Difference between revisions of "Aluminum" - New World Encyclopedia

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{{Elementbox_header | number=13 | symbol=Al | name=aluminium | left=[[magnesium]] | right=[[silicon]] | above=[[boron|B]] | below=[[gallium|Ga]] | color1=#cccccc | color2=black }}
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{{Images OK}}{{Submitted}}{{Approved}}{{Paid}}{{Copyedited}}
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{{Elementbox_series | [[poor metal]]s }}
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{{Infobox aluminium}}
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{{Elementbox_groupperiodblock | group=13 | period=3 | block=p }}
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{{redirect|Aluminium}}
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{{Elementbox_appearance_img | Al,13| silvery }}
 
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{{Elementbox_atomicmass_gpm | [[1 E-26 kg|26.981538(2)]] }}
 
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{{Elementbox_econfig | &#91;[[neon|Ne]]&#93; 3s<sup>2</sup> 3p<sup>1</sup> }}
 
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{{Elementbox_epershell | 2, 8, 3 }}x
 
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{{Elementbox_section_physicalprop | color1=#cccccc | color2=black }}
 
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{{Elementbox_phase | [[solid]] }}
 
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{{Elementbox_density_gpcm3nrt | 2.70 }}
 
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{{Elementbox_densityliq_gpcm3mp | 2.375 }}
 
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{{Elementbox_meltingpoint | k=933.47 | c=660.32 | f=1220.58 }}
 
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{{Elementbox_boilingpoint | k=2792 | c=2519 | f=4566 }}
 
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{{Elementbox_heatfusion_kjpmol | 10.71 }}
 
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{{Elementbox_heatvaporiz_kjpmol | 294.0 }}
 
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{{Elementbox_heatcapacity_jpmolkat25 | 24.200 }}
 
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{{Elementbox_vaporpressure_katpa | 1482 | 1632 | 1817 | 2054 | 2364 | 2790 | comment= }}
 
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{{Elementbox_section_atomicprop | color1=#cccccc | color2=black }}
 
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{{Elementbox_crystalstruct | cubic face centered }}
 
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{{Elementbox_oxistates | 3<br />([[amphoteric]] oxide) }}
 
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{{Elementbox_electroneg_pauling | 1.61 }}
 
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{{Elementbox_ionizationenergies4 | 577.5 | 1816.7 | 2744.8 }}
 
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{{Elementbox_atomicradius_pm | [[1 E-10 m|125]] }}
 
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{{Elementbox_atomicradiuscalc_pm | [[1 E-10 m|118]] }}
 
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{{Elementbox_covalentradius_pm | [[1 E-10 m|118]] }}
 
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{{Elementbox_section_miscellaneous | color1=#cccccc | color2=black }}
 
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{{Elementbox_magnetic | [[paramagnetism|paramagnetic]] }}
 
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{{Elementbox_eresist_ohmmat20 | 26.50 n}}
 
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{{Elementbox_thermalcond_wpmkat300k | 237 }}
 
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{{Elementbox_thermalexpansion_umpmkat25 | 23.1 }}
 
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{{Elementbox_speedofsound_rodmpsatrt | (rolled) 5000 }}
 
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{{Elementbox_youngsmodulus_gpa | 70 }}
 
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{{Elementbox_shearmodulus_gpa | 26 }}
 
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{{Elementbox_bulkmodulus_gpa | 76 }}
 
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{{Elementbox_poissonratio | 0.35 }}
 
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{{Elementbox_mohshardness | 2.75 }}
 
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{{Elementbox_vickershardness_mpa | 167 }}
 
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{{Elementbox_brinellhardness_mpa | 245 }}
 
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{{Elementbox_cas_number | 7429-90-5 }}
 
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{{Elementbox_isotopes_begin | isotopesof=aluminium | color1=#cccccc | color2=black }}
 
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{{Elementbox_isotopes_decay3 | mn=26 | sym=Al | na=[[synthetic radioisotope|syn]] | hl=[[1 E12 s|7.17&times;10<sup>5</sup>]][[year|y]] | dm1=[[Positron emission|&beta;<sup>+</sup>]] | de1=1.17 | pn1=26 | ps1=[[magnesium|Mg]] | dm2=[[electron capture|&epsilon;]] | de2=- | pn2=26 | ps2=[[magnesium|Mg]] | dm3=[[Gamma radiation|&gamma;]] | de3=1.8086 | pn3= | ps3=- }}
 
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{{Elementbox_isotopes_stable | mn=27 | sym=Al | na=100% | n=14 }}
 
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{{Elementbox_isotopes_end}}
 
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{{Elementbox_footer | color1=#cccccc | color2=black }}
 
  
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'''Aluminium''', '''aluminum''' (Symbol '''Al''') (see the [[#Spelling|spelling]] section below) is a silvery and ductile member of the [[poor metal]] group of [[chemical element]]s. Its [[atomic number]] is 13.  Aluminium is found primarily as the ore [[bauxite]] and is remarkable for its resistance to oxidation (due to the phenomenon of [[passivation]]), its strength, and its light weight. Aluminium is used in many industries to make millions of different products and is very important to the [[world economy]]. Structural components made from aluminium are vital to the [[aerospace]] industry and very important in other areas of [[transport]]ation and building in which light weight, durability, and strength are needed.
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'''Aluminum''' (or '''aluminium''') (chemical symbol '''Al''', [[atomic number]] is 13) is a soft, lightweight [[metal]] with a silvery appearance and the ability to resist [[corrosion]]. It is the most abundant metallic element in the [[Earth]]'s crust (estimated at between 7.5 and 8.1 percent). The free element, rarely found in nature, occurs in oxygen-deficient environments such as volcanic mud. Its main [[ore]] is [[bauxite]]. Whether measured in terms of quantity or value, the global use of aluminum exceeds that of any other metal except [[iron]], and it is important in virtually all segments of the world economy.
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{{toc}}
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Structural components made from aluminum and its [[alloy]]s are vital to the [[aerospace]] industry and very important in other areas of [[transport]]ation and building. In addition, aluminum and its alloys are used in packaging, cooking utensils, electrical transmission lines, [[water purification]] processes, [[electronic]] devices and [[compact disc]]s, [[paint]], and [[pyrotechnics]]. Aluminum compounds also serve a wide variety of purposes. For instance, aluminum ammonium sulfate is a [[mordant]] for [[dye]]ing, and is used in water purification and sewage treatment; aluminum acetate solution is an [[astringent]]; [[aluminum chloride]] is used in paints and anti-perspirants; and aluminum borate, phosphate, and fluorosilicate are used in the production of [[glass]] and [[ceramic]]s. Yet, aluminum is one of the few abundant elements that appear to have no beneficial biological role; a small percentage of people are allergic to it.
  
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== Properties ==
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== History ==
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Ancient [[Ancient Greece|Greeks]] and [[Ancient Rome|Romans]] used aluminum [[salt]]s as [[mordant]]s for dyeing and [[astringent]]s for dressing wounds. [[Alum]] (potassium aluminum sulfate or a related salt) 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 named ''alumium'' and later ''aluminum'' (see [[#Spelling|Spelling]] section, below).
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[[Friedrich Woehler|Friedrich Wöhler]] is generally credited with isolating aluminum ([[Latin]] ''alumen,'' [[alum]]) in 1827 by mixing anhydrous [[aluminum chloride]] with [[potassium]]. The metal, however, had been produced (albeit in impure form) for the first time two years earlier by the Danish physicist and chemist [[Hans Christian Ørsted]]. Therefore, Ørsted can also be listed as the discoverer of the metal.<ref>Yinon Bentor. [http://www.chemicalelements.com/elements/al.html Periodic Table: Aluminum] ChemicalElements.com. Retrieved August 13, 2007.</ref> Further, [[Pierre Berthier]] discovered aluminum in bauxite ore and successfully extracted it.<ref>[http://www.todayinsci.com/7/7_03.htm#Berthier Pierre Berthier]. ''Today in Science History''. Retrieved August 13, 2007.</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.<ref>The title of Deville's book is ''De l'aluminium, ses propriétés, sa fabrication'' (Paris, 1859). It is likely that Deville also thought of the idea of the electrolysis of aluminum oxide dissolved in cryolite. However, Charles Martin Hall and Paul Heroult might have developed the more practical process after Deville.</ref>
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[[Image:Eros-piccadilly-circus.jpg|thumb|right|The statue ''Eros'' in [[Piccadilly Circus]] London, constructed in 1893, and is one of the first statues to be cast in aluminum.]]
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Before the development of methods to purify aluminum in large quantities, it was considered a [[precious metal]] more valuable than [[gold]]. [[Napoleon III of France|Napoleon III]], Emperor of France, is reputed to have given a banquet where the most honored guests were given aluminum utensils, while the other guests had to make do with gold ones.<ref>S. Venetski,  1969. "Silver" from clay. ''Metallurgist'' 13(7): 451-453.</ref><ref>'' ChemMatters'' magazine. (1990): 14</ref>
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Aluminum was selected as the material to be used for the apex of the [[Washington Monument]] in 1884, a time when a single [[ounce]] (30 grams) of the substance cost the daily wage of a common worker on the project.<ref>George J. Binczewski, 1995. [http://www.tms.org/pubs/journals/JOM/9511/Binczewski-9511.html The Point of a Monument: A History of the Aluminum Cap of the Washington Monument]. Retrieved August 13, 2007.</ref> It had about the same value as [[silver]].
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In 1886, the American [[Charles Martin Hall]] of [[Oberlin, Ohio]] applied for a [[patent]] ({{US patent|400664}}) for an electrolytic process to extract aluminum using the same technique that was independently being developed by the Frenchman [[Paul Héroult]] in Europe. The invention of the [[Hall-Heroult process|Hall-Héroult process]] in 1886 made extracting aluminum from minerals cheaper, and it is now the principal method used throughout the world. The Hall-Heroult process, however, cannot produce Super Purity Aluminum directly. Upon approval of his patent in 1889, Hall, with the financial backing of [[Alfred E. Hunt]] of [[Pittsburgh, PA]], started the Pittsburgh Reduction Company, which was renamed the Aluminum Company of America in 1907 and later shortened to [[Alcoa]].
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Germany became the world leader in aluminum production soon after [[Adolf Hitler]]'s rise to power. By 1942, however, new hydroelectric power projects such as the [[Grand Coulee Dam]] gave the United States something [[Nazi Germany]] could not compete with, provided them with sufficient generating capacity to produce enough aluminum to manufacture sixty thousand warplanes in four years.
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== Notable characteristics ==
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=== Physical properties ===
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In the [[periodic table]], aluminum is located in group 13 (former group 3A), between [[boron]] and [[gallium]]. In addition, it lies in period 3, between [[magnesium]] and [[silicon]]. It is considered a member of the "[[poor metal]]" group of [[chemical element]]s.<ref>The term '''poor metals''' (or '''post-transition metals''') refers to the metallic elements in the [[p-block]] of the [[periodic table]]. Their [[melting point|melting]] and [[boiling point]]s are generally lower than those of the [[transition metal]]s and their [[electronegativity]] higher, and they are also [[hardness|softer]]. In addition to aluminum, the group includes [[gallium]], [[indium]], [[thallium]], [[tin]], [[lead]], and [[bismuth]].</ref> It is nontoxic, nonmagnetic, and nonsparking. The atoms in the metal are arranged in a [[face-centered cubic]] structure.
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Aluminum is one of the few metals that retain full silvery reflectance in finely powdered form, making it an important component of silver paints. Pure aluminum serves as an excellent reflector (approximately 99%) of [[visible light]] and a good reflector (approximately 95%) of [[infrared]]. It is a good [[Heat conduction|thermal]] and [[electrical conductor]], by weight better than copper. It is capable of being a [[superconductor]], with a superconducting critical temperature of 1.2 [[Kelvin]].
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This metal has about one-third the [[density]] and [[Elastic modulus|stiffness]] of [[steel]]. It is [[Ductility|ductile]], and easily [[machining|machined]], [[casting|cast]], and [[extrusion|extruded]]. The [[Yield (engineering)|yield strength]] of pure aluminum is 7-11 MPa, while [[aluminum alloy]]s have yield strengths ranging from 200 to 600 MPa.<ref name=polmear>Polmear, I. J. 1995. ''Light Alloys''. London, UK: Arnold Publishers. ISBN 0750663715</ref> Also, pure aluminum has a low [[tensile strength]], but its [[alloy]]s display a marked improvement in mechanical properties, especially when [[tempering|tempered]].
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=== Chemical properties ===
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Aluminum is highly resistant to [[corrosion]], due to a thin surface layer of [[aluminum oxide]] that forms when the metal is exposed to air, effectively preventing further [[oxidation]]. The strongest aluminum alloys are less corrosion resistant due to [[Galvanic cell|galvanic]] reactions with alloyed [[Copper|copper]].<ref>Ibid.</ref>
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When combining with other elements, aluminum can have different [[oxidation state]]s: +1, +2, and +3. Of these, the +3 oxidation state is most common.
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'''Oxidation state one:'''<ref>The temperatures in this section seem to be the subject of controversy.</ref>
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* AlH is produced when aluminum is heated at 1500 °C in an atmosphere of [[hydrogen]].
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* 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]].
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* Al<sub>2</sub>S can be made by heating Al<sub>2</sub>S<sub>3</sub> with aluminum shavings at 1300 °C in a vacuum. It quickly breaks up to regenerate the starting materials. The selenide is made in a parallel manner.
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* AlF, AlCl, and AlBr exist in the gaseous phase when the corresponding tri-halide is heated with aluminum.
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'''Oxidation state two:'''
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* [[Aluminum monoxide]], AlO, is present when aluminum powder burns in [[oxygen]].
  
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[[Image:Aluminum_Metal.jpg|thumb|left|A piece of aluminium metal about 15 centimetres long.]]
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'''Oxidation state three:'''
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Aluminium is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of [[oxidation]] that forms quickly when it is exposed to air. Aluminium is about one-third as dense as [[steel]] or [[copper]]; is [[Malleability|malleable]], [[Ductility|ductile]], and easily machined and cast; and has excellent [[corrosion]] resistance and durability due to the protective oxide layer. It is also nonmagnetic and nonsparking and is the second most malleable metal (after [[gold]]) and the sixth most ductile.
 
  
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== Applications ==
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* According to [[Fajans' rules]], 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 aluminum 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]].
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* [[Aluminum hydride]], (AlH<sub>3</sub>)<sub>n</sub>, can be produced from [[trimethylaluminum]] and an excess of hydrogen. It burns explosively in air. It can also be prepared by the action of [[aluminum chloride]] on [[lithium hydride]] in [[ether]] solution, but cannot be isolated free from the solvent.
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* [[Aluminum 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 aluminum.
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* [[Aluminum nitride]], AlN, can be made from the elements at 800 °C. It is hydrolyzed by [[water]] to form [[ammonia]] and [[aluminum hydroxide]].
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* [[Aluminum phosphide]], AlP, is made similarly, and hydrolyses to give [[phosphine]].
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* [[Aluminum oxide]], Al<sub>2</sub>O<sub>3</sub>, occurs naturally as [[corundum]], and can be made by burning aluminum 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.
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* [[Aluminum hydroxide]] may be prepared as a gelatinous precipitate by adding ammonia to an aqueous solution of an aluminum salt. It is [[amphoteric]], being both a very weak acid and forming aluminates with [[alkali]]s. It exists in various crystalline forms.
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* [[Aluminum sulfide]], Al<sub>2</sub>S<sub>3</sub>, may be prepared by passing [[hydrogen sulfide]] over aluminum powder. It is [[Polymorphism (materials science)|polymorphic]].
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* [[Aluminum iodide]], (AlI<sub>3</sub>)<sub>2</sub>, is a [[dimer]] with applications in [[organic synthesis]].
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* [[Aluminum 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.
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* Aluminum fluoride/water complexes: When aluminum 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 aluminum and fluoride, which are both very compact ions, fit together just right to form the octahedral aluminum hexafluoride complex. When aluminum 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.
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* Organo-metallic compounds of empirical formula AlR<sub>3</sub> exist and, if not also giant molecules, are at least [[dimer]]s or trimers. They have some uses in [[organic synthesis]], for instance [[trimethylaluminum]].
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* Alumino-hydrides of the most electropositive elements are known, the most useful being [[lithium aluminum hydride]], Li[AlH<sub>4</sub>]. It decomposes into [[lithium hydride]], aluminum 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.
  
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Whether measured in terms of quantity or value, the use of aluminium exceeds that of any other metal except [[iron]], and it is important in virtually all segments of the world economy.
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===Clusters===
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In the journal ''[[Science (journal)|Science]]'' of January 14, 2005, it was reported that clusters of 13 aluminum atoms (Al<sub>13</sub>) had been made to behave like an [[iodine]] atom; and, 14 aluminum 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 characterization 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>[http://www.science.psu.edu/alert/Castleman1-2005.htm Clusters of Aluminum Atoms Found to Have Properties of Other Elements Reveal a New Form of Chemistry]. Eberly College of Science. Retrieved August 13, 2007.</ref>
  
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Pure aluminium has a low [[tensile strength]], but readily forms [[alloy]]s with many elements such as copper, zinc, magnesium, manganese and silicon. When combined with thermo-mechanical processing these aluminium [[alloy]]s display a marked improvement in mechanical properties. Aluminium alloys form vital components of [[aircraft]] and [[rocket]]s as a result of their high strength to weight ratio.  
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=== Isotopes ===
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Aluminum has many [[isotope]]s, of which 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. The <sup>27</sup>Al isotope has a natural abundance of 99.9+ percent. <sup>26</sup>Al is produced from [[argon]] in the [[Earth's atmosphere|atmosphere]] by [[spallation]] caused by [[cosmic-ray]] [[proton]]s. Aluminum isotopes have found practical application in dating [[ocean|marine]] sediments, [[manganese]] nodules, glacial ice, [[quartz]] in [[Rock (geology)|rock]] exposures, and [[meteorite]]s. 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.
  
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When aluminium is evaporated in a vacuum it forms a coating that reflects both [[visible light]] and [[radiant heat]]. These coatings form a thin layer of protective aluminium oxide that does not deteriorate as [[silver]] coatings do. In particular, nearly all modern [[mirror]]s are made using a thin reflective coating of aluminium on the back surface of a sheet of [[float glass]]. [[Telescope]] mirrors are also coated with a thin layer of aluminium, but are front coated to avoid internal reflections even though this makes the surface more susceptible to damage.
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[[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. Many researchers studying meteorites believe that the energy released by the decay of <sup>26</sup>Al was responsible for the melting and [[planetary differentiation|differentiation]] of some [[asteroids]] after their formation 4.55 billion years ago.<ref>Robert T. Dodd,  1986. ''Thunderstones and Shooting Stars.'' (Cambridge, MA: Harvard University Press.), 89-90.</ref>
  
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Some of the many uses for aluminium are in:
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== Aluminum metal production and refinement ==
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*Transportation ([[automobile]]s, [[airplane]]s, [[truck]]s, [[railroad car]]s, marine vessels, etc.)
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Aluminum is a reactive metal that is difficult to extract from ore, [[aluminum oxide]] (Al<sub>2</sub>[[oxygen|O]]<sub>3</sub>). Direct reduction—with [[carbon]], for example—is not economically viable since aluminum oxide has a melting point of about 2,000 °C. Therefore, it is extracted by [[electrolysis]]; that is, the aluminum 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 aluminum, [[sodium]], and [[calcium]] [[fluoride]]s: (Na<sub>3</sub>AlF<sub>6</sub>). The aluminum oxide (a white powder) is obtained by refining [[bauxite]] in the [[Bayer process]]. (Previously, the [[Deville process]] was the predominant refining technology.)
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*Packaging ([[can]]s, [[aluminium foil|foil]], etc.)
 
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*Water treatment
 
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*Construction ([[window]]s, [[door]]s, siding, building wire, etc.
 
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*Consumer durable goods (appliances, [[cooking utensil]]s, etc.)
 
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*[[electricity|Electrical]] [[transmission lines]] (aluminium conductors are half the weight of copper for equal conductivity and lower in price[http://www.metalprices.com])
 
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*Machinery.
 
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*Although non-[[magnet]]ic itself, aluminium is used in [[MKM steel]] and [[Alnico]] magnets.
 
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*[[Super Purity Aluminium]] (SPA, 99.980% to 99.999% Al) is used in electronics and [[compact disc|CD]]s.
 
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*[[Powder]]ed aluminium is commonly used for [[silvering]] in [[paint]]. Aluminium flakes may also be included in undercoat paints, particularly wood [[primer (paint)|primer]] &mdash; on drying, the flakes overlap to produce a water resistant barrier.
 
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*[[Anodising|Anodized]] aluminium is more stable to further oxidation, and is used in various fields of construction.
 
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*Most modern computer [[Central processing unit|CPU]] [[heat sink]]s are made of aluminium due to its ease of manufacture and good heat conductivity. [[Copper]] heat sinks are smaller although more expensive and harder to manufacture.
 
  
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Aluminium oxide, [[alumina]], is found naturally as [[corundum]], [[emery (mineral)|emery]], [[ruby]], and [[sapphire]] and is used in [[glass]] making. Synthetic ruby and sapphire are used in [[laser]]s for the production of [[coherent light]].
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The electrolytic process replaced the [[Wöhler process]], which involved the reduction of anhydrous [[aluminum chloride]] with [[potassium]]. Both of the [[electrode]]s used in the electrolysis of aluminum 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) produces aluminum metal:
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:Al<sup>3+</sup> + 3 e<sup>−</sup> → Al
  
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Aluminium oxidizes very energetically and as a result has found use in [[solid rocket]] fuels, [[thermite]], and other [[pyrotechnic]] compositions.
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Here, the aluminum ion is [[redox|reduced]] (electrons are added). The aluminum metal then sinks to the bottom and is tapped off.
  
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===Engineering use===
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At the positive electrode ([[anode]]), oxygen is formed:
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Improper use of aluminium can result in problems, particularly in contrast to [[iron]] or [[steel]], which appear "better behaved" to the intuitive designer, mechanic, or technician. The reduction by two thirds of the weight of an aluminium part compared to a similarly sized iron or steel part seems enormously attractive, but it should be noted that it is accompanied by a reduction by two thirds in the stiffness of the part. Therefore, although direct replacement of an iron or steel part with a duplicate made from aluminium may still give acceptable strength to withstand peak loads, the increased flexibility will cause three times more deflection in the part.
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:2 O<sup>2−</sup> → O<sub>2</sub> + 4 e<sup>−</sup>
  
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Where failure is not an issue but excessive flex is undesirable due to requirements for precision of location or efficiency of transmission of power, simple replacement of steel tubing with similarly sized aluminium tubing will result in a degree of flex which is undesirable; for instance, the increased flex under operating loads caused by replacing steel bicycle frame tubing with aluminium tubing of identical dimensions will cause misalignment of the power-train as well as absorbing the operating force. To increase the rigidity by increasing the thickness of the walls of the tubing increases the weight proportionately, so that the advantages of lighter weight are lost as the rigidity is restored.
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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:
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:O<sub>2</sub> + C → CO<sub>2</sub>
  
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Aluminium can best be used by redesigning the part to suit its characteristics; for instance making a bicycle of aluminium tubing which has an oversize diameter rather than thicker walls. In this way, rigidity can be restored or even enhanced without increasing weight. The limit to this process is the increase in susceptibility to what is termed "[[crippling]]" failure, where the deviation of the force from any direction other than directly along the axis of the tubing causes folding of the walls of the tubing. For instance, a common aluminium soft drink can should be able to support an enormous weight directly along its axis; in practice, however, the walls of the can buckle, crumple, and/or fold up under even a mild force, due to minute deviations from the precise axial direction, making possible the common pastime of flattening an empty can by slamming it against one's forehead.  
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Unlike the anodes, the cathodes are not oxidized because there is no oxygen present at the cathode. The carbon cathode is protected by the liquid aluminum 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.
  
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The latest models of the [[Corvette]] automobile, among others, are a good example of redesigning parts to make best use of aluminium's advantages. The aluminium chassis members and suspension parts of these cars have large overall dimensions for stiffness but are lightened by reducing cross-sectional area and removing unneeded metal; as a result, they are not only equally or more durable and stiff as the usual steel parts, but they possess an airy gracefulness which most people find attractive. Similarly, aluminium bicycle frames can be optimally designed so as to provide rigidity where required, yet have flexibility in terms of absorbing the shock of bumps from the road and not transmitting them to the rider.
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[[Image:Aluminium - world production trendnew.png|thumb|250px|World production trend of aluminum.]]
  
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The strength and durability of aluminium varies widely, not only as a result of the components of the specific alloy, but also as a result of the particular manufacturing process; for this reason, it has from time to time gained a bad reputation. For instance, a high frequency of failure in many early aluminium bicycle frames in the [[1970]]s resulted in just such a poor reputation; with a moment's reflection, however,  the widespread use of aluminium components in the [[aerospace]] and automotive high performance industries, where huge stresses are undergone with vanishingly small failure rates, proves that properly built aluminium bicycle components should not be unusually unreliable, and this has subsequently proved to be the case.  
+
Aluminum [[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-hour]]s per kilogram of aluminum produced from alumina. (52 to 56 [[megajoule|MJ]]/kg). The most modern smelters reach approximately 12.8 kW·h/kg (46.1 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.
  
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Similarly, use of aluminium in automotive applications, particularly in engine parts which must survive in difficult conditions, has benefited from development over time. An [[Audi]] engineer commented about the V12 engine, producing over 500 horsepower (370 kW), of an [[Auto Union#The Auto Union racing cars |Auto Union race car]] of the [[1930s]] which was recently restored by the Audi factory, that the aluminium alloy of which the engine was constructed would today be used only for lawn furniture and the like. Even the aluminium [[cylinder head]]s and [[crankcase]] of the [[Corvair]], built as recently as the [[1960s]], earned a reputation for failure and stripping of [[thread]]s in holes, even as large as [[spark plug]] holes, which is not seen in current aluminium cylinder heads.
+
Recovery of the metal via [[recycling]] has become an important facet of the aluminum industry. Recycling involves melting the scrap, a process that uses only five percent of the energy needed to produce aluminum from ore. However, a significant part (up to 15% of input material) is lost as dross (ash-like oxide). Recycling was a low-profile activity until the late 1960s, when the growing use of aluminum [[beverage can]]s brought it to the public consciousness.
  
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Often, aluminium's sensitivity to heat must also be considered. Even a relatively routine procedure such as welding is complicated by the fact that aluminium will melt long before it gets even dully red hot; therefore, unlike steel or iron, where the experienced welder can know from its hue how close the metal is to the melting point, welding aluminium requires a degree of expertise incorporating an almost intuitive sense of the metal's temperature, or else the part suddenly and without warning melts into a puddle. Aluminium also will accumulate internal stresses and strains under conditions of overheating; while not immediately obvious, the tendency of the metal to "creep" under sustained stresses results in delayed distortions, for instance the commonly observed warping or cracking of aluminium automobile cylinder heads after an engine is overheated, sometimes as long as years later, or the tendency of welded aluminium bicycle frames to gradually twist out of alignment from the stresses accumulated during the welding process. For this reason, many uses of aluminium in the aerospace industry avoid heat altogether by joining parts using [[adhesive]]s; this was also used for some of the early aluminium bicycle frames in the 1970s, with unfortunate results when the aluminium tubing corroded slightly, loosening the bond of the adhesive and leading to failure of the frame. Stresses from overheating aluminium can be relieved by heat-treating the parts in an oven and gradually cooling, in effect [[annealing]] the stresses; this can also result, however, in the part becoming distorted as a result of these stresses, so that such heat-treating of welded bicycle frames, for instance, results in a significant fraction becoming misaligned. If the misalignment is not too severe, once cooled they can be bent back into alignment with no negative consequences; of course, if the frame is properly designed for rigidity (see above), this will require enormous force.  
+
Electric power represents about 20 to 40 percent of the cost of producing aluminum, 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]].
  
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====Household wiring====
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Over the last 50 years, Australia has become a major producer of bauxite ore and a major producer and exporter of alumina.<ref>[http://www.aluminium.org.au/Page.php?s=1005 The Australian Industry]. Australian Aluminium Council. Retrieved August 13, 2007.</ref> Australia produced 62 million metric tons 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>[http://www.aluminium.org.au/Page.php?s=1007 Australian Bauxite]. Australian Aluminium Council. Retrieved August 13, 2007.</ref>
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Because of its high conductivity and relatively low price compared to [[copper]] at the time, aluminium was introduced for household [[electrical wiring]] to a large degree in the [[United States]] in the 1960s. Unfortunately, many of the wiring fixtures used with aluminium wiring at the time were not designed to accept aluminium wire; ''i.e.'' the greater [[coefficient of thermal expansion]] of aluminium, causing the wire to expand and contract where it was captured under the head of a dissimilar metal [[screw]] connection, eventually working a degree of looseness into the connection; the tendency of pure aluminium to "creep" under steady sustained pressure (to a greater degree as the temperature rises), again producing a degree of looseness in an initially tight connection; and the tendency of the dissimilar metals to corrode when placed in direct contact, which will increase the resistance in such a loosened connection. In combination, these properties resulted in a tendency of the connections between [[electrical fixture]]s and aluminium wiring to overheat to the point where the material of the walls could ignite, and fires occurred. As a result, aluminium household wiring has become unpopular, and in many jurisdictions is not permitted in very small sizes in new construction. However, existing aluminium wiring can be safely used with fixtures whose connections are designed to avoid this loosening/overheating runaway cycle; older fixtures of this type are marked "Al/Cu", while newer ones are marked "CO/ALR". Otherwise, aluminium wiring can be terminated by [[crimp (metalworking)|crimp]]ing it to a short "[[pigtail]]" of copper wire, which can be treated as any other copper wire; a properly done crimp, requiring the high pressure produced by the proper tool, is tight enough not only to eliminate any thermal expansion of the aluminium, but also to exclude any atmospheric oxygen and thus prevent corrosion between dissimilar metals. New alloys are used for aluminium building wire today in combination with aluminium terminations. Connections made with these standard industry products are as safe and reliable as copper connections.
 
  
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== History ==
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== Applications ==
 +
=== General uses ===
 +
[[Image:Aluminum_Metal_coinless.jpg|thumb|right|250px|A piece of aluminum metal about 15 centimeters long.]]
  
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The oldest suspected (although unprovable) reference to aluminium is in [[Pliny the Elder]]'s [[Naturalis Historia]]:
+
Relatively pure aluminum is prepared only when corrosion resistance or workability is more important than strength or hardness. This metal readily forms alloys with many elements such as [[copper]], [[zinc]], [[magnesium]], [[manganese]], and [[silicon]]. Aluminum alloys form vital components of [[aircraft]] and [[rocket]]s as a result of their high strength-to-weight ratio. Today, almost all bulk metal materials that are referred to loosely as "aluminum," are actually alloys. For example, the common [[aluminum foil]]s are alloys containing 92-99% aluminum.<ref>L. S. Millberg, [http://www.madehow.com/Volume-1/Aluminum-Foil.html Aluminum Foil]. How Products are Made. Retrieved August 13, 2007.</ref>
  
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''One day a goldsmith in Rome was allowed to show the Emperor Tiberius a dinner plate of a new metal. The plate was very light, and almost as bright as silver. The goldsmith told the Emperor that he had produced the metal from ordinary clay. He also assured the Emperor that only he, himself, and the Gods knew how to produce this metal from clay. The Emperor became very interested, and as a financial expert he was also worried. The Emperor immediately feared that all his treasures of gold and silver would fall in value if people started producing this bright metal from clay. Therefore, instead of giving the goldsmith the recognition the latter had anticipated, he ordered him to be beheaded.'' [http://www.findarticles.com/p/articles/mi_m2843/is_n3_v19/ai_16836663 Notes] - [http://www.world-aluminium.org/history/antiquity.html Source]
+
Some of the many uses for aluminum metal are in:
 +
* Transportation (particularly [[automobile]]s, aircraft, [[truck]]s, [[railroad car]]s, marine vessels, and [[bicycle]]s)
 +
* Packaging (such as [[aluminum can|cans]] and [[aluminum foil|foil]])
 +
* [[Optical coating]]s and [[mirror]]s, in which a thin layer of aluminum is deposited on a flat surface.
 +
* [[Water purification|Water treatment]]
 +
* Treatment against fish parasites such as ''[[Gyrodactylus salaris]]''
 +
* Construction ([[window]]s, [[door]]s, [[siding]], building wire, etc.)
 +
* [[Cooking utensil]]s
 +
* [[Electrical transmission line]]s for power distribution
 +
* [[MKM steel]] and [[Alnico]] magnets
 +
* Super purity aluminum (SPA, 99.980 percent to 99.999 percent Al), used in electronics and [[compact disc|CDs]].
 +
* [[Heat sink]]s for electronic appliances such as [[transistor]]s and [[Central processing unit|CPUs]].
 +
* Powdered aluminum is used in [[paint]], and in [[pyrotechnic]]s such as [[solid rocket]] fuels and [[thermite]].
 +
* The blades of [[theatrical property|prop]] [[sword]]s and [[knives]] used in [[stage combat]].
  
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The ancient [[Ancient Greece|Greeks]] and [[Ancient Rome|Romans]] used salts of this metal as dyeing [[mordant]]s and as astringents for dressing wounds, and [[alum]] is still used as a [[styptic]]. Further [[Joseph Needham]] suggested finds in [[1974]] showed the ancient Chinese used aluminium (see the link for "Notes" above). 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 named (see Spelling below for more information on the name).
+
===Aluminum compounds===
  
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[[Friedrich Woehler|Friedrich Wöhler]] is generally credited with isolating aluminium ([[Latin]] ''alumen'', [[alum]]) in [[1827]] by mixing anhydrous aluminium chloride with potassium. However, the metal had been produced for the first time two years earlier in an impure form by the Danish physicist and chemist [[Hans Christian Ørsted]]. Therefore almanacs and chemistry sites often list Oersted as the discoverer of aluminium.[http://www.chemicalelements.com/elements/al.html#isotopes Source] Still it would further be P. Berthier who discovered aluminium in bauxite ore and successfully extracted it. The Frenchman [[Henri Saint-Claire Deville]] improved Wöhler's method ([[1846]]) and described his improvements in a book in [[1859]], chief among these being the substitution of sodium for the considerably more expensive potassium.
+
* Aluminum 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.
  
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The American [[Charles Martin Hall]] obtained a [[patent]] (400655) in [[1886]] for an electrolytic process to extract aluminium (which he smelted in Pittsburgh, USA) using the same technique that was currently being applied by the Frenchman Paul Héroult in Europe. The invention of the [[Hall-Heroult process|Hall-Héroult process]] in 1886 made extracting aluminium from minerals cheaper, and is now the principal method in common use throughout the world.
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* Aluminum acetate is a [[salt]] used in solution as an [[astringent]].
  
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[[Image:Eros-piccadilly-circus.jpg|thumb|right|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.]] Aluminium was selected as the material to be used for the apex of the [[Washington Monument]], at a time when one [[ounce]] cost twice the daily wages of a common worker in the project. [http://www.tms.org/pubs/journals/JOM/9511/Binczewski-9511.html Source]
+
* Aluminum 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]].
  
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Germany became the world leader in aluminium production soon after [[Adolf Hitler]] seized power. By 1942, however, new hydroelectric power projects such as the [[Grand Coulee Dam]] gave the United States something Nazi Germany could not hope to compete with, namely the capability of producing enough aluminium to manufacture sixty thousand warplanes in four years. [http://www.phpsolvent.com/wordpress/?page_id=341]
+
* Aluminum borohydride (Al(BH<sub>4</sub>)<sub>3</sub>) is used as an additive to [[jet fuel]].
  
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== Natural occurrence ==
+
* [[Aluminum chloride]] (AlCl<sub>3</sub>) is used: in [[paint]] manufacturing, in [[antiperspirant]]s, in [[petroleum]] [[refining]] and in the production of synthetic [[rubber]].
  
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Although Al is an abundant element in Earth's crust (7.5% -> 8.1%, it has not been confirmed), it is very rare in its free form and was once considered a [[precious metal]] more valuable than [[gold]] (It is said that [[Napoleon III of France]] had a set of aluminium plates reserved for his finest guests. Others had to make do with gold ones.) It is therefore comparatively new as an [[industrial metal]] and has been produced in commercial quantities for just over 100 years.
+
* Aluminum chlorohydride is used as an [[antiperspirant]] and in the treatment of [[hyperhidrosis]].
  
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Aluminium was, when it was first discovered, extremely difficult to separate from the rocks it was part of. Since the whole of Earth's aluminium was bound up in the form of compounds, it was the most difficult metal on earth to get, despite the fact that it is one of the planet's most common. The reason is that aluminium is oxidized very rapidly and that its oxide is an extremely stable compound that, unlike rust on steel, does not flake off. The very reason for which aluminium is used in many applications is why it is so hard to produce.
+
* Aluminum fluorosilicate (Al<sub>2</sub>(SiF<sub>6</sub>)<sub>3</sub>) is used in the production of synthetic [[gemstone]]s, [[glass]] and [[ceramic]].
  
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Recovery of this metal from scrap (via [[recycling]]) has become an important component of the aluminium industry. Recycling involves simply melting the metal, which is far less expensive than creating it from ore. Refining aluminium requires enormous amounts of [[electricity]]; recycling it requires only 5% of the energy to produce it. A common practice since the early [[20th century|1900s]], aluminium recycling is not new. It was, however, a low-profile activity until the late 1960s when the exploding popularity of aluminium [[beverage can]]s finally placed recycling into the public consciousness. Sources for recycled aluminium include automobiles, windows and doors, appliances, containers and other products.
+
* [[Aluminum 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.
  
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Aluminium is a reactive metal and it is hard to extract it from its ore, [[aluminium oxide]] (Al<sub>2</sub>[[oxygen|O]]<sub>3</sub>). Direct reduction, with e.g. [[carbon]], is not economically viable since aluminium oxide has a melting point of about 2000 °C. Therefore, it is extracted by [[electrolysis]] &mdash; the aluminium oxide is dissolved in molten [[cryolite]] and then reduced to the pure metal. By this process, the actual operational temperature of the reduction cells is around 950 to 980 °C. Cryolite was originally found as a mineral on Greenland, but by has been replaced by a synthetic cryolite. 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]], which is red since it contains 30 to 40% iron oxide. This is done using the so-called [[Bayer process]]. Previous to this, the process used was the [[Deville process]].  
+
* [[Aluminum oxide]] (Al<sub>2</sub>O<sub>3</sub>), alumina, is found naturally as [[corundum]] ([[ruby|rubies]] and [[sapphire]]s), [[emery (mineral)|emery]], and is used in [[glass]] making. Synthetic ruby and sapphire are used in [[laser]]s for the production of [[coherent light]].
  
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The electolytic process replaced the [[Wöhler process]], which involved the reduction of anhydrous [[aluminium chloride]] with [[potassium]].
+
* [[Aluminum phosphate]] (AlPO<sub>4</sub>) is used in the manufacture: of glass and ceramic, [[Wood pulp|pulp]] and [[paper]] products, [[cosmetics]], [[paint]]s and [[varnish]]es and in making dental [[cement]].
  
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The [[electrode]]s used in the electrolysis of aluminium oxide are both [[carbon]]. Once the ore is in the molten state, its ions are free to move around. The reaction at the negative [[cathode]] is
+
* [[Aluminum 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.
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:Al<sup>3+</sup> + 3e<sup>-</sup> &rarr; Al
 
  
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Here the aluminium ion is being reduced (electrons are added). The aluminium metal then sinks to the bottom and is tapped off.
+
* In many vaccines, certain aluminum salts serve as an immune [[Immunologic adjuvant|adjuvant]] (immune response booster) to allow the protein in the vaccine to achieve sufficient potency as an immune stimulant.
  
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At the positive electrode ([[anode]]) oxygen gas is formed:
+
===Aluminum alloys in structural applications===
−
:2O<sup>2-</sup> &rarr; O<sub>2</sub> + 4e<sup>-</sup>
 
  
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This carbon [[anode]] is then oxidized by the oxygen. The anodes in a reduction must therefore be replaced regularly, since they are consumed in the process:
+
Aluminum alloys with a wide range of properties are used in engineering structures. Alloy systems are classified by a number system ([[American National Standards Institute|ANSI]]) or by names indicating their main alloying constituents ([[DIN]] and [[International Organization of Standardization|ISO]]).
−
:O<sub>2</sub> + C &rarr; CO<sub>2</sub>
 
  
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Contrary to the anodes, the cathodes are not consumed during the operation, since there is no oxygen present at the cathode. The carbon cathode is protected by the liquid aluminium inside the cells. Cathodes do erode, mainly due to electrochemical processes. After 5 to 10 years, depending on the current used in the electrolysis, a cell has to be reconstructed completely, because the cathodes are completely worn.
+
Aluminum is used extensively in many places due to its high strength to weight ratio. However, a designer used to working with steel will find aluminum less well-behaved in terms of flexibility. The problems may often be addressed by redesigning parts dimensionally specifically to address issues of stiffness.
  
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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-hour]]s per kilogram of aluminium produced (52 to 56 [[megajoule|MJ]]/kg). The most modern smelters reach approximately 12.8 kW·h/kg (46.1 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.
+
The strength and durability of aluminum alloys varies 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 given aluminum a bad reputation.
  
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Electric power represents about 20 to 40% of the cost of producing aluminium, depending on the location of the aluminium smelter. Smelters tend to be located where electric power is plentiful and inexpensive, such as [[South Africa]], the [[South Island]] of [[New Zealand]], [[Australia]], [[China]], [[Middle-East]], [[Russia]], [[Iceland]] and [[Quebec]] in [[Canada]].
+
One important structural limitation of aluminum alloys is their [[Fatigue (material)|fatigue]] strength. Unlike steels, aluminum 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 [[Fatigue (material)#Design against fatigue|fixed life]] rather than an infinite life.
  
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[[China]] is currently ([[2004]]) the top world producer of aluminium.
+
Another important property of aluminum alloys is their sensitivity to heat. Workshop procedures involving heating are complicated by the fact that aluminum, 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. Aluminum alloys, like all structural alloys, also are subject to internal stresses following heating operations such as welding and casting. The problem with aluminum 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 (metallurgy)|annealing]] the stresses.  
  
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== Isotopes ==
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The low melting point of aluminum alloys has not precluded their use in rocketry; even for use in constructing combustion chambers where gases can reach 3500 K. The [[Agena]] upper stage engine used a regeneratively cooled aluminum design for some parts of the nozzle, including the thermally critical throat region; in fact the extremely high thermal conductivity of aluminum prevented the throat from reaching the melting point even under massive heat flux, resulting in a reliable and lightweight component.
  
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Aluminium has nine [[isotope]]s, whose mass numbers range from 23 to 30. Only Al-27 ([[stable isotope]]) and Al-26 ([[radioactive]] isotope, [[half life|''t''<sub>1/2</sub>]] = 7.2 &times; 10<sup>5</sup> [[year|y]]) occur naturally, however Al-27 has a natural abundance of 100%. Al-26 is produced from [[argon]] in the [[Earth's atmosphere|atmosphere]] by [[spallation]] caused by [[cosmic-ray]] [[proton]]s. Aluminium isotopes have found practical application in dating [[ocean|marine]] sediments, [[manganese]] nodules, glacial ice, [[quartz]] in [[Rock (geology)|rock]] exposures, and [[meteorite]]s. The ratio of Al-26 to [[beryllium]]-10 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.
+
=== Household wiring ===
  
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[[Cosmogenic]] Al-26 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 Al-26 production. After falling to Earth, atmospheric shielding protects the meteorite fragments from further Al-26 production, and its decay can then be used to determine the meteorite's terrestrial age. Meteorite research has also shown that Al-26 was relatively abundant at the time of formation of our planetary system. Possibly, the energy released by the decay of Al-26 was responsible for the remelting and [[planetary differentiation|differentiation]] of some [[asteroids]] after their formation 4.6 billion years ago.
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Aluminum has about 65 percent of the conductivity of [[copper]], the traditional household wiring material. In the 1960s aluminum 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 aluminum wire. However, in some cases the greater [[coefficient of thermal expansion]] of aluminum causes the wire to expand and contract relative to the dissimilar metal [[screw]] connection, eventually loosening the connection. Also, pure aluminum has a tendency to "creep" under steady sustained pressure (to a greater degree as the temperature rises), again loosening the connection. Finally, [[Galvanic cell#Galvanic corrosion|Galvanic corrosion]] from the dissimilar metals increased the electrical resistance of the connection.  
  
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===Clusters===
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All of this resulted in overheated and loose connections, and this in turn resulted in some 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 (metalworking)|crimp]] of the aluminum wire to a short "[[pigtail]]" of copper wire. Today, new alloys, designs, and methods are used for aluminum wiring in combination with aluminum terminations.
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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]]: "[[cluster elements]]". The research teams were led by [[Shiv N. Khanna]] ([[Virginia Commonwealth University]]) and [[A. Welford Castleman Jr]] ([[Penn State University]]). [http://www.science.psu.edu/alert/Castleman1-2005.htm]
 
  
 
== Precautions ==
 
== Precautions ==
  
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Aluminium is one of the few abundant elements that appears to have no beneficial function in living cells, but a few percent of people are 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 [[Rolaids]]® , Amphojel®, and [[Maalox]]® ([[antacid]]s). In other persons, aluminium is not considered as toxic as heavy metals, but there is evidence of some toxicity if it is consumed in excessive amounts, although 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 [[antiperspirant]]s are more likely causes of [[toxicity]]. It has been suggested that aluminium may be linked to [[Alzheimer's disease]], although that research has recently been refuted; 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.
+
Aluminum is a [[neurotoxin]] that alters the function of the blood-brain barrier.<ref>W.A. Banks and A.J. Kastin. 1989. Aluminum-induced neurotoxicity: alterations in membrane function at the blood-brain barrier. ''Neurosci Biobehav Rev'' 13(1):47-53.</ref> It is one of the few abundant elements that appears to have no beneficial function in living cells. A small percent of people are allergic to it &mdash; they experience [[contact dermatitis]] from any form of it: an itchy [[rash]] from using [[styptic]] or [[antiperspirant]] products, [[Digestion|digestive]] disorders, an inability to absorb nutrients from eating food cooked in aluminum pans, and vomiting and other symptoms of poisoning from ingesting such products as [[Amphojel]], and [[Maalox]] ([[antacid]]s). In other people, aluminum is not considered as toxic as heavy metals, but there is evidence of some toxicity if it is consumed in excessive amounts. The use of aluminum cookware, popular because of its corrosion resistance and good [[heat conduction]], has not been shown to lead to aluminum toxicity in general. Excessive consumption of antacids containing aluminum compounds and excessive use of aluminum-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 aluminum salts increase estrogen-related gene expression in human [[breast cancer]] cells grown in the laboratory. These salts' estrogen-like effects have lead to their classification as [[metalloestrogen]]s.
  
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Care must be taken to prevent aluminium from coming into contact with certain chemicals that can cause it to [[corrode]] quickly. For example, just a small amount of [[Mercury (element)|mercury]] applied to the surface of a piece of aluminium can break up the normal aluminium oxide barrier usually present. Within a few hours, even a heavy structural beam can be significantly weakened. For this reason, mercury [[thermometer]]s are not allowed on many [[airliner]]s, as aluminium is a common structural component in aircraft.
+
It has been suggested that aluminum 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; aluminum accumulation may be a consequence of the Alzheimer's damage, not the cause. In any event, if there is any toxicity of aluminum 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> Alzheimer's Disease and Aluminum. National Institute of Environmental Health Sciences.</ref><ref>Michael Hopkin, 2006. Death of Alzheimer victim linked to aluminium pollution. ''news @ nature.com''. </ref>
  
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== Spelling ==
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[[mercury (element)|Mercury]] applied to the surface of an aluminum alloy can damage the protective oxide surface film by forming [[Mercury-aluminum amalgam|amalgam]]. This may cause further corrosion and weakening of the structure. For this reason, mercury [[thermometer]]s are not allowed on many [[airliner]]s, as aluminum is used in many [[aircraft]] structures.
 +
 
 +
Powdered aluminum 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.
 +
 
 +
=== Aluminum and plants ===
  
−
In the English-speaking world, the spellings (and associated pronunciations) ''aluminium'' and ''aluminum'' are both in common use in both scientific and nonscientific contexts. In most English-speaking nations, the spelling ''aluminium'' predominates, and the spelling ''aluminum'' is largely unknown, however in the United States, its former possessions, and Canada, the converse is true: the spelling ''aluminium'' is largely unknown, and the spelling ''aluminum'' predominates.  
+
Aluminum 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.
  
−
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 alumin'''i'''um first.[http://www.iupac.org/reports/periodic_table/index.html] This is because IUPAC officially prefers the use of ''aluminium'' in its internal publications, while recognizing both. Also an advantage of the "ium" spelling is that the non-English-speaking world prefers the -ium spelling: ''aluminium'' is the name used in [[French language|French]] and [[German language|German]], and identical or similar forms are used in many other languages. As the non-English speaking world has more people the forms used in languages other than English are one of the reasons IUPAC chose to officially prefer ''aluminium'' over ''aluminum''.
+
The [[adaptation]] of [[wheat]] to allow aluminum tolerance is such that the aluminum induces a release of [[organic compound]]s that bind to the harmful aluminum [[cations]]. [[Sorghum]] is believed to have the same tolerance mechanism. The first gene for aluminum tolerance has been identified in wheat. A group in the U.S. Department of Agriculture showed that sorghum's aluminum tolerance is controlled by a single gene, as for wheat. This is not the case in all plants.
  
−
===Nomenclature history===
+
== Spelling ==
−
In 1808, [[Humphry Davy]] originally proposed the name ''alumium'' while trying to isolate the new metal electrolytically from the mineral ''alumina''. In [[1812]] he changed the name to ''aluminum'' to match its [[Latin]] root.  The same year, an anonymous contributor to the [[Quarterly Review]], a British political-literary journal, objected to ''aluminum'', and proposed the name ''aluminium''.
+
===Etymology/nomenclature history===
−
:Aluminium, for so we shall take the liberty of writing the word, in preference to aluminum, which has a less classical sound. (Q. Review VIII. 72, 1812. Cited in [[Oxford English Dictionary|OED]].)
+
The earliest citation given in the [[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,'' 2nd ed. Edited by J.A. Simpson and E.S.C. Weiner. (Oxford, UK: 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>
−
This had the advantage of conforming to the -ium suffix precedent set by other newly discovered elements of the period: [[potassium]], [[sodium]], [[magnesium]], [[calcium]], and [[strontium]] (all of which Davy had isolated himself). Nevertheless, -um spellings for elements were not unknown at the time: [[platinum]], which had been known to Europeans since the 16th century, [[molybdenum]], which was discovered in 1778, and [[tantalum]], which was discovered in 1802, all have spellings ending in -um. For the thirty years following its discovery, both the -um and -ium endings were used interchangeably in the scientific literature.
 
  
−
Curiously, the United States adopted the -ium for most of the [[19th century]] with ''aluminium'' appearing in [[Noah Webster|Webster]]'s Dictionary of [[1828]]. However [[Charles Martin Hall]] selected the -um spelling in an advertising handbill for his new efficient electrolytic method for the production of aluminium, four years after he had patented the process in [[1888]]. Although this spelling may have been an accident, Hall's domination of production of the metal ensured that the spelling ''aluminum'' became the standard in North America, even though the ''Webster Unabridged Dictionary'' of [[1913]] continued to use the -ium version.
+
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>
  
−
In [[1926]], the [[American Chemical Society]] officially decided to use ''aluminum'' in its publications, and American dictionaries typically label the spelling ''aluminium'' as a British variant.
+
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.  
  
−
==Chemistry==
+
Americans adopted ''-ium'' for most of the nineteenth century, with ''aluminium'' appearing in [[Noah Webster|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 he filed between 1886 and 1903.<ref>Peter Meiers. [http://www.fluoride-history.de/p-aluminum.htm Manufacture of Aluminum]. The History of Fluorine, Fluoride and Fluoridation. Retrieved August 13, 2007.</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.
  
−
===Oxidation state 1===
+
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.
−
*AlH is produced when aluminium is heated at 1500 °C 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.
 
  
−
===Oxidation state 2===
+
===Present-day spelling===
−
*Aluminium suboxide, AlO can be shown to be present when aluminium powder burns in oxygen.
 
  
−
===Oxidation state 3===
+
In the UK and other countries using [[American and British English spelling differences|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. 1980. ''Words on Words: A Dictionary for Writers and Others Who Care about Words.'' (New York, NY: Columbia University Press), 22–23. </ref> The [[Canadian Oxford Dictionary]] prefers ''aluminum,'' whereas the [[Australia]]n [[Macquarie Dictionary]] prefers ''aluminium.''
−
*[[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 bases, 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 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 [[polymorphic]].
 
−
*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.
 
−
*Organo-metallic compounds of empirical formula AlR<sub>3</sub> exist and, if not also giant molecules, are at least [[dimer]]s 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. The aluminohalides have a similar structure.
 
  
−
==Aluminium in fiction==
+
In other [[English language|English-speaking]] countries, the spellings (and associated pronunciations) ''aluminium'' and ''aluminum'' are both in common use in scientific and nonscientific contexts. The spelling in virtually all other languages is analogous to the ''-ium'' ending.
  
−
* In the film ''[[Star Trek IV: The Voyage Home]]'', [[Montgomery Scott|Scotty]] devises the fictional material [[transparent aluminum]]. <!-- He also says "aluminum" rather than "aluminium" (if I recall correctly). —>
+
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]. Retrieved August 13, 2007.</ref> IUPAC officially prefers the use of ''aluminium'' in its internal publications, although several IUPAC publications use the spelling ''aluminum.''
  
 
== See also ==
 
== See also ==
  
−
* [[List of alloys#Alloys of aluminium|Alloys of aluminium]].
+
* [[Alloy]]
 +
* [[Beverage can]]
 +
* [[Chemical element]]
 +
* [[Periodic table]]
  
−
==References==
+
== Notes ==
 +
{{reflist|2}}
  
−
*[http://periodic.lanl.gov/elements/13.html Los Alamos National Laboratory &ndash; Aluminum]
+
== References ==
−
*[http://www.worldwidewords.org/articles/aluminium.htm World Wide Words] A history of the spelling of aluminium from a British viewpoint.
 
−
*[[Oxford English Dictionary]] Entries "aluminum" and "aluminium", available by subscription.  [http://www.oed.com]
 
  
−
==External links==
+
* Bremner, John. 1980. ''Words on Words: A Dictionary for Writers and Others Who Care about Words.'' New York, NY: Columbia University Press. ISBN 0231044933
−
*[http://www.webelements.com/webelements/elements/text/Al/index.html WebElements.com &ndash; Aluminium]
+
* Chang, Raymond. 2006. ''Chemistry,'' 9th ed. New York, NY: McGraw-Hill Science/Engineering/Math. ISBN 0073221031.
−
*[http://www.world-aluminium.org/ World Aluminium]
+
* Cotton, F. Albert, and Geoffrey Wilkinson. 1980. ''Advanced Inorganic Chemistry,'' 4th ed. New York, NY: Wiley. ISBN 0471027758.
−
*[http://www.indexmundi.com/en/commodities/minerals/aluminum/aluminum_table12.html World production of primary aluminum, by country]
+
* Dodd, Robert T. 1986. ''Thunderstones and Shooting Stars.'' Cambridge, MA: Harvard University Press. ISBN 0674891376.
−
*[http://www.saanet.org/kashipur/docs/seenalum.htm Social and Environmental Impact of the Aluminium Industry]
+
* Greenwood, N.N., and A. Earnshaw. 1998. ''Chemistry of the Elements,'' 2nd ed. Oxford, U.K.; Burlington, MA: Butterworth-Heinemann, Elsevier Science. ISBN 0750633654. Online version available [http://www.knovel.com/knovel2/Toc.jsp?BookID=402&VerticalID=0 here]. Retrieved August 11, 2007.
−
*[http://153rd.com/sam/as/physics/aluminium/normal/redirect.html Sam's Aluminium Information Site]
+
* Los Alamos National Laboratory Periodic Table [http://periodic.lanl.gov/elements/13.html Aluminum.] ''Chemistry Division, Los Alamos National Laboratory''. Retrieved August 11, 2007.
 +
* Polmear, I. J. 1995. ''Light Alloys.'' London, UK: Arnold Publishers. ISBN 0750663715
  
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'''Patents'''
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== External links ==
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*US[http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/srchnum.htm&r=1&f=G&l=50&s1=400664.WKU.&OS=PN/400664&RS=PN/400664 400664] – ''Process of reducing aluminum from its floride salts by electrolysis'' – C. M. Hall
+
All links retrieved July 23, 2023.  
  
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[[Category:Chemical elements]]
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*[http://www.webelements.com/webelements/elements/text/Al/index.html Aluminium] WebElements.com.
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[[Category:Poor metals]]
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*[http://www.indexmundi.com/en/commodities/minerals/aluminum/aluminum_table12.html World production of primary aluminium, by country].
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{{credits|Aluminium|150640787}}

Latest revision as of 08:41, 23 July 2023


13 magnesium ← aluminum → silicon
B
↑
Al
↓
Ga
Al-TableImage.png
Periodic Table - Extended Periodic Table
General
Name, Symbol, Number aluminum, Al, 13
Chemical seriespoor metals
Group, Period, Block 13, 3, p
Appearancesilvery
Al,13.jpg
Standard atomic weight 26.9815386(8) g·mol−1
Electron configuration [Ne] 3s2 3p1
Electrons per shell 2, 8, 3
Physical properties
Phasesolid
Density (near r.t.)2.70 g·cm−3
Liquid density at m.p.2.375 g·cm−3
Melting point933.47 K
(660.32 °C, 1220.58 °F)
Boiling point2792 K
(2519 °C, 4566 °F)
Heat of fusion10.71 kJ·mol−1
Heat of vaporization294.0 kJ·mol−1
Heat capacity(25 °C) 24.200 J·mol−1·K−1
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 1482 1632 1817 2054 2364 2790
Atomic properties
Crystal structureface centered cubic
0.4032 nm
Oxidation states3
(amphoteric oxide)
Electronegativity1.61 (Pauling scale)
Ionization energies
(more) 		1st: 577.5 kJ·mol−1
2nd: 1816.7 kJ·mol−1
3rd: 2744.8 kJ·mol−1
Atomic radius125 pm
Atomic radius (calc.)118 pm
Covalent radius118 pm
Miscellaneous
Magnetic orderingparamagnetic
Electrical resistivity(20 °C) 26.50 nΩ·m
Thermal conductivity(300 K) 237 W·m−1·K−1
Thermal expansion(25 °C) 23.1 µm·m−1·K−1
Speed of sound (thin rod)(r.t.) (rolled) 5000 m·s−1
Young's modulus70 GPa
Shear modulus26 GPa
Bulk modulus76 GPa
Poisson ratio0.35
Mohs hardness2.75
Vickers hardness167 MPa
Brinell hardness245 MPa
CAS registry number7429-90-5
Selected isotopes
Main article: Isotopes of aluminum
iso NA half-life DM DE (MeV) DP
26Al syn 7.17×105y β+ 1.17 26Mg
ε - 26Mg
γ 1.8086 -
27Al 100% Al is stable with 14 neutrons
"Aluminium" redirects here.

Aluminum (or aluminium) (chemical symbol Al, atomic number is 13) is a soft, lightweight metal with a silvery appearance and the ability to resist corrosion. It is the most abundant metallic element in the Earth's crust (estimated at between 7.5 and 8.1 percent). The free element, rarely found in nature, occurs in oxygen-deficient environments such as volcanic mud. Its main ore is bauxite. Whether measured in terms of quantity or value, the global use of aluminum exceeds that of any other metal except iron, and it is important in virtually all segments of the world economy.

Structural components made from aluminum and its alloys are vital to the aerospace industry and very important in other areas of transportation and building. In addition, aluminum and its alloys are used in packaging, cooking utensils, electrical transmission lines, water purification processes, electronic devices and compact discs, paint, and pyrotechnics. Aluminum compounds also serve a wide variety of purposes. For instance, aluminum ammonium sulfate is a mordant for dyeing, and is used in water purification and sewage treatment; aluminum acetate solution is an astringent; aluminum chloride is used in paints and anti-perspirants; and aluminum borate, phosphate, and fluorosilicate are used in the production of glass and ceramics. Yet, aluminum is one of the few abundant elements that appear to have no beneficial biological role; a small percentage of people are allergic to it.

History

Ancient Greeks and Romans used aluminum salts as mordants for dyeing and astringents for dressing wounds. Alum (potassium aluminum sulfate or a related salt) 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 named alumium and later aluminum (see Spelling section, below).

Friedrich Wöhler is generally credited with isolating aluminum (Latin alumen, alum) in 1827 by mixing anhydrous aluminum chloride with potassium. The metal, however, had been produced (albeit in impure form) for the first time two years earlier by the Danish physicist and chemist Hans Christian Ørsted. Therefore, Ørsted can also be listed as the discoverer of the metal.[1] Further, Pierre Berthier discovered aluminum in bauxite ore and successfully extracted it.[2] 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.[3]

The statue Eros in Piccadilly Circus London, constructed in 1893, and is one of the first statues to be cast in aluminum.

Before the development of methods to purify aluminum in large quantities, it was considered a precious metal more valuable than gold. Napoleon III, Emperor of France, is reputed to have given a banquet where the most honored guests were given aluminum utensils, while the other guests had to make do with gold ones.[4][5]

Aluminum was selected as the material to be used for the apex of the Washington Monument in 1884, a time when a single ounce (30 grams) of the substance cost the daily wage of a common worker on the project.[6] It had about the same value as silver.

In 1886, the American Charles Martin Hall of Oberlin, Ohio applied for a patent (U.S. Patent 400664 (PDF)) for an electrolytic process to extract aluminum using the same technique that was independently being developed by the Frenchman Paul Héroult in Europe. The invention of the Hall-Héroult process in 1886 made extracting aluminum from minerals cheaper, and it is now the principal method used throughout the world. The Hall-Heroult process, however, cannot produce Super Purity Aluminum directly. Upon approval of his patent in 1889, Hall, with the financial backing of Alfred E. Hunt of Pittsburgh, PA, started the Pittsburgh Reduction Company, which was renamed the Aluminum Company of America in 1907 and later shortened to Alcoa.

Germany became the world leader in aluminum production soon after Adolf Hitler's rise to power. By 1942, however, new hydroelectric power projects such as the Grand Coulee Dam gave the United States something Nazi Germany could not compete with, provided them with sufficient generating capacity to produce enough aluminum to manufacture sixty thousand warplanes in four years.

Notable characteristics

Physical properties

In the periodic table, aluminum is located in group 13 (former group 3A), between boron and gallium. In addition, it lies in period 3, between magnesium and silicon. It is considered a member of the "poor metal" group of chemical elements.[7] It is nontoxic, nonmagnetic, and nonsparking. The atoms in the metal are arranged in a face-centered cubic structure.

Aluminum is one of the few metals that retain full silvery reflectance in finely powdered form, making it an important component of silver paints. Pure aluminum serves as an excellent reflector (approximately 99%) of visible light and a good reflector (approximately 95%) of infrared. It is a good thermal and electrical conductor, by weight better than copper. It is capable of being a superconductor, with a superconducting critical temperature of 1.2 Kelvin.

This metal has about one-third the density and stiffness of steel. It is ductile, and easily machined, cast, and extruded. The yield strength of pure aluminum is 7-11 MPa, while aluminum alloys have yield strengths ranging from 200 to 600 MPa.[8] Also, pure aluminum has a low tensile strength, but its alloys display a marked improvement in mechanical properties, especially when tempered.

Chemical properties

Aluminum is highly resistant to corrosion, due to a thin surface layer of aluminum oxide that forms when the metal is exposed to air, effectively preventing further oxidation. The strongest aluminum alloys are less corrosion resistant due to galvanic reactions with alloyed copper.[9]

When combining with other elements, aluminum can have different oxidation states: +1, +2, and +3. Of these, the +3 oxidation state is most common.

Oxidation state one:[10]

  • AlH is produced when aluminum is heated at 1500 °C in an atmosphere of hydrogen.
  • Al2O is made by heating the normal oxide, Al2O3, with silicon at 1800 °C in a vacuum.
  • Al2S can be made by heating Al2S3 with aluminum shavings at 1300 °C in a vacuum. It quickly breaks up to regenerate the starting materials. The selenide is made in a parallel manner.
  • AlF, AlCl, and AlBr exist in the gaseous phase when the corresponding tri-halide is heated with aluminum.

Oxidation state two:

  • Aluminum monoxide, AlO, is present when aluminum powder burns in oxygen.

Oxidation state three:

  • According to Fajans' rules, the simple trivalent cation Al3+ is not expected to be found in anhydrous salts or binary compounds such as Al2O3. The hydroxide is a weak base and aluminum 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.
  • Aluminum hydride, (AlH3)n, can be produced from trimethylaluminum and an excess of hydrogen. It burns explosively in air. It can also be prepared by the action of aluminum chloride on lithium hydride in ether solution, but cannot be isolated free from the solvent.
  • Aluminum carbide, Al4C3 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 acetylide, Al2(C2)3, is made by passing acetylene over heated aluminum.
  • Aluminum nitride, AlN, can be made from the elements at 800 °C. It is hydrolyzed by water to form ammonia and aluminum hydroxide.
  • Aluminum phosphide, AlP, is made similarly, and hydrolyses to give phosphine.
  • Aluminum oxide, Al2O3, occurs naturally as corundum, and can be made by burning aluminum 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.
  • Aluminum hydroxide may be prepared as a gelatinous precipitate by adding ammonia to an aqueous solution of an aluminum salt. It is amphoteric, being both a very weak acid and forming aluminates with alkalis. It exists in various crystalline forms.
  • Aluminum sulfide, Al2S3, may be prepared by passing hydrogen sulfide over aluminum powder. It is polymorphic.
  • Aluminum iodide, (AlI3)2, is a dimer with applications in organic synthesis.
  • Aluminum fluoride, AlF3, 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.
  • Aluminum fluoride/water complexes: When aluminum and fluoride are together in aqueous solution, they readily form complex ions such as AlF(H2O)5+2, AlF3(H2O)30, AlF6-3. Of these, AlF6-3 is the most stable. This is explained by the fact that aluminum and fluoride, which are both very compact ions, fit together just right to form the octahedral aluminum hexafluoride complex. When aluminum and fluoride are together in water in a 1:6 molar ratio, AlF6-3 is the most common form, even in rather low concentrations.
  • Organo-metallic compounds of empirical formula AlR3 exist and, if not also giant molecules, are at least dimers or trimers. They have some uses in organic synthesis, for instance trimethylaluminum.
  • Alumino-hydrides of the most electropositive elements are known, the most useful being lithium aluminum hydride, Li[AlH4]. It decomposes into lithium hydride, aluminum 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 of January 14, 2005, it was reported that clusters of 13 aluminum atoms (Al13) had been made to behave like an iodine atom; and, 14 aluminum atoms (Al14) behaved like an alkaline earth atom. The researchers also bound 12 iodine atoms to an Al13 cluster to form a new class of polyiodide. This discovery is reported to give rise to the possibility of a new characterization of the periodic table: superatoms. The research teams were led by Shiv N. Khanna (Virginia Commonwealth University) and A. Welford Castleman, Jr. (Penn State University).[11]

Isotopes

Aluminum has many isotopes, of which only 27Al (stable isotope) and 26Al (radioactive isotope, t1/2 = 7.2 × 105 y) occur naturally. The 27Al isotope has a natural abundance of 99.9+ percent. 26Al is produced from argon in the atmosphere by spallation caused by cosmic-ray protons. Aluminum isotopes have found practical application in dating marine sediments, manganese nodules, glacial ice, quartz in rock exposures, and meteorites. The ratio of 26Al to 10Be has been used to study the role of transport, deposition, sediment storage, burial times, and erosion on 105 to 106 year time scales.

Cosmogenic 26Al 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 26Al production. After falling to Earth, atmospheric shielding protects the meteorite fragments from further 26Al production, and its decay can then be used to determine the meteorite's terrestrial age. Meteorite research has also shown that 26Al was relatively abundant at the time of formation of our planetary system. Many researchers studying meteorites believe that the energy released by the decay of 26Al was responsible for the melting and differentiation of some asteroids after their formation 4.55 billion years ago.[12]

Aluminum metal production and refinement

Aluminum is a reactive metal that is difficult to extract from ore, aluminum oxide (Al2O3). Direct reduction—with carbon, for example—is not economically viable since aluminum oxide has a melting point of about 2,000 °C. Therefore, it is extracted by electrolysis; that is, the aluminum 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 aluminum, sodium, and calcium fluorides: (Na3AlF6). The aluminum oxide (a white powder) is obtained by refining bauxite in the Bayer process. (Previously, the Deville process was the predominant refining technology.)

The electrolytic process replaced the Wöhler process, which involved the reduction of anhydrous aluminum chloride with potassium. Both of the electrodes used in the electrolysis of aluminum 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) produces aluminum metal:

Al3+ + 3 e− → Al

Here, the aluminum ion is reduced (electrons are added). The aluminum metal then sinks to the bottom and is tapped off.

At the positive electrode (anode), oxygen is formed:

2 O2− → O2 + 4 e−

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:

O2 + C → CO2

Unlike the anodes, the cathodes are not oxidized because there is no oxygen present at the cathode. The carbon cathode is protected by the liquid aluminum 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.

World production trend of aluminum.

Aluminum 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 aluminum produced from alumina. (52 to 56 MJ/kg). The most modern smelters reach approximately 12.8 kW·h/kg (46.1 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 aluminum industry. Recycling involves melting the scrap, a process that uses only five percent of the energy needed to produce aluminum from ore. However, a significant part (up to 15% of input material) is lost as dross (ash-like oxide). Recycling was a low-profile activity until the late 1960s, when the growing use of aluminum beverage cans brought it to the public consciousness.

Electric power represents about 20 to 40 percent of the cost of producing aluminum, 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.

Over the last 50 years, Australia has become a major producer of bauxite ore and a major producer and exporter of alumina.[13] Australia produced 62 million metric tons 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.[14]

Applications

General uses

A piece of aluminum metal about 15 centimeters long.

Relatively pure aluminum is prepared only when corrosion resistance or workability is more important than strength or hardness. This metal readily forms alloys with many elements such as copper, zinc, magnesium, manganese, and silicon. Aluminum alloys form vital components of aircraft and rockets as a result of their high strength-to-weight ratio. Today, almost all bulk metal materials that are referred to loosely as "aluminum," are actually alloys. For example, the common aluminum foils are alloys containing 92-99% aluminum.[15]

Some of the many uses for aluminum metal are in:

  • Transportation (particularly automobiles, aircraft, trucks, railroad cars, marine vessels, and bicycles)
  • Packaging (such as cans and foil)
  • Optical coatings and mirrors, in which a thin layer of aluminum is deposited on a flat surface.
  • 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 aluminum (SPA, 99.980 percent to 99.999 percent Al), used in electronics and CDs.
  • Heat sinks for electronic appliances such as transistors and CPUs.
  • Powdered aluminum is used in paint, and in pyrotechnics such as solid rocket fuels and thermite.
  • The blades of prop swords and knives used in stage combat.

Aluminum compounds

  • Aluminum ammonium sulfate ([Al(NH4)](SO4)2), ammonium alum is used as a mordant, in water purification and sewage treatment, in paper production, as a food additive, and in leather tanning.
  • Aluminum acetate is a salt used in solution as an astringent.
  • Aluminum borate (Al2O3 B2O3) is used in the production of glass and ceramic.
  • Aluminum borohydride (Al(BH4)3) is used as an additive to jet fuel.
  • Aluminum chloride (AlCl3) is used: in paint manufacturing, in antiperspirants, in petroleum refining and in the production of synthetic rubber.
  • Aluminum chlorohydride is used as an antiperspirant and in the treatment of hyperhidrosis.
  • Aluminum fluorosilicate (Al2(SiF6)3) is used in the production of synthetic gemstones, glass and ceramic.
  • Aluminum hydroxide (Al(OH)3) is used: as an antacid, as a mordant, in water purification, in the manufacture of glass and ceramic and in the waterproofing of fabrics.
  • Aluminum oxide (Al2O3), alumina, is found naturally as corundum (rubies and sapphires), emery, and is used in glass making. Synthetic ruby and sapphire are used in lasers for the production of coherent light.
  • In many vaccines, certain aluminum salts serve as an immune adjuvant (immune response booster) to allow the protein in the vaccine to achieve sufficient potency as an immune stimulant.

Aluminum alloys in structural applications

Aluminum 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).

Aluminum is used extensively in many places due to its high strength to weight ratio. However, a designer used to working with steel will find aluminum less well-behaved in terms of flexibility. The problems may often be addressed by redesigning parts dimensionally specifically to address issues of stiffness.

The strength and durability of aluminum alloys varies 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 given aluminum a bad reputation.

One important structural limitation of aluminum alloys is their fatigue strength. Unlike steels, aluminum 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 aluminum alloys is their sensitivity to heat. Workshop procedures involving heating are complicated by the fact that aluminum, 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. Aluminum alloys, like all structural alloys, also are subject to internal stresses following heating operations such as welding and casting. The problem with aluminum 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 aluminum alloys has not precluded their use in rocketry; even for use in constructing combustion chambers where gases can reach 3500 K. The Agena upper stage engine used a regeneratively cooled aluminum design for some parts of the nozzle, including the thermally critical throat region; in fact the extremely high thermal conductivity of aluminum prevented the throat from reaching the melting point even under massive heat flux, resulting in a reliable and lightweight component.

Household wiring

Aluminum has about 65 percent of the conductivity of copper, the traditional household wiring material. In the 1960s aluminum 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 aluminum wire. However, in some cases the greater coefficient of thermal expansion of aluminum causes the wire to expand and contract relative to the dissimilar metal screw connection, eventually loosening the connection. Also, pure aluminum 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 some 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 aluminum wire to a short "pigtail" of copper wire. Today, new alloys, designs, and methods are used for aluminum wiring in combination with aluminum terminations.

Precautions

Aluminum is a neurotoxin that alters the function of the blood-brain barrier.[16] It is one of the few abundant elements that appears to have no beneficial function in living cells. A small percent of people are allergic to it — they experience contact dermatitis from any form of it: an itchy rash from using styptic or antiperspirant products, digestive disorders, an inability to absorb nutrients from eating food cooked in aluminum pans, and vomiting and other symptoms of poisoning from ingesting such products as Amphojel, and Maalox (antacids). In other people, aluminum is not considered as toxic as heavy metals, but there is evidence of some toxicity if it is consumed in excessive amounts. The use of aluminum cookware, popular because of its corrosion resistance and good heat conduction, has not been shown to lead to aluminum toxicity in general. Excessive consumption of antacids containing aluminum compounds and excessive use of aluminum-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 aluminum salts increase estrogen-related gene expression in human breast cancer cells grown in the laboratory. These salts' estrogen-like effects have lead to their classification as metalloestrogens.

It has been suggested that aluminum 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; aluminum accumulation may be a consequence of the Alzheimer's damage, not the cause. In any event, if there is any toxicity of aluminum 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.[17][18]

Mercury applied to the surface of an aluminum 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 thermometers are not allowed on many airliners, as aluminum is used in many aircraft structures.

Powdered aluminum can react with Fe2O3 to form Fe and Al2O3. 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.

Aluminum and plants

Aluminum 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 Al3+ cations increases and disturbs root growth and function.

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

Spelling

Etymology/nomenclature history

The earliest citation given in the 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."[19]

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."[20] 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."[21]

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 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 he filed between 1886 and 1903.[22] 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.[23][24] The Canadian Oxford Dictionary prefers aluminum, whereas the Australian Macquarie Dictionary prefers aluminium.

In other English-speaking countries, the spellings (and associated pronunciations) aluminium and aluminum are both in common use in scientific and nonscientific contexts. 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.[25] IUPAC officially prefers the use of aluminium in its internal publications, although several IUPAC publications use the spelling aluminum.

See also

Notes

  1. ↑ Yinon Bentor. Periodic Table: Aluminum ChemicalElements.com. Retrieved August 13, 2007.
  2. ↑ Pierre Berthier. Today in Science History. Retrieved August 13, 2007.
  3. ↑ The title of Deville's book is De l'aluminium, ses propriétés, sa fabrication (Paris, 1859). It is likely that Deville also thought of the idea of the electrolysis of aluminum oxide dissolved in cryolite. However, Charles Martin Hall and Paul Heroult might have developed the more practical process after Deville.
  4. ↑ S. Venetski, 1969. "Silver" from clay. Metallurgist 13(7): 451-453.
  5. ↑ ChemMatters magazine. (1990): 14
  6. ↑ George J. Binczewski, 1995. The Point of a Monument: A History of the Aluminum Cap of the Washington Monument. Retrieved August 13, 2007.
  7. ↑ The term poor metals (or post-transition metals) refers to the metallic elements in the p-block of the periodic table. Their melting and boiling points are generally lower than those of the transition metals and their electronegativity higher, and they are also softer. In addition to aluminum, the group includes gallium, indium, thallium, tin, lead, and bismuth.
  8. ↑ Polmear, I. J. 1995. Light Alloys. London, UK: Arnold Publishers. ISBN 0750663715
  9. ↑ Ibid.
  10. ↑ The temperatures in this section seem to be the subject of controversy.
  11. ↑ Clusters of Aluminum Atoms Found to Have Properties of Other Elements Reveal a New Form of Chemistry. Eberly College of Science. Retrieved August 13, 2007.
  12. ↑ Robert T. Dodd, 1986. Thunderstones and Shooting Stars. (Cambridge, MA: Harvard University Press.), 89-90.
  13. ↑ The Australian Industry. Australian Aluminium Council. Retrieved August 13, 2007.
  14. ↑ Australian Bauxite. Australian Aluminium Council. Retrieved August 13, 2007.
  15. ↑ L. S. Millberg, Aluminum Foil. How Products are Made. Retrieved August 13, 2007.
  16. ↑ W.A. Banks and A.J. Kastin. 1989. Aluminum-induced neurotoxicity: alterations in membrane function at the blood-brain barrier. Neurosci Biobehav Rev 13(1):47-53.
  17. ↑ Alzheimer's Disease and Aluminum. National Institute of Environmental Health Sciences.
  18. ↑ Michael Hopkin, 2006. Death of Alzheimer victim linked to aluminium pollution. news @ nature.com.
  19. ↑ "alumium," Oxford English Dictionary, 2nd ed. Edited by J.A. Simpson and E.S.C. Weiner. (Oxford, UK: 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.
  20. ↑ "aluminum," Ibid. Citation is listed as "1812 SIR H. DAVY Chem. Philos. I. 355"
  21. ↑ "aluminium," Ibid. Citation is listed as "1812 Q. Rev. VIII. 72"
  22. ↑ Peter Meiers. Manufacture of Aluminum. The History of Fluorine, Fluoride and Fluoridation. Retrieved August 13, 2007.
  23. ↑ Greenwood, N. N.; & Earnshaw, A. 1997. Chemistry of the Elements (2nd Edn.). Oxford, UK: Butterworth-Heinemann. ISBN 0-7506-3365-4.
  24. ↑ John Bremner. 1980. Words on Words: A Dictionary for Writers and Others Who Care about Words. (New York, NY: Columbia University Press), 22–23.
  25. ↑ IUPAC Periodic Table of the Elements. Retrieved August 13, 2007.

References
ISBN links support NWE through referral fees

  • Bremner, John. 1980. Words on Words: A Dictionary for Writers and Others Who Care about Words. New York, NY: Columbia University Press. ISBN 0231044933
  • Chang, Raymond. 2006. Chemistry, 9th ed. New York, NY: McGraw-Hill Science/Engineering/Math. ISBN 0073221031.
  • Cotton, F. Albert, and Geoffrey Wilkinson. 1980. Advanced Inorganic Chemistry, 4th ed. New York, NY: Wiley. ISBN 0471027758.
  • Dodd, Robert T. 1986. Thunderstones and Shooting Stars. Cambridge, MA: Harvard University Press. ISBN 0674891376.
  • Greenwood, N.N., and A. Earnshaw. 1998. Chemistry of the Elements, 2nd ed. Oxford, U.K.; Burlington, MA: Butterworth-Heinemann, Elsevier Science. ISBN 0750633654. Online version available here. Retrieved August 11, 2007.
  • Los Alamos National Laboratory Periodic Table Aluminum. Chemistry Division, Los Alamos National Laboratory. Retrieved August 11, 2007.
  • Polmear, I. J. 1995. Light Alloys. London, UK: Arnold Publishers. ISBN 0750663715

External links

All links retrieved July 23, 2023.

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