Atomic mass of gallium. Gallium is a metal that melts in your hands

About the element with atomic number 31, most readers only remember that it is one of the three elements predicted and described in most detail by D.I. Mendeleev, and that gallium is a very fusible metal: the heat of the palm is enough to turn it into liquid.

However, gallium is not the most fusible of metals (even if you don’t count mercury). Its melting point is 29.75°C, and cesium melts at 28.5°C; only cesium, like any alkali metal, cannot be taken into your hands, so it is naturally easier to melt gallium in the palm of your hand than cesium.

We deliberately began our story about element No. 31 by mentioning something that is known to almost everyone. Because this “known” requires explanation. Everyone knows that gallium was predicted by Mendeleev and discovered by Lecoq de Boisbaudran, but not everyone knows how the discovery happened. Almost everyone knows that gallium is fusible, but almost no one can answer the question why it is fusible.

How was gallium discovered?

French chemist Paul Emile 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 and was primarily 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 spectral analysis.

In 1875, Lecoq de Boisbaudran examined the spectrum of zinc blende brought from Pierrefitte (Pyrenees). A new violet line (wavelength 4170 Ǻ) was discovered in this spectrum. 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 turned out to be difficult 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 obtain a new element, but in a very small quantity. So small (less than 0.1 g) that Lecoq de Boisbaudrap was not able to fully study its physical and chemical properties.

How gallium is obtained from zinc blende is described below.

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

This message was read by D.I. Mendeleev and recognized in gallium eka-aluminium, which he had predicted five years earlier. Mendeleev immediately wrote to Paris. “The method of discovery and isolation, as well as the few properties described, lead us to believe that the new metal is none other than eka-aluminium,” his letter said. He then repeated the properties predicted for that element. Moreover, without ever holding grains of gallium in his hands, without seeing it in person, the Russian chemist argued that the discoverer of the element was mistaken, that the density of the new metal cannot be equal to 4.7, as Lecoq de Boisbaudran wrote, - it must be greater, approximately 5.9...6.0 g/cm 3!

Oddly enough, but about the existence periodic law the first of it is affirmative, “strengthening,” I learned only from this letter. He once again isolated and carefully purified grains of gallium to check the results of the first experiments. Some historians of science believe that this was done with the aim of disgracing the self-confident Russian “predictor”. But experience showed the opposite: the discoverer was mistaken. He later wrote: “There is no need, I think, to point out the exceptional importance that the density of a new element has in relation to the confirmation of Mendeleev’s theoretical views.”

Other properties of element No. 31 predicted by Mendeleev coincided almost exactly with the experimental data. “Mendeleev’s predictions came true with minor deviations: eka-aluminum turned into gallium.” This is how Engels characterizes this event in “Dialectics of Nature.”

Needless to say, the discovery of the first of the elements predicted by Mendeleev significantly strengthened the position of the periodic law.

Why is gallium fusible?

Predicting the properties of gallium, Mendeleev believed that this metal should be fusible, since its analogues in the group - aluminum and indium - are also not refractory.

But the melting point of gallium is unusually low, five times lower than that of indium. This is explained by the unusual structure of gallium crystals. Its crystal lattice is formed not by individual atoms (as in “normal” metals), but by diatomic molecules. Ga 2 molecules are very stable; they are preserved even when gallium is transferred to a liquid state. But these molecules are connected to each other only by weak van der Waals forces, and very little energy is needed to destroy their bond.

Some other properties of element No. 31 are associated with the diatomicity of molecules. In the liquid state, gallium is denser and heavier than in the solid state. The electrical conductivity of liquid gallium is also greater than that of solid gallium.

What does gallium look like?

Externally, it looks more like tin: a silvery-white soft metal; it does not oxidize or tarnish in air.

And in most chemical properties, gallium is close to aluminum. Like aluminum, the gallium atom has three electrons in its outer orbit. Like aluminum, gallium easily, even in the cold, reacts with halogens (except iodine). Both metals are easily dissolved in sulfuric and hydrochloric acids, and both react with alkalis and give amphoteric hydroxides. Reaction dissociation constants

Ga(OH) 3 → Ga 3+ + 3OH –

H 3 GaO 3 → 3H + + GaO 3– 3

– quantities of the same order.

There are, however, differences in chemical properties gallium and aluminum.

Gallium is noticeably oxidized by dry oxygen only at temperatures above 260°C, and aluminum, if deprived of its protective oxide film, is oxidized by oxygen very quickly.

With hydrogen, gallium forms hydrides similar to boron hydrides. Aluminum can only dissolve hydrogen, but not react with it.

Gallium is also similar to graphite, quartz, and water.

On graphite - because it leaves a gray mark on the paper.

For quartz – electrical and thermal anisotropy.

The magnitude of the electrical resistance of gallium crystals depends on which axis the current flows along. The maximum to minimum ratio is 7, more than any other metal. The same goes for the coefficient of thermal expansion.

Its values in the direction of three crystallographic axes (gallium crystals are rhombic) are in the ratio 31:16:11.

And gallium is similar to water in that when it hardens, it expands. The volume increase is noticeable – 3.2%.

The combination of these contradictory similarities alone speaks of the unique individuality of element No. 31.

In addition, it has properties not found in any other element. Once molten, it can remain in a supercooled state for many months at a temperature below its melting point. This is the only metal that remains a liquid in a huge temperature range from 30 to 2230°C, and the volatility of its vapors is minimal. Even in a deep vacuum, it evaporates noticeably only at 1000°C. Gallium vapor, in contrast to solid and liquid metal monatomic. The Ga 2 → 2Ga transition requires large amounts of energy; This explains the difficulty of gallium evaporation.

The large temperature range of the liquid state is the basis of one of the main technical applications of element No. 31.

What is gallium good for?

Gallium thermometers can in principle measure temperatures from 30 to 2230°C. Gallium thermometers are now available for temperatures up to 1200°C.

Element No. 31 is used for the production of low-melting alloys used in signaling devices. The gallium-indium alloy melts already at 16°C. This is the most fusible of all known alloys.

As a group III element that enhances “hole” conductivity in a semiconductor, gallium (with a purity of at least 99.999%) is used as an additive to germanium and silicon.

Intermetallic compounds of gallium with group V elements - antimony and arsenic - themselves have semiconductor properties.

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 light incident on it, solid gallium reflects slightly less. Therefore, they make gallium mirrors that are very easy to manufacture - the gallium coating can even be applied with a brush.

Sometimes the ability of gallium to wet solid surfaces well is used, replacing mercury in diffusion vacuum pumps. Such pumps “hold” vacuum better than mercury pumps.

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 barns), it also reacts at elevated temperatures with most metals.

Gallium did 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 detecting the radiation characteristic of this isotope, doctors almost accurately determine the size of foreign formations.

As you can see, the practical possibilities of element No. 31 are quite wide. It has not yet been possible to use them completely due to the difficulty of obtaining gallium - a rather rare element (1.5 10 -3% of the weight of the earth's crust) and very scattered. Few native gallium minerals are known. Its first and most famous mineral, gallite CuGaS 2, was discovered only in 1956. Later, two more minerals, already very rare, were found.

Typically, gallium is found in zinc, aluminum, iron ores, as well as in coal - as a minor impurity. And what is characteristic: the larger this impurity, the more difficult it is to extract it, because there is more gallium in the ores of those metals (aluminum, zinc) that are similar to it in properties. The bulk of terrestrial gallium is contained in aluminum minerals.

Gallium(lat. Gallium), Ga, chemical element of group III periodic table 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 Gallium (“eka-aluminium”) 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 Gallium with those predicted was the first triumph of the periodic system.

Average gallium content in earth's crust relatively high, 1.5·10 -3% by weight, which is equal to the content of lead and molybdenum. Gallium is a typical trace element. Gallium's only 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 physical and chemical properties. The main part of Gallium in the lithosphere is contained in aluminum minerals. The Gallium content in bauxites and nephelines ranges from 0.002 to 0.01%. Elevated concentrations Gallium is also observed in sphalerites (0.01-0.02%), in hard coals (together with germanium), as well as in some iron ores.

Physical properties of Gallium. Gallium has an orthorhombic (pseudo-tetragonal) lattice with parameters a = 4.5197Å, b = 7.6601Å, c = 4.5257Å. Density (g/cm3) of solid metal is 5.904 (20°C), liquid metal is 6.095 (29.8°C), that is, when solidifying, the volume of Gallium increases; melting temperature 29.8°C, boiling temperature 2230°C. Distinctive feature Gallium has a large range of liquid state (2200°C) and low vapor pressure at temperatures up to 1100-1200°C. The specific heat capacity of solid Gallium is 376.7 J/(kg K), that is, 0.09 cal/(g deg) in the range of 0-24°C, of liquid gallium, respectively, 410 J/(kg K), that is, 0.098 cal /(g deg) in the range of 29-100°C. The electrical resistivity (ohm cm) of solid Gallium is 53.4·10 -6 (0°C), liquid 27.2·10 -6 (30°C). Viscosity (poise = 0.1 n sec/m2): 1.612 (98°C), 0.578 (1100°C), surface tension 0.735 n/m (735 dyne/cm) (30°C in H2 atmosphere) . The reflection coefficients for wavelengths 4360Å and 5890Å are 75.6% and 71.3%, respectively. Thermal neutron capture cross section is 2.71 barns (2.7·10 -28 m2).

Chemical properties of Gallium. Gallium is stable in air at ordinary temperatures. Above 260°C, slow oxidation is observed in dry oxygen (the oxide film protects the metal). Gallium dissolves slowly in sulfuric and hydrochloric acids, quickly in hydrofluoric acid, and is stable in the cold in nitric acid. Gallium dissolves slowly in hot alkali solutions. 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.

The most stable are trivalent compounds of Gallium, which in many respects are similar in properties to chemical compounds of aluminum. In addition, mono- and divalent compounds are known. Higher oxide Ga 2 O 3 - substance white, insoluble in water. The corresponding hydroxide precipitates from solutions of Gallium salts in the form of a white gelatinous precipitate. It has a pronounced amphoteric character. When dissolved in alkalis, gallates (for example, Na) are formed, when dissolved in acids, Gallium salts are formed: Ga 2 (SO 4) 3, GaCl 3, etc. The acidic properties of Gallium hydroxide are more pronounced than those of aluminum hydroxide [Al release range ( OH) 3 lies within the pH range = 10.6-4.1, and Ga(OH) 3 within the pH range = 9.7-3.4].

Unlike Al(OH) 3, Gallium hydroxide dissolves not only in strong alkalis, but also in ammonia solutions. When boiled, gallium hydroxide precipitates from the ammonia solution again.

From salts of Gallium highest value have GaCl 3 chloride (melt 78°C, boil 200°C) and Ga 2 (SO 4) 3 sulfate. The latter, with sulfates of alkali metals and ammonium, forms double salts of the alum type, for example (NH 4)Ga(SO 4) 2 12H 2 O. Gallium forms ferrocyanide Ga 4 3, which is poorly soluble in water and dilute acids, which can be used to separate it from Al and a number of other elements.

Obtaining Gallium. The main source of obtaining Gallium is aluminum production. When processing bauxite using the Bayer method, gallium is concentrated in circulating mother liquors after the separation of Al(OH) 3 . Gallium is isolated from such solutions by electrolysis at 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 Gallium is isolated by electrolysis.

In the soda-lime method of processing bauxite or nepheline ore, Gallium is concentrated in the last fractions of sediment released during the carbonization process. For additional enrichment, the hydroxide precipitate is treated with lime milk. In this case, most of the Al remains in the sediment, and Gallium goes 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 gallium is isolated electrolytically.

The source of Gallium can also be the residual anode alloy from the Al refining process using the three-layer electrolysis method. In the production of zinc, the sources of Gallium are sublimates (Welz oxides) formed 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 purer metal is obtained by vacuum melting, zone melting, or by drawing a single crystal from the melt.

Application of Gallium. The most promising application of Gallium 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 cells and other devices where the photoelectric effect in the blocking layer can be used, as well as in infrared radiation receivers. Gallium can be used to make optical mirrors that are highly reflective. An alloy of aluminum with gallium has been proposed instead of mercury as the cathode of ultraviolet radiation lamps used in medicine. It is proposed to use liquid gallium and its alloys for the manufacture of high-temperature thermometers (600-1300°C) and pressure gauges. Of interest is the use of Gallium and its alloys as a liquid coolant in power nuclear reactors (this is hampered by the active interaction of Gallium at operating temperatures with structural materials; the eutectic Ga-Zn-Sn alloy has a less corrosive effect than pure Gallium).

Metal GALLIUM

Gallium is an element of the main subgroup of the third group of the fourth period of the periodic table chemical elements 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.

Metal GALLIUM

Gallium: Melting point 29.76 °C

Low toxicity, you can pick it up and melt it!

Material for semiconductor electronics

Gallium arsenide GaAs

- a promising material for semiconductor electronics.

Gallium nitride

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.

Gallium-71 isotope

is the most important material for detecting neutrinos and in connection with this, 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 71Ga 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.

Chemical properties

Gallium is expensive; in 2005, a ton of gallium cost $1.2 million on the world market, and due to the high price and at the same time great demand for this metal, it is very important to establish its complete extraction during aluminum production and processing hard coals for 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 significantly more high temperature boiling compared to mercury.

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

Gallium has not yet received widespread industrial use. Currently, the following areas of gallium use have been identified.
Thermometers for high temperature. Gallium has a low melting point (29.8°) and a high boiling point (~2200°). This allows it to be used for the manufacture of quartz thermometers for measuring high temperatures (600-1300°).
Low-melting alloys. Gallium with a number of metals (bismuth, lead, tin, cadmium, indium, thallium, etc.) forms low-melting alloys with a melting point below 60°. For example, a gallium alloy with 25% In melts at a temperature of 16°, the melting point of a gallium alloy with 8% Sn is 20°. The melting point of a eutectic alloy (82% Ga, 12% Sn and 6% Zn) is 17°.
A number of low-melting alloys containing gallium have been proposed for signaling devices (sprinkler fuses) used in firefighting, the action of which is based on the melting of the alloy when a certain temperature is exceeded, which causes automatic switching on water spray systems.
A low-melting alloy containing 60% Sn, 30% Ga and 10% In has been proposed for thermometers to replace mercury.
IN Lately attention was drawn to the possibility of using gallium and its alloys as a liquid medium for heat removal to power plants, for example, the heat released in nuclear boilers. The advantage of gallium as a thermally conductive liquid is its high boiling point, combined with high thermal conductivity. However, an obstacle to the use of gallium coolant is the interaction of gallium with most metals at high temperatures.
It has been proposed to use gallium alloys in dentistry instead of mercury amalgams. The following alloys are recommended for dental fillings; 40-80% Bi; 30-60% Sn; 0.5-0.8% Ga and 61.5% Bi; 37.2% Sn; 1.3% Ga.
Mirrors. Gallium has the ability to adhere well to glass, which makes it possible to produce gallium mirrors. The mirror can be made by squeezing gallium between two heated sheets of glass. Gallium mirrors have high
reflectivity. For a wavelength of 4.360 A, the reflectivity is 75.6%, for a wavelength of 5.890 A - 71.3%. Liquid gallium reflects 88% of the light incident on the mirror.
Other applications. It is proposed to use an aluminum alloy with gallium instead of mercury as the cathode of ultraviolet radiation lamps used in medicine. The resulting radiation is enriched with rays of the blue and red parts of the spectrum, which improves therapeutic effect radiation.
It is possible to replace gallium with mercury in mercury rectifiers. The very high boiling point of the metal makes it possible to work with significantly heavy loads than when using mercury.
It is known to use gallium salts as a component of luminous paints (to excite the fluorescent glow of compounds). Gallium salts are also used in analytical chemistry, medicine and as catalysts in organic synthesis.

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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. Denoted by the symbol Ga (lat. Gallium). Belongs to the group of light metals. The simple substance gallium is a soft, ductile metal of silvery-white color with a bluish tint.

Atomic number - 31

Atomic mass - 69.723

Density, kg/m³ - 5910

Melting point, °C - 29.8

Heat capacity, kJ/(kg °C) - 0.331

Electronegativity - 1.8

Covalent radius, Å - 1.26

1st ionization potential, eV - 6.00

History of the discovery of gallium

In 1875, Lecoq de Boisbaudran examined the spectrum of zinc blende brought from Pierrefitte (Pyrenees). A new violet line was discovered in this spectrum. 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 turned out to be difficult 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 obtain a new element, but in a very small quantity. So small (less than 0.1 g) that Lecoq de Boisbaudran was not able to fully study its physical and chemical properties.

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

Finding Gaulin 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. Gallium's only 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 main part of Gallium in the lithosphere is contained in aluminum minerals. 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%).

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 metal while holding it in your hand. Gallium is one of the few metals that expand when the melt solidifies (the others are Bi, Ge).

Crystalline gallium has several polymorphic modifications, but only one (I) is thermodynamically stable, having an orthorhombic (pseudo-tetragonal) lattice with parameters a = 4.5186 Å, b = 7.6570 Å, c = 4.5256 Å. Other modifications of gallium (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 T=20 °C is 5.904 g/cm³.

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. Specific heat 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). Viscosity of liquid gallium at different temperatures equal to 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 reflectances for wavelengths 4360 Å and 5890 Å are 75.6% and 71.3%, respectively.

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

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

At high temperatures, gallium is a very aggressive substance. 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) are highly 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. The oxide film formed on the surface of the metal in air protects gallium from further oxidation. When heated under pressure, gallium reacts with water, forming the 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 = 2GaCl3 + 3H2

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

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. Thus, graphite and tungsten are resistant to gallium melt up to 800 °C, alundum and beryllium oxide BeO - up to 1000 °C, tantalum, molybdenum and niobium 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 V 3 Ga gallides has a rather high transition temperature to the superconducting state of 16.8 K.

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 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 * 12H2O.

An interesting interaction between gallium and sulfuric acid occurs. 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 hot water, the reaction will resume and will continue until a new “skin” of sulfur grows on gallium.

Basic connections Gaul

Ga2H6- volatile liquid, melting point −21.4 °C, boiling point 139 °C. In an ethereal suspension with lithium or thallium hydrate it forms the compounds LiGaH 4 and TlGaH 4 . Formed by treating tetramethyldigallane with triethylamine. There are banana bonds, as in diborane

Ga2O3- white or yellow powder, melting point 1795 °C. Exists in the form of 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 gallium metal 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 basic properties, compared to 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 when treating solutions of trivalent gallium salts with hydroxides and carbonates of alkali metals (pH 9.7). Dissolves in concentrated ammonia and concentrated ammonium carbonate solution, and precipitates when boiled. 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 melt >1000 °C, t boil 950 °C, density - 4.47 g/cm³. Slightly soluble in water. GaF 3 ·3H 2 O crystalline hydrate is known. It is obtained by heating gallium oxide in a fluorine atmosphere.

GaCl3- colorless hygroscopic crystals. t melt 78 °C, boil t 215 °C, density - 2.47 g/cm³. Let's dissolve well in water. IN aqueous solutions hydrolyzes. Obtained directly from the elements. Used as a catalyst in organic syntheses.

GaBr 3- colorless hygroscopic crystals. t melt 122 °C, t boil 279 °C density - 3.69 g/cm³. Dissolves in water. Hydrolyzes in aqueous solutions. Slightly soluble in ammonia. Obtained directly from the elements.

GaI 3- hygroscopic light yellow needles. t melt 212 °C, t boil 346 °C, density - 4.15 g/cm³. Hydrolyzes with warm water. Obtained directly from the 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. It is obtained by reacting gallium with sulfur or hydrogen sulfide.

Ga 2 (SO 4) 3 18H 2 O- colorless, highly soluble substance in water. It is obtained by reacting gallium, its oxide and hydroxide with sulfuric acid. It easily forms alum with sulfates of alkali metals and ammonium, for example, KGa(SO 4) 2 12H 2 O.

Ga(NO 3) 3 8H 2 O- colorless crystals soluble in water and ethanol. When heated, it decomposes to form gallium(III) oxide. Obtained by action nitric acid for gallium hydroxide.

Obtaining gallium

The main source of obtaining Gallium is aluminum production. When processing bauxite using the Bayer method, gallium is concentrated in circulating mother liquors after the separation of Al(OH) 3 . Gallium is isolated from such solutions by electrolysis at 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 Gallium is isolated by electrolysis.

Applications of gallium

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.

As a group III element that enhances “hole” conductivity in a semiconductor, gallium (with a purity of at least 99.999%) is used as an additive to germanium and silicon. Intermetallic compounds of gallium with group V elements - antimony and arsenic - themselves have semiconductor properties.

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.

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.

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, but on the other hand, gallium (alloys to a lesser extent) is quite aggressive to most structural materials (cracking and erosion of alloys at high temperature), and As a coolant, it is ineffective and often simply unacceptable.

Gallium is an excellent lubricant. Almost very important metal adhesives have been created on the basis of 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 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 Canyon, Nevada, USA and in 2005 in Inner Mongolia, China - gallium is not found in industrial concentrations anywhere in the world. (In the latter 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 the mentioned deposit in China contains 958 thousand tons of gallium in coal - doubling 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 a plant in Stade (Germany), where about 33 tons per year is mined, a plant in Salindres, processing 20 tons/year (France) and in Pinjarra (Western Australia) - potential (but not introduced into construction) capacity up to 50 tons/year.

In 2006, the position of the No. 1 manufacturer weakened - the Stade enterprise was purchased 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 as a by-product of zinc production. The full capacity for primary material of Dowa Mining is estimated to be up to 20 tons/year. In Kazakhstan, the Aluminum of Kazakhstan enterprise in Pavlodar has a full capacity of up to 20 tons/year.

China has become a very serious supplier of gallium. There are 3 large producers of primary gallium 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 co-productions. Sumitomo Chemical has established joint ventures in China with a capacity of up to 40 tons/year. The American company AXT has created a joint venture Beijing JiYa semiconductor Material Co. with the largest Chinese aluminum enterprise Shanxi Aluminum Factory. with a productivity 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 owners of gallium sites created at alumina refineries.

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

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

Actual 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 from Ukraine.

When preparing the material, information from the Kvar company was used.

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