The melting point of gallium, 29.7646 °C (85.5763 °F; 302.9146 K), is used as a temperature reference point. Gallium alloys are used in thermometers as a non-toxic and environmentally friendly alternative tomercury, and can withstand higher temperatures than mercury. A melting point of −19 °C (−2 °F), well below the freezing point of water, is claimed for the alloygalinstan (62–95% gallium, 5–22%indium, and 0–16%tin by weight), but that may be the freezing point with the effect ofsupercooling.
Gallium does not occur as a free element in nature, but rather as gallium(III) compounds in trace amounts inzinc ores (such assphalerite) and inbauxite. Elemental gallium is a liquid at temperatures greater than 29.76 °C (85.57 °F), and will melt in a person's hands at normal human body temperature of 37.0 °C (98.6 °F).
Gallium is predominantly used in electronics.Gallium arsenide, the primary chemical compound of gallium in electronics, is used inmicrowave circuits, high-speed switching circuits, andinfrared circuits. Semiconductinggallium nitride andindium gallium nitride produce blue and violetlight-emitting diodes anddiode lasers. Gallium is also used in the production of artificialgadolinium gallium garnet for jewelry. It has no known natural role in biology. Gallium(III) behaves in a similar manner toferric salts in biological systems and has been used in some medical applications, including pharmaceuticals andradiopharmaceuticals.
Elemental gallium is not found in nature, but it is easily obtained bysmelting. Very pure gallium is a silvery blue metal that fracturesconchoidally likeglass. Gallium's volume expands by 3.10% when it changes from a liquid to a solid so care must be taken when storing it in containers that may rupture when it changes state. Gallium shares the higher-density liquid state with a short list of other materials that includeswater,silicon,germanium,bismuth, andplutonium.[14]: 222
The melting point of gallium allows it to melt in the human hand, and then solidify if removed. The liquid metal has a strong tendency tosupercool below itsmelting point/freezing point: Gananoparticles can be kept in the liquid state below 90 K.[21]Seeding with a crystal helps to initiate freezing. Gallium is one of the four non-radioactive metals (withcaesium,rubidium, andmercury) that are known to be liquid at, or near, normal room temperature. Of the four, gallium is the only one that is neither highly reactive (as are rubidium and caesium) nor highly toxic (as is mercury) and can, therefore, be used in metal-in-glass high-temperature thermometers. It is also notable for having one of the largest liquid ranges for a metal, and for having (unlike mercury) a lowvapor pressure at high temperatures. Gallium's boiling point, 2676 K, is nearly nine times higher than its melting point on theabsolute scale, the greatest ratio between melting point and boiling point of any element.[14]: 224 Unlike mercury, liquid gallium metalwets glass and skin, along with most other materials (with the exceptions of quartz, graphite,gallium(III) oxide[22] andPTFE),[14]: 221 making it mechanically more difficult to handle even though it is substantially less toxic and requires far fewer precautions than mercury. Gallium painted onto glass is a brilliant mirror.[14]: 221 For this reason as well as the metal contamination and freezing-expansion problems, samples of gallium metal are usually supplied in polyethylene packets within other containers.
Gallium does notcrystallize in any of the simplecrystal structures. The stable phase under normal conditions isorthorhombic with 8 atoms in the conventionalunit cell. Within a unit cell, each atom has only one nearest neighbor (at a distance of 244 pm). The remaining six unit cell neighbors are spaced 27, 30 and 39 pm farther away, and they are grouped in pairs with the same distance.[23] Many stable andmetastable phases are found as function of temperature and pressure.[24]
The bonding between the two nearest neighbors iscovalent; hence Ga2dimers are seen as the fundamental building blocks of the crystal. This explains the low melting point relative to the neighbor elements, aluminium and indium. This structure is strikingly similar to that ofiodine and may form because of interactions between the single 4p electrons of gallium atoms, further away from the nucleus than the 4s electrons and the [Ar]3d10 core. This phenomenon recurs withmercury with its "pseudo-noble-gas" [Xe]4f145d106s2 electron configuration, which is liquid at room temperature.[14]: 223 The 3d10 electrons do not shield the outer electrons very well from the nucleus and hence the first ionisation energy of gallium is greater than that of aluminium.[14]: 222 Ga2 dimers do not persist in the liquid state and liquid gallium exhibits a complex low-coordinated structure in which each gallium atom is surrounded by 10 others, rather than 11–12 neighbors typical of most liquid metals.[25][26]
The physical properties of gallium are highlyanisotropic, i.e. have different values along the three major crystallographic axesa,b, andc (see table), producing a significant difference between the linear (α) and volumethermal expansion coefficients. The properties of gallium are strongly temperature-dependent, particularly near the melting point. For example, the coefficient of thermal expansion increases by several hundred percent upon melting.[27]
Properties of gallium for different crystal axes[27]
Gallium has 30 known isotopes, ranging inmass number from 60 to 89. Only two isotopes are stable and occur naturally, gallium-69 and gallium-71. Gallium-69 is more abundant: it makes up about 60.1% of natural gallium, while gallium-71 makes up the remaining 39.9%. All the other isotopes are radioactive, with gallium-67 being the longest-lived (half-life 3.2617 days). Isotopes lighter than gallium-69 usually decay throughbeta plus decay (positron emission) orelectron capture to isotopes ofzinc, while isotopes heavier than gallium-71 decay throughbeta minus decay (electron emission), possibly with delayedneutron emission, to isotopes ofgermanium. Gallium-70 can decay both ways, to zinc-70 or to germanium-70.[28]
Gallium is found primarily in the +3oxidation state. The +1 oxidation state is also found in some compounds, although it is less common than it is for gallium's heavier congenersindium andthallium. For example, the very stable GaCl2 contains both gallium(I) and gallium(III) and can be formulated as GaIGaIIICl4; in contrast, the monochloride is unstable above 0 °C,disproportionating into elemental gallium and gallium(III) chloride. Compounds containing Ga–Ga bonds are true gallium(II) compounds, such asGaS (which can be formulated as Ga24+(S2−)2) and thedioxane complex Ga2Cl4(C4H8O2)2.[14]: 240
Strong acids dissolve gallium, forming gallium(III) salts such asGa(NO 3) 3 (gallium nitrate).Aqueous solutions of gallium(III) salts contain the hydrated gallium ion,[Ga(H 2O) 6]3+ .[29]: 1033 Gallium(III) hydroxide,Ga(OH) 3, may be precipitated from gallium(III) solutions by addingammonia. DehydratingGa(OH) 3 at 100 °C produces gallium oxide hydroxide, GaO(OH).[30]: 140–141
Alkalinehydroxide solutions dissolve gallium, forminggallate salts (not to be confused with identically namedgallic acid salts) containing theGa(OH)− 4 anion.[31][29]: 1033 [32] Gallium hydroxide, which isamphoteric, also dissolves in alkali to form gallate salts.[30]: 141 Although earlier work suggestedGa(OH)3− 6 as another possible gallate anion,[33] it was not found in later work.[32]
Gallium reacts with thechalcogens only at relatively high temperatures. At room temperature, gallium metal is not reactive with air and water because it forms apassive, protectiveoxide layer. At higher temperatures, however, it reacts with atmosphericoxygen to formgallium(III) oxide,Ga 2O 3.[31] ReducingGa 2O 3 with elemental gallium in vacuum at 500 °C to 700 °C yields the dark browngallium(I) oxide,Ga 2O.[30]: 285 Ga 2O is a very strongreducing agent, capable of reducingH 2SO 4 toH 2S.[30]: 207 It disproportionates at 800 °C back to gallium andGa 2O 3.[34]
Gallium(III) sulfide,Ga 2S 3, has 3 possible crystal modifications.[34]: 104 It can be made by the reaction of gallium withhydrogen sulfide (H 2S) at 950 °C.[30]: 162 Alternatively,Ga(OH) 3 can be used at 747 °C:[35]
2Ga(OH) 3 + 3H 2S →Ga 2S 3 + 6H 2O
Reacting a mixture of alkali metal carbonates andGa 2O 3 withH 2S leads to the formation ofthiogallates containing the[Ga 2S 4]2− anion. Strong acids decompose these salts, releasingH 2S in the process.[34]: 104–105 The mercury salt,HgGa 2S 4, can be used as aphosphor.[36]
Gallium also forms sulfides in lower oxidation states, such asgallium(II) sulfide and the greengallium(I) sulfide, the latter of which is produced from the former by heating to 1000 °C under a stream of nitrogen.[34]: 94
The other binary chalcogenides,Ga 2Se 3 andGa 2Te 3, have thezincblende structure. They are all semiconductors but are easilyhydrolysed and have limited utility.[34]: 104
Gallium nitride (left) and gallium arsenide (right) wafers
Gallium reacts with ammonia at 1050 °C to formgallium nitride, GaN. Gallium also forms binary compounds withphosphorus,arsenic, andantimony:gallium phosphide (GaP),gallium arsenide (GaAs), andgallium antimonide (GaSb). These compounds have the same structure asZnS, and have importantsemiconducting properties.[29]: 1034 GaP, GaAs, and GaSb can be synthesized by the direct reaction of gallium with elemental phosphorus, arsenic, or antimony.[34]: 99 They exhibit higher electrical conductivity than GaN.[34]: 101 GaP can also be synthesized by reactingGa 2O with phosphorus at low temperatures.[37]
Gallium forms ternarynitrides; for example:[34]: 99
Li 3Ga +N 2 →Li 3GaN 2
Similar compounds with phosphorus and arsenic are possible:Li 3GaP 2 andLi 3GaAs 2. These compounds are easily hydrolyzed by diluteacids and water.[34]: 101
Gallium(III) oxide reacts withfluorinating agents such asHF orF 2 to formgallium(III) fluoride,GaF 3. It is an ionic compound strongly insoluble in water. However, it dissolves inhydrofluoric acid, in which it forms anadduct with water,GaF 3·3H 2O. Attempting to dehydrate this adduct formsGaF 2OH·nH 2O. The adduct reacts with ammonia to formGaF 3·3NH 3, which can then be heated to form anhydrousGaF 3.[30]: 128–129
Gallium trichloride is formed by the reaction of gallium metal withchlorine gas.[31] Unlike the trifluoride, gallium(III) chloride exists as dimeric molecules,Ga 2Cl 6, with a melting point of 78 °C. Equivalent compounds are formed with bromine and iodine,Ga 2Br 6 andGa 2I 6.[30]: 133
Like the other group 13 trihalides, gallium(III) halides areLewis acids, reacting as halide acceptors with alkali metal halides to form salts containingGaX− 4 anions, where X is a halogen. They also react withalkyl halides to formcarbocations andGaX− 4.[30]: 136–137
When heated to a high temperature, gallium(III) halides react with elemental gallium to form the respective gallium(I) halides. For example,GaCl 3 reacts with Ga to formGaCl:
2 Ga +GaCl 3 ⇌ 3 GaCl (g)
At lower temperatures, the equilibrium shifts toward the left and GaCl disproportionates back to elemental gallium andGaCl 3. GaCl can also be produced by reacting Ga with HCl at 950 °C; the product can be condensed as a red solid.[29]: 1036
Gallium(I) compounds can be stabilized by forming adducts with Lewis acids. For example:
GaCl +AlCl 3 →Ga+ [AlCl 4]−
The so-called "gallium(II) halides",GaX 2, are actually adducts of gallium(I) halides with the respective gallium(III) halides, having the structureGa+ [GaX 4]− . For example:[31][29]: 1036 [38]
In the presence ofdimethyl ether as solvent,GaH 3 polymerizes to(GaH 3) n. If no solvent is used, the dimerGa 2H 6 (digallane) is formed as a gas. Its structure is similar todiborane, having two hydrogen atoms bridging the two gallium centers,[29]: 1031 unlike α-AlH 3 in which aluminium has a coordination number of 6.[29]: 1008
Gallane is unstable above −10 °C, decomposing to elemental gallium andhydrogen.[39]
Organogallium compounds are of similar reactivity toorganoindium compounds, less reactive thanorganoaluminium compounds, but more reactive thanorganothallium compounds.[14]: 262–5 Alkylgalliums are monomeric.Lewis acidity decreases in the order Al > Ga > In and as a result organogallium compounds do not form bridged dimers as organoaluminium compounds do. Organogallium compounds are also less reactive than organoaluminium compounds. They do form stable peroxides.[40] These alkylgalliums are liquids at room temperature, having low melting points, and are quite mobile and flammable. Triphenylgallium is monomeric in solution, but its crystals form chain structures due to weak intermolecluar Ga···C interactions.[14]: 262–5
Gallium trichloride is a common starting reagent for the formation of organogallium compounds, such as incarbogallation reactions.[41] Gallium trichloride reacts withlithium cyclopentadienide indiethyl ether to form the trigonal planar gallium cyclopentadienyl complex GaCp3. Gallium(I) forms complexes withareneligands such ashexamethylbenzene. Because this ligand is quite bulky, the structure of the [Ga(η6-C6Me6)]+ is that of ahalf-sandwich. Less bulky ligands such asmesitylene allow two ligands to be attached to the central gallium atom in a bent sandwich structure.Benzene is even less bulky and allows the formation of dimers: an example is [Ga(η6-C6H6)2] [GaCl4]·3C6H6.[14]: 262–5
In 1871, the existence of gallium was first predicted by Russian chemistDmitri Mendeleev, who named it "eka-aluminium" from its position in hisperiodic table. He also predicted several properties of eka-aluminium that correspond closely to the real properties of gallium, such as itsdensity,melting point, oxide character, and bonding in chloride.[42]
Comparison between Mendeleev's 1871 predictions and the known properties of gallium[14]: 217
Mendeleev further predicted that eka-aluminium would be discovered by means of thespectroscope, and that metallic eka-aluminium would dissolve slowly in both acids and alkalis and would not react with air. He also predicted that M2O3 would dissolve in acids to give MX3 salts, that eka-aluminium salts would form basic salts, that eka-aluminium sulfate should formalums, and that anhydrous MCl3 should have a greater volatility than ZnCl2. All of these predictions were later proven accurate.[14]: 217
He named the element "gallia", fromLatinGallia meaning 'Gaul', a name for his native land of France. It was later claimed that, in a multilingualpun of a kind favoured by men of science in the 19th century, he had also named gallium after himself:Le coq is French for 'the rooster', and the Latin word for 'rooster' isgallus. In an 1877 article, Lecoq denied this conjecture.[44]
Originally, de Boisbaudran determined the density of gallium as 4.7 g/cm3, the only property that failed to match Mendeleev's predictions; Mendeleev then wrote to him and suggested that he should remeasure the density, and de Boisbaudran then obtained the correct value of 5.9 g/cm3, that Mendeleev had predicted exactly.[14]: 217
From its discovery in 1875 until the era of semiconductors, the primary uses of gallium were high-temperature thermometrics and metal alloys with unusual properties of stability or ease of melting (some such being liquid at room temperature).
The development ofgallium arsenide as adirect bandgap semiconductor in the 1960s ushered in the most important stage in the applications of gallium.[14]: 221 In the late 1960s, theelectronics industry started using gallium on a commercial scale to fabricate light emitting diodes,photovoltaics and semiconductors, while the metals industry used it[45] to reduce the melting point ofalloys.[46]
First bluegallium nitride LED were developed in 1971–1973, but they were feeble.[47] Only in the early 1990sShuji Nakamura managed to combine GaN withindium gallium nitride and develop the modern blue LED, now making the basis of ubiquitous white LEDs, whichNichia commercialized in 1993. He and two other Japanese scientists received aNobel in Physics in 2014 for this work.[48][49]
Global gallium production slowly grew from several tens of t/year in the 1970s til ca. 2010, when it passed 100 t/yr and rapidly accelerated,[50] by 2024 reaching about 450 t/yr.[51]
Gallium does not exist as a free element in the Earth's crust, and the few high-content minerals, such as gallite (CuGaS2), are too rare to serve as a primary source.[52] The abundancein the Earth's crust is approximately 16.9 ppm. It is the 34th most abundant element in the crust.[53] This is comparable to the crustal abundances oflead,cobalt, andniobium. Yet unlike these elements, gallium does not form its own ore deposits with concentrations of > 0.1 wt.% in ore. Rather it occurs at trace concentrations similar to the crustal value in zinc ores,[52][54] and at somewhat higher values (~ 50 ppm) in aluminium ores, from both of which it is extracted as a by-product. This lack of independent deposits is due to gallium's geochemical behaviour, showing no strong enrichment in the processes relevant to the formation of most ore deposits.[52]
TheUnited States Geological Survey (USGS) estimates that more than 1 million tons of gallium is contained in known reserves of bauxite and zinc ores.[55][56] Some coalfluedusts contain small quantities of gallium, typically less than 1% by weight.[57][58][59][60] However, these amounts are not extractable without mining of the host materials (see below). Thus, the availability of gallium is fundamentally determined by the rate at which bauxite, zinc ores, and coal are extracted.
Gallium is produced exclusively as aby-product during the processing of the ores of other metals. Its main source material isbauxite, the chief ore ofaluminium, but minor amounts are also extracted from sulfidic zinc ores (sphalerite being the main host mineral).[61][54] In the past, certain coals were an important source.
During the processing ofbauxite toalumina in theBayer process, gallium accumulates in thesodium hydroxide liquor. From this it can be extracted by a variety of methods. The most recent is the use ofion-exchange resin.[61] Achievable extraction efficiencies critically depend on the original concentration in the feed bauxite. At a typical feed concentration of 50 ppm, about 15% of the contained gallium is extractable.[61] The remainder reports to thered mud andaluminium hydroxide streams. Gallium is removed from the ion-exchange resin in solution. Electrolysis then gives gallium metal. Forsemiconductor use, it is further purified withzone melting or single-crystal extraction from a melt (Czochralski process). Purities of 99.9999% are routinely achieved and commercially available.[62]
Its by-product status means that gallium production is constrained by the amount of bauxite, sulfidic zinc ores (and coal) extracted per year. Therefore, its availability needs to be discussed in terms of supply potential. The supply potential of a by-product is defined as that amount which is economically extractable from its host materialsper year under current market conditions (i.e. technology and price).[63] Reserves and resources are not relevant for by-products, since theycannot be extracted independently from the main-products.[64] Recent estimates put the supply potential of gallium at a minimum of 2,100 t/yr from bauxite, 85 t/yr from sulfidic zinc ores, and potentially 590 t/yr from coal.[61] These figures are significantly greater than current production (375 t in 2016).[65] Thus, major future increases in the by-product production of gallium will be possible without significant increases in production costs or price. The average price for low-grade gallium was $120 per kilogram in 2016 and $135–140 per kilogram in 2017.[66]
China producedc. 250 tons of low-grade gallium in 2016 andc. 300 tons in 2017. It also accounted for more than half of globalLED production.[66] As of July 2023, China accounted for between 80%[67] and 95% of its production.[68] As oft August 2023, China produced 80% of the world's gallium and 60% of germanium (source: Critical Raw Materials Alliance (CRMA)). China started restricting exports of both materials. They are key to the semiconductor industry and there is a 'chip war' between China and the US.[69]In 2025,Rio Tinto andIndium Corporation partnered to mine the first primary gallium in North America.[70]In July 2025, the US think tankCenter for Strategic and International Studies wrote: "China is increasingly weaponizing its chokehold over critical minerals amid intensifying economic and technological competition with the United States. The critical mineral gallium, which is crucial to defense industry supply chains and new energy technologies, has been at the front line of China’s strategy."[71]In 2024, China produced 98 percent of the world’s low-purity gallium (source:United States Geological Survey (USGS)).[71]
Semiconductor applications dominate the commercial demand for gallium, accounting for 98% of the total. The next major application is forgadolinium gallium garnets.[72] As of 2022, 44% of world use went to light fixtures and 36% to integrated circuits, with smaller shares equal to ~7% going to photovoltaics and magnets each.[73]
Extremely high-purity (>99.9999%) gallium is commercially available to serve thesemiconductor industry.Gallium arsenide (GaAs) andgallium nitride (GaN) used in electronic components represented about 98% of the gallium consumption in the United States in 2007. About 66% of semiconductor gallium is used in the U.S. in integrated circuits (mostly gallium arsenide), such as the manufacture of ultra-high-speed logic chips andMESFETs for low-noise microwave preamplifiers in cell phones. About 20% of this gallium is used inoptoelectronics.[55]
Worldwide, gallium arsenide makes up 95% of the annual global gallium consumption.[62] It amounted to $7.5 billion in 2016, with 53% originating from cell phones, 27% from wireless communications, and the rest from automotive, consumer, fiber-optic, and military applications. The recent increase in GaAs consumption is mostly related to the emergence of3G and4Gsmartphones, which employ up to 10 times the amount of GaAs in older models.[66]
Gallium arsenide and gallium nitride can also be found in a variety of optoelectronic devices which had a market share of $15.3 billion in 2015 and $18.5 billion in 2016.[66]Aluminium gallium arsenide (AlGaAs) is used in high-power infrared laser diodes. The semiconductors gallium nitride andindium gallium nitride are used in blue and violet optoelectronic devices, mostlylaser diodes andlight-emitting diodes. For example, gallium nitride 405 nm diode lasers are used as a violet light source for higher-densityBlu-ray Disc compact data disc drives.[74]
Other major applications of gallium nitride are cable television transmission, commercial wireless infrastructure, power electronics, and satellites. The GaN radio frequency device market alone was estimated at $370 million in 2016 and $420 million in 2016.[66]
Galinstan easily wetting a piece of ordinary glassOwing to their low melting points, gallium and its alloys can be shaped into various 3D forms using3D printing andadditive manufacturing.
Gallium readilyalloys with most metals, and is used as an ingredient inlow-melting alloys. The nearlyeutectic alloy of gallium,indium, andtin is a room temperature liquid used in medical thermometers. This alloy, with the trade-nameGalinstan (with the "-stan" referring to the tin,stannum in Latin), has a low melting point of −19 °C (−2.2 °F).[77] this family of alloys can also be used to cool computer chips in place of water, and as a replacement forthermal paste in high-performance computing.[78][79] Gallium alloys have been evaluated as substitutes for mercurydental amalgams, but these materials have yet to see wide acceptance. Liquid alloys containing mostly gallium and indium have been found to precipitate gaseous CO2 into solid carbon and are being researched as potential methodologies forcarbon capture and possiblycarbon removal.[80][81]
Because galliumwets glass orporcelain, gallium can be used to create brilliantmirrors. When the wetting action of gallium-alloys is not desired (as in Galinstan glass thermometers), the glass must be protected with a transparent layer ofgallium(III) oxide.[82]
Although gallium has no natural function in biology, gallium ions interact with processes in the body in a manner similar toiron(III). Because these processes includeinflammation, a marker for many disease states, several gallium salts are used (or are in development) aspharmaceuticals andradiopharmaceuticals in medicine. Interest in the anticancer properties of gallium emerged when it was discovered that67Ga(III) citrate injected in tumor-bearing animals localized to sites of tumor. Clinical trials have shown gallium nitrate to have antineoplastic activity against non-Hodgkin's lymphoma and urothelial cancers. A new generation of gallium-ligand complexes such as tris(8-quinolinolato)gallium(III) (KP46) and gallium maltolate has emerged.[91]Gallium nitrate (brand name Ganite) has been used as an intravenous pharmaceutical to treathypercalcemia associated with tumormetastasis to bones. Gallium is thought to interfere withosteoclast function, and the therapy may be effective when other treatments have failed.[92]Gallium maltolate, an oral, highly absorbable form of gallium(III) ion, is an anti-proliferative to pathologically proliferating cells, particularly cancer cells and some bacteria that accept it in place of ferric iron (Fe3+). Researchers are conducting clinical and preclinical trials on this compound as a potential treatment for a number of cancers, infectious diseases, and inflammatory diseases.[93]
When gallium ions are mistakenly taken up in place of iron(III) by bacteria such asPseudomonas, the ions interfere with respiration, and the bacteria die. This happens because iron is redox-active, allowing the transfer of electrons during respiration, while gallium is redox-inactive.[94][95]
A complexamine-phenol Ga(III) compound MR045 is selectively toxic to parasites resistant tochloroquine, a common drug againstmalaria. Both the Ga(III) complex and chloroquine act by inhibiting crystallization ofhemozoin, a disposal product formed from the digestion of blood by the parasites.[96][97]
Gallium-67salts such as galliumcitrate and galliumnitrate are used asradiopharmaceutical agents in thenuclear medicine imaging known asgallium scan. Theradioactive isotope67Ga is used, and the compound or salt of gallium is unimportant. The body handles Ga3+ in many ways as though it were Fe3+, and the ion is bound (and concentrates) in areas of inflammation, such as infection, and in areas of rapid cell division. This allows such sites to be imaged by nuclear scan techniques.[98]
Neutrino detection: Gallium is used forneutrino detection. Possibly the largest amount of pure gallium ever collected in a single location is the Gallium-Germanium Neutrino Telescope used by theSAGE experiment at theBaksan Neutrino Observatory in Russia. This detector contains 55–57 tonnes (~9 cubic metres) of liquid gallium.[100] Another experiment was theGALLEX neutrino detector operated in the early 1990s in an Italian mountain tunnel. The detector contained 12.2 tons of watered gallium-71.Solar neutrinos caused a few atoms of71Ga to become radioactive71Ge, which were detected. This experiment showed that the solar neutrino flux is 40% less than theory predicted. This deficit (solar neutrino problem) was not explained until better solar neutrino detectors and theories were constructed (seeSNO).[101]
Lubricants: Gallium serves as an additive inglide wax for skis and other low-friction surface materials.[103]
Flexible electronics: Materials scientists speculate that the properties of gallium could make it suitable for the development of flexible and wearable devices.[104][105]
Hydrogen generation: Gallium disrupts theprotective oxide layer on aluminium, allowing water to react with the aluminium inAlGa to produce hydrogen gas.[106]
Humor: A well-knownpractical joke among chemists is to fashion gallium spoons and use them to serve tea to unsuspecting guests, since gallium has a similar appearance to its lighter homolog aluminium. The spoons then melt in the hot tea.[107]
Advances in trace element testing have allowed scientists to discover traces of dissolved gallium in the Atlantic and Pacific Oceans.[108] In recent years, dissolved gallium concentrations have presented in theBeaufort Sea.[108][109] These reports reflect the possible profiles of the Pacific and Atlantic Ocean waters.[109] For the Pacific Oceans, typical dissolved gallium concentrations are between 4 and 6 pmol/kg at depths <~150 m. In comparison, for Atlantic waters 25–28 pmol/kg at depths >~350 m.[109]
Gallium has entered oceans mainly through aeolian input, but having gallium in our oceans can be used to resolve aluminium distribution in the oceans.[110] The reason for this is that gallium is geochemically similar to aluminium, just less reactive. Gallium also has a slightly larger surface water residence time than aluminium.[110] Gallium has a similar dissolved profile similar to that of aluminium, due to this gallium can be used as a tracer for aluminium.[110] Gallium can also be used as a tracer of aeolian inputs of iron.[111] Gallium is used as a tracer for iron in the northwest Pacific, south and central Atlantic Oceans.[111] For example, in the northwest Pacific, low gallium surface waters, in the subpolar region suggest that there is low dust input, which can subsequently explain the followinghigh-nutrient, low-chlorophyll environmental behavior.[111]
Metallic gallium is not toxic. However, several gallium compounds are toxic.
Gallium halide complexes can be toxic.[114] The Ga3+ ion of soluble gallium salts tends to form the insoluble hydroxide when injected in large doses; precipitation of this hydroxide resulted innephrotoxicity in animals. In lower doses, soluble gallium is tolerated well and does not accumulate as a poison, instead being excreted mostly through urine. Excretion of gallium occurs in two phases: the first phase has abiological half-life of 1 hour, while the second has a biological half-life of 25 hours.[98]
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