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{{Infobox magnesium}}
{{Details|Magnesium chloride|'''Magnesium chloride'''}}
{{Details|Magnesium citrate|'''Magnesium citrate'''}}
{{Details|Magnesium oxide|'''Magnesium oxide'''}}
'''Magnesium''' ({{pronEng|mægˈniːziəm}}) is a [[chemical element]] with the symbol '''Mg''', the [[atomic number]] 12, and an [[atomic mass]] of 24.31. Magnesium is the ninth most abundant element in the universe by mass. It constitutes about 2% of the [[Earth]]'s [[Crust (geology)|crust]] by mass,<ref name="Abundance"/> and it is the third most abundant element dissolved in [[seawater]]. Magnesium ions are essential to all living cells, and is the 11th most abundant element by mass in the human body. The free element (metal) is not found in nature. Once produced from magnesium salts, this [[alkaline earth metal]] is used as an [[alloy]]ing agent to make [[aluminium]]-magnesium alloys, sometimes called "[[magnalium]]" or "magnelium".
== Notable characteristics ==
Elemental magnesium is a fairly strong, silvery-white, light-weight metal (two thirds the density of [[aluminium]]). It [[tarnish]]es slightly when exposed to air, although unlike the alkaline metals, storage in an oxygen free environment is unnecessary because magnesium is protected by a thin layer of oxide which is fairly impermeable and hard to remove. Like its lower [[periodic table group]] neighbor [[calcium]], magnesium reacts with water at room temperature, though it reacts much more slowly than calcium.  When it is 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 rapidly. Magnesium also reacts with [[hydrochloric acid]] (HCl) and produces heat and hydrogen when added to it. The magnesium will begin to bubble and become hot – too hot to touch comfortably. The reaction will occur faster with higher temperatures (see precautions).
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 both [[nitrogen]] (forming magnesium nitride), and [[carbon dioxide]] (forming magnesium [[oxide]] and [[carbon]]). When it burns in air, Magnesium produces a brilliant white light. Thus magnesium powder ([[flash powder]]) was used as a source of illumination in the early days of [[photography]]. Later, magnesium ribbon was used in electrically ignited flash bulbs. Magnesium powder is used in the manufacture of [[fireworks]] and marine [[flare (pyrotechnic)|flare]]s where a brilliant white light is required.
Magnesium compounds are typically white crystals. Most are soluble in water, providing the sour-tasting magnesium ion Mg<sup>2+</sup>. Small amounts of dissolved magnesium ion contributes to the tartness and taste of natural waters. Magnesium ion in large amounts is an ionic laxative, and magnesium sulfate ([[Epsom salts]]) is sometimes used for this purpose. So-called "[[Milk of Magnesia|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 and is commonly used as an antacid.
== Applications ==
===As the metal===
Magnesium is the third most commonly used structural metal, following [[steel]] and [[aluminium]].
Magnesium compounds, primarily [[magnesium oxide]], are used mainly as [[refractory]] material in [[furnace]] linings for producing [[iron]], [[steel]], nonferrous metals, [[glass]] and [[cement]].  Magnesium oxide and other compounds also are used in agricultural, chemical and construction industries. 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 can]]s.
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 components.  Specialty, high-grade car wheels of magnesium alloy are called "[[Magnesium alloy wheel|mag wheels]]".  In 1957 a [[Corvette]] SS, designed for racing, was constructed with magnesium body panels.  Porsche's all-out quest to decrease the weight of their racecars led to the use of magnesium frames in the famous 917/053 which won Le Mans in 1971, and still holds the absolute distance record.  The 917/30 Can-Am car also featured a magnesium spaceframe, helping it to make the most of its prodigious 1100-1500hp.  [[Volkswagen]] has used magnesium in its engine components for many years.  For a long time, [[Porsche]] used magnesium alloy for its [[engine block]]s due to the weight advantage. 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 magnesium.  Both of these alloys are recent developments in high temperature low [[Creep (deformation)|creep]] magnesium alloys.  The general strategy for such alloys is to form [[intermetallic]] precipitates at the [[crystallite|grain boundaries]], for example by adding [[mischmetal]] or [[calcium]].<ref>{{cite paper |title=Tensile and Compressive Creep of Magnesium-Aluminum-Calcium Based Alloys |format=PDF |date=2001 |author=Alan A. Luo and Bob R. Powell |publisher=Materials & Processes Laboratory, General Motors Research & Development Center |accessdate=2007-08-21 |url=http://doc.tms.org/ezmerchant/prodtms.nsf/productlookupitemid/01-481x-137/%24FILE/01-481X-137F.pdf}}</ref>  New alloy development and lower costs, which are becoming competitive to aluminium, will further the number of automotive applications.
[[Image:Magnesium-products.jpg|thumb|left|Products made of magnesium: firestarter and shavings, sharpener, magnesium ribbon]]
The second application field of magnesium is electronic devices. Due to low weight, good mechanical and electrical properties, magnesium is widely used for manufacturing of mobile phones, laptop computers, cameras, and other electronic components. Magnesium is even used to make some higher end [[yo-yo]]s, such as the [[Duncan Freehand Mg]].
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 which is still used today. Due to perceived hazards with magnesium parts in the event of fire, 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. The development and testing of new magnesium alloys notably Elektron 21 which has successfully undergone extensive aerospace testing for suitability in both engine, internal and airframe components. European Community runs three R&D magnesium projects in Aerospace priority of Six Framework Program.
[[Image:Magnesium Sparks.jpg|thumb|Magnesium firestarter (in left hand), used with a [[pocket knife]] and flint to create sparks which ignite the shavings]]
*Incendiary use: Magnesium is flammable, burning at a temperature of approximately 2500 K (2200 °C, 4000 °F), and the [[autoignition temperature]] of magnesium is approximately 744 K (473 °C, 883 °F) in air. The extremely high temperature at which magnesium burns makes it a handy tool for starting emergency fires during outdoor recreation. Other related uses include flashlight [[photography]], flares, [[pyrotechnics]], fireworks sparklers, and incendiary bombs.
Other uses include:
* Removal of [[sulfur]] from iron and steel.
*Production of [[titanium]]
* [[photoengraving|Photoengraved]] plates in the printing industry.
* Combined in alloys, this metal is essential for [[fixed-wing aircraft|airplane]] and [[missile]] construction.
* When used as an alloying agent, this metal improves the mechanical, [[fabrication]] and [[welding]] characteristics of aluminium.
* Additive agent for conventional propellants and used in producing nodular graphite in cast iron.
* Reducing agent for the production of pure [[uranium]] and other metals from their [[salt]]s.
* Magnesium turnings or ribbon are used to prepare [[Grignard reagent]]s, which are useful in [[organic synthesis]]
* Easily reacting with water, it can serve as a [[desiccant]]
===In magnesium compounds===
* The magnesium ion is necessary for all life (see [[magnesium in biological systems]]), so magnesium salts are an additive for foods, fertilizers (Mg is a component of chlorophyll), and culture media.
* [[Magnesium hydroxide]] is used in [[milk of magnesia]], its [[magnesium chloride|chloride]], [[magnesium oxide|oxide]], [[magnesium gluconate|gluconate]] and [[magnesium citrate|citrate]] used as oral magnesium supplements, and its [[magnesium sulfate|sulfate]] ([[Epsom salt]]s) for various purposes in medicine, and elsewhere (see the article for more). Oral magnesium supplements have been claimed to be therapeutic for some individuals who suffer from [[Restless leg syndrome|Restless Leg Syndrome (RLS)]].
* Magnesium borate, magnesium salicylate and magnesium sulfate are used as [[antiseptic]]s.
* [[Magnesium bromide]] is used as a mild [[sedative]] (this action is due to the [[bromide]], not the magnesium).
* Dead-burned magnesite is used for refractory purposes such as brick and liners in furnaces and converters.
* [[Magnesium carbonate]] (Mg[[carbonate|CO<sub>3</sub>]]) powder is also used by athletes, such as [[gymnastics|gymnasts]] and [[weightlifting|weightlifters]], to improve the grip on objects &ndash; the apparatus or lifting bar.
* [[Magnesium stearate]] is a slightly [[fire|flammable]] white [[powder]] with [[lubricant|lubricative]] properties. In [[pharmacology|pharmaceutical]] technology it is used in the manufacturing of [[tablet]]s, 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).
* Magnesium sulfite is used in the manufacture of [[paper]] ([[sulfite process]]).
* Magnesium phosphate is used to fireproof wood for construction.
* Magnesium hexafluorosilicate is used in mothproofing of [[textile]]s.
== History ==
The name originates from the [[Ancient Greek|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 history.
Magnesium is the seventh most abundant element in the earth's crust by mass and eighth by molarity.<ref name="Abundance">{{cite paper |title=Abundance and form of the most abundant elements in Earth’s continental crust |format=PDF |accessdate=2008-02-15 |url=http://www.gly.uga.edu/railsback/Fundamentals/ElementalAbundanceTableP.pdf}}</ref> It is found in large deposits of [[magnesite]], [[dolomite]], and other [[mineral]]s, 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.  They refused to drink because of the water's bitter taste. However the farmer noticed that the water seemed to heal scratches and rashes. The fame of [[Epsom salts]] spread. Eventually they were recognized to be hydrated magnesium sulfate, MgSO<sub>4</sub>.
In England, Sir [[Humphry Davy]] electrolytically isolated pure magnesium metal in 1808 from a mix of magnesia and [[mercury (element)|Hg]][[oxygen|O]], and [[A. A. B. Bussy]] prepared it in  coherent form in 1831. Davy's first suggestion for a name was magnium, but the name magnesium is now used.
== Sources ==
Although magnesium is found in over 60 [[mineral]]s, only [[dolomite]], [[magnesite]], [[brucite]], [[carnallite]], [[talc]], and [[olivine]] are of commercial importance.
In the [[United States]] this metal is principally obtained by [[electrolysis]] of fused [[magnesium chloride]] from [[brine]]s, wells, and [[sea water]]:
:[[cathode]]: Mg<sup>2+</sup> + 2 [[electron|e]]<sup>-</sup> → Mg
:[[anode]]: 2 [[chlorine|Cl]]<sup>-</sup> → Cl<sub>2 ([[gas]])</sub> + 2 e<sup>-</sup>
[[Image:Magnesium crystals.jpg|thumb|Vapor-deposited magnesium crystals from the [[Pidgeon process]]]]
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 company born from now-defunct [[Magcorp]].<ref>{{cite web| url=http://www.forbes.com/forbes/2002/0722/044_print.html| publisher=Forbes.com| title=Man With Many Enemies| first=Nathan| last= Vardi |date=[[February 22]] [[2007]] | accessdate=2006-06-26}}</ref> 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 [[electrolyte|electrolytic]] process, China is almost completely reliant on a different method of obtaining the metal from its ores, the [[Silicothermic reaction|silicothermic]] [[Pidgeon process]] (the reduction of the oxide at high temperatures with silicon).
===Magnesium from sea water===
The Mg<sup>2+</sup> 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 carbonate]] is added to sea water to form [[magnesium carbonate]] precipitate.
MgCl<sub>2</sub> + CaCO<sub>3</sub> → MgCO<sub>3</sub> + CaCl<sub>2</sub>
[[Magnesium carbonate]] is insoluble in water so it can be filtered out, and reacted with [[hydrochloric acid]] to obtain concentrated [[magnesium chloride]]. 
MgCO<sub>3</sub> + 2HCl → MgCl<sub>2</sub> + CO<sub>2</sub> + H<sub>2</sub>O
From [[magnesium chloride]], electrolysis produces magnesium.
{{seealso|Category:Magnesium minerals}}
== Biology ==
{{main|Magnesium in biology}}
Magnesium ions are essential to the basic [[nucleic acid]] chemistry of life, and thus are essential to all cells of all known living organisms. [[Plants]] have an additional use for magnesium in that [[chlorophyll]]s are magnesium-centered [[porphyrin]]s. Many [[enzyme]]s require the presence of magnesium ions for their catalytic action, especially enzymes utilizing [[Adenosine triphosphate|ATP]], or those which use other nucleotides to synthesize [[DNA]] and [[RNA]]. [[Magnesium deficiency]] in plants causes late-season yellowing between leaf veins, especially in older leaves, and can be corrected by applying epsom salts (which is rapidly [[leaching|leached]]), or else crushed [[dolomite|dolomitic]] [[limestone]] to the soil.
[[Image:FoodSourcesOfMagnesium.jpg|thumb|right|Food sources of magnesium]]
Magnesium is a vital component of a healthy human diet and deficiency has been implicated in a number of human diseases. Magnesium is readily available in many common foods but studies indicate that many Americans are magnesium deficient. Excess magnesium in the blood is freely filtered at the kidneys, and for this reason it is very difficult to overdose on magnesium from dietary sources alone.<ref>[http://www.umm.edu/altmed/articles/magnesium-000313.htm Magnesium<!-- Bot generated title -->]</ref> However, there are a number of magnesium supplements available which make overdose possible, particularly in people with poor renal function, but severe [[hypermagnesemia]] can also occur without renal dysfunction.<ref>{{cite journal |author=Kontani M, Hara A, Ohta S, Ikeda T |title=Hypermagnesemia induced by massive cathartic ingestion in an elderly woman without pre-existing renal dysfunction |journal=Intern. Med. |volume=44 |issue=5 |pages=448–52 |year=2005 |pmid=15942092 |doi= | doi = 10.2169/internalmedicine.44.448 <!--Retrieved from CrossRef by DOI bot-->}}</ref>
== Isotopes ==
Magnesium has three stable [[isotope]]s: <sup>24</sup>Mg, <sup>25</sup>Mg, <sup>26</sup>Mg. All are present in significant amounts (see table of isotopes above). About 79% of Mg is <sup>24</sup>Mg. The isotope <sup>28</sup>Mg 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 times.
<sup>26</sup>Mg has found application in [[isotope|isotopic]] [[geology]], similar to that of [[aluminium]]. <sup>26</sup>Mg is a [[radiogenic]] daughter product of <sup>26</sup>Al, which has a [[half-life]] of 717,000 years. Large enrichments of stable <sup>26</sup>Mg have been observed in the [[Ca-Al-rich inclusions]] of some [[carbonaceous chondrite]] [[meteorite]]s. The anomalous abundance of <sup>26</sup>Mg is attributed to the decay of its parent <sup>26</sup>Al in the inclusions. Therefore, the meteorite must have formed in the [[solar nebula]] before the <sup>26</sup>Al had decayed. Hence, these fragments are among the oldest objects in the [[solar system]] and have preserved information about its early history.
It is conventional to plot <sup>26</sup>Mg/<sup>24</sup>Mg against an Al/Mg ratio. In an [[isochron dating]] plot, the Al/Mg ratio plotted is<sup>27</sup>Al/<sup>24</sup>Mg. The slope of the isochron has no age significance, but indicates the initial <sup>26</sup>Al/<sup>27</sup>Al ratio in the sample at the time when the systems were separated from a common reservoir.
== Precautions ==
Magnesium metal and alloys are highly flammable in their pure form when molten, as a powder, or in ribbon form. Burning or molten magnesium metal reacts violently with water. Magnesium powder is an explosive hazard. One should wear safety glasses while working with magnesium, and if burning it, these should include a heavy U.V. filter, similar to welding eye protection. The bright white light (including [[ultraviolet]]) produced by burning magnesium can permanently damage the retinas of the eyes, similar to welding arc burns.<ref>{{cite web |url=http://www.edu.gov.mb.ca/k12/docs/support/scisafe/chapter8.html |title=Science Safety: Chapter 8 |publisher=Government of Manitoba |accessdate=2007-08-21}}</ref>
Water should not be used to extinguish magnesium fires, because it can produce hydrogen which will feed the fire, according to the reaction:<ref>{{cite web| url=http://www.webelements.com/webelements/elements/text/Mg/chem.html| title=Chemistry : Periodic Table : magnesium : chemical reaction data| accessdate=2006-06-26| publisher=webelements.com}}</ref>
:Mg <sub>(s)</sub> + 2 H<sub>2</sub>O <sub>(g)</sub> → Mg(OH)<sub>2</sub> <sub>(s)</sub> + H<sub>2</sub> <sub>(g)</sub>
:or in words:
:Magnesium <sub>(solid)</sub> + steam → Magnesium hydroxide <sub>(solid)</sub> + Hydrogen <sub>(gas)</sub>
Carbon dioxide [[fire extinguisher]]s should not be used either, because magnesium can burn in carbon dioxide (forming [[magnesium oxide]], MgO, and [[carbon]]).<ref>{{cite web| url=http://www.ilpi.com/genchem/demo/co2mg/| title=Demo Lab: Reaction Of Magnesium Metal With Carbon Dioxide| accessdate=2006-06-26}}</ref> A [[Class D Fire Extinguisher|Class D]] dry chemical fire extinguisher should be used if available, or else the fire should be covered with [[sand]] or magnesium foundry flux. An easy way to put out small metal fires is to place a polyethylene bag filled with dry sand on top of the fire. The heat of the fire will melt the bag and the sand will flow out onto the fire.
== See also ==
* [[:Category:Magnesium minerals|Magnesium minerals]]
* [[:Category:Magnesium compounds|Magnesium compounds]]
== References ==
{{Compact periodic table}}
[[Category:Chemical elements]]
[[Category:Alkaline earth metals]]
[[Category:Dietary minerals]]
[[Category:Food additives]]
[[Category:Pyrotechnic fuels]]
[[qu:Qunta q'illay]]
{{WikiDoc Sources}}

Latest revision as of 23:31, 15 April 2015