Magnesium (pronounced /mæɡˈniːziəm/, mag-NEE-zee-əm) is a chemical element A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons. Common examples of elements are iron, copper, silver, gold, hydrogen, carbon, with the symbol Mg, atomic number In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element. In an atom of neutral charge, the atomic number is also equal to the number of 12 and common oxidation number +2. It is an alkaline earth metal The alkaline earth metals are a series of elements comprising Group 2 (Group IIA) of the periodic table: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). This specific group in the periodic table owes its name to their oxides that simply give basic alkaline solutions. These elements melt at such high and the eighth most abundant element The abundance of a chemical element measures how relatively common the element is, or how much of the element there is by comparison to all other elements. Abundance may be variously measured by the mass-fraction , or mole-fraction (fraction of atoms, or sometimes fraction of molecules, in gases), or by volume fraction. Measurement by volume- in the Earth's crust In geology, a crust is the outermost solid shell of a rocky planet or moon, which is chemically distinct from the underlying mantle. The crusts of Earth, our Moon, Mercury, Venus, Mars, Io, and other planetary bodies have been generated largely by igneous processes, and these crusts are richer in incompatible elements than their respective mantles, where it constitutes about 2% by mass,^[2] and ninth in the known Universe The Universe is commonly defined as the totality of everything that exists, including all physical matter and energy, the planets, stars, galaxies, and the contents of intergalactic space, although this usage may differ with the context . The term Universe may be used in slightly different contextual senses, denoting such concepts as the cosmos, as a whole.^[3][4] This preponderance of magnesium is related to the fact that it is easily built up in supernova A supernova is a stellar explosion that is more energetic than a nova. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months. During this short interval a supernova can radiate as much energy as the Sun is expected to emit over its entire stars from a sequential addition of three helium nuclei to carbon (which in turn is made from three helium nuclei). Magnesium ion's high solubility Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a liquid solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on temperature and pressure. The extent of the solubility of a substance in a in water helps ensure that it is the third most abundant element dissolved in seawater Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5%. This means that every kilogram, or every litre, of seawater has approximately 35 grams of dissolved salts (mostly, but not entirely, the ions of sodium chloride: Na+, Cl−). The average density of seawater at the ocean surface is 1.025.^[5]

Magnesium is the 11th most abundant element by mass in the human body; its ions are essential to all living cells The cell is the functional basic unit of life. It was discovered by Robert Hooke and is the functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. Some organisms, such as most bacteria, are unicellular . Other organisms, such as humans,, where they play a major role in manipulating important biological polyphosphate compounds like ATP Adenosine-5'-triphosphate is a multifunctional nucleotide used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism. It is produced by photophosphorylation and cellular respiration and used by enzymes and structural, DNA Deoxyribonucleic acid ( /diːˌɒksɨˌraɪbɵ.nuːˈkleɪ.ɪk ˈæsɪd/ (help·info)) (DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of, and RNA Ribonucleic acid is a biologically important type of molecule that consists of a long chain of nucleotide units. Each nucleotide consists of a nitrogenous base, a ribose sugar, and a phosphate. RNA is very similar to DNA, but differs in a few important structural details: in the cell, RNA is usually single-stranded, while DNA is usually double-. Hundreds of enzymes Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at significant rates. Since enzymes are selective for their thus require magnesium ions to function. Magnesium is also the metallic ion at the center of chlorophyll Chlorophyll is a green pigment found in all plants, algae, and cyanobacteria. Its name is derived from the Greek χλωρός and φύλλον (phyllon "leaf"). Chlorophyll absorbs light most strongly in the blue portion of the electromagnetic spectrum, followed by the red portion. However, it is a poor absorber of green and near-green, and is thus a common additive to fertilizers Fertilizers are soil amendments applied to promote plant growth; the main nutrients present in fertilizer are nitrogen, phosphorus, and potassium and other nutrients ('micronutrients') are added in smaller amounts. Fertilizers are usually directly applied to soil, and also sprayed on leaves ('foliar feeding').^[6] Magnesium compounds are used medicinally as common laxatives Laxatives are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant, and saline laxatives are used to evacuate the colon for rectal and bowel examinations, and may be supplemented by enemas in that circumstance. Sufficiently high doses of laxatives, antacids (i.e., milk of magnesia Magnesium hydroxide is an inorganic compound with the chemical formula Mg2. As a suspension in water, it is often called milk of magnesia because of its milk-like appearance. The solid mineral form of magnesium hydroxide is known as brucite), and in a number of situations where stabilization of abnormal nerve A peripheral nerve, or simply nerve is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system. In the central nervous system, the analogous structures are known as tracts excitation and blood vessel spasm is required (i.e., to treat eclampsia Eclampsia , an acute and life-threatening complication of pregnancy, is characterized by the appearance of tonic-clonic seizures, usually in a patient who had developed preeclampsia. (Preeclampsia and eclampsia are collectively called Hypertensive disorder of pregnancy and toxemia of pregnancy.)). Magnesium ions are sour to the taste, and in low concentrations help to impart a natural tartness to fresh mineral waters Mineral water is water containing minerals or other dissolved substances that alter its taste or give it therapeutic value, generally obtained from a naturally occurring mineral spring or source. Dissolved substances in the water may include various salts and sulfur compounds. Mineral water can be sparkling , or still (without effervescence).

The free element (metal) is not found naturally on Earth, as it is highly reactive (though once produced, is coated in a thin layer of oxide (see passivation Passivation is the process of making a material "passive" in relation to another material prior to using the materials together. For example, prior to storing hydrogen peroxide in an aluminium container, the container can be passivated by rinsing it with a dilute solution of nitric acid and peroxide alternating with deionized water. The), 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 Brine is water saturated or nearly saturated with a salt . It is used to preserve vegetables, fish, and meat, in a process known as brining (now less popular than historically). Brine is also commonly used to age Halloumi and Feta cheeses. Brine is also used for pickling foodstuffs, as a means of preserving them (or increasing for taste). Almost. Commercially, the chief use for the metal is as an alloying An alloy is a partial or complete solid solution of one or more elements in a metallic matrix. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may be homogeneous in distribution depending on thermal history. Alloys usually have different properties from those of the agent to make aluminium Aluminium (UK: /ˌæljʉˈmɪniəm/ AL-yew-MIN-ee-əm) or aluminum (US: /əˈluːmɨnəm/ ( listen) ə-LOO-mi-nəm) 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 circumstances. Aluminium is the most abundant metal in the Earth's crust,-magnesium alloys, sometimes called "magnalium Magnalium refers to an alloy of aluminium with 5-50% magnesium. Trace amounts of other elements are added to improve hardness. It finds use in engineering and pyrotechnics" or "magnelium". Since magnesium is less dense than aluminium, these alloys are prized for their relative lightness and strength.

Origin and characteristics

Physical and chemical

Elemental magnesium is a fairly strong, silvery-white, light-weight metal (two thirds the density of aluminium). It tarnishes Tarnish is a thin layer that forms over copper, brass, silver, aluminum, and other semi-reactive metals as their outermost layer undergoes a chemical reaction. Tarnish is mainly caused by chemicals in the air, such as sulfur dioxide. It often appears as a usually dull, gray or black film or coat over metal. Tarnish is a surface phenomena, that is slightly when exposed to air, although unlike the alkali metals The alkali metals are a series of chemical elements forming Group 1 of the periodic table: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). (Hydrogen, although nominally also a member of Group 1, very rarely exhibits behavior comparable to the alkali metals). The alkali metals provide one of the best, storage in an oxygen-free environment is unnecessary because magnesium is protected by a thin layer of oxide that is fairly impermeable and hard to remove. Like its lower periodic table group In chemistry, a group is a vertical column in the periodic table of the chemical elements. There are 18 groups in the standard periodic table neighbor calcium Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth most abundant element by mass in the Earth's crust. Calcium is also the fifth most abundant dissolved ion in seawater by both molarity and mass, after sodium, chloride,, magnesium reacts with water at room temperature, though it reacts much more slowly than calcium. When it is submerged in water, hydrogen Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of 1.00794 u (1.007825 u for Hydrogen-1), hydrogen is the lightest and most abundant chemical element, constituting roughly 75 % of the Universe's elemental mass. Stars in the main sequence are mainly composed of hydrogen in its bubbles will almost unnoticeably begin to form on the surface of the metal, though if powdered it will react much more rapidly. The reaction will occur faster with higher temperatures (see precautions). Magnesium also reacts exothermically with most acids, such as hydrochloric acid Hydrochloric acid is the solution of hydrogen chloride (H (HCl). As with aluminium, zinc and many other metals, the reaction with hydrochloric acid produces the chloride of the metal and releases hydrogen gas.

Magnesium is a highly flammable Flammability is defined as how easily something will burn or ignite, causing fire or combustion. The degree of difficulty required to cause the combustion of a substance is quantified through fire testing. Internationally, a variety of test protocols exist to quantify flammability. The ratings achieved are used in building codes, insurance 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 Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere (forming magnesium nitride Magnesium nitride, Mg3N2, is an inorganic compound of magnesium and nitrogen. At room temperature and pressure it is a greenish yellow powder. It reacts with water to produce ammonia gas, as do many metal nitrides), carbon dioxide Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state. CO2 is a trace gas comprising 0.039% of the atmosphere (forming magnesium oxide An oxide is a chemical compound containing at least one oxygen atom as well as at least one other element. Most of the Earth's crust consists of oxides. Oxides result when elements are oxidized by oxygen in air. Combustion of hydrocarbons affords the two principal oxides of carbon, carbon monoxide and carbon dioxide. Even materials that are and carbon Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. There are three naturally occurring isotopes, with 12C and 13C being stable, while 14C is radioactive, decaying with a half-life of) and water (forming magnesium oxide and hydrogen). This property was used in incendiary weapons used in the firebombing Firebombing is a bombing technique designed to damage a target, generally an urban area, through the use of fire, caused by incendiary devices, rather than from the blast effect of large bombs of cities in World War II Albania · Australia · Austria · Azerbaijan · Belarus · Belgium · Brazil · Bulgaria · Burma · Cambodia · Canada · Ceylon (Sri Lanka) · Channel Islands · China · Czechoslovakia · Denmark · Dutch East Indies · Egypt · Estonia · Finland · France · Germany · Gibraltar · Greece · Greenland · Hong Kong · Hungary · Iceland ·, the only practical civil defense Civil defense, civil defence or civil protection is an effort to prepare non-combatants for military attack. It uses the principles of emergency operations: prevention, mitigation, preparation, response, or emergency evacuation, and recovery. Programmes of this sort were initially discussed at least as early as the 1920s but only became widespread being to smother a burning flare under dry sand to exclude the atmosphere. On burning in air, magnesium produces a brilliant white light. Thus magnesium powder (flash powder Flash powder is pyrotechnic composition, a mixture of oxidizer and metallic fuel which burns quickly and if confined will produce a loud report. It is widely used in theatrical pyrotechnics and fireworks , and was once used for flashes in photography) was used as a source of illumination in the early days of photography Photography is the process, activity and art of creating still or moving pictures by recording radiation on a radiation-sensitive medium, such as a photographic film, or an electronic sensor. Photography uses foremost radiation in the UV, visible and near-IR spectrum. For common purposes the term light is used in stead of radiation. Light. Later, magnesium ribbon was used in electrically ignited flash bulbs. Magnesium powder is used in the manufacture of fireworks Fireworks are a class of low explosive pyrotechnic devices used for aesthetic and entertainment purposes. The most common use of a firework is as part of a fireworks display. A fireworks event is a display of the effects produced by firework devices. Fireworks competitions are also regularly held at a number of places. Fireworks (devices) take and marine flares A flare, also sometimes called a fusee, is a type of pyrotechnic that produces a brilliant light or intense heat without an explosion. Flares are used for signaling, illumination, or defensive countermeasures in civilian and military applications. Flares may be ground pyrotechnics, projectile pyrotechnics, or parachute-suspended to provide maximum 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).^[8] Magnesium may be used as an ignition source for thermite Thermite is a pyrotechnic composition of a metal powder and a metal oxide, which produces an aluminothermic reaction known as a thermite reaction. Most varieties are not explosive, but can create short bursts of extremely high temperatures focused on a very small area for a short period of time, 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 Magnesium sulfate is a chemical compound containing magnesium, sulfur and oxygen, with the formula MgSO4. In its hydrated form, the pH is 6.0 (5.5 to 6.5). It is often encountered as the heptahydrate, MgSO4·7H2O, commonly called Epsom salt. Anhydrous magnesium sulfate is used as a drying agent. Since the anhydrous form is hygroscopic (readily (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 Magnesium hydroxide is an inorganic compound with the chemical formula Mg2. As a suspension in water, it is often called milk of magnesia because of its milk-like appearance. The solid mineral form of magnesium hydroxide is known as brucite. The undissolved particles give rise to its appearance and name. Milk of magnesia is a mild base In chemistry, a base is most commonly thought of as an aqueous substance that can accept hydrogen ions. Bases are also the oxides or hydroxides of metals. A soluble base is also often referred to as an alkali if hydroxide ions are involved. This refers to the Brønsted-Lowry theory of acids and bases. Alternative definitions of bases include commonly used as an antacid An antacid is any substance, generally a base or basic salt, which neutralizes stomach acidity, which has some laxative side effect.

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 times.

²⁶Mg has found application in isotopic geology, similar to that of aluminium. ²⁶Mg is a radiogenic daughter product of²⁶Al, 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 meteorites. 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 history.

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.

Creation

Stable forms of magnesium are produced in stars. It is made from fusing helium and neon, in the so-called alpha process. Creation requires temperatures above 600 megakelvins and masses greater than 3 solar masses.

Occurrence

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 precipitate.

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 metal:

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 company born from now-defunct Magcorp.^[9]

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).

History

The name 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 history.

Magnesium is the seventh most abundant element in the Earth's crust by mass and eighth by 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. 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, MgSO₄.

The metal itself was first produced in England by Sir Humphry Davy in 1808 using electrolysis of a mixture of magnesia and mercury oxide.^[10] Antoine Bussy prepared it in coherent form in 1831. Davy's first suggestion for a name was magnium, but the name magnesium is now used.

Applications

As metal

Magnesium is the third most commonly used structural metal, following iron and aluminium. The main applications of magnesium are, in order: component of aluminium alloys, in die-casting (alloyed with zinc),^[11] to remove sulfur in the production of iron and steel, the production of titanium in the Kroll process.^[12]

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 "mag wheels", although the term is often more broadly misapplied to include aluminum wheels. In 1957, a 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 alloy; 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 1971, 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 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 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.^[13] New alloy development and lower costs, which are becoming competitive to aluminium, will further the number of automotive applications.^{[citation needed]}

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 components.

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 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.^{[citation needed]} The development and testing of new magnesium alloys continues, 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.

Niche uses of the metal

Magnesium, being cheaply 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) ^[14], and the autoignition temperature of magnesium ribbon is approximately 630 °C (903 K; 1,166 °F) in air.^[15] 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 sparklers. 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 iron.
• 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 roofing.^[11]

As magnesium compounds

Magnesium ion is necessary for all life (see magnesium in biology), so magnesium salts are an additive for foods, fertilizers (Mg is a component of chlorophyll), and culture media.

Magnesium compounds, primarily magnesium oxide (MgO), 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 cans.

Niche and illustrative uses of magnesium compounds

• Magnesium hydroxide is used in milk of magnesia, its chloride, oxide, gluconate, malate, orotate and citrate used as oral magnesium supplements, and its sulfate (Epsom salts) 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 (RLS).^{[citation needed]}
• Magnesium borate, magnesium salicylate and magnesium sulfate are used as antiseptics.
• 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 (MgCO₃) powder is also used by athletes, such as gymnasts and weightlifters, to improve the grip on objects – the apparatus or lifting bar.
• Magnesium stearate is a slightly flammable white powder with lubricating properties. In pharmaceutical technology it is used in the manufacturing 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).
• 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 textiles.

Biological role

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, 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, and can be corrected by applying Epsom salts (which is rapidly leached), or else crushed dolomitic limestone to the soil.

Magnesium is a vital component of a healthy human diet. Human magnesium deficiency (including conditions that show few overt symptoms) is relatively common, with only 32% of the United States meeting the RDA-DRI;^[16] 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.^[17]

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 - 2.4mEq/L. Serum magnesium levels may appear normal even in cases of underlying intracellular deficiency, 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. Low and high protein intake inhibit magnesium absorption, 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.^[18] Magnesium status may be assessed roughly through serum and erythrocyte Mg concentrations and urinary and fecal excretion, but intravenous magnesium loading tests are likely the most accurate and practical in most people.^[19] In these tests, magnesium is injected intravenously; a retention of 20% or more indicates deficiency.^[20] Other nutrient deficiencies are identified through biomarkers, but none are established for magnesium.^[21]

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, which is rich in magnesium. 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.^[18]

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.^[22][23] Magnesium citrate has been reported as more bioavailable than oxide or amino-acid chelate (glycinate) forms.^[24]

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.^[17] With supplements, overdose is possible, however, particularly in people with poor renal function; occasionally, with use of high cathartic doses of magnesium salts, severe hypermagnesemia has been reported to occur even without renal dysfunction.^[25] Alcoholism can produce a magnesium deficiency, which is easily reversed by oral or parenteral administration, depending on the degree of deficiency.^[26]

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. 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.^[27]

Magnesium in treatment-resistant depression

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. 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.^{[28][unreliable source?]}

Precautions

Magnesium metal and its alloys are explosive hazards; they are highly flammable in their pure form when molten or in powder or in ribbon form. Burning or molten magnesium metal reacts violently with water. When working with powdered magnesium, safety glasses with welding eye protection are employed, because the bright white light produced by burning magnesium contains ultraviolet light that can permanently damage the retinas of the eyes.^[29]

Magnesium is capable of reducing water to the highly flammable hydrogen gas:^[30]

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.

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.^[31]

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.

References

1. ^ Bernath, P. F., Black, J. H., & Brault, J. W. (1985). "The spectrum of magnesium hydride". Astrophysical Journal 298: 375. http://bernath.uwaterloo.ca/media/24.pdf.
2. ^ ^{a b} (PDF) Abundance and form of the most abundant elements in Earth’s continental crust. http://www.gly.uga.edu/railsback/Fundamentals/ElementalAbundanceTableP.pdf. Retrieved 2008-02-15.
3. ^ Housecroft, C. E.; Sharpe, A. G. (2008). Inorganic Chemistry (3rd ed.). Prentice Hall. pp. 305–306. ISBN 978-0131755536.
4. ^ Ash, Russell (2005). The Top 10 of Everything 2006: The Ultimate Book of Lists. Dk Pub. ISBN 0756613213. http://plymouthlibrary.org/faqelements.htm. .
5. ^ Anthoni, J Floor (2006). "The chemical composition of seawater". http://www.seafriends.org.nz/oceano/seawater.htm#composition.
6. ^ "Magnesium in health". http://www.mg12.info.
7. ^ Dreizin, Edward L.; Berman, Charles H. and Vicenzi, Edward P. (2000). "Condensed-phase modifications in magnesium particle combustion in air". Scripta Materialia 122: 30. doi:10.1016/S0010-2180(00)00101-2.
8. ^ DOE Handbook - Primer on Spontaneous Heating and Pyrophoricity. U.S. Department of Energy. December 1994. p. 20. DOE-HDBK-1081-94. http://www.hss.doe.gov/nuclearsafety/ns/techstds/standard/hdbk1081/hbk1081c.html.
9. ^ Vardi, Nathan (February 22, 2007). "Man With Many Enemies". Forbes.com. http://www.forbes.com/forbes/2002/0722/044_print.html. Retrieved 2006-06-26.
10. ^ Davy, H. (1808) "Electro-chemical researches on the decomposition of the earths; with observations on the metals obtained from the alkaline earths, and on the amalgam procured from ammonia," Philosophical Transactions of the Royal Society of London, vol. 98, pages 333-370.
11. ^ ^{a b} Baker, Hugh D. R.; Avedesian, Michael (1999). Magnesium and magnesium alloys. Materials Park, OH: Materials Information Society. p. 4. ISBN 0-87170-657-1.
12. ^ Ketil Amundsen, Terje Kr. Aune, Per Bakke, Hans R. Eklund, Johanna Ö. Haagensen, Carlos Nicolas, Christian Rosenkilde, Sia Van den Bremt, Oddmund Wallevik “Magnesium” in Ullmann’s Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH. doi: 10.1002/14356007.a15_559
13. ^ Luo, Alan A. and Powell, Bob R. (2001) (PDF). Tensile and Compressive Creep of Magnesium-Aluminum-Calcium Based Alloys. Materials & Processes Laboratory, General Motors Research & Development Center. http://doc.tms.org/ezmerchant/prodtms.nsf/productlookupitemid/01-481x-137/%24FILE/01-481X-137F.pdf. Retrieved 2007-08-21.
14. ^ Dreizin, Edward L.; Berman, Charles H. and Vicenzi, Edward P. (2000). "Condensed-phase modifications in magnesium particle combustion in air". Scripta Materialia 122: 30. doi:10.1016/S0010-2180(00)00101-2.
15. ^ Ravi Kumar, N. V. et al. (2003). "Effect of alloying elements on the ignition resistance of magnesium alloys". Scripta Materialia 49: 225. doi:10.1016/S1359-6462(03)00263-X.
16. ^ "Lack Energy? Maybe It's Your Magnesium Level". United States Department of Agriculture. http://www.ars.usda.gov/is/AR/archive/may04/energy0504.htm?pf=1. Retrieved 2008-09-18. Last paragraph
17. ^ ^{a b} University of Maryland Medical Center. Magnesium
18. ^ ^{a b} Wester PO (May 1987). "Magnesium". Am. J. Clin. Nutr. 45 (5 Suppl): 1305–12. PMID 3578120. http://www.ajcn.org/cgi/pmidlookup?view=long&pmid=3578120.
19. ^ Arnaud MJ (2008). "Update on the assessment of magnesium status". Br. J. Nutr. 99 Suppl 3: S24–36. doi:10.1017/S000711450800682X. PMID 18598586.
20. ^ Rob PM, Dick K, Bley N, et al. (October 1999). "Can one really measure magnesium deficiency using the short-term magnesium loading test?". J. Intern. Med. 246 (4): 373–8. doi:10.1046/j.1365-2796.1999.00580.x. PMID 10583708. http://www.blackwell-synergy.com/openurl?genre=article&sid=nlm:pubmed&issn=0954-6820&date=1999&volume=246&issue=4&spage=373.
21. ^ Franz KB (2004). "A functional biological marker is needed for diagnosing magnesium deficiency". J Am Coll Nutr 23 (6): 738S–41S. PMID 15637224.
22. ^ Firoz M, Graber M (December 2001). "Bioavailability of US commercial magnesium preparations". Magnes Res 14 (4): 257–62. PMID 11794633.
23. ^ Lindberg JS, Zobitz MM, Poindexter JR, Pak CY (1990). "Magnesium bioavailability from magnesium citrate and magnesium oxide". J Am Coll Nutr 9 (1): 48–55. PMID 2407766.
24. ^ Walker AF, Marakis G, Christie S, Byng M (2003). "Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study" (free text on-line). Magnes Res 16 (3): 183–91. PMID 14596323. http://www.john-libbey-eurotext.fr/medline.md?issn=0953-1424&vol=16&iss=3&page=183.
25. ^ Kontani M, Hara A, Ohta S, Ikeda T (2005). "Hypermagnesemia induced by massive cathartic ingestion in an elderly woman without pre-existing renal dysfunction". Intern. Med. 44 (5): 448–52. doi:10.2169/internalmedicine.44.448. PMID 15942092.
26. ^ Giannini, A. J. (1997). Drugs of Abuse (Second ed.). Los Angeles: Physicians Management Information Co..
27. ^ R. Baselt, Disposition of Toxic Drugs and Chemicals in Man, 8th edition, Biomedical Publications, Foster City, CA, 2008, pp. 875-877.
28. ^ Eby GA, Eby KL.Magnesium for treatment-resistant depression: a review and hypothesis. Med Hypotheses. 2010 Apr;74(4):649-60.
29. ^ "Science Safety: Chapter 8". Government of Manitoba. http://www.edu.gov.mb.ca/k12/docs/support/scisafe/chapter8.html. Retrieved 2007-08-21.
30. ^ "Chemistry : Periodic Table : magnesium : chemical reaction data". webelements.com. http://www.webelements.com/webelements/elements/text/Mg/chem.html. Retrieved 2006-06-26.
31. ^ "Demo Lab: Reaction Of Magnesium Metal With Carbon Dioxide". http://www.ilpi.com/genchem/demo/co2mg/. Retrieved 2006-06-26.

External links

• The Periodic Table of Videos video of Magnesium at YouTube
• WebElements.com – Magnesium
• Online Resource for industry professionals - Magnesium.com
• The Magnesium Website – Includes full text papers and textbook chapters by leading magnesium authorities Mildred Seelig, Jean Durlach, Burton M. Altura and Bella T. Altura. Links to over 300 articles discussing magnesium and magnesium deficiency.
• Magnesium in Health - Mg12.info
• Chemistry in its element podcast (MP3) from the Royal Society of Chemistry's Chemistry World: Magnesium

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