Hg in rectifiers electric current. A eutectic alloy of gallium and 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 polyethylene bags, which are poorly wetted by liquid gallium.

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Metal, a simple body, the existence of which was foreseen by Mendeleev and which was discovered by Lecoq de Boubaudran. Dictionary of foreign words included in the Russian language. Chudinov A.N., 1910. GALLIUM is an indecomposable mineral, blue-white in color; solid,… … Dictionary of foreign words of the Russian language

- (Gallium), Ga, chemical element of group III 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), chemical. element of group III periodic. Mendeleev system, at. n. 31, at. m. 69.73. It 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. names of France, where it was discovered in 1875 by the chemist Lecoq de Boisbaudran. ES. Chemical element, soft, fusible, silvery-white metal; used instead of mercury for the manufacture of pressure gauges and high-temperature... ... Historical Dictionary of Gallicisms of the Russian Language

Gallium- (Gallium), Ga, chemical element of group III 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

Gamlium is an element of the main subgroup of the third group of the fourth period of the periodic system of chemical elements of D.I. Mendeleev, with atomic number 31. Denoted by the symbol Ga (lat. Gallium). Belongs to the group of light metals. The simple substance gallium (CAS number: 7440-55-3) is a soft ductile metal of silver-white (according to other sources, light gray) color with a bluish tint.

Gallium was soon discovered and isolated as simple substance and studied by the French chemist Paul Emile Lecoq de Boisbaudran. In 1875, Lecoq de Boisbaudran examined the spectrum of zinc blende brought from Pierrefitte (Pyrenees). In this spectrum he discovered a new violet line, indicating the presence of an unknown element in the mineral. Isolation of the element was fraught with considerable difficulties, since the content of the new element in the ore was less than 0.1%. As a result, Lecoq de Boisbaudran managed to obtain a new element in an amount of less than 0.1 g and study it. The properties of the new element turned out to be similar to zinc.

On September 20, 1875, at a meeting of the Paris Academy of Sciences, a letter from Lecoq de Boisbaudran was read about the discovery of a new element and the study of its properties. The news about the name of the element in honor of France caused great delight. Mendeleev, having learned about the discovery from a published report, discovered that the description of the new element almost exactly coincides with the description of eka-aluminum he had previously predicted. He sent a letter about this to Lecoq de Boisbaudran, indicating that the density of the new metal was determined incorrectly and should be 5.9-6.0, and not 4.7 g/cm3. A thorough check showed that Mendeleev was right, and Lecoq de Boisbaudran himself wrote about this:

I think... there is no need to point out the exceptional importance that the density of the new element has in relation to confirming the theoretical views of Mendeleev

The discovery of gallium and the subsequent discoveries of germanium and scandium strengthened the position periodic law, clearly demonstrating its prognostic potential. Mendeleev called Lecoq de Boisbaudran one of the “ strengtheners of the periodic law».

Origin of name. Paul Emile Lecoq de Boisbaudran named the element in honor of his homeland France, after its Latin name - Gaul ( Gallia).

There is an undocumented legend that in the name of the element its discoverer implicitly immortalized his last name ( Lecoq). Latin name of the element ( Gallium) consonant gallus --"rooster" (lat.). It is noteworthy that it is the rooster le coq(French) is a symbol of France

Being in nature. The average gallium content in the earth's crust is 19 g/t. Gallium is a typical trace element with a dual geochemical nature. Due to the similarity 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 clarke value. 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%), hecmanite (0.01 -- 0.07%), natrolite (0 -- 0.1%). The concentration of gallium in sea water is 3·10 ?5 mg/l. Place of Birth

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

Receipt. The most powerful potential source of gallium is alumina production solutions during the processing of bauxite and nepheline. The concentration of gallium in the alkaline aluminate solution after decomposition in the Bayer process: 100--150 mg/l, by sintering method: 50--65 mg/l. By these methods, gallium is separated from most of the aluminum by carbonization, concentrating in the last fraction of the sediment. Then the enriched sediment is treated with lime, gallium goes into solution, from where the rough metal is released by electrolysis. Gallium can be obtained by processing polymetallic ores and coal. Contaminated gallium is washed with water, then filtered through porous plates and heated in a vacuum to remove volatile impurities. To obtain gallium of high purity, chemical (reactions between salts), electrochemical (electrolysis of solutions) and physical (decomposition) methods are used.

Physical properties. Crystalline gallium has several polymorphic modifications, but only one (I) is thermodynamically stable, having an orthorhombic (pseudo-tetragonal) lattice with parameters a = 4.5186 A, b = 7.6570 A, c = 4.5256 A. Other modifications of gallium (c, d, e, f) 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 T=20 °C is 5.904 g/cm?, liquid gallium at T=29.8 °C has a density of 6.095 g/cm?, that is, when solidifying, the volume of gallium increases. The melting point of gallium is slightly higher than room temperature and is equal to Melt.=29.8 °C, gallium boils at Boil.=2230 °C.

One of the features of gallium is the wide temperature range of existence of the 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 electrical resistivity in the solid and liquid states is equal to, 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. Surface tension measured at 30 °C in a hydrogen atmosphere is 0.735 n/m. The reflection coefficients for wavelengths 4360 A and 5890 A 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 for thermal neutron capture for them is 2.1·10?28 m? and 5.1·10?28 m?, respectively.

Chemical properties. The chemical properties of gallium are close to those of aluminum. The oxide film formed on the surface of the metal in air protects gallium from further oxidation.

Gallium reacts with hot water:

When reacting with superheated steam (350 °C), the compound GaOOH (gallium oxide hydrate or metagallic acid) is formed:

Gallium reacts with mineral acids to release hydrogen and form salts:

The reaction products with alkalis and potassium and sodium carbonates are hydroxogallates containing Ga(OH) ions 4 ? and Ga(OH) 6 3?

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. Thus, 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 inobium are resistant up to 400–450 °C.

With most metals, gallium forms gallides, with the exception of bismuth, as well as metals of the subgroups of zinc, scandium, and titanium. One of the Gallides V3Ga has a fairly high transition temperature to the superconducting state of 16.8 K.

Gallium forms hydride gallates:

The stability of ions decreases in the series BH4 ? > AlH4 ? > GaH4? . And he BH4? stable in aqueous solution, AlH4? And GaH4? hydrolyze quickly:

When Ga(OH) 3 is dissolved and Ga2O3 3+ aqua complexes are formed in acids; therefore, gallium salts are isolated from aqueous solutions in the form of crystalline hydrates, for example, gallium chloride GaCl3*6H2O, gallium potassium alum KGa( SO4)2 *12H2O. Gallium aqua complexes in solutions are colorless.

Basic connections. Ga2H6 -- volatile liquid, tpl?21.4 °C, tboil 139 °C. In ether suspension with lithium or thallium hydride it forms compounds LiGaH4 And TlGaH4. Formed by treating tetramethyldigallane with triethylamine. There are banana bonds, as in diborane

Ga 2 O3 -- white or yellow powder, tpl 1795 °C. Exists in the form of two modifications. b-Ga2O3 -- colorless trigonal crystals with a density of 6.48 g/cm?, slightly soluble in water, soluble in acids. V-Ga2O3 -- colorless monoclinic crystals with a density of 5.88 g/cm?, slightly soluble in water, acids and alkalis. It is obtained by heating gallium metal in air at 260 °C or in an oxygen atmosphere, or by calcining gallium nitrate or sulfate. DH° 298(rev)?1089.10 kJ/mol; ДG° 298(rev)?998.24 kJ/mol; S° 298 84.98 J/mol·K.

Application. Gallium arsenide GaAs is a promising material for semiconductor electronics.

Gallium nitride is used in the creation of semiconductor lasers and LEDs in the blue and ultraviolet range. Gallium nitride has excellent chemical and mechanical properties typical of all nitride compounds.

The gallium-71 isotope is the most important material for detecting neutrinos, and in this regard, technology faces a very urgent task of isolating this isotope from a natural mixture in order to increase the sensitivity of neutrino detectors. Since the content of 71 Ga in a 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.

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 the great need for this metal, it is very important to establish its complete extraction in aluminum production and processing of coal in 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 decrease in strength, Rehbinder effect). This property of gallium was most clearly demonstrated and studied in detail by P. A. Rebinder and E. D. Shchukin during the contact of aluminum with gallium or its eutectic alloys (liquid metal embrittlement). As a coolant, gallium is ineffective and often simply unacceptable.

Gallium is an excellent lubricant. Metal adhesives that are very important in practical terms have been created based on gallium and nickel, gallium and scandium.

Gallium metal is also used to fill quartz thermometers (instead of mercury) to measure high temperatures. This is due to the fact that gallium has a significantly higher boiling point compared to mercury.

Gallium oxide is part of a number of strategically important laser materials of the garnet group - GSGG, YAG, ISGG, etc.

Biological role and handling features. Does not play biological role. Contact of the skin with gallium leads to the fact that ultra-small dispersed particles of the metal remain on it. Outwardly it looks like a gray spot.

Clinical picture of acute poisoning: short-term excitement, then lethargy, impaired coordination of movements, adynamia, areflexia, slow 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/m? causes kidney damage in humans, as does intravenous administration of 10-25 mg/kg of gallium salts. Proteinuria, azotemia, and impaired urea clearance are noted.

Due to the low melting point, gallium ingots are recommended to be transported in polyethylene bags, which are poorly wetted by liquid gallium.

Gallium is an element of the main subgroup of the third group of the fourth period of the periodic system of chemical elements of D.I. 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 (CAS number: 7440-55-3) is a soft ductile metal of silver-white (according to other sources, light gray) color with a bluish tint.

Story

The existence of gallium was scientifically predicted by D.I. Mendeleev. When creating the periodic system of chemical elements in 1869, based on the Periodic Law he discovered, he left vacant places in the third group for unknown elements - analogues of aluminum and silicon (eka-aluminum and eca-silicon). Mendeleev, based on the properties of neighboring, well-studied elements, quite accurately described not only the most important physical and chemical properties, but also the discovery method - spectroscopy. In particular, in an article in the Journal of the Russian Chemical Society in 1871, Mendeleev indicated that the atomic weight of eka-aluminum is close to 68, the specific gravity is about 6 g/cm3. In the metallic state, the metal will be fusible.
Gallium was soon discovered, isolated as a simple substance and studied by the French chemist Paul Emile Lecoq de Boisbaudran. In 1875, Lecoq de Boisbaudran examined the spectrum of zinc blende brought from Pierrefitte (Pyrenees). In this spectrum he discovered a new violet line, indicating the presence of an unknown element in the mineral. Isolation of the element was fraught with considerable difficulties, since the content of the new element in the ore was less than 0.1%. As a result, Lecoq de Boisbaudran managed to obtain a new element in an amount of less than 0.1 g and study it. The properties of the new element turned out to be similar to zinc.
On September 20, 1875, at a meeting of the Paris Academy of Sciences, a letter from Lecoq de Boisbaudran was read about the discovery of a new element and the study of its properties. The news about the name of the element in honor of France caused great delight. Mendeleev, having learned about the discovery from a published report, discovered that the description of the new element almost exactly coincides with the description of eka-aluminum he had previously predicted. He sent a letter about this to Lecoq de Boisbaudran, indicating that the density of the new metal was determined incorrectly and should be 5.9-6.0, and not 4.7 g/cm3. A thorough check showed that Mendeleev was right, and Lecoq de Boisbaudran himself wrote about this: “I think ... there is no need to point out the exceptional importance that the density of the new element has in relation to the confirmation of Mendeleev’s theoretical views.”
The discovery of gallium and the subsequent discoveries of germanium and scandium strengthened the position of the Periodic Law, clearly demonstrating its predictive potential. Mendeleev called Lecoq de Boisbaudran one of the “strengtheners of the periodic law.”

origin of name

Paul Emile Lecoq de Boisbaudran named the element in honor of his homeland France, after its Latin name - Gallia.
There is an undocumented legend that in the name of the element its discoverer implicitly immortalized his last name (Lecoq). The Latin name of the element (Gallium) is consonant with gallus - “rooster” (Latin). It is noteworthy that the rooster le coq) (French) is a symbol of France.

Receipt

The most powerful potential source of gallium is alumina production solutions during the processing of bauxite and nepheline. Gallium concentration in alkaline aluminate solution after decomposition in the Bayer process: 100-150 mg/l, by sintering method: 50-65 mg/l. By these methods, gallium is separated from most of the aluminum by carbonization, concentrating in the last fraction of the sediment. Then the enriched sediment is treated with lime, gallium goes into solution, from where the rough metal is released by electrolysis. Gallium can be obtained by processing polymetallic ores and coal. Contaminated gallium is washed with water, then filtered through porous plates and heated in a vacuum to remove volatile impurities. To obtain gallium of high purity, chemical (reactions between salts), electrochemical (electrolysis of solutions) and physical (decomposition) methods are used.

Gallium(lat. gallium), ga, chemical element of group III of the periodic system of D. I. Mendeleev, serial number 31, atomic mass 69.72; silvery-white soft metal. Consists of two stable isotopes with mass numbers 69 (60.5%) and 71 (39.5%).

The existence of aluminum (“eka-aluminum”) and its basic 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. Lecoq de Boisbaudran; named after France (lat. gallia). The exact coincidence of the properties of geology with those predicted was the first triumph of the periodic system.

The average content of hydrogen in the earth's crust is relatively high, 1.5–10–30% by weight, which is equal to the content of lead and molybdenum. G. is a typical scattered element. The only mineral of G. - galdite cugas 2 is very rare. Geochemistry of geology is closely related to geochemistry aluminum, which is due to the similarity of their physicochemical properties. The main part of gold in the lithosphere is contained in aluminum minerals. The G. content in bauxites and nephelines ranges from 0.002 to 0.01%. Increased concentrations of germanium are also observed in sphalerites (0.01-0.02%), in hard coals (together with germanium), and also in some iron ores.

Physical and chemical properties. G. has a rhombic (pseudo-tetragonal) lattice with the parameters A= 4.5197A, b= 7.6601a, c = 4.5257A. Density. ( g/cm 3) solid metal 5.904 (20°C), liquid metal 6.095 (29.8°C), that is, during solidification, the volume of the gas increases; t pl 29.8°C, t kip 2230°C. A distinctive feature of hydrocarbons is the wide range of the liquid state (2200°C) and low vapor pressure at temperatures up to 1100-1200°C. Specific heat capacity of solid G. 376.7 j/(kg K) , i.e. 0.09 cal/(g hail) in the range 0-24°C, liquid, respectively 410 j /(kg K.), that is 0.098 cal/(g hail) in the range of 29-100°C. Electrical resistivity ( ohm cm) solid G. 53.4-10 -6 (0°C), liquid 27.2·10 -6 (30°C). Viscosity ( poise = 0,1 n sec/m 2) : 1.612(98°С), 0.578 (1100°С), surface tension 0.735 n/m (735 dyn/cm) (30 °C in h2 atmosphere). The reflection coefficients for wavelengths 4360A and 5890A are 75.6% and 71.3%, respectively. Thermal neutron capture cross section 2.71 barn (2.7 10 -28 m 2) .

In air at ordinary temperatures, G. is stable. Above 260° C, slow oxidation is observed in dry oxygen (the oxide film protects the metal). In sulfur and hydrochloric acids G. dissolves slowly, in hydrofluoric acid - quickly, in nitric acid in the cold G. is stable. G. dissolves slowly in hot alkali solutions. Chlorine and bromine react with hydrogen in the cold, and with oxygen when heated. Molten gas at temperatures above 300° C interacts with all structural metals and alloys.

The most stable are trivalent aluminum compounds, which in many respects are similar in properties to chemical compounds of aluminum. In addition, mono- and divalent compounds are known. Higher oxide g a 2 o 3 - white substance, insoluble in water. The corresponding hydroxide precipitates from solutions of hydrochloric acid salts in the form of a white gelatinous precipitate. It has a pronounced amphoteric character. When dissolved in alkalis, gallates are formed (for example, na); when dissolved in acids, gallates are formed: ga 2 (s0 4) 3, gacl 3, etc. Acid properties in G. hydroxide are more pronounced than in aluminum hydroxide [the release range of A1(OH) 3 lies within the range of ph = 10.6-4.1, and ca(oh) 3 within the range of ph = 9.7-3.4] .

Unlike a1(oh) 3, G. hydroxide dissolves not only in strong alkalis, but also in ammonia solutions. When boiling, hydroxide G again precipitates from the ammonia solution.

From salts G. highest value have chloride gac1 3 ( t pl 78°C, t kip 200°C) and sulfate ga 2 (so 4) 3. Last one with sulfates alkali metals and ammonium forms double salts like alum, for example (nh 4) ga(so 4) 2 -12h 2 o.G. forms ferrocyanide ga 4 3, which is slightly soluble in water and dilute acids, which can be used to separate it from al and a number of other elements.

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

In the soda-lime method of processing bauxite or nepheline ore, hydrogen is concentrated in the last fractions of sediment released during carbonization. For additional enrichment, the hydroxide precipitate is treated with lime milk. In this case, most of the a1 remains in the sediment, and the gallium passes into solution, from which gallium concentrate (6-8% ga 2 o 3) is isolated by passing co 2; the latter is dissolved in alkali and gas is isolated electrolytically.

The source of gas can also be the residual anodic alloy of the a1 refining process using the three-layer electrolysis method. In the production of zinc, the sources of zinc are sublimations (Welz oxides), formed during the processing of zinc cinder leaching tailings.

Liquid gas obtained by electrolysis of an alkaline solution, washed with water and acids (hc1, hno3), contains 99.9-99.95% ga. A purer metal is obtained by vacuum melting, zone melting, or by drawing a single crystal from the melt.

G. does not yet have widespread industrial use. The potential scale of by-product production of hydrocarbons in aluminum production still significantly exceeds the demand for the metal. The most promising use of G. is in the form chemical compounds such as gaas, gap, gasb, which have semiconductor properties. They can be used in high-temperature rectifiers and transistors, solar batteries and other devices where the photoelectric effect in the blocking layer can be used, as well as in infrared radiation receivers. G. can be used for the manufacture of optical mirrors characterized by high reflectivity. An alloy of aluminum and hydroxide has been proposed instead of mercury as the cathode of ultraviolet radiation lamps used in medicine. It is proposed to use liquid gas and its alloys for the manufacture of high-temperature thermometers (600-1300° C) and pressure gauges. Of interest is the use of gas and its alloys as a liquid coolant in power nuclear reactors (this is hampered by the active interaction of gas at operating temperatures with structural materials; the eutectic ga-zn-sn alloy has a less corrosive effect than pure gas).

Lit.: Sheka I. A., Chaus I. S., Mityureva T. T., Galliy, K., 1963; Eremin N.I., Galliy, M., 1964; Elikman A.N., Krein O.E., Samsonov G.V., Metallurgy of rare metals, 2nd ed., M., 1964; einecke E., das gallium, lpz., .

A. N. Zelikman.

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The chemical element galium is practically never found in nature in free form. It exists in mineral impurities, from which it is quite difficult to separate. Gallium is considered a rare substance; some of its properties have not been fully studied. However, it is used in medicine and electronics. What is this element? What properties does it have?

Is gallium a metal or a non-metal?

The element belongs to the thirteenth group of the fourth period. It is named after the historical region of Gaul, of which France, the homeland of the discoverer of the element, was a part. The symbol Ga is used to designate it.

Galium is included in the group of light metals along with aluminum, indium, germanium, tin, antimony and other elements. As a simple substance, it is brittle and soft, and has a silvery-white color with a slight bluish tint.

History of discovery

Mendeleev “predicted” gallium, leaving a place for it in the third group of the periodic table (according to the outdated system). He approximately named its atomic mass and even predicted that the element would be discovered spectroscopically.

A few years later, the metal was discovered by the Frenchman Paul Emile Lecoq. In August 1875, a scientist was studying a spectrum from a deposit in the Pyrenees and noticed new violet lines. The element was named galium. Its content in the mineral was extremely small and Lecoq managed to isolate only 0.1 grams. The discovery of the metal was one of the confirmations of the correctness of Mendeleev's prediction.

Physical properties

Gallium metal is very ductile and fusible. At low temperatures it remains in a solid state. To turn it into liquid, a temperature of 29.76 degrees Celsius or 302.93 Calvin is sufficient. You can melt it by holding it in your hand or dipping it into a hot liquid. Too high temperatures make it very aggressive: at 500 degrees Celsius and above, it is capable of corroding other metals.

The crystal lattice of galium is formed by diatomic molecules. They are very stable, but weakly connected to each other. To break their connection, it is necessary not at all a large number of energy, so gallium easily becomes liquid. It is five times more fusible than indium.

In the liquid state, the metal is denser and heavier than in the solid state. In addition, it conducts electricity better. Under normal conditions, its density is 5.91 g/cm³. Metal boils at -2230 degrees Celsius. When hardened, it expands approximately 3.2%.

Chemical properties

In many chemical properties, gallium is similar to aluminum, but is less active and reactions with it are slower. It does not react with air, instantly forming an oxide film that prevents its oxidation. It does not react to hydrogen, boron, silicon, nitrogen and carbon.

The metal interacts well with almost any halogens. It reacts with iodine only when heated; it reacts with chlorine and bromine even at room temperature. In hot water it begins to displace hydrogen, forms salts with mineral acids and also releases hydrogen.

Galium can form amalgams with other metals. If liquid gallium is dropped onto a solid piece of aluminum, it will begin to penetrate into it. Invading the crystal lattice of aluminum, liquid substance will make it fragile. After just a few days, a solid metal block can be crushed by hand without much effort.

Application

In medicine, galium metal is used to combat tumors and hypercalcemia, and is also suitable for radioisotope diagnostics of bone cancer. However, medications containing the substance may cause side effects such as nausea and vomiting.

Gallium metal is also used in microwave electronics. It is used for the manufacture of semiconductors and LEDs, as a piezomaterial. Metal adhesives are obtained from an alloy of gallium with scandium or nickel. When alloyed with plutonium, it plays the role of a stabilizer and is used in nuclear bombs.

Glasses with this metal have a high refractive index of rays, and its oxide Ga 2 O 3 allows the glass to transmit infrared rays. Pure gallium can be used to make simple mirrors because it reflects light well.

Galium abundance and deposits

Where can I get gallium? Metal can be easily ordered online. Its cost ranges from 115 to 360 dollars per kilogram. The metal is considered rare, it is very dispersed in the earth's crust and practically does not form its own minerals. Since 1956, all three have been found.

Gallium is often found in zinc and iron. Its impurities are found in coal, beryl, garnet, magnetite, tourmaline, feldspar, chlorites and other minerals. On average, its content in nature is about 19 g/t.

Most galium is found in substances that are close to it in composition. Because of this, it is difficult and expensive to extract it from them. The metal's own mineral is called gallite with the formula CuGaS 2 . It also contains copper and sulfur.

Impact on humans

Little is known about the biological role of the metal and its effects on the human body. In the periodic table it is located next to the elements that are vital for us (aluminum, iron, zinc, chromium). There is an opinion that gallium, as an ultramicroelement, is part of the blood, accelerating its flow and preventing the formation of blood clots.

One way or another, a small amount of the substance is contained in the human body (10 -6 - 10 -5%). Galium enters it along with water and agricultural food products. It is retained in bone tissue and liver.

Gallium metal is considered low-toxic or conditionally toxic. Upon contact with skin, small particles remain on it. It looks like a gray dirty stain that can be easily removed with water. The substance does not leave burns, but in some cases it can cause dermatitis. It is known that high levels of galium in the body cause disorders in the liver, kidneys and nervous system, but this requires a very large amount of metal.