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{{Infobox aluminium}}

{{SI}}


==Overview==
'''Aluminium''' ({{IPAEng|ˌæljʊˈmɪniəm}}, {{IPA|/ˌæljəˈmɪniəm/}}) or '''aluminum''' ({{IPA|/əˈluːmɪnəm/}}, see ''[[#Present-day spelling|spelling]]'' below) is a silvery white and [[ductile]] member of the [[poor metal]] group of [[chemical element]]s. It has the symbol '''Al'''; its [[atomic number]] is 13. 
Aluminium is the most abundant metal in the Earth's crust, and the third most abundant element overall, after [[oxygen]] and [[silicon]]. It makes up about 8% by weight of the Earth’s solid surface. Aluminium is too reactive chemically to occur in nature as the free metal. Instead, it is found combined in over 270 different [[mineral]]s.<ref>{{cite web | publisher = Science is Fun | author = Bassam Z. Shakhashiri | url = http://scifun.chem.wisc.edu/chemweek/Aluminum/ALUMINUM.html | title = Chemical of the Week: Aluminum | accessdate = 2007-08-28}}</ref> The chief source of aluminium is [[bauxite]] [[ore]]. Aluminium is remarkable for its ability to resist [[corrosion]] (due to the phenomenon of [[passivation]]) and its light weight. Structural components made from aluminium and its alloys are vital to the aerospace industry and very important in other areas of transportation and building.

==History==
Ancient Greeks and Romans used aluminium salts as dyeing mordants and as astringents for dressing wounds; [[alum]] is still used as a [[styptic]]. In 1761 Guyton de Morveau suggested calling the base alum ''alumine.''  In 1808, [[Humphry Davy]] identified the existence of a metal base of alum, which he at first termed ''alumium'' and later ''aluminum'' (see [[#Etymology|Etymology]] section, below).

[[Image:Eros-piccadilly-circus.jpg|thumb|left|The statue known as ''Eros'' in Piccadilly Circus London, was made in 1893 and is one of the first statues to be cast in aluminium.]]
[[Friedrich Woehler|Friedrich Wöhler]] is generally credited with isolating aluminium ([[Latin]] ''alumen'', alum) in 1827 by mixing [[anhydrous]] [[aluminium chloride]] with [[potassium]]. The metal was, however, produced for the first time two years earlier (in an impure form) by the Danish physicist and chemist [[Hans Christian Ørsted]].  Therefore, Ørsted can also be listed as the discoverer of the metal.<ref>{{cite web | publisher = ChemicalElements.com | title = Periodic Table: Aluminum | url = http://www.chemicalelements.com/elements/al.html | author = Yinon Bentor | accessdate = 2007-08-11}}</ref> Further, [[Pierre Berthier]] discovered aluminium in bauxite ore and successfully extracted it.<ref>{{cite web | publisher = Today in Science History | title = Pierre Berthier | url = http://www.todayinsci.com/7/7_03.htm#Berthier | accessdate = 2007-08-11}}</ref> The Frenchman [[Henri Etienne Sainte-Claire Deville]] improved Wöhler's method in 1846 and described his improvements in a book in 1859, chief among these being the substitution of sodium for the considerably more expensive potassium.

(Note: The title of Deville's book is "De l'aluminium, ses propriétés, sa fabrication" (Paris, 1859). It was rather likely that Deville also conceived  the idea of the [[electrolysis]] of aluminium oxide dissolved in cryolite; however, Charles Martin Hall and Paul Héroult might have developed the more practical process after Deville.)

Before the Hall-Héroult process was developed, aluminium was initially found to be exceedingly difficult to extract from its various [[ore]]s. This made pure aluminium more valuable than gold. Bars of aluminium were exhibited alongside the French crown jewels at the Exposition Universelle of 1855, and Napoleon III was said to have reserved a set of aluminium dinner plates for his most honored guests.

Aluminium was selected as the material to be used for the apex of the Washington Monument in 1884, a time when one [[ounce]] (30 grams) cost the daily wage of a common worker on the project;<ref>{{cite journal | author = George J. Binczewski | title = The Point of a Monument: A History of the Aluminum Cap of the Washington Monument | journal = JOM | volume = 47 | issue = 11 | pages = 20- 25 | year = 1995 | url = http://www.tms.org/pubs/journals/JOM/9511/Binczewski-9511.html}}</ref> aluminium was about the same value as silver. 

The Cowles companies supplied aluminium alloy in quantity in the United States and England using smelters like the furnace of Carl Wilhelm Siemens by 1886.<ref>{{cite journal|title=Cowles' Aluminium Alloys|pages=13|date=January 1886|journal=The Manufacturer and Builder|location=New York|volume=18|issue=1|publisher=Western and Company, via Cornell University Library|url=http://moa.cit.cornell.edu/cgi-bin/moa/pageviewer?frames=1&coll=moa&view=50&root=%2Fmoa%2Fmanu%2Fmanu0018%2F&tif=00019.TIF|accessdate=2007-10-27}} and {{cite book|author=McMillan, Walter George|title=A Treatise on Electro-Metallurgy|publisher=Charles Griffin and Company, J.B. Lippincott Company, via Google Books scan of New York Public Library copy|location=London, Philadelphia|date=1891|url=http://books.google.com/books?id=DDAKAAAAIAAJ&pg=PA302|pages=302-305|accessdate=2007-10-26}} and {{cite book|author=Sackett, William Edgar, John James Scannell and Mary Eleanor Watson|title=New Jersey's First Citizens|url=http://books.google.com/books?id=cNgDAAAAYAAJ&pg=PA103|publisher=J.J. Scannell via Google Books scan of New York Public Library copy|location=New Jersey|date=1917/1918|pages=103-105|accessdate=2007-10-25}}</ref> Charles Martin Hall of Ohio in the U.S. and Paul Héroult of France independently developed the Hall-Héroult electrolytic process that made extracting aluminium from minerals cheaper and is now the principal method used worldwide. The Hall-Heroult process cannot produce Super Purity Aluminium directly. Hall's process,<ref name="Hall-patent">{{US patent reference|number = 400664|y = 1889 | m=04|d=02|inventor=Charles Martin Hall|title=Process of Reducing Aluminium from its Fluoride Salts by Electrolysis}}</ref> in 1888 with the financial backing of Alfred E. Hunt, started the Pittsburgh Reduction Company today known as Alcoa. Héroult's process was in production by 1889 in Switzerland at Aluminium Industrie, now Alcan, and atBritish Aluminium, now Luxfer Group and Alcoa, by 1896 in Scotland.<ref name=Wallace>{{cite book|author=Donald Holmes Wallace|title=Market Control in the Aluminum Industry|url=http://books.google.com/books?id=E-acdJWbo90C&pg=PA6|date=1977|origyear=1937|pages=6|isbn=0-4050-9786-7|publisher=Harvard University Press via Ayer Publishing via Google Books limited view|accessdate=2007-10-27}}</ref>

By 1895 the metal was being used as a building material as far away as Sydney, Australia in the dome of the Chief Secretary's Building.

==Etymology==
===Nomenclature history===
The earliest citation given in the gay Oxford English Dictionary for any word used as a name for this element is ''alumium'', which Humphry Davy employed in 1808 for the metal he was trying to isolate electrolytically from the mineral ''alumina''. The citation is from his journal ''Philosophical Transactions'': "Had I been so fortunate as..to have procured the metallic substances I was in search of, I should have proposed for them the names of silicium, alumium, zirconium, and glucium."<ref>"alumium", ''Oxford English Dictionary''. Ed. J.A. Simpson and E.S.C. Weiner, second edition Oxford: Clarendon Press, 1989. OED Online Oxford University Press. Accessed October 29 2006. Citation is listed as "1808 SIR H. DAVY in Phil. Trans. XCVIII. 353". The ellipsis in the quotation is as it appears in the ''OED'' citation. </ref>

By 1812, Davy had settled on  ''aluminum,'' which, as other sources note,  matches its Latin root. He wrote in the journal ''Chemical Philosophy'': "As yet Aluminum has not been obtained in a perfectly free state."<ref>"aluminum", ''ibid''. Citation is listed as "1812 SIR H. DAVY ''Chem. Philos.'' I. 355"</ref> But the same year, an anonymous contributor to the ''Quarterly Review,'' a British political-literary journal, objected to ''aluminum'' and proposed the name ''aluminium'', "for so we shall take the liberty of writing the word, in preference to aluminum, which has a less classical sound."<ref>"aluminium", ''ibid''. Citation is listed as "1812 ''Q. Rev.'' VIII. 72"</ref>

The ''-ium'' suffix had the advantage of conforming to the precedent set in other newly discovered elements of the time: potassium, sodium, magnesium, calcium, and [[strontium]] (all of which Davy had isolated himself). Nevertheless, ''-um'' spellings for elements were not unknown at the time, as for example [[platinum]], known to Europeans since the sixteenth century, [[molybdenum]], discovered in 1778, and [[tantalum]], discovered in 1802. 

Americans adopted ''-ium'' to fit the standard form of the periodic table of elements, for most of the nineteenth century, with ''aluminium'' appearing in Webster's Dictionary of 1828. In 1892, however, Charles Martin Hall used the ''-um'' spelling in an advertising handbill for his new electrolytic method of producing the metal, despite his constant use of the ''-ium'' spelling in all the patents<ref name="Hall-patent"/> he filed between 1886 and 1903.<ref>{{cite web | author = Peter Meiers | publisher = The History of Fluorine, Fluoride and Fluoridation | title = Manufacture of Aluminum | url =http://www.fluoride-history.de/p-aluminum.htm}}</ref> It has consequently been suggested that the spelling reflects an easier to pronounce word with one fewer syllable, or that the spelling on the flier was a spelling mistake. Hall's domination of production of the metal ensured that the spelling ''aluminum'' became the standard in North America; the ''Webster Unabridged Dictionary'' of 1913, though, continued to use the ''-ium'' version.

In 1926, the [[American Chemical Society]] officially decided to use ''aluminum'' in its publications; American dictionaries typically label the spelling ''aluminium'' as a British variant.

===Present-day spelling===
In the UK and other countries using British spelling, only ''aluminium'' is used. In the United States, the spelling ''aluminium'' is largely unknown, and the spelling ''aluminum'' predominates.<ref>{{Greenwood&Earnshaw}}</ref><ref>John Bremner, ''Words on Words: A Dictionary for Writers and Others Who Care about Words'', page 22–23. ISBN 0-231-04493-3</ref> The Canadian Oxford Dictionary prefers ''aluminum'', whereas the Australian Macquarie Dictionary prefers ''aluminium''. The spelling in virtually all other languages is analogous to the ''-ium'' ending.

The International Union of Pure and Applied Chemistry (IUPAC) adopted ''Aluminium'' as the standard international name for the element in 1990, but three years later recognized ''aluminum'' as an acceptable variant. Hence their periodic table includes both, but places ''aluminium'' first.<ref>[http://www.iupac.org/reports/periodic_table/index.html IUPAC Periodic Table of the Elements]</ref> IUPAC officially prefers the use of ''Aluminium'' in its internal publications, although several IUPAC publications use the spelling ''aluminum''.<ref>[http://www.iupac.org/general/search.php?restrict=publications&query=aluminum&submit=Search IUPAC Web site publication search for 'aluminum']</ref>

==Isotopes==
Aluminium has nine [[isotope]]s, whose mass numbers range from 23 to 30. Only <sup>27</sup>Al ([[stable isotope]]) and <sup>26</sup>Al ([[radioactive decay|radioactive]] isotope, [[half life|''t''<sub>1/2</sub>]] = 7.2 × 10<sup>5</sup> [[year|y]]) occur naturally, however <sup>27</sup>Al has a natural abundance of 99.9+ %.  <sup>26</sup>Al is produced from [[argon]] in the atmosphere by spallation caused by cosmic-ray [[proton]]s. Aluminium isotopes have found practical application in dating marine sediments, manganese nodules, glacial ice, [[quartz]] in [[Rock (geology)|rock]] exposures, and meteorites. The ratio of <sup>26</sup>Al to <sup>10</sup>[[beryllium|Be]] has been used to study the role of transport, deposition, sediment storage, burial times, and erosion on 10<sup>5</sup> to 10<sup>6</sup> year time scales. Cosmogenic <sup>26</sup>Al was first applied in studies of the Moon and meteorites. Meteorite fragments, after departure from their parent bodies, are exposed to intense cosmic-ray bombardment during their travel through space, causing substantial <sup>26</sup>Al production. After falling to Earth, atmospheric shielding protects the meteorite fragments from further <sup>26</sup>Al production, and its decay can then be used to determine the meteorite's terrestrial age. Meteorite research has also shown that <sup>26</sup>Al was relatively abundant at the time of formation of our planetary system. Most meteoriticists believe that the energy released by the decay of <sup>26</sup>Al was responsible for the melting and differentiation of some asteroids after their formation 4.55 billion years ago.<ref>Robert T. Dodd, ''Thunderstones and Shooting Stars'', pp. 89-90. ISBN 0-674-89137-6.</ref>

==Properties==
Aluminium is a soft, lightweight, malleable [[metal]] with appearance ranging from silvery to dull gray, depending on the surface roughness. Aluminium is nontoxic, nonmagnetic, and nonsparking. The yield strength of pure aluminium is 7–11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa.<ref name=polmear>I. J. Polmear, ''Light Alloys'', Arnold, 1995 </ref> Aluminium has about one-third the [[density]] and stiffness of steel. It is [[Ductility|ductile]], and easily machined, [[casting|cast]], and extruded.

[[Corrosion]] resistance is excellent due to a thin surface layer of [[aluminium oxide]] that forms when the metal is exposed to air, effectively preventing further [[oxidation]]. The strongest aluminium alloys are less corrosion resistant due to [[Galvanic cell|galvanic]] reactions with alloyed [[copper]].<ref name=polmear/>

Aluminium atoms are arranged in an [[Face-centered cubic|FCC]] structure. Aluminium has a high stacking-fault energy of approximately 200 mJ/m².<ref>G. E. Dieter, ''Mechanical Metallurgy'', McGraw-Hill, 1988</ref>

Aluminium is one of the few metals that retain full silvery reflectance in finely powdered form, making it an important component of silver paints. Aluminium mirror finish has the highest reflectance of any metal in the 200–400 nm ([[ultraviolet|UV]]) and the 3000–10000 nm (far [[infrared|IR]]) regions, while in the 400–700 nm visible range it is slightly outdone by [[silver]] and in the 700–3000 (near IR) by silver, [[gold]], and copper.

Aluminium is a good [[Heat conduction|thermal]] and [[electrical conductor]], by weight better than copper. Aluminium is capable of being a [[superconductor]], with a superconducting critical temperature of 1.2 [[Kelvin|kelvins]].<ref>{{cite journal|author= John F. Cochran and D. E. Mapother|title=Superconducting Transition in Aluminum |doi=10.1103/PhysRev.111.132| journal=Physical Review |volume=111 |issue=1 |pages=132-142| month=July| year=1958}}</ref>

==Production and refinement==
Although aluminium is the most abundant metallic element in the Earth's crust (believed to be 7.5 to 8.1 percent), it is rare in its free form, occurring in oxygen-deficient environments such as volcanic mud, and it was once considered a precious metal more valuable than gold. Napoleon III, emperor of the French, is reputed to have given a banquet where the most honoured guests were given aluminium utensils, while the other guests had to make do with gold ones.<ref>{{cite journal | title = "Silver" from clay | author = S Venetski | journal = [[Metallurgist]] | volume = 13 | issue = 7 | pages = 451-453 | date = July 1969 | doi = 10.1007/BF00741130 | format = translated}}</ref><ref>ChemMatters October 1990 Page 14</ref> Aluminium has been produced in commercial quantities for just over 100 years. 

Aluminium is a reactive metal that is difficult to extract from ore, aluminium oxide (Al<sub>2</sub>O<sub>3</sub>). For example, direct reduction with [[carbon]] is not economically viable, since aluminium oxide has a melting point of about 2,000 °C. Therefore, it is extracted by electrolysis; that is, the aluminium oxide is dissolved in molten cryolite and then reduced to the pure metal. By this process, the operational temperature of the reduction cells is around 950 to 980 °C. Cryolite is found as a mineral in Greenland, but in industrial use it has been replaced by a synthetic substance. Cryolite is a mixture of aluminium, [[sodium]], and [[calcium]] [[fluoride]]s: (Na<sub>3</sub>AlF<sub>6</sub>). The aluminium oxide (a white powder) is obtained by refining bauxite in the Bayer process of Karl Bayer. (Previously, the Deville process was the predominant refining technology.)

The electrolytic process replaced the Wöhler process, which involved the reduction of anhydrous aluminium chloride with [[potassium]]. Both of the [[electrode]]s used in the electrolysis of aluminium oxide are carbon. Once the ore is in the molten state, its ions are free to move around. The reaction at the [[cathode]] — the negative terminal — is
:Al<sup>3+</sup> + 3 e<sup>−</sup> → Al

Here the aluminium ion is being [[redox|reduced]] (electrons are added). The aluminium metal then sinks to the bottom and is tapped off.

At the positive electrode ([[anode]]), oxygen is formed:
:2 O<sup>2−</sup> → O<sub>2</sub> + 4 e<sup>−</sup>

This carbon anode is then oxidized by the oxygen, releasing carbon dioxide. The anodes in a reduction cell must therefore be replaced regularly, since they are consumed in the process:
:O<sub>2</sub> + C → CO<sub>2</sub>

Unlike the anodes, the cathodes are not oxidised because there is no oxygen present at the cathode. The carbon cathode is protected by the liquid aluminium inside the cells. Nevertheless, cathodes do erode, mainly due to electrochemical processes. After five to ten years, depending on the current used in the electrolysis, a cell has to be rebuilt because of cathode wear.

[[Image:Aluminium - world production trend.svg|thumb|World production trend of aluminium]]
Aluminium electrolysis with the Hall-Héroult process consumes a lot of energy, but alternative processes were always found to be less viable economically and/or ecologically. The world-wide average specific energy consumption is approximately 15±0.5 kilowatt-hours per kilogram of aluminium produced from alumina. (52 to 56 MJ/kg). The most modern smelters reach approximately 12.8 kW·h/kg (46.1 MJ/kg). (Compare this to the [[heat of reaction]], 31 MJ/kg, and the [[Gibbs free energy]] of reaction, 29 MJ/kg.) Reduction line current for older technologies are typically 100 to 200 kA. State-of-the-art smelters operate with about 350 kA. Trials have been reported with 500 kA cells.

Recovery of the metal via recycling has become an important facet of the aluminium industry. Recycling involves melting the scrap, a process that uses only five percent of the energy needed to produce aluminium from ore. However, a significant part (up to 15% of input material) is lost as dross (ash-like oxide).<ref>{{cite web | title = Benefits of Recycling | publisher = Ohio Department of Natural Resources | url = http://www.dnr.state.oh.us/recycling/awareness/facts/benefits.htm}}</ref> Recycling was a low-profile activity until the late 1960s, when the growing use of aluminium beverage cans brought it to the public consciousness.

Electric power represents about 20% to 40% of the cost of producing aluminium, depending on the location of the smelter. Smelters tend to be situated where electric power is both plentiful and inexpensive, such as South Africa, the South Island of New Zealand, Australia, the People's Republic of China, the Middle East, Russia, Quebec and British Columbia in Canada, and Iceland.
[[Image:Aluminium output2.jpg|thumb|right|Aluminium output in 2005]]
In 2005, the People's Republic of China was the top producer of aluminium with almost one-fifth world share followed by Russia, Canada and USA reports the British Geological Survey.

Over the last 50 years, Australia has become a major producer of bauxite ore and a major producer and exporter of alumina.<ref>{{cite web | publisher = Australian Aluminium Council | url = http://www.aluminium.org.au/Page.php?s=1005 | title = The Australian Industry | accessdate = 2007-08-11}}</ref> Australia produced 62 million tonnes of bauxite in 2005. The Australian deposits have some refining problems, some being high in silica but have the advantage of being shallow and relatively easy to mine.<ref>{{cite web | publisher = Australian Aluminium Council | url = http://www.aluminium.org.au/Page.php?s=1007 | title = Australian Bauxite | accessdate = 2007-08-11}}</ref>

==Chemistry==
===Oxidation state one===
* AlH is produced when aluminium is heated in an atmosphere of [[hydrogen]].
* Al<sub>2</sub>O is made by heating the normal oxide, Al<sub>2</sub>O<sub>3</sub>, with silicon at 1800 °C in a [[vacuum]].
* Al<sub>2</sub>S can be made by heating Al<sub>2</sub>S<sub>3</sub> with aluminium shavings at 1300 °C in a vacuum. It quickly disproportionates to the starting materials. The selenide is made in a parallel manner.
*AlF, AlCl and AlBr exist in the gaseous phase when the tri-halide is heated with aluminium.
Aluminium halides usually exist in the form AlX<sub>3</sub>.
e.g. AlF<sub>3</sub>, AlCl<sub>3</sub>, AlBr<sub>3</sub>, AlI<sub>3</sub> etc.

===Oxidation state two===
* [[Aluminium monoxide]], AlO, is present when aluminium powder burns in oxygen.

===Oxidation state three===
* [[Fajans' rules]] show that the simple trivalent cation Al<sup>3+</sup> is not expected to be found in anhydrous salts or binary compounds such as Al<sub>2</sub>O<sub>3</sub>. The hydroxide is a weak base and aluminium salts of weak acids, such as carbonate, can't be prepared. The salts of strong acids, such as nitrate, are stable and soluble in water, forming hydrates with at least six molecules of [[water of crystallization]].
* [[Aluminium hydride]], (AlH<sub>3</sub>)<sub>n</sub>, can be produced from [[trimethylaluminium]] and an excess of hydrogen. It burns explosively in air. It can also be prepared by the action of aluminium chloride on [[lithium hydride]] in [[ether]] solution, but cannot be isolated free from the solvent.
* [[Aluminium carbide]], Al<sub>4</sub>C<sub>3</sub> is made by heating a mixture of the elements above 1000 °C. The pale yellow crystals have a complex lattice structure, and react with water or dilute acids to give [[methane]]. The [[metal acetylide|acetylide]], Al<sub>2</sub>(C<sub>2</sub>)<sub>3</sub>, is made by passing [[acetylene]] over heated aluminium.
* [[Aluminium nitride]], AlN, can be made from the elements at 800 °C. It is hydrolysed by water to form [[ammonia]] and [[aluminium hydroxide]].
* [[Aluminium phosphide]], AlP, is made similarly, and hydrolyses to give [[phosphine]].
* Aluminium oxide, Al<sub>2</sub>O<sub>3</sub>, occurs naturally as corundum, and can be made by burning aluminium in oxygen or by heating the hydroxide, nitrate or sulfate. As a gemstone, its hardness is only exceeded by [[diamond]], [[boron nitride]], and [[carborundum]]. It is almost insoluble in water.
* [[Aluminium hydroxide]] may be prepared as a gelatinous precipitate by adding ammonia to an aqueous solution of an aluminium salt. It is [[amphoteric]], being both a very weak acid, and forming aluminates with [[alkali]]s. It exists in various crystalline forms.
* [[Aluminium sulfide]], Al<sub>2</sub>S<sub>3</sub>, may be prepared by passing [[hydrogen sulfide]] over aluminium powder. It is [[Polymorphism (materials science)|polymorphic]].
* [[Aluminium iodide]], (AlI<sub>3</sub>)<sub>2</sub>, is a [[dimer]] with applications in [[organic synthesis]].
* [[Aluminium fluoride]], AlF<sub>3</sub>, is made by treating the hydroxide with HF, or can be made from the elements. It consists of a giant molecule which sublimes without melting at 1291 °C. It is very inert. The other trihalides are dimeric, having a bridge-like structure.
* Aluminium fluoride/water complexes: When aluminium and fluoride are together in aqueous solution, they readily form complex ions such as AlF(H<sub>2</sub>O)<sub>5</sub><sup>+2</sup>, AlF<sub>3</sub>(H<sub>2</sub>O)<sub>3</sub><sup>0</sup>, AlF<sub>6</sub><sup>-3</sup>. Of these, AlF<sub>6</sub><sup>-3</sup> is the most stable. This is explained by the fact that aluminium and fluoride, which are both very compact ions, fit together just right to form the octahedral aluminium hexafluoride complex. When aluminium and fluoride are together in water in a 1:6 molar ratio, AlF<sub>6</sub><sup>-3</sup> is the most common form, even in rather low concentrations.
* Organo-metallic compounds of empirical formula AlR<sub>3</sub> exist and, if not also giant molecules, are at least dimers or trimers. They have some uses in organic synthesis, for instance trimethylaluminium.
* Alumino-hydrides of the most electropositive elements are known, the most useful being [[lithium aluminium hydride]], Li[AlH<sub>4</sub>]. It decomposes into lithium hydride, aluminium and hydrogen when heated, and is hydrolysed by water. It has many uses in organic chemistry, particularly as a reducing agent. The aluminohalides have a similar structure.
===Clusters===
In the journal ''[[Science (journal)|Science]]'' of 14 January 2005 it was reported that clusters of 13 aluminium atoms (Al<sub>13</sub>) had been made to behave like an [[iodine]] atom; and, 14 aluminium atoms (Al<sub>14</sub>) behaved like an alkaline earth atom. The researchers also bound 12 iodine atoms to an Al<sub>13</sub> cluster to form a new class of polyiodide. This discovery is reported to give rise to the possibility of a new characterisation of the [[periodic table]]: [[superatom]]s. The research teams were led by Shiv N. Khanna (Virginia Commonwealth University) and A. Welford Castleman Jr (Penn State University).<ref>{{cite press release | title = Clusters of Aluminum Atoms Found to Have Properties of Other Elements Reveal a New Form of Chemistry | date = [[13 January]] [[2005]] | publisher = Eberly College of Science | url = http://www.science.psu.edu/alert/Castleman1-2005.htm}}</ref>


==Applications==
===General use===
[[Image:Aluminum Metal coinless.jpg|thumb|left|A piece of aluminium metal.]]
Aluminium is the most widely used non-ferrous metal.<ref>{{cite encyclopedia |year= |title = aluminum | encyclopedia=[[Encyclopedia Britannica]] |publisher= |location= |url = http://www.britannica.com/eb/art-64454}}</ref> Global production of aluminium in 2005 was 31.9 million tonnes. It exceeded that of any other metal except [[iron]] (837.5 million tonnes).<ref>{{cite book | title = World Mineral Production: 2001 - 2005 | author = L E Hetherington, T J Brown, A J Benham, P A J Lusty, N E Idoine | year = 2007 | publisher = British Geological Survey | isbn = 978-0-85272-592-4 | format = available online | url = http://www.mineralsuk.com/britmin/wmp_2001_2005.pdf}}</ref>
Relatively pure aluminium is encountered only when corrosion resistance and/or workability is more important than strength or hardness. A thin layer of aluminium can be deposited onto a flat surface by physical vapor deposition or (very infrequently) chemical vapor deposition or other chemical means to form optical coatings and mirrors. When so deposited, a fresh, pure aluminium film serves as a good reflector (approximately 92%) of visible light and an excellent reflector (as much as 98%) of medium and far infrared.

Pure aluminium has a low tensile strength, but when combined with thermo-mechanical processing, aluminium alloys display a marked improvement in mechanical properties, especially when tempered. Aluminium alloys form vital components of aircraft and rockets as a result of their high strength-to-weight ratio. Aluminium readily forms alloys with many elements such as copper, [[zinc]], [[magnesium]], [[manganese]] and [[silicon]] (e.g., duralumin). Today, almost all bulk metal materials that are referred to loosely as "aluminium," are actually alloys. For example, the common aluminium foils are alloys of 92% to 99% aluminium.<ref>{{cite web | publisher = How Products are Made | author = L. S. Millberg | url = http://www.madehow.com/Volume-1/Aluminum-Foil.html | title = Aluminum Foil | accessdate = 2007-08-11}}</ref>

Some of the many uses for aluminium metal are in:
* Transportation (automobiles, aircraft, trucks, railway cars, marine vessels, bicycles etc.)
* Packaging (cans, foil, etc.)
* Water treatment
* Treatment against fish parasites such as ''Gyrodactylus salaris''.
* Construction (windows, doors, siding, building wire, etc.)
* Cooking utensils
* Electrical transmission lines for power distribution
* MKM steel and Alnico magnets
* Super purity aluminium (SPA, 99.980% to 99.999% Al), used in electronics and CDs.
* Heat sinks for electronic appliances such as transistors and CPUs.
* Powdered aluminium is used in paint, and in pyrotechnics such as solid rocket fuels and thermite.
* In the blades of prop swords and knives used in stage combat.

===Aluminium compounds===
* Aluminium ammonium sulfate ([Al(NH<sub>4</sub>)](SO<sub>4</sub>)<sub>2</sub>), ammonium alum is used as a mordant, in water purification and sewage treatment, in paper production, as a food additive, and in leather tanning.

* Aluminium acetate is a [[salt]] used in solution as an astringent.

* Aluminium borate (Al<sub>2</sub>O<sub>3</sub> B<sub>2</sub>O<sub>3</sub>) is used in the production of glass and ceramic.

* Aluminium borohydride (Al(BH<sub>4</sub>)<sub>3</sub>) is used as an additive to jet fuel.

* [[Aluminium chloride]] (AlCl<sub>3</sub>) is used: in paint manufacturing, in antiperspirants, in petroleum refining and in the production of synthetic rubber.

* Aluminium chlorohydride is used as an antiperspirant and in the treatment of [[hyperhidrosis]].

* Aluminium fluorosilicate (Al<sub>2</sub>(SiF<sub>6</sub>)<sub>3</sub>) is used in the production of synthetic gemstones, glass and ceramic.

* [[Aluminium hydroxide]] (Al(OH)<sub>3</sub>) is used: as an antacid, as a mordant, in water purification, in the manufacture of glass and ceramic and in the waterproofing of fabrics.

* [[Aluminium oxide]] (Al<sub>2</sub>O<sub>3</sub>), alumina, is found naturally as [[corundum]] (rubies and sapphires), emery, and is used in glass making. Synthetic ruby and sapphire are used in [[laser]]s for the production of coherent light.

* [[Aluminium phosphate]] (AlPO<sub>4</sub>) is used in the manufacture: of glass and ceramic, pulp and paper products, cosmetics, paints and varnishes and in making dental cement.

* [[Aluminium sulfate]] (Al<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>) is used: in the manufacture of paper, as a mordant, in a fire extinguisher, in water purification and sewage treatment, as a food additive, in fireproofing, and in leather tanning.

* In many vaccines, certain aluminium salts serve as an immune adjuvant (immune response booster) to allow the protein in the vaccine to achieve sufficient potency as an immune stimulant.

===Aluminium alloys in structural applications===
[[Image:Aluminium_foam.jpg|thumb|Aluminium foam]]
Aluminium alloys with a wide range of properties are used in engineering structures. Alloy systems are classified by a number system (ANSI) or by names indicating their main alloying constituents (DIN and ISO). 

The strength and durability of aluminium alloys vary widely, not only as a result of the components of the specific alloy, but also as a result of heat treatments and manufacturing processes. A lack of knowledge of these aspects has from time to time led to improperly designed structures and gained aluminium a bad reputation. (See main article)

One important structural limitation of aluminium alloys is their fatigue strength.  Unlike steels, aluminium alloys have no well-defined fatigue limit, meaning that fatigue failure will eventually occur under even very small cyclic loadings. This implies that engineers must assess these loads and design for a fixed life rather than an infinite life.

Another important property of aluminium alloys is their sensitivity to heat.
Workshop procedures involving heating are complicated by the fact that aluminium, unlike steel, will melt without first glowing red. Forming operations where a blow torch is used therefore requires some expertise, since no visual signs reveal how close the material is to melting. Aluminium alloys, like all structural alloys, also are subject to internal stresses following heating operations such as welding and casting. The problem with aluminium alloys in this regard is their low melting point, which make them more susceptible to distortions from thermally induced stress relief. Controlled stress relief can be done during manufacturing by heat-treating the parts in an oven, followed by gradual cooling -- in effect annealing the stresses. 

The low melting point of aluminium alloys has not precluded their use in rocketry; even for use in constructing combustion chambers where gases can reach 3500&nbsp;K. The Agena upper stage engine used a regeneratively cooled aluminium design for some parts of the nozzle, including the thermally critical throat region.

===Household wiring===

Aluminium has about 65% of the conductivity of copper, the traditional household wiring material.  In the 1960s aluminium was considerably cheaper than copper, and so was introduced for household electrical wiring in the United States, even though many fixtures had not been designed to accept aluminium wire.  However, in some cases the greater coefficient of thermal expansion of aluminium causes the wire to expand and contract relative to the dissimilar metal screw connection, eventually loosening the connection.  Also, pure aluminium has a tendency to ''creep'' under steady sustained pressure (to a greater degree as the temperature rises), again loosening the connection.  Finally, Galvanic corrosion from the dissimilar metals increased the electrical resistance of the connection. 

All of this resulted in overheated and loose connections, and this in turn resulted in fires.  Builders then became wary of using the wire, and many jurisdictions outlawed its use in very small sizes in new construction.  Eventually, newer fixtures were introduced with connections designed to avoid loosening and overheating.  At first they were marked "Al/Cu", but they now bear a "CO/ALR" coding.  In older assemblies, workers forestall the heating problem using a properly-done crimp of the aluminium wire to a short "pigtail" of copper wire.  Today, new alloys, designs, and methods are used for aluminium wiring in combination with aluminium terminations.

==Precautions==
Aluminium is a [[neurotoxin]] that alters the function of the blood-brain barrier.<ref>{{cite journal | author = Banks, W.A. | coauthors = Kastin, A.J. | year = 1989 | title = Aluminum-induced neurotoxicity: alterations in membrane function at the blood-brain barrier. | journal = Neurosci Biobehav Rev | volume = 13 | issue = 1 | pages = 47-53 | doi = 10.1016/S0149-7634(89)80051-X}}</ref> It is one of the few abundant elements that appear to have no beneficial function to living cells. A small percent of people are [[allergy|allergic]] to it &mdash; they experience [[contact dermatitis]] from any form of it: an itchy [[rash]] from using styptic or antiperspirant products, digestive disorders and inability to absorb nutrients from eating food cooked in aluminium pans, and [[vomiting]] and other symptoms of [[poisoning]] from ingesting such products as [[Amphojel]], and [[Maalox]] (antacids). In other people, aluminium is not considered as toxic as [[heavy metal]]s, but there is evidence of some toxicity if it is consumed in excessive amounts. The use of aluminium cookware, popular because of its [[corrosion]] resistance and good [[heat conduction]], has not been shown to lead to aluminium toxicity in general. Excessive consumption of [[antacid]]s containing aluminium compounds and excessive use of aluminium-containing antiperspirants are more likely causes of [[toxicity]].  In research published in the Journal of Applied Toxicology, Dr. Philippa D. Darby of the University of Reading has shown that aluminium [[salt]]s increase [[estrogen]]-related [[gene expression]] in human [[breast cancer]] cells grown in the laboratory. These salts' estrogen-like effects have led to their classification as a [[metalloestrogen]].

It has been suggested that aluminium is a cause of [[Alzheimer's disease]], as some brain plaques have been found to contain the metal. Research in this area has been inconclusive; aluminium accumulation may be a consequence of the Alzheimer's damage, not the cause. In any event, if there is any toxicity of aluminium it must be via a very specific mechanism, since total human exposure to the element in the form of naturally occurring clay in soil and dust is enormously large over a lifetime.<ref>{{cite web | publisher = National Institute of Environmental Health Sciences | title = Alzheimer's Disease and Aluminum | date = October 2005 | url = http://www.niehs.nih.gov/external/faq/aluminum.htm}}</ref><ref>{{cite news | author = Michael Hopkin | title = Death of Alzheimer victim linked to aluminium pollution| publisher = news @ nature.com | id = {{doi|10.1038/news060417-10}} | date = [[21 April]] [[2006]]}}</ref> 

[[mercury (element)|Mercury]] applied to the surface of an aluminium alloy can damage the protective oxide surface film by forming amalgam. This may cause further corrosion and weakening of the structure. For this reason, mercury [[thermometer]]s are not allowed on many airliners, as aluminium is used in many aircraft structures.

Powdered aluminium can react with [[Iron(III) oxide|Fe<sub>2</sub>O<sub>3</sub>]] to form [[Iron|Fe]] and [[Al2O3|Al<sub>2</sub>O<sub>3</sub>]]. This mixture is known as thermite, which burns with a high energy output. Thermite can be produced inadvertently during grinding operations, but the high ignition temperature makes incidents unlikely in most workshop environments.

===Aluminium and plants (phytoremediation)===
<!-- Am hoping to fill up this section with a bit more chemistry when I come across it. If you feel that this does not deserve a sub-paragraph, thank you for moving it to the discussion page where I can come back to it as information comes -->
Aluminium is primary among the factors that contribute to the loss of plant production on acid soils. Although it is generally harmless to plant growth in pH-neutral soils, the concentration in acid soils of toxic Al<sup>3+</sup> [[cation]]s increases and disturbs root growth and function.

[[Wheat]]'s [[adaptation]] to allow aluminium tolerance is such that the aluminium induces a release of [[organic compound]]s that bind to the harmful aluminium [[cations]]. Sorghum is believed to have the same tolerance mechanism. The first gene for aluminium tolerance has been identified in wheat. A group in the U.S. Department of Agriculture showed that sorghum's aluminium tolerance is controlled by a single gene, as for wheat. This is not the case in all plants.


==References==
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==External links==
*[http://www.crnindia.com/commodity/aluminium.html Aluminium as a traded commodity]
*[http://www.webelements.com/webelements/elements/text/Al/index.html WebElements.com &ndash; Aluminium]
*[http://www.indexmundi.com/en/commodities/minerals/aluminum/aluminum_table12.html World production of primary aluminium, by country]
*[http://www.world-aluminium.org/About+Aluminium/Story+of/In+history History of Aluminium]
*[http://aluminium.matter.org.uk aluMATTER: Free on-line e-Learning resources on aluminium science and technology]

[[Category:Aluminium| ]]

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