Aluminium and Magnesium

Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstancesHP Pavilion dv6-1103au battery.

Aluminium is the third most abundant element (after oxygen and silicon), and the most abundant metal, in the Earth's crust. It makes up about 8% by weight of the Earth's solid surface. Aluminium metal is too reactive chemically to occur natively. Instead, it is found combined in over 270 different mineralsHP Pavilion dv6-1102tx battery.[4] The chief ore of aluminium is bauxite.

Aluminium is remarkable for the metal's low density and for its ability to resist corrosion due to the phenomenon of passivation. Structural components made from aluminium and its alloys are vital to the aerospace industry and are important in other areas of transportation and structural materialsHP Pavilion dv6-1102tu battery. The most useful compounds of aluminium, at least on a weight basis, are the oxides and sulfates.

Despite its prevalence in the environment, aluminium salts are not known to be used by any form of life. In keeping with its pervasiveness, aluminium is well tolerated by plants and animals.[5] Due to their prevalence, potential beneficial (or otherwise) biological roles of aluminium compounds are of continuing interestHP Pavilion dv6-1102ax battery.

Characteristics

Etched surface from a high purity (99.9998%) aluminium bar, size 55×37 mm

Physical

Aluminium is a relatively soft, durable, lightweight, ductile and malleable metal with appearance ranging from silvery to dull gray, depending on the surface roughness. It is nonmagnetic and does not easily ignite. A fresh film of aluminium film serves as a good reflector (approximately 92%) of visible light and an excellent reflector (as much as 98%) of medium and far infrared radiationHP Pavilion dv6-1102au battery. The yield strength of pure aluminium is 7–11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa.[6] Aluminium has about one-third the density and stiffness of steel. It is easily machined, cast, drawn and extruded.

Aluminium atoms are arranged in a face-centered cubic (fcc) structure. Aluminium has a stacking-fault energy of approximately 200 mJ/m2HP Pavilion dv6-1101tx battery.[7]

Aluminium is a good thermal and electrical conductor, having 59% the conductivity of copper, both thermal and electrical. Aluminium is capable of being a superconductor, with a superconducting critical temperature of 1.2 Kelvin and a critical magnetic field of about 100 gauss (10 milliteslas) HP Pavilion dv6-1101tu battery.[8]

Chemical

Corrosion resistance can be excellent due to a thin surface layer of aluminium oxide that forms when the metal is exposed to air, effectively preventing further oxidation. The strongest aluminium alloys are less corrosion resistant due to galvanic reactions with alloyed copper.[6] This corrosion resistance is also often greatly reduced by aqueous salts, particularly in the presence of dissimilar metalsHP Pavilion dv6-1101so battery.

Owing to its resistance to corrosion, aluminium is one of the few metals that retain silvery reflectance in finely powdered form, making it an important component of silver-colored paints. Aluminium mirror finish has the highest reflectance of any metal in the 200–400 nm (UV) and the 3,000–10,000 nm (far IR) regionsHP Pavilion dv6-1101ax battery; in the 400–700 nm visible range it is slightly outperformed by tin and silver and in the 700–3000 (near IR) by silver, gold, and copper.[9]

Aluminium is oxidized by water to produce hydrogen and heat:

2 Al + 3 H2O → Al2O3 + 3H2

This conversion is of interest for the production or storage of energy. Challenges include the expenses associated with the regeneration of the Al metalHP Pavilion dv6-1101au battery.[10]

Isotopes

Main article: Isotopes of aluminium

Aluminium has many known isotopes, whose mass numbers range from 21 to 43; however, only 27Al (stable isotope) and 26Al (radioactive isotope, t1/2 = 7.2×105 y) occur naturally. 27Al has a natural abundance above 99.9%. 26Al is produced from argon in the atmosphere by spallation caused by cosmic-ray protonsHP Pavilion dv6-1100sv battery. Aluminium 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 scalesHP Pavilion dv6-1100ss battery.[11] Cosmogenic 26Al was first applied in studies of the Moon and meteorites. Meteoroid 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 drastically reduces 26Al production, and its decay can then be used to determine the meteorite's terrestrial ageHP Pavilion dv6-1100so battery. Meteorite research has also shown that 26Al was relatively abundant at the time of formation of our planetary system. Most meteorite scientists 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 agoHP Pavilion dv6-1100eo battery.[12]

Natural occurrence

See also: List of countries by bauxite production

Stable aluminium is created when hydrogen fuses with magnesium either in large stars or in supernovae.[13]

In the Earth's crust, aluminium is the most abundant (8.3% by weight) metallic element and the third most abundant of all elements (after oxygen and silicon).[14] Because of its strong affinity to oxygen, it is almost never found in the elemental stateHP Pavilion dv6-1099ef battery; instead it is found in oxides or silicates. Feldspars, the most common group of minerals in the Earth's crust, are aluminosilicates. Native aluminium metal can only be found as a minor phase in low oxygen fugacity environments, such as the interiors of certain volcanoes.[15] Native aluminium has been reported in cold seeps in the northeastern continental slope of the South China Sea and Chen et al. HP Pavilion dv6-1090es battery (2011)[16] have proposed a theory of its origin as resulting by reduction from tetrahydroxoaluminate Al(OH)4– to metallic aluminium by bacteria.[16]

It also occurs in the minerals beryl, cryolite, garnet, spinel and turquoise. Impurities in Al2O3, such as chromium or iron yield the gemstones ruby and sapphire, respectively.

Although aluminium is an extremely common and widespread element, the common aluminium minerals are not economic sources of the metalHP Pavilion dv6-1090eo battery. Almost all metallic aluminium is produced from the ore bauxite (AlOx(OH)3–2x). Bauxite occurs as a weathering product of low iron and silica bedrock in tropical climatic conditions.[17] Large deposits of bauxite occur in Australia, Brazil, Guinea and Jamaica and the primary mining areas for the ore are in Australia, Brazil, China, India, Guinea, Indonesia, Jamaica, Russia and SurinamHP Pavilion dv6-1080es battery.

Production and refinement

See also: Category:Aluminium minerals and List of countries by aluminium production

Bauxite, a major aluminium ore. The red-brown colour is due to the presence of iron minerals.

Aluminium forms strong chemical bonds with oxygen. Compared to most other metals, it is difficult to extract from ore, such as bauxite, due to the high reactivity of aluminum and the high melting point of most of its oresHP Pavilion dv6-1080eq battery. For example, direct reduction with carbon, as is used to produce iron, is not chemically possible because aluminium is a stronger reducing agent than carbon. Indirect carbothermic reduction can be carried out using carbon and Al2O3, which forms an intermediate Al4C3 and this can further yield aluminium metal at a temperature of 1900–2000 °C. This process is still under developmentHP Pavilion dv6-1080el battery; it requires less energy and yields less CO2 than the Hall-Héroult process, the major industrial process for aluminium extraction.[18] Electrolytic smelting of alumina was originally cost-prohibitive in part because of the high melting point of alumina, or aluminium oxide, (about 2,000 °C (3,600 °F)). Many mineralsHP Pavilion dv6-1070eo battery, however, will disolve into a second already molten mineral, even if the temperature of the melt is significantly lower than the melting point of the first mineral. Molten cryolite was discovered to disolve alumina at temperatures signifcanlty lower than the melting point of pure alumina without interfering in the smelting process. In the Hall-Héroult processHP Pavilion dv6-1068el battery, alumina is first disolved into molten cryolite with calcium fluoride and then electolytically reduced to aluminium at a temperature between 950 and 980 °C (1,740 to 1,800 °F). Cryolite is a chemical compound of aluminium and sodium fluorides: (Na3AlF6). Although cryolite is found as a mineral in Greenland, its synthetic form is used in the industry. The aluminium oxide itself is obtained by refining bauxite in the Bayer processHP Pavilion dv6-1066el battery.

The electrolytic process replaced the Wöhler process, which involved the reduction of anhydrous aluminium chloride with potassium. Both of the electrodes used in the electrolysis of aluminium oxide are carbon. Once the refined alumina is dissolved in the electrolyte, it disassociates and its ions are free to move around. The reaction at the cathode isHP Pavilion dv6-1062el battery:

Al3+ + 3 e− → Al

Here the aluminium ion is being reduced. The aluminium metal then sinks to the bottom and is tapped off, usually cast into large blocks called aluminium billets for further processing.

At the anode, oxygen is formed:

2 O2− → O2 + 4 e−

To some extent, the carbon anode is consumed by subsequent reaction with oxygen to form carbon dioxide. The anodes in a reduction cell must therefore be replaced regularly, since they are consumed in the processHP Pavilion dv6-1060ev battery. The cathodes do erode, mainly due to electrochemical processes and metal movement. 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 aluminium

Aluminium electrolysis with the Hall-Héroult process consumes a lot of energy, but alternative processes were always found to be less viable economically and/or ecologicallyHP Pavilion dv6-1060es battery. The worldwide average specific energy consumption is approximately 15±0.5 kilowatt-hours per kilogram of aluminium produced (52 to 56 MJ/kg). The most modern smelters achieve approximately 12.8 kW·h/kg (46.1 MJ/kg). (Compare this to the heat of reaction, 31 MJ/kg, and the Gibbs free energy of reaction, 29 MJ/kg.) Reduction line currents for older technologies are typically 100 to 200 kiloamperesHP Pavilion dv6-1060eo battery; state-of-the-art smelters operate at about 350 kA. Trials have been reported with 500 kA cells.[citation needed]

The Hall-Heroult process produces aluminium with a purity of above 99%. Further purification can be done by the Hoope process. The process involves the electrolysis of molten aluminium with a sodium, barium and aluminium fluoride electrolyte. The resulting aluminium has a purity of 99.99%.HP Pavilion dv6-1060el battery

Electric power represents about 20% to 40% of the cost of producing aluminium, depending on the location of the smelter. Aluminium production consumes roughly 5% of electricity generated in the U.S.[21] Smelters tend to be situated where electric power is both plentiful and inexpensive, such as the United Arab Emirates with excess natural gas supplies and Iceland and Norway with energy generated from renewable sourcesHP Pavilion dv6-1058el battery. The world's largest smelters of alumina are People's Republic of China, Russia, and Quebec and British Columbia in Canada.[21][22][23]

Aluminium output in 2005

In 2005, the People's Republic of China was the top producer of aluminium with almost a one-fifth world share, followed by Russia, Canada, and the USA, reports the British Geological SurveyHP Pavilion dv6-1056el battery.

Over the last 50 years, Australia has become a major producer of bauxite ore and a major producer and exporter of alumina (before being overtaken by China in 2007).[22][24] Australia produced 62 million tonnes of bauxite in 2005. The Australian deposits have some refining problems, some being high in silica, but have the advantage of being shallow and relatively easy to mineHP Pavilion dv6-1055ee battery.[25]

Recycling

Aluminium recycling code

Main article: Aluminium recycling

Aluminium is theoretically 100% recyclable without any loss of its natural qualities. According to the International Resource Panel's Metal Stocks in Society report, the global per capita stock of aluminium in use in society (i.e. in cars, buildings, electronics etc.) is 80 kg. Much of this is in more-developed countries (350–500 kg per capita) HP Pavilion dv6-1053cl batteryrather than less-developed countries (35 kg per capita). Knowing the per capita stocks and their approximate lifespans is important for planning recycling.

Recovery of the metal via recycling has become an important facet of the aluminium industry. Recycling was a low-profile activity until the late 1960s, when the growing use of aluminium beverage cans brought it to the public awarenessHP Pavilion dv6-1050us battery.

Recycling involves melting the scrap, a process that requires only 5% of the energy used to produce aluminium from ore, though a significant part (up to 15% of the input material) is lost as dross (ash-like oxide).[26] The dross can undergo a further process to extract aluminiumHP Pavilion dv6-1050et battery.

In Europe aluminium experiences high rates of recycling, ranging from 42% of beverage cans, 85% of construction materials and 95% of transport vehicles.[27]

Recycled aluminium is known as secondary aluminium, but maintains the same physical properties as primary aluminium. Secondary aluminium is produced in a wide range of formats and is employed in 80% of alloy injectionsHP Pavilion dv6-1050ep battery. Another important use is for extrusion.

White dross from primary aluminium production and from secondary recycling operations still contains useful quantities of aluminium that can be extracted industrially.[28] The process produces aluminium billets, together with a highly complex waste material. This waste is difficult to manageHP Pavilion dv6-1050eo battery. It reacts with water, releasing a mixture of gases (including, among others, hydrogen, acetylene, and ammonia), which spontaneously ignites on contact with air;[29] contact with damp air results in the release of copious quantities of ammonia gas. Despite these difficulties, the waste has found use as a filler in asphalt and concreteHP Pavilion dv6-1050en battery.[30]

Compounds

Oxidation state +3

The vast majority of compounds, including all Al-containing minerals and all commercially significant aluminium compounds, feature aluminium in the oxidation state 3+. The coordination number of such compounds varies, but generally Al3+ is six-coordinate or tetracoordinate. Almost all compounds of aluminium(III) are colorlessHP Pavilion dv6-1050ei battery.[14]

Halides

All four trihalides are well known. Unlike the structures of the three heavier trihalides, aluminium fluoride (AlF3) features six-coordinate Al. The octahedral coordination environment for AlF3 is related to the compactness of fluoride ion, six of which can fit around the small Al3+ centre. AlF3 sublimes (with cracking) at 1,291 °C (2,356 °F) HP Pavilion dv6-1050ef battery. With heavier halides, the coordination numbers are lower. The other trihalides are dimeric or polymeric with tetrahedral Al centers. These materials are prepared by treating aluminium metal with the halogen, although other methods exist. Acidification of the oxides or hydroxides affords hydrates. In aqueous solution, the halides often form mixturesHP Pavilion dv6-1046el battery, generally containing six-coordinate Al centres, which are feature both halide and aquo ligands. When aluminium and fluoride are together in aqueous solution, they readily form complex ions such as [AlF(H2O)5]2+, AlF3(H2O)3, and [AlF6]3−. In the case of chloride, polyaluminium clusters are formed such as [Al13O4(OH)24(H2O)12]7+HP Pavilion dv6-1045ez battery.

Oxide and hydroxides

Aluminium forms one stable oxide, known by its mineral name corundum. Sapphire and ruby are impure corundum contaminated with trace amounts of other metals. The two oxide-hydroxides (AlO(OH) are boehmite and diaspore. There are three trihydroxides: bayerite, gibbsiteHP Pavilion dv6-1045eo battery, and nordstrandite, which differ in their crystalline structure (polymorphs). Most are produced from ores by a variety of wet processes using acid and base. Heating the hydroxides leads to formation of corundrum. These materials are of central importance to the production of aluminium and are themselves extremely usefulHP Pavilion dv6-1045ei battery.

Carbide, nitride, and related materials

Aluminium carbide (Al4C3) is made by heating a mixture of the elements above 1,000 °C (1,832 °F). The pale yellow crystals consist of tetrahedral aluminium centres. It reacts with water or dilute acids to give methane. The acetylide, Al2(C2)3, is made by passing acetylene over heated aluminiumHP Pavilion dv6-1045ee battery.

Aluminium nitride (AlN) is the only nitride known for aluminium. Unlike the oxides it features tetrahedral Al centres. It can be made from the elements at 800 °C (1,472 °F). It is air-stable material with a usefully high thermal conductivity. Aluminium phosphide (AlP) is made similarly, and hydrolyses to give phosphineHP Pavilion dv6-1044el battery:

AlP + 3 H2O → Al(OH)3 + PH3

Organoaluminium compounds and related hydrides

Main article: Organoaluminium compound

Structure of trimethylaluminium, a compound that features five-coordinate carbon.

A variety of compounds of empirical formula AlR3 and AlR1.5Cl1.5 exist.[31] These species usually feature tetrahedral Al centres, e.g. "trimethylaluminium" has the formula Al2(CH3)6 (see figure). With large organic groups, triorganoaluminium exist as three-coordinate monomers, such as triisobutylaluminiumHP Pavilion dv6-1042el battery. Such compounds are widely used in industrial chemistry, despite the fact that they are often highly pyrophoric. Few analogues exist between organoaluminium and organoboron compounds except for large organic groups.

The important aluminium hydride is lithium aluminium hydride (LiAlH4), which is used in as a reducing agent in organic chemistry. It can be produced from lithium hydride and aluminium trichlorideHP Pavilion dv6-1040ez battery:

4 LiH + AlCl3 → LiAlH4 + 3 LiCl

Several useful derivatives of LiAlH4 are known, e.g. Sodium bis(2-methoxyethoxy)dihydridoaluminate. The simplest hydride, aluminium hydride or alane, remains a laboratory curiosity. It is a polymer with the formula (AlH3)n, in contrast to the corresponding boron hydride with the formula (BH3)2HP Pavilion dv6-1040ev battery.

Oxidation states +1 and +2

Although the great majority of aluminium compounds feature Al3+ centres, compounds with lower oxidation states are known and sometime of significance as precursors to the Al3+ species.

Aluminium(I)

AlF, AlCl and AlBr exist in the gaseous phase when the tri-halide is heated with aluminium. The composition AlI is unstable at room temperature with respect to the triiodideHP Pavilion dv6-1040el battery:[32]

3 AlI → AlI3 + 2 Al

A stable derivative of aluminium monoiodide is the cyclic adduct formed with triethylamine, Al4I4(NEt3)4. Also of theoretical interest but only of fleeting existence are Al2O and Al2S is made by heating the normal oxide, Al2O3, with silicon at 1,800 °C (3,272 °F) in a vacuum.[32] Such materials quickly disproportionates to the starting materialsHP Pavilion dv6-1040ek battery.

Aluminium(II)

Very simple Al(II) compounds are invoked or observed in the reactions of Al metal with oxidants. For example, aluminium monoxide, AlO, has been detected in the gas phase after explosion[33] and in stellar absorption spectra.[34] More thoroughly investigated are compounds of the formula R4Al2 where R is a large organic ligandHP Pavilion dv6-1040ei battery.[35]

Analysis

The presence of aluminium can be detected in qualitative analysis using aluminon.

Applications

General use

Aluminium is the most widely used non-ferrous metal.[36] Global production of aluminium in 2005 was 31.9 million tonnes. It exceeded that of any other metal except iron (837.5 million tonnes).[37] Forecast for 2012 is 42–45 million tonnes, driven by rising Chinese outputHP Pavilion dv6-1040ed battery.[38]

Aluminium is almost always alloyed, which markedly improves its mechanical properties, especially when tempered. For example, the common aluminium foils and beverage cans are alloys of 92% to 99% aluminium.[39] The main alloying agents are copper, zinc, magnesium, manganese, and silicon (e.g., duralumin) and the levels of these other metals are in the range of a few percent by weightHP Pavilion dv6-1040eb battery.[40]

Household aluminium foil

Aluminium-bodied Austin "A40 Sports" (circa 1951)

Aluminium slabs being transported from a smelter

Some of the many uses for aluminium metal are in:

Transportation (automobiles, aircraft, trucks, railway cars, marine vessels, bicycles, etc.) as sheet, tube, castings, etc.

Packaging (cans, foil, etc.)

Construction (windows, doors, siding, building wire, etc.).[41]

A wide range of household items, from cooking utensils to baseball bats, watches.[42]

Street lighting poles, sailing ship masts, walking poles, etcHP Pavilion dv6-1038ca battery.

Outer shells of consumer electronics, also cases for equipment e.g. photographic equipment.

Electrical transmission lines for power distribution

MKM steel and Alnico magnets

Super purity aluminium (SPA, 99.980% to 99.999% Al), used in electronics and CDs.

Heat sinks for electronic appliances such as transistors and CPUs.

Substrate material of metal-core copper clad laminates used in high brightness LED lightingHP Pavilion dv6-1030us battery.

Powdered aluminium is used in paint, and in pyrotechnics such as solid rocket fuels and thermite.

Aluminium can be reacted with hydrochloric acid or with sodium hydroxide to produce hydrogen gas.

A variety of countries, including France, Italy, Poland, Finland, Romania, Israel, and the former Yugoslavia, have issued coins struck in aluminium or aluminium-copper alloys. HP Pavilion dv6-1030eq battery

Some guitar models sports aluminium diamond plates on the surface of the instruments, usually either chrome or black. Kramer Guitars and Travis Bean are both known for having produced guitars with necks made of aluminium, which gives the instrument a very distinct soundHP Pavilion dv6-1030eo battery.

Aluminium is usually alloyed – it is used as pure metal only when corrosion resistance and/or workability is more important than strength or hardness. A thin layer of aluminium can be deposited onto a flat surface by physical vapour deposition or (very infrequently) chemical vapour deposition or other chemical means to form optical coatings and mirrorsHP Pavilion dv6-1030em battery.

Aluminium compounds

Because aluminium is abundant and most of its derivative exhibit low toxicity, the compounds of aluminium enjoy wide and sometimes large-scale applications.

Alumina

Main article: Aluminium oxide

Aluminium oxide (Al2O3) and the associated oxy-hydroxides and trihydroxides are produced or extracted from minerals on a large scaleHP Pavilion dv6-1030ef battery. The great majority of this material is converted to metallic aluminium. About 10% of the production capacity is used for other applications. A major use is as an absorbent, for example alumina will remove water from hydrocarbons, to enable subsequent processes that are poisoned by moisture. Aluminium oxides are common catalysts for industrial processesHP Pavilion dv6-1030ed battery, e.g. the Claus process for converting hydrogen sulfide to sulfur in refineries and for the alkylation of amines. Many industrial catalysts are "supported", meaning generally that an expensive catalyst (e.g., platinum) is dispersed over a high surface area material such as alumina. Being a very hard material (Mohs hardness 9) HP Pavilion dv6-1030ec battery, alumina is widely used as an abrasive and the production of applications that exploit its inertness, e.g., in high pressure sodium lamps.

Sulfates

Several sulfates of aluminium find applications. Aluminium sulfate (Al2(SO4)3(H2O)18) is produced on the annual scale of several billions of kilograms. About half of the production is consumed in water treatment. The next major application is in the manufacture of paper. It is also used as a mordantHP Pavilion dv6-1030ca battery, in fire extinguisher, as a food additive, in fireproofing, and in leather tanning. Aluminium ammonium sulfate, which is also called ammonium alum, (NH4)Al(SO4)2·12H2O, is used as a mordant and in leather tanning.[5] Aluminium potassium sulfate ([Al(K)](SO4)2)(H2O)12 is used similarly. The consumption of both alums is decliningHP Pavilion dv6-1027ef battery.

Chlorides

Aluminium chloride (AlCl3) is used in petroleum refining and in the production of synthetic rubber and polymers. Although it has a similar name, aluminium chlorohydrate has fewer and very different applications, e.g. as a hardening agent and an antiperspirant. It is an intermediate in the production of aluminium metalHP Pavilion dv6-1025ez battery.

Niche compounds

Given the scale of aluminium compounds, a small scale application could still involve thousands of tonnes. One of the many compounds used at this intermediate level include aluminium acetate, a salt used in solution as an astringent. Aluminium borate (Al2O3·B2O3) is used in the production of glass and ceramicsHP Pavilion dv6-1025ei battery. Aluminium fluorosilicate (Al2(SiF6)3) is used in the production of synthetic gemstones, glass and ceramic. Aluminium phosphate (AlPO4) is used in the manufacture: of glass and ceramic, pulp and paper products, cosmetics, paints and varnishes and in making dental cement. Aluminium hydroxide (Al(OH)3) is used as an antacid, as a mordant, in water purificationHP Pavilion dv6-1025ef battery, in the manufacture of glass and ceramic and in the waterproofing of fabrics. Lithium aluminium hydride is a powerful reducing agent used in organic chemistry. Organoaluminiums are used as Lewis acids and cocatalysts. For example, methylaluminoxane is a cocatalyst for Ziegler-Natta olefin polymerization to produce vinyl polymers such as polyetheneHP Pavilion dv6-1023em battery.

Aluminium alloys in structural applications

Main article: Aluminium alloy

Aluminium foam

Aluminium alloys with a wide range of properties are used in engineering structures. Alloy systems are classified by a number system (ANSI) or by names indicating their main alloying constituents (DIN and ISO).

The strength and durability of aluminium alloys vary widely, not only as a result of the components of the specific alloy, but also as a result of heat treatments and manufacturing processesHP Pavilion dv6-1023ef battery. A lack of knowledge of these aspects has from time to time led to improperly designed structures and gained aluminium a bad reputation.

One important structural limitation of aluminium alloys is their fatigue strength. Unlike steels, aluminium alloys have no well-defined fatigue limit, meaning that fatigue failure eventually occurs, under even very small cyclic loadings. This implies that engineers must assess these loads and design for a fixed life rather than an infinite lifeHP Pavilion dv6-1022el battery.

Another important property of aluminium alloys is their sensitivity to heat. Workshop procedures involving heating are complicated by the fact that aluminium, unlike steel, melts without first glowing red. Forming operations where a blow torch is used therefore require some expertise, since no visual signs reveal how close the material is to melting. Aluminium alloysHP Pavilion dv6-1020et battery, like all structural alloys, also are subject to internal stresses following heating operations such as welding and casting. The problem with aluminium alloys in this regard is their low melting point, which make them more susceptible to distortions from thermally induced stress relief. Controlled stress relief can be done during manufacturing by heat-treating the parts in an ovenHP Pavilion dv6-1020eg battery, followed by gradual cooling—in effect annealing the stresses.

The low melting point of aluminium alloys has not precluded their use in rocketry; even for use in constructing combustion chambers where gases can reach 3500 K. The Agena upper stage engine used a regeneratively cooled aluminium design for some parts of the nozzle, including the thermally critical throat regionHP Pavilion dv6-1020el battery.

Another alloy of some value is aluminium bronze (Cu-Al alloy).

History

The statue of the Anteros (commonly mistaken for either The Angel of Christian Charity or Eros) in Piccadilly Circus, London, was made in 1893 and is one of the first statues to be cast in aluminium.

Ancient Greeks and Romans used aluminium salts as dyeing mordants and as astringents for dressing wounds; alum is still used as a stypticHP Pavilion dv6-1020ek battery. In 1761, Guyton de Morveau suggested calling the base alum alumine. In 1808, Humphry Davy identified the existence of a metal base of alum, which he at first termed alumium and later aluminum (see etymology section, below).

The metal was first produced in 1825 in an impure form by Danish physicist and chemist Hans Christian Ørsted. He reacted anhydrous aluminium chloride with potassium amalgam, yielding a lump of metal looking similar to tinHP Pavilion dv6-1020ei battery.[45] Friedrich Wöhler was aware of these experiments and cited them, but after redoing the experiments of Ørsted he concluded that this metal was pure potassium. He conducted a similar experiment in 1827 by mixing anhydrous aluminium chloride with potassium and yielded aluminium.[45] Wöhler is generally credited with isolating aluminium (Latin alumen, alum) HP Pavilion dv6-1020ed battery, but also Ørsted can be listed as its discoverer.[46] Further, Pierre Berthier discovered aluminium in bauxite ore and successfully extracted it.[47] 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. HP Pavilion dv6-1020ec battery Deville likely also conceived the idea of the electrolysis of aluminium oxide dissolved in cryolite; Charles Martin Hall and Paul Héroult might have developed the more practical process after Deville.

Before the Hall-Héroult process was developed in the late 1880s, aluminium was exceedingly difficult to extract from its various ores. This made pure aluminium more valuable than goldHP Pavilion dv6-1018el battery.[49] Bars of aluminium were exhibited at the Exposition Universelle of 1855.[50] Napoleon III, Emperor of France, is reputed to have given a banquet where the most honoured guests were given aluminium utensils, while the others made do with gold.[51][52]

Aluminium was selected as the material to be used for the 100 ounce (2.8 kg) capstone of the Washington Monument in 1884, a time when one ounce (30 grams) cost the daily wage of a common worker on the projectHP Pavilion dv6-1001et battery;[53] The capstone, which was set in place on December 6, 1884, in an elaborate dedication ceremony, was the largest single piece of aluminium cast at the time, when aluminium was as expensive as silver.[53]

The Cowles companies supplied aluminium alloy in quantity in the United States and England using smelters like the furnace of Carl Wilhelm Siemens by 1886. HP Pavilion dv6-1001tx batteryCharles Martin Hall of Ohio in the U.S. and Paul Héroult of France independently developed the Hall-Héroult electrolytic process that made extracting aluminium from minerals cheaper and is now the principal method used worldwide. Hall's process,[57] in 1888 with the financial backing of Alfred E. Hunt, started the Pittsburgh Reduction Company today known as AlcoaHP Pavilion dv6-1001xx battery. Héroult's process was in production by 1889 in Switzerland at Aluminium Industrie, now Alcan, and at British Aluminium, now Luxfer Group and Alcoa, by 1896 in Scotland.[58]

By 1895, the metal was being used as a building material as far away as Sydney, Australia in the dome of the Chief Secretary's BuildingHP Pavilion dv6-1002tx battery.

Many navies have used an aluminium superstructure for their vessels; the 1975 fire aboard USS Belknap that gutted her aluminium superstructure, as well as observation of battle damage to British ships during the Falklands War, led to many navies switching to all steel superstructures. The Arleigh Burke class was the first such U.S. ship, being constructed entirely of steelHP Pavilion dv6-1003tx battery.

Aluminium wire was once widely used for domestic electrical wiring. Owing to corrosion-induced failures, a number of fires resulted. This discontinuation thus illustrates one failed application of the otherwise highly useful metal.

Etymology

Two variants of the metal's name are in current use, aluminium and aluminum (besides the obsolete alumium) HP Pavilion dv6-1004tx battery. 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.[59] IUPAC prefers the use of aluminium in its internal publications, although nearly as many IUPAC publications use the spelling aluminumHP Pavilion dv6-1005ea battery.[60]

Most countries use the spelling aluminium. In the United States, the spelling aluminum predominates.[14][61] The Canadian Oxford Dictionary prefers aluminum, whereas the Australian Macquarie Dictionary prefers aluminium. In 1926, the American Chemical Society officially decided to use aluminum in its publications; American dictionaries typically label the spelling aluminium as a British variantHP Pavilion dv6-1005ez battery.

The name aluminium derives from its status as a base of alum. It is borrowed from Old French; its ultimate source, alumen, in turn is a Latin word that literally means "bitter salt".[62]

The earliest citation given in the Oxford English Dictionary for any word used as a name for this element is alumium, which British chemist and inventor Humphry Davy employed in 1808 for the metal he was trying to isolate electrolytically from the mineral aluminaHP Pavilion dv6-1005tx battery. The citation is from the journal Philosophical Transactions of the Royal Society of London: "Had I been so fortunate as to have obtained more certain evidences on this subject, and 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." HP Pavilion dv6-1006tx battery

Davy settled on aluminum by the time he published his 1812 book Chemical Philosophy: "This substance appears to contain a peculiar metal, but as yet Aluminum has not been obtained in a perfectly free state, though alloys of it with other metalline substances have been procured sufficiently distinct to indicate the probable nature of aluminaHP Pavilion dv6-1007tx battery."[65] But the same year, an anonymous contributor to the Quarterly Review, a British political-literary journal, in a review of Davy's book, 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." HP Pavilion dv6-1008tx battery

The -ium suffix conformed to the precedent set in other newly discovered elements of the time: potassium, sodium, magnesium, calcium, and strontium (all of which Davy isolated himself). Nevertheless, -um spellings for elements were not unknown at the time, as for example platinum, known to Europeans since the 16th centuryHP Pavilion dv6-1009el battery, molybdenum, discovered in 1778, and tantalum, discovered in 1802. The -um suffix is consistent with the universal spelling alumina for the oxide, as lanthana is the oxide of lanthanum, and magnesia, ceria, and thoria are the oxides of magnesium, cerium, and thorium respectively.

The spelling used throughout the 19th century by most U.S. chemists was aluminium, but common usage is less clearHP Pavilion dv6-1009tx battery.[67] The aluminum spelling is used in the Webster's Dictionary of 1828. In his advertising handbill for his new electrolytic method of producing the metal 1892, Charles Martin Hall used the -um spelling, despite his constant use of the -ium spelling in all the patents[57] he filed between 1886 and 1903HP Pavilion dv6-1010ea battery.[68] 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 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 versionHP Pavilion dv6-1010ed battery.

Health concerns

NFPA 704

000

Fire diamond for aluminium shot

Despite its natural abundance, aluminium has no known function in biology. It is remarkably nontoxic, aluminium sulfate having an LD50 of 6207 mg/kg (oral, mouse), which corresponds to 500 grams for a 80 kg person.[5] Despite the extremely low acute toxicity, the health effects of aluminium are of interest in view of the widespread occurrence of the element in the environment and in commerceHP Pavilion dv6-1010et battery.

Some toxicity can be traced to deposition in bone and the central nervous system, which is particularly increased in patients with reduced renal function. Because aluminium competes with calcium for absorption, increased amounts of dietary aluminium may contribute to the reduced skeletal mineralization (osteopenia) observed in preterm infants and infants with growth retardationHP Pavilion dv6-1010tx battery. In very high doses, aluminium can cause neurotoxicity, and is associated with altered function of the blood-brain barrier.[69] A small percentage of people are allergic to aluminium and experience contact dermatitis, digestive disorders, vomiting or other symptoms upon contact or ingestion of products containing aluminiumHP Pavilion dv6-1011tx battery, such as deodorants or antacids. In those without allergies, aluminium is not as toxic as heavy metals, but there is evidence of some toxicity if it is consumed in excessive amounts.[70] Although the use of aluminium cookware has not been shown to lead to aluminium toxicity in generalHP Pavilion dv6-1012tx battery, excessive consumption of antacids containing aluminium compounds and excessive use of aluminium-containing antiperspirants provide more significant exposure levels. Studies have shown that consumption of acidic foods or liquids with aluminium significantly increases aluminium absorption,[71] and maltol has been shown to increase the accumulation of aluminium in nervous and osseus tissueHP Pavilion dv6-1013ea battery.[72] Furthermore, aluminium increases estrogen-related gene expression in human breast cancer cells cultured in the laboratory.[73] The estrogen-like effects of these salts have led to their classification as a metalloestrogen.

The effects of aluminium in antiperspirants has been examined over the course of decades with little evidence of skin irritationHP Pavilion dv6-1013tx battery.[5] Nonetheless, its occurrence in antiperspirants, dyes (such as aluminium lake), and food additives is controversial in some quarters. Although there is little evidence that normal exposure to aluminium presents a risk to healthy adults,[74] some studies point to risks associated with increased exposure to the metal.[75] Aluminium in food may be absorbed more than aluminium from waterHP Pavilion dv6-1016ez battery.[76] Some researchers have expressed concerns that the aluminium in antiperspirants may increase the risk of breast cancer,[77] and aluminium has controversially been implicated as a factor in Alzheimer's disease.[78] The Camelford water pollution incident involved a number of people consuming aluminium sulfateHP Pavilion dv6-6091nr battery. Investigations of the long-term health effects are still ongoing, but elevated brain aluminium concentrations have been found in post-mortem examinations of victims, and further research to determine if there is a link with cerebral amyloid angiopathy has been commissionedHP Pavilion dv6-6090us battery.[79]

According to The Alzheimer's Society, the overwhelming medical and scientific opinion is that studies have not convincingly demonstrated a causal relationship between aluminium and Alzheimer's disease.[80] Nevertheless, some studies, such as those on the PAQUID cohort,[81] cite aluminium exposure as a risk factor for Alzheimer's diseaseHP Pavilion dv6-6090sf battery. Some brain plaques have been found to contain increased levels of the metal.[82] Research in this area has been inconclusive; aluminium accumulation may be a consequence of the disease rather than a causal agent. In any event, if there is any toxicity of aluminium, it must be via a very specific mechanismHP Pavilion dv6-6087eg battery, since total human exposure to the element in the form of naturally occurring clay in soil and dust is enormously large over a lifetime.[83][84] Scientific consensus does not yet exist about whether aluminium exposure could directly increase the risk of Alzheimer's disease.[80]

Effect on plants

Aluminium is primary among the factors that reduce plant growth on acid soils. Although it is generally harmless to plaHP Pavilion dv6-6063sf battery

Origin and characteristics

[edit]Physical and chemical properties

Elemental magnesium is a fairly strong, silvery-white, light-weight metal (two thirds the density of aluminium). It tarnishes slightly when exposed to air, although unlike the alkali metals, storage in an oxygen-free environment is unnecessary because magnesium is protected by a thin layer of oxide that is fairly impermeable and difficult to removeHP Pavilion dv6-6054sf battery. Like its lower periodic table group neighbor calcium, magnesium reacts with water at room temperature, though it reacts much more slowly than calcium. When submerged in water, hydrogen bubbles will almost unnoticeably begin to form on the surface of the metal, though if powdered it will react much more rapidlyHP Pavilion dv6-6054ef battery. The reaction will occur faster with higher temperatures (see precautions). Magnesium's ability to react with water can be harnessed to produce energy and run a magnesium-based engine. Magnesium also reacts exothermically with most acids, such as hydrochloric acid (HCl). As with aluminium, zinc and many other metals, the reaction with hydrochloric acid produces the chloride of the metal and releases hydrogen gasHP Pavilion dv6-6051xx battery.

Magnesium is a highly flammable metal, but while it is easy to ignite when powdered or shaved into thin strips, it is difficult to ignite in mass or bulk. Once ignited, it is difficult to extinguish, being able to burn in nitrogen (forming magnesium nitride), carbon dioxide (forming magnesium oxide and carbon) and water (forming magnesium oxide and hydrogen) HP Pavilion dv6-6051sf battery. This property was used in incendiary weapons used in the firebombing of cities in World War II, the only practical civil defense being to smother a burning flare under dry sand to exclude the atmosphere. On burning in air, magnesium produces a brilliant white light which includes strong ultraviolet. Thus magnesium powder (flash powder) was used as a source of illumination in the early days of photographyHP Pavilion dv6-6042sf battery. Later, magnesium ribbon was used in electrically ignited flash bulbs. Magnesium powder is used in the manufacture of fireworks and marine flares where a brilliant white light is required. Flame temperatures of magnesium and magnesium alloys can reach 3,100 °C (3,370 K; 5,610 °F),[7] although flame height above the burning metal is usually less than 300 mm (12 in) HP Pavilion dv6-6029tx battery.[8] Magnesium may be used as an ignition source for thermite, an otherwise difficult to ignite mixture of aluminium and iron oxide powder.

Magnesium compounds are typically white crystals. Most are soluble in water, providing the sour-tasting magnesium ion Mg2+. Small amounts of dissolved magnesium ion contribute to the tartness and taste of natural waters. Magnesium ion in large amounts is an ionic laxative, and magnesium sulfate HP Pavilion dv6-6027tx battery (common name: Epsom salt) is sometimes used for this purpose. So-called "milk of magnesia" is a water suspension of one of the few insoluble magnesium compounds, magnesium hydroxide. The undissolved particles give rise to its appearance and name. Milk of magnesia is a mild base commonly used as an antacid, which has some laxative side effectHP Pavilion dv6-6026tx battery.

[edit]Isotopes

Magnesium has three stable isotopes: 24Mg, 25Mg and 26Mg. All are present in significant amounts (see table of isotopes above). About 79% of Mg is 24Mg. The isotope 28Mg is radioactive and in the 1950s to 1970s was made commercially by several nuclear power plants for use in scientific experiments. This isotope has a relatively short half-life (21 hours) and so its use was limited by shipping timesHP Pavilion dv6-6025tx battery.

26Mg has found application in isotopic geology, similar to that of aluminium. 26Mg is a radiogenic daughter product of 26Al, which has a half-life of 717,000 years. Large enrichments of stable 26Mg have been observed in the Ca-Al-rich inclusions of some carbonaceous chondrite meteoritesHP Pavilion dv6-6024tx battery. The anomalous abundance of 26Mg is attributed to the decay of its parent 26Al in the inclusions. Therefore, the meteorite must have formed in the solar nebula before the 26Al had decayed. Hence, these fragments are among the oldest objects in the solar system and have preserved information about its early historyHP Pavilion dv6-6023tx battery.

It is conventional to plot 26Mg/24Mg against an Al/Mg ratio. In an isochron dating plot, the Al/Mg ratio plotted is27Al/24Mg. The slope of the isochron has no age significance, but indicates the initial 26Al/27Al ratio in the sample at the time when the systems were separated from a common reservoir.

[edit]Creation

Magnesium is produced in stars larger than 3 solar masses by fusing helium and neon in the alpha process at temperatures above 600 megakelvinsHP Pavilion dv6-6022eg battery.

[edit]Occurrence

See also Category: Magnesium minerals

Country 2010 production

(tonnes)[9]

China      650,000

Russia     40,000

Israel       30,000

Kazakhstan   20,000

Brazil      16,000

Ukraine  2,000

Serbia     2,000

Although magnesium is found in over 60 minerals, only dolomite, magnesite, brucite, carnallite, talc, and olivine are of commercial importance.

The Mg2+ cation is the second most abundant cation in seawater (occurring at about 12% of the mass of sodium there), which makes seawater and sea-salt an attractive commercial source of Mg. To extract the magnesium, calcium hydroxide is added to seawater to form magnesium hydroxide precipitateHP Pavilion dv6-6013tu battery.

MgCl2 + Ca(OH)2 → Mg(OH)2 + CaCl2

Magnesium hydroxide (brucite) is insoluble in water so it can be filtered out, and reacted with hydrochloric acid to obtain concentrated magnesium chloride.

Mg(OH)2 + 2 HCl → MgCl2 + 2 H2O

From magnesium chloride, electrolysis produces magnesium.

In the United States, magnesium is principally obtained by electrolysis of fused magnesium chloride from brines, wells, and sea water. At the cathode, the Mg2+ ion is reduced by two electrons to magnesium metalHP Pavilion dv6-6013cl battery:

Mg2+ + 2 e−

 → Mg

At the anode, each pair of Cl− ions is oxidized to chlorine gas, releasing two electrons to complete the circuit:

2 Cl− → Cl2 (g) + 2 e−

The United States has traditionally been the major world supplier of this metal, supplying 45% of world production even as recently as 1995. Today, the US market share is at 7%, with a single domestic producer left, US Magnesium, a Renco Group company in Utah born from now-defunct MagcorpHP Pavilion dv6-6012tu battery.[10]

As of 2005, China has taken over as the dominant supplier, pegged at 60% world market share, which increased from 4% in 1995. Unlike the above-described electrolytic process, China is almost completely reliant on a different method of obtaining the metal from its ores, the silicothermic Pidgeon process (the reduction of the oxide at high temperatures with silicon). HP Pavilion dv6-6011tu battery

[edit]History

Sir Humphry Davy

The name magnesium originates from the Greek word for a district in Thessaly called Magnesia. It is related to magnetite and manganese, which also originated from this area, and required differentiation as separate substances. See manganese for this historyHP Pavilion dv6-6008tx battery.

Magnesium is the seventh most abundant element in the Earth's crust by mass or molarity.[2] It is found in large deposits of magnesite, dolomite, and other minerals, and in mineral waters, where magnesium ion is soluble. In 1618, a farmer at Epsom in England attempted to give his cows water from a well thereHP Pavilion dv6-6008sa battery. The cows refused to drink because of the water's bitter taste, but the farmer noticed that the water seemed to heal scratches and rashes. The substance became known as Epsom salts and its fame spread; it was eventually recognized to be hydrated magnesium sulfate, MgSO4.

The metal itself was first produced by Sir Humphry Davy in England in 1808 using electrolysis of a mixture of magnesia and mercuric oxideHP Pavilion dv6-6008eg battery.[11] Antoine Bussy prepared it in coherent form in 1831. Davy's first suggestion for a name was magnium,[11] but the name magnesium is now used.

[edit]Applications

[edit]As metal

An unusual application of magnesium as an illumination source while wakeskating in 1931

Magnesium is the third most commonly used structural metal, following iron and aluminium. It has been called the lightest useful metal by The Periodic Table of VideosHP Pavilion dv6-6007tx battery.[12]

The main applications of magnesium are, in order: component of aluminium alloys, in die-casting (alloyed with zinc),[13] to remove sulfur in the production of iron and steel, the production of titanium in the Kroll process.[14]

Magnesium, in its purest form, can be compared with aluminium, and is strong and light, so it is used in several high volume part manufacturing applications, including automotive and truck componentsHP Pavilion dv6-6007sg battery. Specialty, high-grade car wheels of magnesium alloy are called "mag wheels", although the term is often more broadly misapplied to include aluminum wheels. In 1957, a Chevrolet Corvette SS, designed for racing, was constructed with magnesium body panels. An earlier Mercedes-Benz race car model, the Mercedes-Benz 300 SLR, had a body made from Elektron, a magnesium alloyHP Pavilion dv6-6006ea battery; these cars ran (with successes) at Le Mans, the Mille Miglia, and other world-class race events in 1955 (though one was involved in the single worst accident in auto racing history, in terms of human casualties, at the Le Mans race.) Porsche's all-out quest to decrease the weight of their race cars led to the use of magnesium frames in the famous 917/053 that won Le Mans in 1971HP Pavilion dv6-6005sg battery, and still holds the absolute distance record. The 917/30 Can-Am car also featured a magnesium frame, helping it to make the most of its prodigious 1100–1500 hp. Volkswagen Group has used magnesium in its engine components for many years. For a long time, Porsche used magnesium alloy for its engine blocks due to the weight advantageHP Pavilion dv6-6005eg battery. There is renewed interest in magnesium engine blocks, as featured in the 2006 BMW 325i and 330i models. The BMW engine uses an aluminium alloy insert for the cylinder walls and cooling jackets surrounded by a high-temperature magnesium alloy AJ62A. The application of magnesium AE44 alloy in the 2006 Corvette Z06 engine cradle has advanced the technology of designing robust automotive parts in magnesiumHP Pavilion dv6-6005ea battery. Both these alloys are recent developments in high-temperature low creep magnesium alloys. Mitsubishi Motors also uses magnesium (branded magnesium alloy) for its paddle shifters. The general strategy for such alloys is to form intermetallic precipitates at the grain boundaries, for example by adding mischmetal or calcium.[15] New alloy development and lower costsHP Pavilion dv6-6004sa battery, which are becoming competitive to aluminium, will further the number of automotive applications.[citation needed]

Products made of magnesium: firestarter and shavings, sharpener, magnesium ribbon

The second application field of magnesium is electronic devices. Because of low weight, good mechanical and electrical properties, magnesium is widely used for manufacturing of mobile phones, laptop computers, cameras, and other electronic componentsHP Pavilion dv6-6003eg battery.

Historically, magnesium was one of the main aerospace construction metals and was used for German military aircraft as early as World War I and extensively for German aircraft in World War II. The Germans coined the name 'Elektron' for magnesium alloy. The term is still used today. Because of perceived hazards with magnesium parts in the event of fireHP Pavilion dv6-6002sg battery, the application of magnesium in the commercial aerospace industry was generally restricted to engine related components. Currently the use of magnesium alloys in aerospace is increasing, mostly driven by the increasing importance of fuel economy and the need to reduce weight.[citation needed] The development and testing of new magnesium alloys continuesHP Pavilion dv6-6002eg battery, notably Elektron 21, which has successfully undergone extensive aerospace testing for suitability in engine, internal and airframe components. The European Community runs three R&D magnesium projects in the Aerospace priority of Six Framework Program.

[edit]Niche uses of the metal

Magnesium, being available and relatively nontoxic, has variety of uses:

Magnesium is flammable, burning at a temperature of approximately 3,100 °C (3,370 K; 5,610 °F) HP Pavilion dv6-6001sg battery,[7] and the autoignition temperature of magnesium ribbon is approximately 473 °C (746 K; 883 °F).[16] It produces intense, bright, white light when it burns. Magnesium's high burning temperature makes it a useful tool for starting emergency fires during outdoor recreation. Other uses include flash photography, flares, pyrotechnics and fireworks sparklersHP Pavilion dv6-6001eg battery.

Magnesium firestarter (in left hand), used with a pocket knife and flint to create sparks that ignite the shavings

In the form of turnings or ribbons, to prepare Grignard reagents, which are useful in organic synthesis.

As an additive agent in conventional propellants and the production of nodular graphite in cast ironHP Pavilion dv6-6001ea battery.

As a reducing agent for the production of uranium and other metals from their salts.

As a sacrificial (galvanic) anode to protect underground tanks, pipelines, buried structures, and water heaters.

Alloyed with zinc to produce the zinc sheet used in photoengraving plates in the printing industry, dry-cell battery walls, and roofingHP Pavilion dv6-6000eg battery.[13]

As a metal, this element's principal use is as an alloying additive to aluminium with these aluminium-magnesium alloys being used mainly for beverage cans.

[edit]In magnesium compounds

Magnesium compounds, primarily magnesium oxide (MgO), are used as refractory a material in furnace linings for producing iron, steel, nonferrous metals, glass and cement(HP Pavilion dv6-3362sf battery). Magnesium oxide and other magnesium compounds are also used in the agricultural, chemical, and construction industries.

Magnesium reacted with an alkyl halide gives a Gringard reagent, which is a very useful tool for preparing alcohols.

In agriculture and biology, the magnesium ion is necessary for all life (see magnesium in biology), so magnesium salts are frequently included in various foods, fertilizers (magnesium is a component of chlorophyll), and culture media(HP Pavilion dv6-3362ef battery).

[edit]Niche and illustrative uses of magnesium compounds

[edit]Biological

Magnesium sulfate, as the heptahydrate called Epsom salts, is used as bath salts, as a laxative, and as a highly soluble fertilizer.

Magnesium hydroxide, suspended in water, is used in milk of magnesia antacids and laxatives.

Magnesium chloride, oxide, gluconate, malate, orotate, glycinate and citrate are all used as oral magnesium supplements(HP Pavilion dv6-3355sf battery). Oral magnesium supplements have been claimed to be therapeutic for some individuals who suffer from Restless Leg Syndrome (RLS).[citation needed]

Magnesium borate, magnesium salicylate, and magnesium sulfate are all used as antiseptics.

Magnesium bromide is used as a mild sedative (this action is due to the bromide, not the magnesium) (HP Pavilion dv6-3355ef battery).

Magnesium stearate is a slightly flammable white powder with lubricating properties. In pharmaceutical technology, it is used in the manufacturing of numerous kinds of tablets to prevent the tablets from sticking to the equipment during the tablet compression process (i.e., when the tablet's substance is pressed into tablet form) (HP Pavilion dv6-3351sf battery).

Magnesium carbonate powder is used by athletes such as gymnasts, weightlifters and climbers to eliminate moisture and improving the grip on a gymnastic apparatus, lifting bar and climbing rocks.

[edit]Non biological

Dead-burned magnesite (magnesium carbonate) is used for refractory purposes such as brick and liners in furnaces and converters.

Magnesium sulfite is used in the manufacture of paper (sulfite process).

Magnesium phosphate is used to fireproof wood used in construction.

Magnesium hexafluorosilicate is used in mothproofing of textiles(HP Pavilion dv6-3351ef battery).

[edit]Biological role

Main article: Magnesium in biology

Because of the important interaction between phosphate and magnesium ions, magnesium ions are essential to the basic nucleic acid chemistry of life, and thus are essential to all cells of all known living organisms. Over 300 enzymes require the presence of magnesium ions for their catalytic action(HP Pavilion dv6-3350sf battery), including all enzymes utilizing or synthesizing ATP, or those that use other nucleotides to synthesize DNA and RNA. ATP exists in cells normally as a chelate of ATP and a magnesium ion.

Plants have an additional use for magnesium in that chlorophylls are magnesium-centered porphyrins. Magnesium deficiency in plants causes late-season yellowing between leaf veins, especially in older leaves(HP Pavilion dv6-3350ef battery), and can be corrected by applying Epsom salts (which is rapidly leached), or else crushed dolomitic limestone to the soil.

Examples of food sources of magnesium

Magnesium is a vital component of a healthy human diet. Human magnesium deficiency (including conditions that show few overt symptoms) is relatively rare[17] although only 32% of the United States meet the RDA-DRI;[18] low levels of magnesium in the body has been associated with the development of a number of human illnesses such as asthma, diabetes, and osteoporosis(HP Pavilion dv6-3300sg battery).[19]

Adult human bodies contain about 24 grams of magnesium, with 60% in the skeleton, 39% intracellular (20% in skeletal muscle), and 1% extracellular. Serum levels are typically 0.7–1.0 mmol/L or 1.8–2.4 mEq/L. Serum magnesium levels may appear normal even in cases of underlying intracellular deficiency(HP Pavilion dv6-3300 battery), although no known mechanism maintains a homeostatic level in the blood other than renal excretion of high blood levels.

Intracellular magnesium is correlated with intracellular potassium. Magnesium is absorbed in the gastrointestinal tract, with more absorbed when status is lower. In humans, magnesium appears to facilitate calcium absorption[citation needed]. Low and high protein intake inhibit magnesium absorption(HP Pavilion dv6-3299ea battery), and other factors such as phosphate, phytate, and fat affect absorption. Absorbed dietary magnesium is largely excreted through the urine, although most magnesium "administered orally" is excreted through the feces.[20] Magnesium status may be assessed roughly through serum and erythrocyte Mg concentrations and urinary and fecal excretion(HP Pavilion dv6-3298ea battery), but intravenous magnesium loading tests are likely the most accurate and practical in most people.[21] In these tests, magnesium is injected intravenously; a retention of 20% or more indicates deficiency.[22] Other nutrient deficiencies are identified through biomarkers, but none are established for magnesium(HP Pavilion dv6-3180ea battery).[23]

Spices, nuts, cereals, coffee, cocoa, tea, and vegetables are rich sources of magnesium. Green leafy vegetables such as spinach are also rich in magnesium as they contain chlorophyll. Observations of reduced dietary magnesium intake in modern Western countries compared to earlier generations may be related to food refining and modern fertilizers that contain no magnesium(HP Pavilion dv6-3163eo battery).[20]

Numerous magnesium dietary supplements are available. Magnesium oxide, one of the most common because it has high magnesium content per weight, has been reported to be the least bioavailable.[24][25] Magnesium citrate has been reported as more bioavailable than oxide or amino-acid chelate (glycinate) forms(HP Pavilion dv6-3150sa battery).[26]

Excess magnesium in the blood is freely filtered at the kidneys, and for this reason it is difficult to overdose on magnesium from dietary sources alone.[19] With supplements, overdose is possible, however, particularly in people with poor renal function; occasionally, with use of high cathartic doses of magnesium salts(HP Pavilion dv6-3141sa battery), severe hypermagnesemia has been reported to occur even without renal dysfunction.[27] Alcoholism can produce a magnesium deficiency, which is easily reversed by oral or parenteral administration, depending on the degree of deficiency.[28]

[edit]Detection in biological fluids

Magnesium concentrations in plasma or serum may be measured to monitor for efficacy and safety in those receiving the drug therapeutically, to confirm the diagnosis in potential poisoning victims or to assist in the forensic investigation in a case of fatal overdosage(HP Pavilion dv6-3140sa battery). The newborn children of mothers who received parenteral magnesium sulfate during labor may exhibit toxicity at serum magnesium levels that were considered appropriate for the mothers.[29]

[edit]Magnesium in treatment-resistant depression (TRD)

There has been some speculation that magnesium deficiency can lead to depression. Cerebral spinal fluid (CSF) magnesium has been found low in treatment-resistant suicidal depression and in patients that have attempted suicide(HP Pavilion dv6-3131sa battery). Brain magnesium has been found low in TRD using phosphorus nuclear magnetic resonance spectroscopy, an accurate means for measuring brain magnesium. Blood and CSF magnesium do not appear well-correlated with major depression.[30] Magnesium chloride in relatively small doses was found to be as effective in the treatment of depressed elderly type 2 diabetics with hypomagnesemia as imipramine 50 mg daily(HP Pavilion dv6-3130sa battery).[31]

[edit]Safety precautions for magnesium metal

The magnesium-bodied Honda RA302 of Jo Schlesser crashes and burns during the 1968 French Grand Prix. Schlesser was killed. The magnesium car body did not cause the fire or the death, but it greatly hindered attempts to douse the fire with water(HP Pavilion dv6-3127sa battery).

[citation needed]

Magnesium metal and its alloys are explosive hazards; they are highly flammable in their pure form when molten or in powder or ribbon form. Burning or molten magnesium metal reacts violently with water. When working with powdered magnesium, safety glasses with welding eye protection are employed(HP Pavilion dv6-3125sa battery), because the bright white light produced by burning magnesium contains ultraviolet light that can permanently damage the retinas of the eyes.[32]

Magnesium is capable of reducing water to the highly flammable hydrogen gas:[33]

Mg (s) + 2 H2O (l) → Mg(OH)2 (s) + H2 (g)

As a result, water cannot be used to extinguish magnesium fires; the hydrogen gas produced will only intensify the fire. Dry sand is an effective smothering agent but is usable only on relatively level and flat surfaces(HP Pavilion dv6-3123sa battery).

Magnesium also reacts with carbon dioxide to form magnesium oxide and carbon:

2 Mg (s) + CO2 → 2 MgO (s) + C (s)

hence, carbon dioxide fire extinguishers cannot be used for extinguishing magnesium fires either.[34]

Burning magnesium is usually quenched by using a Class D dry chemical fire extinguisher, or by covering the fire with sand or magnesium foundry flux to remove its air source.nt growth in pH-neutral soils, the concentration in acid soils of toxic Al3+ cations increases and disturbs root growth and function. (HP Pavilion dv6-3122sa battery)

Most acid soils are saturated with aluminium rather than hydrogen ions. The acidity of the soil is therefore a result of hydrolysis of aluminium compounds.[89] This concept of "corrected lime potential"[90] to define the degree of base saturation in soils became the basis for procedures now used in soil testing laboratories to determine the "lime requirement"[91] of soils. (HP Pavilion dv6-3121sa battery)

Wheat's adaptation to allow aluminium tolerance is such that the aluminium induces a release of organic compounds that bind to the harmful aluminium cations. Sorghum is believed to have the same tolerance mechanism. The first gene for aluminium tolerance has been identified in wheat. It was shown that sorghum's aluminium tolerance is controlled by a single gene, as for wheat.[93] This is not the case in all plants(HP Pavilion dv6-3120sa battery).

Magnesium ( /mæɡˈniːziəm/ mag-nee-zee-əm) is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust [2] and ninth in the known universe as a whole.[3][4] Magnesium is the fourth most common element in the Earth as a whole (behind iron, oxygen and silicon) (HP Pavilion dv6-3119sa battery), making up 13% of the planet's mass and a large fraction of the planet's mantle. The relative abundance of magnesium is related to the fact that it is easily built up in supernova stars from a sequential addition of three helium nuclei to carbon (which in turn is made from three helium nuclei). Due to magnesium ion's high solubility in water, it is the third most abundant element dissolved in seawater. (HP Pavilion dv6-3118sa battery)

The free element (metal) is not found naturally on Earth, as it is highly reactive (though once produced, it is coated in a thin layer of oxide [see passivation], which partly masks this reactivity). The free metal burns with a characteristic brilliant white light, making it a useful ingredient in flares. The metal is now mainly obtained by electrolysis of magnesium salts obtained from brine. Commercially(HP Pavilion dv6-3117sa battery), the chief use for the metal is as an alloying agent to make aluminium-magnesium alloys, sometimes called "magnalium" or "magnelium". Since magnesium is less dense than aluminium, these alloys are prized for their relative lightness and strength.

In human biology, magnesium is the eleventh most abundant element by mass in the human body; its ions are essential to all living cells(HP Pavilion dv6-3116tx battery), where they play a major role in manipulating important biological polyphosphate compounds like ATP, DNA, and RNA. Hundreds of enzymes thus require magnesium ions to function. Magnesium compounds are used medicinally as common laxatives, antacids (e.g., milk of magnesia) (HP Pavilion dv6-3116sa battery), and in a number of situations where stabilization of abnormal nerve excitation and blood vessel spasm is required (e.g., to treat eclampsia). Magnesium ions are sour to the taste, and in low concentrations they help to impart a natural tartness to fresh mineral waters.

In vegetation magnesium is the metallic ion at the center of chlorophyll, and is thus a common additive to fertilizers(HP Pavilion dv6-3115tx battery).[6]