GALLIUM metal that melts in the hands.

Metal 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.

Metal GALLIUM

Gallium: Melting point 29.76 °C

low toxicity, you can pick up and melt!

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.

Isotope gallium-71

is the most important material for detecting neutrinos, and in connection with this, technology faces a very urgent task of isotope isolation from a 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 2.5 times.

Chemical properties

Gallium is expensive, in 2005 a ton of gallium cost 1.2 million US dollars on the world market, and due to the high price and at the same time the great demand for this metal, it is very important to establish its complete extraction in aluminum production and coal processing 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 temperature). For example, in relation to aluminum and its alloys, gallium is a powerful strength reducer (see adsorption strength reduction, 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

On the basis of gallium and nickel, gallium and scandium, metal adhesives that are very important in practical terms have been created.

Gallium metal is also filled into quartz thermometers (instead of mercury) to measure high temperatures. This is because gallium has a much higher boiling point than mercury.

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

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). The fusibility, as well as the low toxicity of metallic gallium, made it possible to take this photograph. By the way, gallium is one of the few metals that expand when the melt solidifies (others are Bi, Ge).

Gallodent, eutectic of gallium with tin
Gallium metal has low toxicity, at one time it was even used to make fillings (instead of amalgam fillings). This application is based on the fact that when copper powder is mixed 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. Gallium is very brittle (it can be broken like glass).

Large crystals of gallium
Another interesting feature of gallium is the ability of its melt to supercool. Molten gallium can be cooled about 10-30 degrees below its melting point, and it will remain liquid, but if you throw a piece of solid gallium or dry ice into such a melt, large crystals will instantly begin to grow from it. In the photo - a solidifying ingot of gallium. The photo clearly shows that crystallization began in three places, and at the same time three large single crystals began to grow, which then met and formed an ingot (this happened about two hours after the shooting).

gallium spoon
Homemade gallium spoon. Video with melting this spoon:

High temperature gallium thermometer Quartz gallium thermometer Gallium in thermometer
And here is another use of gallium.
Gallium is in a liquid state in a very wide temperature range, and, in theory, gallium thermometers could measure temperatures up to 2000 degrees. For the first time, the use of gallium as a thermometric liquid was proposed quite a long time ago. Gallium thermometers already measure temperatures up to 1200 degrees, but it is not often possible for an ordinary person to see these thermometers live in the laboratory.
Such thermometers are not widely used for several reasons. First, 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 because quartz (as well as most other glasses) is highly wettable by this metal. That is, gallium will simply stick to the walls of the thermometer from the inside, and it will be impossible to know the temperature. Another problem can arise when the thermometer is cooled below 28 degrees. When solidified, gallium behaves like water - it expands and can simply break the thermometer from the inside. Well, the last reason why a high-temperature gallium thermometer is now very rare is the development of technology and electronics. It is no secret that a digital thermometer is much more convenient to use than a liquid one. Modern temperature controllers, complete with, for example, platinum-platinum-rhodium thermocouples, make it possible to measure temperatures in the range from -200 to +1600°C with an accuracy unattainable for liquid thermometers. In addition, the thermocouple may be located at a considerable distance from the controller.

Gallium forms low-melting eutectic alloys with many metals, and some of them melt even at temperatures below room temperature.
An alloy of gallium and indium melts at a temperature of 15.7 ° C, that is, at room temperature it is a liquid. To prepare such an alloy, it is not even necessary to heat the metal bar to melt, it is enough just to tightly squeeze the pieces of gallium and indium. The video shows that from the point of contact of two metals (a large cylinder is gallium, a small one is indium), a eutectic alloy begins to drip.

An interesting experiment can be carried out not only with the melting, but also with the solidification of gallium. Firstly, gallium is one of the few substances that expand when solidified (just like water), and secondly, the color of the molten metal is quite different from the color of the solid.
A small amount of liquid gallium is poured into a glass vial and a small piece of solid gallium is placed on top (seed for crystallization, since gallium is able to supercool). The video clearly shows how metal crystals begin to grow (they have a bluish tint, in contrast to the silvery-white melt). After a while, the expanding gallium bursts the bubble.
The middle part of the video (growth of gallium crystals) is sped up ten times to keep the video from being too long.

Just like mercury, molten gallium can be used to make a "beating heart", however, due to the fact that gallium is a more electropositive metal than iron, it works the other way around. When the tip of the nail touches a drop of molten gallium, it "spreads" due to a decrease in surface tension. And as soon as contact with the nail is broken, the surface tension increases and the drop gathers again, until it touches the nail.

Those interested can download

Chemistry

Gallium #31

subgroup of gallium. The content of each of the members of this subgroup in the earth's crust in the series gallium (4-10~4%) - indium (2-10~6) - thallium (8-10-7) is decreasing. All three "elements are extremely dispersed, and being in the form of certain minerals is not typical for them. On the contrary, minor impurities of their compounds contain ores of many metals. Ga, In and Ti are obtained from waste during the processing of such ores.
In the free state, gallium, indium and thallium are silver-white metals. Their most important constants are compared below:
Ga InTl

Physical properties of gallium

Density, g/cjH3 5.9 7.3 11.9
Melting point, °С. . . 30 157 304
Boiling point, °С... . 2200 2020 1475
Electrical conductivity (Hg = 1) . . 2 11 6

By hardness gallium close to lead, In and Ti - even softer 6-13.
Gallium and indium do not change in dry air, and thallium is covered with a gray film of oxide. When heated, all three elements combine vigorously with oxygen and sulfur. They interact with chlorine and bromine already at ordinary temperatures, with iodine only when heated. Located in a series of voltages near iron, Ga, In and Ti are soluble in acids.14 '15
The usual valency of gallium and indium is three. Thallium gives derivatives in which it is tri- and monovalent. 18
The oxides of gallium and its analogues - white Ga 2 O 3, yellow 1p203 and brown T1203 - are insoluble in water - the corresponding hydroxides E (OH) 3 (which can be obtained from salts) are gelatinous sediments, practically insoluble in water, but soluble in acids. White hydroxides of Ga and In are also soluble in solutions of strong alkalis with the formation of gallates and indates similar to aluminates. They therefore have an amphoteric character, and the acidic properties are less pronounced in 1n(OH) 3, and stronger in Ga(OH) 3 than in Al(OH) 3 . So, in addition to strong alkalis, Ga (OH) 3 is soluble in strong solutions of NH 4 OH. On the contrary, red-brown Ti(OH) 3 does not dissolve in alkalis.
The Ga"" and In" ions are colorless, the Ti" ion has a yellowish color. The salts of most acids produced from them are highly soluble in water, but highly hydrolyzed; Of the soluble salts of weak acids, many undergo almost complete hydrolysis. While derivatives of the lower valences Ga and In are not typical for them, for thallium the most characteristic are precisely those compounds in which it is monovalent. Therefore, T13+ salts have markedly pronounced oxidizing properties.

Thallium oxide (T120) is formed as a result of the interaction of elements at high temperatures. It is a black hygroscopic powder. With water, thallium oxide forms yellow nitrous oxide (T10H), which, when heated, easily splits off water and goes back to T120.
Thallium oxide hydrate is highly soluble in water and is a strong base. The salts it forms are mostly colorless and
crystallize without water. Chloride, bromide and iodide are almost insoluble, but some other salts are soluble in water. Arbitrary TiOH and weak acids due to hydrolysis give an alkaline reaction in solution. Under the action of strong oxidizing agents (for example, chlorine water), monovalent thallium is oxidized to trivalent.57-66
In terms of the chemical properties of the elements and their compounds, the gallium subgroup is in many ways similar to the germanium subgroup. So, for Ge and Ga, the higher valence is more stable, for Pb and T1 it is lower, the chemical nature of the hydroxides in the series Ge-Sn-Pb and Ga-In-Ti changes of the same type.Sometimes more subtle "features of similarity appear further, for example, the low solubility of halide (Cl, Br, I) salts of both Pbn and Ti. For all that, there are significant differences between the elements of both subgroups (partly due to their different valence): the acidic nature of the hydroxides of Ga and its analogues is much less pronounced than that of the corresponding elements of the germanium subgroup, in contrast to PbF 2, thallium fluoride is highly soluble, etc.

Gallium Supplement

1. All three members of the subgroup under consideration were discovered using a spectroscope: 1 thallium - in 1861, indium - in 1863 and gallium - in 1875. The last of these elements was predicted and described by D. I. Mendeleev 4 years before its discovery (VI § 1). Natural gallium is composed of isotopes with mass numbers 69 (60.2%) and 71 (39.8); indium-113 (4.3) and 115 (95.7); thallium - 203 (29.5) and 205 (70.5%).
2. In the ground state, the atoms of the elements of the gallium subgroup have the structure of outer electron shells 4s2 34p (Ga), 5s25p (In), 6s26p (Tl) and are univalent, i ) kcal/g-atom. Successive ionization energies are 6.00; 20.51; 30.70 for Ga; 5.785; 18.86; 28.03 for In: 6.106; 20.42; 29.8 eV for T1. The affinity of a thallium atom for an electron is estimated at 12 kcal/g-atom.
3. For gallium, the rare mineral gallite (CuGaS 2) is known. Traces of this element are constantly found in zinc ores. Significantly large amounts of it: E (up to 1.5%) were found in the ashes of some hard coals. However, the main raw material for the industrial production of gallium is bauxite, usually containing minor impurities (up to 0.1%). It is extracted by electrolysis from alkaline liquids, which are an intermediate product of the processing of natural bauxite into commercial alumina. The size of the annual world production of gallium is still estimated at a few tons, but can be significantly increased.
4. Indium is obtained mainly as a by-product in the complex processing of sulfur ores Zn, Pb and Cu. Its annual world production is several tens of tons.
5. Thallium is concentrated mainly in pyrite (FeS2). Therefore, sulfuric acid production sludge is a good raw material for obtaining this element. The annual world production of thallium is less than that of India, but is also in the tens of tons.
6. To isolate Ga, In, and T1 in the free state, either the electrolysis of solutions of their salts or the incandescence of oxides in a hydrogen flow is used. The heats of melting and evaporation of metals have the following values: 1.3 and 61 (Ga), 0.8 and 54 (In), 1.0 and 39 kcal/g-atom (T1). The heats of their sublimation (at 25°C) are 65 (Ga), 57 (In), and 43 kcal/g-atom (T1). In pairs, all three elements are composed almost exclusively of monatomic molecules.
7. The crystal lattice of gallium is formed not by individual atoms (as is usual for metals), but by diatomic molecules (rf = 2.48A). It is thus an interesting case of the coexistence of molecular and metallic structures (III § 8). Ga2 molecules are also preserved in liquid gallium, whose density (6.1 g/cm) is greater than that of a solid metal (an analogy with water and bismuth). An increase in pressure is accompanied by a decrease in the melting point of gallium. At high pressures, in addition to the usual modification (Gal), the existence of two other forms of it has been established. Triple points (with a liquid phase) lie for Gal - Gall at 12 thousand atm and 3 °C, and for Gall - Galll ​​- at 30 thousand atm and 45 °C.
8. Gallium is very prone to hypothermia, and it was possible to keep it in a liquid state down to -40 ° C. Repeated repetition of rapid crystallization of a supercooled melt can serve as a method for purifying gallium. In a very pure state (99.999%), it was also obtained by electrolytic refining, as well as by hydrogen reduction of carefully purified GaCl3. The high boiling point and fairly uniform expansion on heating make gallium a valuable material for filling high-temperature thermometers. Despite its outward resemblance to mercury, the mutual solubility of both metals is relatively low (in the range from 10 to 95 °C, it varies from 2.4 to 6.1 atomic percent for Ga in Hg and from 1.3 to 3.8 atomic percent for Hg to Ga). Unlike mercury, liquid gallium does not dissolve alkali metals and well wets many non-metallic surfaces. In particular, this applies to glass, on which gallium can be applied to mirrors that strongly reflect light (however, there is an indication that very pure gallium, which does not contain indium impurities, does not wet glass). The deposition of gallium on a plastic base is sometimes used to quickly obtain radio circuits. An alloy of 88% Ga and 12% Sn melts at 15°C, and several other alloys containing gallium (eg 61.5% Bi, 37.2% Sn and 1.3% Ga) have been proposed for dental fillings. They do not change their volume with temperature and hold well. Gallium can also be used as a valve seal in vacuum technology. However, it should be borne in mind that at high temperatures it is aggressive towards both glass and many metals.
9. In connection with the possibility of expanding the production of gallium, the problem of assimilation (i.e., mastering by practice) of this element and its compounds becomes relevant, which requires research to find areas for their rational use. There is a review article and monographs on gallium.
10. The compressibility of indium is slightly higher than that of aluminum (at 10 thousand atm, the volume is 0.84 of the original). With increasing pressure, its electrical resistance decreases (up to 0.5 of the initial value at 70,000 atm) and the melting point increases (up to 400°C at 65,000 atm). Sticks of metallic indium crunch when bent, like pewter. On paper, it leaves a dark line. An important use of indium is associated with the manufacture of germanium AC rectifiers (X § 6 add. 15). Due to its fusibility, it can play the role of a lubricant in bearings.
11. The introduction of a small amount of indium into copper alloys greatly increases their resistance to sea water, and the addition of indium to silver enhances its brilliance and prevents tarnishing in air. The addition of indium gives alloys for dental fillings increased strength. The electrolytic indium coating of other metals well protects them from corrosion. An alloy of indium with tin (1:1 by weight) solders glass well with glass or metal, and an alloy of 24% In and 76% Ga melts at 16°C. An alloy melting at 47 ° C 18.1% In with 41.0 - Bi, 22.1 - Pb, 10.6 - Sn and 8.2 - Cd finds medical use in complex bone fractures (instead of gypsum). There is a monograph on the chemistry of indium
12. The compressibility of thallium is approximately the same as indium, but two allotropic modifications (hexagonal and cubic) are known for it, the transition point between which lies at 235 ° C. Under high pressure, another one arises. The triple point of all three forms lies at 37 thousand atm and 110°C. This pressure corresponds to an abrupt decrease by about 1.5 times in the electrical resistance of the metal (which at 70 thousand atm is about 0.3 of the usual one). Under a pressure of 90,000 atm, the third form of thallium melts at 650°C.
13. Thallium is used mainly for the manufacture of alloys with tin and lead, which have high acid resistance. In particular, the alloy composition of 70% Pb, 20% Sn and 10% T1 well withstands the action of mixtures of sulfuric, hydrochloric and nitric acids. There is a monograph on thallium.
14. With respect to water, gallium and compact indium are stable, while thallium in the presence of air is slowly destroyed by it from the surface. Gallium reacts with nitric acid only slowly, while thallium reacts very vigorously. On the contrary, sulfuric, and especially hydrochloric, acid easily dissolves Ga and In, while T1 interacts with them much more slowly (due to the formation of a protective film of sparingly soluble salts on the surface). Solutions of strong alkalis easily dissolve gallium, act only slowly on indium and do not react with thallium. Gallium also noticeably dissolves in NH4OH. Volatile compounds of all three elements color a colorless flame in characteristic colors: Ga - in dark purple (L. \u003d 4171 A), almost imperceptible to the eye, In - in dark blue (L, \u003d 4511 A), T1 - in emerald green (A, \u003d \u003d 5351 A).
15. Gallium and indium do not appear to be poisonous. On the contrary, thallium is highly poisonous, and in the nature of the action it is similar to Pb and As. It affects the nervous system, digestive tract and kidneys. Symptoms of acute poisoning do not appear immediately, but after 12-20 hours. With slowly developing chronic poisoning (including through the skin), excitation and sleep disturbance are observed primarily. In medicine, thallium preparations are used to remove hair (for lichen, etc.). Thallium salts have found application in luminous compositions as substances that increase the duration of the glow. They also proved to be a good remedy for mice and rats.
16. In the voltage series, gallium is located between Zn and Fe, while indium and thallium are between Fe and Sn. The Ga and In transitions according to the E + 3 + Ze = E scheme correspond to normal potentials: -0.56 and -0.33 V (in an acidic environment) or -1.2 and -1.0 V (in an alkaline environment). Thallium is converted by acids into a monovalent state (normal potential -0.34 V). The transition T1 + 3 + 2e \u003d T1 + is characterized by a normal potential of + 1.28 V in an acidic environment or + 0.02 V - in an alkaline one.
17. The heats of formation of E203 oxides of gallium and its analogues decrease along the series 260 (Ga), 221 (In), and 93 kcal/mol (T1). When heated in air, gallium is practically oxidized only to GaO. Therefore, Ga203 is usually obtained by dehydration of Ga (OH) h. Indium, when heated in air, forms In2O3, and thallium forms a mixture of T12O3 and T120, with the higher the content of the higher oxide, the lower the temperature. Up to T1203, thallium can be oxidized by the action of ozone.
18. The solubility of E2O3 oxides in acids increases along the series Ga - In - Tl. In the same series, the strength of the bond between the element and oxygen decreases: Ga2O3 melts at 1795°С without decomposition, ln203 transforms into ln304 only above 850°C, and finely divided T1203 begins to split off oxygen already at about 90°C. However, much higher temperatures are required for complete conversion of T1203 to T120. Under an excess pressure of oxygen, In203 melts at 1910°C, while T1203 melts at 716°C.
19. The heats of hydration of oxides according to the scheme E2O3 + ZH20 = 2E(OH)3 are +22 kcal (Ga), +1 (In) and -45 (T1). In accordance with this, the ease of splitting off water by hydroxides increases from Ga to T1: if Ga(OH)3 is completely dehydrated only upon calcination, then T1(OH)3 passes into T1203 even when standing under the liquid from which it was isolated.
20. When acidic solutions of gallium salts are neutralized, its hydroxide precipitates approximately in the pH range = 3-4. Freshly precipitated Ga(OH)3 is highly soluble in strong ammonia solutions, but as it ages, the solubility decreases more and more. Its isoelectric point lies at pH = 6.8, and PR = 2 10~37. For lp(OH)3, PR = 1 10-31 was found, and for T1(OH)3 - 1 10~45.
21. The following values ​​were determined for the second and third dissociation constants of Ga(OH)3 according to the acidic and basic types:

H3Ga03 /C2 = 5-10_I K3 = 2-10-12
Ga(OH)3 K2“2. Yu-P / Nz \u003d 4 -10 12
Thus, gallium hydroxide is a case of an electrolyte very close to ideal amphotericity.

1. The difference in the acidic properties of gallium hydroxides and its analogues is clearly manifested when they interact with solutions of strong alkalis (NaOH, KOH). Gallium hydroxide readily dissolves to form type M gallates, which are stable both in solution and in the solid state. When heated, they easily lose water (Na salt - at 120, K salt - at 137 ° C) and pass into the corresponding anhydrous salts of the MGa02 type. Divalent metals (Ca, Sr) obtained from solutions of gallates are characterized by another type - M3 ■ 2H20, which are also almost insoluble. They are completely hydrolyzed by water.
   Thallium hydroxide is easily peptized by strong alkalis (with the formation of a negative sol), but is insoluble in them and does not give tallates. Dry way (by fusion of oxides with the corresponding carbonates) derivatives of the ME02 type were obtained for all three elements of the gallium subgroup. However, in the case of thallium, they turned out to be mixtures of oxides.
   1. The effective radii of the Ga3+, In3*, and T13* ions are 0.62, 0.92, and 1.05 A, respectively. In an aqueous medium, they are apparently directly surrounded by six water molecules. Such hydrated ions are somewhat dissociated according to the scheme E(OH2)a T * E (OH2)5 OH + H, and their dissociation constants are estimated at 3 ■ 10-3°(Ga) and 2 10-4 (In).
   2. The halide salts of Ga3+, In3* and T13*' are generally similar to the corresponding salts of A13*. In addition to fluorides, they are relatively fusible and highly soluble not only in water, but also in a number of organic solvents. Of these, only yellow Gal3 are painted

   The existence of gallium ("ekaaluminum") 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. 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.

   Being in nature, getting:

   Consists of two stable isotopes with mass numbers 69 (60.5%) and 71 (39.5%). The average content of gallium 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, CuGaS 2 gallite, 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 enclosed in aluminum minerals. The content of gallium in bauxite and nepheline ranges from 0.002 to 0.01%. Elevated concentrations of gallium are also observed in sphalerites (0.01-0.02%), in hard coals (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. During the processing of bauxites, gallium is concentrated in the mother liquors after the isolation of Al(OH) 3 . Gallium is isolated from such solutions by electrolysis on a mercury cathode. From the alkaline solution obtained after treatment of the amalgam with water, Ga(OH) 3 is precipitated, 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 purer metal is obtained by vacuum melting, zone melting, or by drawing a single crystal from the melt.

   Physical properties:

   Silver-white metal, soft, heavy. A distinctive feature of gallium is a large interval of the liquid state (tmelt 29.8°C, tbp 2230°C) and low vapor pressure at temperatures up to 1100-1200°C. The density of a solid metal is 5.904 g/cm 3 (20°C), lower than that of a liquid one, so crystallizing gallium, like ice, can break 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 in dry oxygen, slow oxidation is observed (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 to release hydrogen: 2Ga + 6HCl = 2GaCl 3 + 3H 2
   At the same time, gallium dissolves slowly in sulfuric and hydrochloric acids, quickly in hydrofluoric acid, and gallium is stable in nitric acid in the cold.
   Gallium slowly dissolves in hot alkali solutions. 2Ga + 6H 2 O + 2NaOH = 2Na + 3H 2

   The most important connections:

   gallium oxide, Ga 2 O 3 - white or yellow powder, mp 1795°C. Obtained by heating metallic gallium in air at 260 °C or in an oxygen atmosphere, or by calcining gallium nitrate or sulfate. It exists in the form of two modifications. Slowly reacts with acids and alkalis in solution, exhibiting amphoteric properties:
   gallium hydroxide, Ga (OH) 3 - precipitates in the form of a jelly-like precipitate when treating solutions of trivalent gallium salts with alkali metal hydroxides and carbonates (pH 9.7). Can be obtained by hydrolysis of salts of trivalent gallium.
   Shows amphoteric, with a certain predominance of acid properties, when dissolved in alkalis forms gallates(for example, Na). It dissolves in concentrated ammonia and concentrated ammonium carbonate solution, 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.
   gallium salts. GaCl 3 - colorless hygroscopic crystals. mp 78 °C, tbp 215 °C Ga 2 (SO 4) 3 *18H 2 O is a colorless, water-soluble substance that forms double salts of the alum type. Ga(NO 3) 3 * 8H 2 O - colorless crystals soluble in water and ethanol
   gallium sulfide, Ga 2 S 3 - yellow crystals or white amorphous powder with mp 1250°C, decomposed by water.
   Gallium hydrides obtained from organo-gallium compounds. Similar to boron and aluminum hydrides: Ga 2 H 6 - digallan, volatile liquid, tmelt − 21.4 °C, tbp 139 °C. x - polygallan, 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, hydrolyzes with water to release hydrogen.

   Application:

   Gallium can be used to make optical mirrors that are highly reflective.
   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, which have semiconductor properties, are promising materials for semiconductor electronics. They can be used in high-temperature rectifiers and transistors, solar panels, and infrared receivers.
   Gallium oxide is a component of important laser materials of the garnet group - GSHG, YAG, ISGG, etc.
   Gallium is expensive, in 2005 a ton of gallium cost 1.2 million US dollars on the world market, and due to the high price and at the same time the great demand for this metal, it is very important to establish its complete extraction in aluminum production and coal processing at liquid fuel.
   

   Ivanov Alexey
   KhF Tyumen State University, 561 groups.

   Gallium is a chemical element with atomic number 31. It belongs to the group of light metals and is denoted by the symbol “Ga”. Gallium in its pure form is not found in nature, but its compounds are found in negligible amounts in bauxite and zinc ores. Gallium is a soft, ductile, silvery metal. At low temperatures, it is in a solid state, but already melts at a temperature not much higher than room temperature (29.8 ° C). In the video below, you can see how a gallium spoon melts in a cup of hot tea.

   

   1. From the discovery of the element in 1875 until the advent of the semiconductor era, gallium was mainly used to create low-melting alloys.

   

   2. Currently, all gallium is used in microelectronics.

   

   3. Gallium arsenide, the element's main compound used, is applied in microwave circuits and infrared applications.

   

   4. Gallium nitride is used less in the creation of semiconductor lasers and LEDs in the blue and ultraviolet range.

   

   5. Gallium has no biological role known to science. But, since gallium compounds and iron salts behave similarly in biological systems, gallium ions often replace iron ions in medical applications.

   

   6. Pharmaceuticals and radiopharmaceuticals containing gallium have now been developed.

   

   
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