Sodium is a chemical element with the symbol Na (from Latin: natrium) and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. The free metal does not occur in nature, but instead must be prepared from its compoundsSony VAIO VPCF135Z1E/B battery; it was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide. Sodium is the sixth most abundant element in the Earth's crust, and exists in numerous minerals such as feldspars, sodalite and rock salt. Many salts of sodium are highly water-soluble, and their sodium has been leached by the action of water so that chloride and sodium are the most common dissolved elements by weight in the Earth's bodies of oceanic waterSony VAIO VPCF137HG/BI battery.
Many sodium compounds are useful, such as sodium hydroxide (lye) for soapmaking, and sodium chloride for use as a deicing agent and a nutrient. Sodium is an essential element for all animals and some plants. In animals, sodium ions are used against potassium ions to build up charges on cell membranes, allowing transmission of nerve impulses when the charge is dissipatedSony VAIO VPCF136FG/BI battery. The consequent need of animals for sodium causes it to classified as a dietary inorganic macro-mineral.
Physical
Emission spectrum for sodium, showing the D line.
A positive flame test for sodium has a bright yellow color.
Sodium at standard temperature and pressure is a soft metal that can be readily cut with a knife and is a good conductor of electricity. Freshly exposed, sodium has a bright, silvery luster that rapidly tarnishes, forming a white coating of sodium hydroxide and sodium carbonate. These properties change at elevated pressures: at 1.5 Mbar, the color changes to blackSony VAIO VPCF135FG/B battery, then to red transparent at 1.9 Mbar, and finally clear transparent at 3 Mbar. All of these allotropes are insulators and electrides.[2]
When sodium or its compounds are introduced into a flame, they turn it yellow,[3] because the excited 3s electrons of sodium emit a photon when they fall from 3p to 3s; the wavelength of this photon corresponds to the D line at 589.3 nm. Spin-orbit interactions involving the electron in the 3p orbital split the D line into two; hyperfine structures involving both orbitals cause many more linesSony VAIO VPCF127HG/BI battery.[4]
[edit]Chemical
Sodium is generally less reactive than potassium and more reactive than lithium.[5] Like all the alkali metals, it reacts exothermically with water, to the point that sufficiently large pieces melt to a sphere and may explode; this reaction produces caustic sodium hydroxide and flammable hydrogen gasSony VAIO VPCF11Z1E battery. When burned in dry air, it mainly forms sodium peroxide as well as some sodium oxide. In moist air, sodium hydroxide results.[6] Sodium metal is highly reducing, with the reduction of sodium ions requiring −2.71 volts[7] but potassium and lithium have even more negative potentials.[8] Hence, the extraction of sodium metal from its compounds (such as with sodium chloride) uses a significant amount of energySony VAIO VPCF11S1E battery.[6]
[edit]Isotopes
Main article: Isotopes of sodium
20 isotopes of sodium are known, but only 23Na is stable. Two radioactive, cosmogenic isotopes are the byproduct of cosmic ray spallation: 22Na with a half-life of 2.6 years and 24Na with a half-life of 15 hours; all other isotopes have a half-life of less than one minute.[9] Two nuclear isomers have been discovered, the longer-lived one being 24mNa with a half-life of around 20.2 microsecondsSony VAIO VPCF11M1E/H battery. Acute neutron radiation, such as from a nuclear criticality accident, converts some of the stable 23Na in human blood to 24Na; by measuring the concentration of 24Na in relation to 23Na, the neutron radiation dosage of the victim can be calculated.[10]
[edit]Occurrence
23Na is created in the carbon-burning process by fusing two carbon atoms together; this requires temperatures above 600 megakelvins and a star with at least three solar masses.[11] The Earth's crust has 2.6% sodium by weight, making it the sixth most abundant element thereSony VAIO VPCF11M1E battery.[12] Because of its high reactivity, it is never found as a pure element. It is found in many different minerals, some very soluble, such as halite and natron, others much less soluble such as amphibole, and zeolite. The insolubility of certain sodium minerals such as cryolite and feldspar arises from their polymeric anions, which in the case of feldspar is a polysilicateSony VAIO VPCF11JFX/B battery. In the interstellar medium, sodium is identified by the D line; though it has a high vaporization temperature, its abundance allowed it to be detected by Mariner 10 in Mercury's atmosphere.[13]
[edit]Compounds
See also Category: Sodium compounds
Structure of sodium chloride, showing octahedral coordination around Na+ and Cl- centres. This framework disintegrates upon dissolution in water and reassembles upon evaporation.
Sodium compounds are of immense commercial importance, being particularly central to industries producing glass, paper, soap, and textilesSony VAIO VPCF119FJ battery.[14] The sodium compounds that are the most important are common salt (NaCl), soda ash (Na2CO3), baking soda (NaHCO3), caustic soda (NaOH), sodium nitrate (NaNO3), di- and tri-sodium phosphates, sodium thiosulfate (Na2S2O3·5H2O), and borax (Na2B4O7·10H2O).[15] In its compounds, sodium is usually ionically bonded to water and anions, and is viewed as a hard Lewis acidSony VAIO VPCF119FC/BI battery.[16]
[edit]Aqueous solutions
Sodium tends to form water-soluble compounds, such as halides, sulfates, nitrates, carboxylates and carbonates. The main aqueous species are the aquo complexes [Na(H2O)n]+, where n = 4–6.[17] The high affinity of sodium for oxygen-based ligands is the basis of crown ethers; macrolide antibiotics, which interfere with Na+ transport in the infecting organism, are functionally related and more complexSony VAIO VPCF119FC battery.
Direct precipitation of sodium salts from aqueous solutions is rare, because sodium salts typically have a high affinity for water; an exception is sodium bismuthate (NaBiO3).[18] Because of this, sodium salts are usually isolated as solids by evaporation or by precipitation with an organic solvent, such as ethanol; for example, only 0.35 g/L of sodium chloride will dissolve in ethanol.[19] Crown ethers, like 15-crown-5, may be used as a phase-transfer catalystSony VAIO VPCF117HG/BI battery.[20]
Sodium content in bulk may be determined by treating with a large excess of uranyl zinc acetate; the hexahydrate (UO2)2ZnNa(CH3CO2)·6H2O precipitates, which can be weighed. Caesium and rubidium do not interfere with this reaction, but potassium and lithium do.[21] Lower concentrations of sodium may be determined by atomic absorption spectrophotometry[22] or by potentiometry using ion-selective electrodesSony VAIO VPCF116FG/BI battery.[23]
[edit]Electrides and sodides
Like the other alkali metals, sodium dissolves in ammonia and some amines to give deeply coloured solutions; evaporation of these solutions leaves a shiny film of metallic sodium. The solutions contain the coordination complex (Na(NH3)6)+, whose positive charge is counterbalanced by electrons as anions; cryptands permit the isolation of these complexes as crystalline solidsSony VAIO VPCF115FG/B battery. Cryptands, like crown ethers and other ionophores, have a high affinity for the sodium ion; derivatives of the alkalide Na- are obtainable[24] by the addition of cryptands to solutions of sodium in ammonia via disproportionation.[25]
[edit]Organosodium compounds
The structure of the complex of sodium (Na+, shown in yellow) and the antibiotic monensin-A.
Many organosodium compounds have been prepared. Because of the high polarity of the C-Na bonds, they behave like sources of carbanions (salts with organic anions) Sony VAIO VPCF21ZHJ battery. Some well known derivatives include sodium cyclopentadienide (NaC5H5) and trityl sodium ((C6H5)3CNa).[26]
[edit]History
Salt has been an important commodity in human activities, as shown by the English word salary, which derives from salarium, the wafers of salt sometimes given to Roman soldiers along with their other wages. In medieval Europe, a compound of sodium with the Latin name of sodanum was used as a headache remedy. The name sodium is thought to originate from the Arabic sudaSony VAIO VPCF21Z1E/BI battery, meaning headache, as the headache-alleviating properties of sodium carbonate or soda were well known in early times.[27] The chemical abbreviation for sodium was first published by Jöns Jakob Berzelius in his system of atomic symbols,[28] and is a contraction of the element's new Latin name natrium, which refers to the Egyptian natronSony VAIO VPCF21AHJ battery,[27] a natural mineral salt primarily made of hydrated sodium carbonate. Natron historically had several important industrial and household uses, later eclipsed by other sodium compounds. Although sodium, sometimes called soda, had long been recognised in compounds, the metal itself was not isolated until 1807 by Sir Humphry Davy through the electrolysis of sodium hydroxide. Sony VAIO VPCF21AGJ battery
Sodium imparts an intense yellow color to flames. As early as 1860, Kirchhoff and Bunsen noted the high sensitivity of a sodium flame test, and stated in Annalen der Physik und Chemie:[31]
“In a corner of our 60 m3 room farthest away from the apparatus, we exploded 3 mg. of sodium chlorate with milk sugar while observing the nonluminous flame before the slit. After a while, it glowed a bright yellow and showed a strong sodium line that disappeared only after 10 minutesSony VAIO VPCF21AFJ battery. From the weight of the sodium salt and the volume of air in the room, we easily calculate that one part by weight of air could not contain more than 1/20 millionth weight of sodium. ”
[edit]Commercial production
Enjoying rather specialized applications, only about 100,000 tonnes of metallic sodium are produced annually.[14] Metallic sodium was first produced commercially in 1855 by carbothermal reduction of sodium carbonate at 1100 °C, in what is known as the Deville process: Sony VAIO VPCF219FJ/BI battery
Na2CO3 + 2 C → 2 Na + 3 CO
A related process based on the reduction of sodium hydroxide was developed in 1886.[32]
Sodium is now produced commercially through the electrolysis of molten sodium chloride, based on a process patented in 1924.[35][36] This is done in a Downs Cell in which the NaCl is mixed with calcium chloride to lower the melting point below 700 °C. As calcium is less electropositive than sodium, no calcium will be formed at the anodeSony VAIO VPCF217HG/BI battery. This method is less expensive than the previous Castner process of electrolyzing sodium hydroxide.
Reagent-grade sodium in tonne quantities sold for about US$3.30/kg in 2009; lower purity metal sells for considerably less. The market for sodium is volatile due to the difficulty in its storage and shipping; it must be stored under a dry inert gas atmosphere or anhydrous mineral oil to prevent the formation of a surface layer of sodium oxide or sodium superoxideSony VAIO VPCF217HG battery. These oxides can react violently in the presence of organic materials. Sodium will also burn violently when heated in air.[37] Smaller quantities of sodium cost far more, in the range of US$165/kg; the high cost is partially due to the expense of shipping hazardous material.[38]
[edit]Applications
Though metallic sodium has some important uses, the major applications of sodium use it in its many compounds; millions of tons of the chloride, hydroxide, and carbonate are produced annuallySony VAIO VPCF14ZHJ battery.
[edit]Free element
Metallic sodium is mainly used for the production of sodium borohydride, sodium azide, indigo, and triphenylphosphine. Previous uses were for the making of tetraethyllead and titanium metal; because applications for these chemicals were discontinued, the production of sodium declined after 1970.[14] Sodium is also used as an alloying metal, an anti-scaling agentSony VAIO VPCF14AHJ battery,[39] and as a reducing agent for metals when other materials are ineffective. Sodium vapor lamps are often used for street lighting in cities and give colours ranging from yellow-orange to peach as the pressure increases.[40] By itself or with potassium, sodium is a desiccant; it gives an intense blue colouration with benzophenone when the desiccate is dry.[41] In organic synthesisSony VAIO VPCF14AGJ battery, sodium is used in various reactions such as the Birch reduction, and the sodium fusion test is conducted to qualitatively analyse compounds.[42] Lasers emitting light at the D line, utilising sodium, are used to create artificial laser guide stars that assist in the adaptive optics for land-based visible light telescopes. Sony VAIO VPCF14AFJ battery
[edit]Heat transfer
Liquid sodium is used as a heat transfer fluid in some fast reactors,[44] due to its high thermal conductivity and low neutron absorption cross section, which is required to achieve a high neutron flux; the high boiling point allows the reactor to operate at ambient pressure. Drawbacks of using sodium include its opacity, which hinders visual maintenanceSony VAIO VPCF149FJ/BI battery, and its explosive properties. Radioactive sodium-24 may be formed by neutron activation during operation, posing a slight radiation hazard; the radioactivity stops within a few days after removal from the reactor. If a reactor needs to be frequently shut down, NaK is used; due to it being liquid at room temperature, cooling pipes do not freeze. In this case, the pyrophoricity of potassium means extra precautions against leaks need to be takenSony VAIO VPCF148FJ/B battery. Another heat transfer application is in high-performance internal combustion engines with poppet valves, where valve stems partially filled with sodium are used as a heat pipe to cool the valves.
[edit]Compounds
Two equivalent images of the chemical structure of sodium stearate, a typical soap.
Most soaps are sodium salts of fatty acids. Sodium soaps are harder (higher melting) soaps than potassium soaps.[15] Sodium chloride is extensively used for anti-icing and de-icing and as a preservative; sodium bicarbonate is mainly used for cookingSony VAIO VPCF13ZHJ battery. Along with potassium, many important medicines have sodium added to improve their bioavailability; although in most cases potassium is the better ion, sodium is selected for its lower price and atomic weight.[45] Sodium hydride is used as a base for various reactions (such as the aldol reaction) in organic chemistry, and as a reducing agent in inorganic chemistry. Sony VAIO VPCF13Z0E/B battery
[edit]Biological role
Main article: Sodium in biology
Sodium is an essential nutrient that regulates blood volume, blood pressure, osmotic equilibrium and pH; the minimum physiological requirement for sodium is 500 milligrams per day.[47] Sodium chloride is the principal source of sodium in the diet, and is used as seasoning and preservative, such as for pickling and jerky; most of it comes from processed foodsSony VAIO VPCF13M8E/B battery.[48] The DRI for sodium is 2.3 grams per day,[49] but on average people in the United States consume 3.4 grams per day,[50] the minimum amount that promotes hypertension;[51] this in turn causes 7.6 million premature deaths worldwide.[52]
The renin-angiotensin system regulates the amount of fluids and sodium in the body. Reduction of blood pressure and sodium concentration in the kidney result in the production of renin, which in turn produces aldosterone and angiotensinSony VAIO VPCF13AHJ battery, retaining sodium in the urine. Because of the increase in sodium concentration, the production of renin decreases, and the sodium concentration returns to normal.[53] Sodium is also important in neuron function and osmoregulation between cells and the extracellular fluid, their distribution mediated in all animals by Na+/K+-ATPase;[54] hence, sodium is the most prominent cation in extracellular fluidSony VAIO VPCF13AGJ battery.[55]
In C4 plants, sodium is a micronutrient that aids in metabolism, specifically in regeneration of phosphoenolpyruvate and synthesis of chlorophyll.[56] In others, it substitutes for potassium in several roles, such as maintaining turgor pressure and aiding in the opening and closing of stomata.[57] Excess sodium in the soil limits the uptake of water due to decreased water potentialSony VAIO VPCF13AFJ battery, which may result in wilting; similar concentrations in the cytoplasm can lead to enzyme inhibition, which in turn causes necrosis and chlorosis.[58] To avoid these problems, plants developed mechanisms that limit sodium uptake by roots, store them in cell vacuoles, and control them over long distances;[59] excess sodium may also be stored in old plant tissue, limiting the damage to new growthSony VAIO VPCF138FJ/BI battery.
[edit]Precautions
Care is required in handling elemental sodium, as it is potentially explosive and generates flammable hydrogen and caustic sodium hydroxide upon contact with water; powdered sodium may combust spontaneously in air or oxygen.[60] Excess sodium can be safely removed by hydrolysis in a ventilated cabinet; this is typically done by sequential treatment with isopropanolSony VAIO VPCF138FJ/B battery, ethanol and water. Isopropanol reacts very slowly, generating the corresponding alkoxide and hydrogen.[61] Fire extinguishers based on water accelerate sodium fires; those based on carbon dioxide and bromochlorodifluoromethane lose their effectiveness when they dissipate. An effective extinguishing agent is Met-L-X, which comprises approximately 5% Saran in sodium chloride together with flow agentsSony VAIO VPCF138FC/BI battery; it is most commonly hand-applied with a scoop. Other materials include Lith+, which has graphite powder and an organophosphate flame retardant, and dry sand.
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 Sony VAIO VPCF135FG battery (behind iron, oxygen and silicon), 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 seawaterSony VAIO VPCF12AHJ battery.[5]
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 brineSony VAIO VPCF12AGJ battery. Commercially, 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, where they play a major role in manipulating important biological polyphosphate compounds like ATP, DNA, and RNASony VAIO VPCF12AFJ battery. Hundreds of enzymes thus require magnesium ions to function. Magnesium compounds are used medicinally as common laxatives, antacids (e.g., milk of magnesia), 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 watersSony VAIO VPCF129FJ/BI battery.
In vegetation magnesium is the metallic ion at the center of chlorophyll, and is thus a common additive to fertilizers.[6]
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 removeSony VAIO VPCF128FJ/B 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 rapidly. The reaction will occur faster with higher temperatures (see precautions) Sony VAIO VPCF127FJ/W battery. 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 gasSony VAIO VPCF11ZHJ 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) Sony VAIO VPCF11AHJ 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 photographySony VAIO VPCF11AGJ 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) Sony VAIO VPCF11AFJ 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 (common name: Epsom salt) is sometimes used for this purposeSony VAIO VPCF118FJ battery. 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 effectSony VAIO VPCF117FJ 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 timesSony VAIO VGN-CS33H 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 meteorites. The anomalous abundance of 26Mg is attributed to the decay of its parent 26Al in the inclusionsSony VAIO VGN-CS33H/Z battery. 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 reservoirSony VAIO VGN-CS33H/B battery.
[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 megakelvins.
[edit]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 precipitateSony VAIO VGN-CS31Z/Q 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 metalSony VAIO VGN-CS31S/W 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 Magcorp. Sony VAIO VGN-CS31S/V battery
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). Sony VAIO VGN-CS31S/T 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 history.
Magnesium is the seventh most abundant element in the Earth's crust by mass or molarity.[2] It is found in large deposits of magnesiteSony VAIO VGN-CS31S/R battery, 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 there. 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, MgSO4Sony VAIO VGN-CS31S/P battery.
The metal itself was first produced by Sir Humphry Davy in England in 1808 using electrolysis of a mixture of magnesia and mercuric oxide.[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 usedSony VAIO VGN-CS28 battery.
[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 Videos.[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 processSony VAIO VGN-CS28/Q battery.[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 components. Specialty, high-grade car wheels of magnesium alloy are called "mag wheels", although the term is often more broadly misapplied to include aluminum wheelsSony VAIO VGN-CS27 battery. 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 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 historySony VAIO VGN-CS27/W battery, 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 hpSony VAIO VGN-CS27/R battery. 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 AJ62ASony VAIO VGN-CS27/P battery. 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 boundariesSony VAIO VGN-CS27/C battery, for example by adding mischmetal or calcium.[15] New alloy development and lower costs, 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 componentsSony VAIO VGN-CS26T/W 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 fireSony VAIO VGN-CS26T/V 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 continues, notably Elektron 21Sony VAIO VGN-CS26T/T battery, 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),[7] and the autoignition temperature of magnesium ribbon is approximately 473 °C (746 K; 883 °F). Sony VAIO VGN-CS26T/R battery 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 shavingsSony VAIO VGN-CS26T/Q battery
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 heatersSony VAIO VGN-CS26T/P battery.
Alloyed with zinc to produce the zinc sheet used in photoengraving plates in the printing industry, dry-cell battery walls, and roofing.[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 cementSony VAIO VGN-CS26T/C 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 mediaSony VAIO VGN-CS25H 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. Oral magnesium supplements have been claimed to be therapeutic for some individuals who suffer from Restless Leg Syndrome (RLS). Sony VAIO VGN-CS25H/W battery
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).
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 Sony VAIO VGN-CS25H/R battery (i.e., when the tablet's substance is pressed into tablet form).
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 textilesSony VAIO VGN-CS25H/Q 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, including all enzymes utilizing or synthesizing ATP, or those that use other nucleotides to synthesize DNA and RNASony VAIO VGN-CS25H/P battery. 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 soilSony VAIO VGN-CS25H/C battery.
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, diabetesSony VAIO VGN-CS23T/W battery, and osteoporosis.[19] Taken in the proper amount magnesium plays a role in preventing both stroke and heart attack. The symptoms of people with fibromyalgia, migraines, and girls going through their premenstrual syndrome are less severe and magnesium can shorten the length of the migraine symptoms. Sony VAIO VGN-CS23T/Q battery
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, although no known mechanism maintains a homeostatic level in the blood other than renal excretion of high blood levelsSony VAIO VGN-CS23H battery.
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, and other factors such as phosphate, phytate, and fat affect absorptionSony VAIO VGN-CS23H/S battery. Absorbed dietary magnesium is largely excreted through the urine, although most magnesium "administered orally" is excreted through the feces.[22] 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 peopleSony VAIO VGN-CS23H/B battery.[23] In these tests, magnesium is injected intravenously; a retention of 20% or more indicates deficiency.[24] Other nutrient deficiencies are identified through biomarkers, but none are established for magnesium.[25]
Spices, nuts, cereals, coffee, cocoa, tea, and vegetables are rich sources of magnesium[26]. Green leafy vegetables such as spinach are also rich in magnesium as they contain chlorophyllSony VAIO VGN-CS23G battery. 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.[22]
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.[27][28] Magnesium citrate has been reported as more bioavailable than oxide or amino-acid chelate (glycinate) formsSony VAIO VGN-CS23G/W battery.[29]
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, severe hypermagnesemia has been reported to occur even without renal dysfunction.[30] Alcoholism can produce a magnesium deficiencySony VAIO VGN-CS23G/Q battery, which is easily reversed by oral or parenteral administration, depending on the degree of deficiency.[31]
[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. 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 mothersSony VAIO VGN-CS23G/P battery.[32]
[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. Brain magnesium has been found low in TRD using phosphorus nuclear magnetic resonance spectroscopySony VAIO VGN-CS21Z/Q battery, an accurate means for measuring brain magnesium. Blood and CSF magnesium do not appear well-correlated with major depression.[33] 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. Sony VAIO VGN-CS21S/W battery
[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.
[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 magnesiumSony VAIO VGN-CS21S/V battery, 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.[35]
Magnesium is capable of reducing water to the highly flammable hydrogen gas:[36]
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 surfacesSony VAIO VGN-CS21S/T 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.[37]
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 sourceSony VAIO VGN-CS21S/R battery.
Many sodium compounds are useful, such as sodium hydroxide (lye) for soapmaking, and sodium chloride for use as a deicing agent and a nutrient. Sodium is an essential element for all animals and some plants. In animals, sodium ions are used against potassium ions to build up charges on cell membranes, allowing transmission of nerve impulses when the charge is dissipatedSony VAIO VPCF136FG/BI battery. The consequent need of animals for sodium causes it to classified as a dietary inorganic macro-mineral.
Physical
Emission spectrum for sodium, showing the D line.
A positive flame test for sodium has a bright yellow color.
Sodium at standard temperature and pressure is a soft metal that can be readily cut with a knife and is a good conductor of electricity. Freshly exposed, sodium has a bright, silvery luster that rapidly tarnishes, forming a white coating of sodium hydroxide and sodium carbonate. These properties change at elevated pressures: at 1.5 Mbar, the color changes to blackSony VAIO VPCF135FG/B battery, then to red transparent at 1.9 Mbar, and finally clear transparent at 3 Mbar. All of these allotropes are insulators and electrides.[2]
When sodium or its compounds are introduced into a flame, they turn it yellow,[3] because the excited 3s electrons of sodium emit a photon when they fall from 3p to 3s; the wavelength of this photon corresponds to the D line at 589.3 nm. Spin-orbit interactions involving the electron in the 3p orbital split the D line into two; hyperfine structures involving both orbitals cause many more linesSony VAIO VPCF127HG/BI battery.[4]
[edit]Chemical
Sodium is generally less reactive than potassium and more reactive than lithium.[5] Like all the alkali metals, it reacts exothermically with water, to the point that sufficiently large pieces melt to a sphere and may explode; this reaction produces caustic sodium hydroxide and flammable hydrogen gasSony VAIO VPCF11Z1E battery. When burned in dry air, it mainly forms sodium peroxide as well as some sodium oxide. In moist air, sodium hydroxide results.[6] Sodium metal is highly reducing, with the reduction of sodium ions requiring −2.71 volts[7] but potassium and lithium have even more negative potentials.[8] Hence, the extraction of sodium metal from its compounds (such as with sodium chloride) uses a significant amount of energySony VAIO VPCF11S1E battery.[6]
[edit]Isotopes
Main article: Isotopes of sodium
20 isotopes of sodium are known, but only 23Na is stable. Two radioactive, cosmogenic isotopes are the byproduct of cosmic ray spallation: 22Na with a half-life of 2.6 years and 24Na with a half-life of 15 hours; all other isotopes have a half-life of less than one minute.[9] Two nuclear isomers have been discovered, the longer-lived one being 24mNa with a half-life of around 20.2 microsecondsSony VAIO VPCF11M1E/H battery. Acute neutron radiation, such as from a nuclear criticality accident, converts some of the stable 23Na in human blood to 24Na; by measuring the concentration of 24Na in relation to 23Na, the neutron radiation dosage of the victim can be calculated.[10]
[edit]Occurrence
23Na is created in the carbon-burning process by fusing two carbon atoms together; this requires temperatures above 600 megakelvins and a star with at least three solar masses.[11] The Earth's crust has 2.6% sodium by weight, making it the sixth most abundant element thereSony VAIO VPCF11M1E battery.[12] Because of its high reactivity, it is never found as a pure element. It is found in many different minerals, some very soluble, such as halite and natron, others much less soluble such as amphibole, and zeolite. The insolubility of certain sodium minerals such as cryolite and feldspar arises from their polymeric anions, which in the case of feldspar is a polysilicateSony VAIO VPCF11JFX/B battery. In the interstellar medium, sodium is identified by the D line; though it has a high vaporization temperature, its abundance allowed it to be detected by Mariner 10 in Mercury's atmosphere.[13]
[edit]Compounds
See also Category: Sodium compounds
Structure of sodium chloride, showing octahedral coordination around Na+ and Cl- centres. This framework disintegrates upon dissolution in water and reassembles upon evaporation.
Sodium compounds are of immense commercial importance, being particularly central to industries producing glass, paper, soap, and textilesSony VAIO VPCF119FJ battery.[14] The sodium compounds that are the most important are common salt (NaCl), soda ash (Na2CO3), baking soda (NaHCO3), caustic soda (NaOH), sodium nitrate (NaNO3), di- and tri-sodium phosphates, sodium thiosulfate (Na2S2O3·5H2O), and borax (Na2B4O7·10H2O).[15] In its compounds, sodium is usually ionically bonded to water and anions, and is viewed as a hard Lewis acidSony VAIO VPCF119FC/BI battery.[16]
[edit]Aqueous solutions
Sodium tends to form water-soluble compounds, such as halides, sulfates, nitrates, carboxylates and carbonates. The main aqueous species are the aquo complexes [Na(H2O)n]+, where n = 4–6.[17] The high affinity of sodium for oxygen-based ligands is the basis of crown ethers; macrolide antibiotics, which interfere with Na+ transport in the infecting organism, are functionally related and more complexSony VAIO VPCF119FC battery.
Direct precipitation of sodium salts from aqueous solutions is rare, because sodium salts typically have a high affinity for water; an exception is sodium bismuthate (NaBiO3).[18] Because of this, sodium salts are usually isolated as solids by evaporation or by precipitation with an organic solvent, such as ethanol; for example, only 0.35 g/L of sodium chloride will dissolve in ethanol.[19] Crown ethers, like 15-crown-5, may be used as a phase-transfer catalystSony VAIO VPCF117HG/BI battery.[20]
Sodium content in bulk may be determined by treating with a large excess of uranyl zinc acetate; the hexahydrate (UO2)2ZnNa(CH3CO2)·6H2O precipitates, which can be weighed. Caesium and rubidium do not interfere with this reaction, but potassium and lithium do.[21] Lower concentrations of sodium may be determined by atomic absorption spectrophotometry[22] or by potentiometry using ion-selective electrodesSony VAIO VPCF116FG/BI battery.[23]
[edit]Electrides and sodides
Like the other alkali metals, sodium dissolves in ammonia and some amines to give deeply coloured solutions; evaporation of these solutions leaves a shiny film of metallic sodium. The solutions contain the coordination complex (Na(NH3)6)+, whose positive charge is counterbalanced by electrons as anions; cryptands permit the isolation of these complexes as crystalline solidsSony VAIO VPCF115FG/B battery. Cryptands, like crown ethers and other ionophores, have a high affinity for the sodium ion; derivatives of the alkalide Na- are obtainable[24] by the addition of cryptands to solutions of sodium in ammonia via disproportionation.[25]
[edit]Organosodium compounds
The structure of the complex of sodium (Na+, shown in yellow) and the antibiotic monensin-A.
Many organosodium compounds have been prepared. Because of the high polarity of the C-Na bonds, they behave like sources of carbanions (salts with organic anions) Sony VAIO VPCF21ZHJ battery. Some well known derivatives include sodium cyclopentadienide (NaC5H5) and trityl sodium ((C6H5)3CNa).[26]
[edit]History
Salt has been an important commodity in human activities, as shown by the English word salary, which derives from salarium, the wafers of salt sometimes given to Roman soldiers along with their other wages. In medieval Europe, a compound of sodium with the Latin name of sodanum was used as a headache remedy. The name sodium is thought to originate from the Arabic sudaSony VAIO VPCF21Z1E/BI battery, meaning headache, as the headache-alleviating properties of sodium carbonate or soda were well known in early times.[27] The chemical abbreviation for sodium was first published by Jöns Jakob Berzelius in his system of atomic symbols,[28] and is a contraction of the element's new Latin name natrium, which refers to the Egyptian natronSony VAIO VPCF21AHJ battery,[27] a natural mineral salt primarily made of hydrated sodium carbonate. Natron historically had several important industrial and household uses, later eclipsed by other sodium compounds. Although sodium, sometimes called soda, had long been recognised in compounds, the metal itself was not isolated until 1807 by Sir Humphry Davy through the electrolysis of sodium hydroxide. Sony VAIO VPCF21AGJ battery
Sodium imparts an intense yellow color to flames. As early as 1860, Kirchhoff and Bunsen noted the high sensitivity of a sodium flame test, and stated in Annalen der Physik und Chemie:[31]
“In a corner of our 60 m3 room farthest away from the apparatus, we exploded 3 mg. of sodium chlorate with milk sugar while observing the nonluminous flame before the slit. After a while, it glowed a bright yellow and showed a strong sodium line that disappeared only after 10 minutesSony VAIO VPCF21AFJ battery. From the weight of the sodium salt and the volume of air in the room, we easily calculate that one part by weight of air could not contain more than 1/20 millionth weight of sodium. ”
[edit]Commercial production
Enjoying rather specialized applications, only about 100,000 tonnes of metallic sodium are produced annually.[14] Metallic sodium was first produced commercially in 1855 by carbothermal reduction of sodium carbonate at 1100 °C, in what is known as the Deville process: Sony VAIO VPCF219FJ/BI battery
Na2CO3 + 2 C → 2 Na + 3 CO
A related process based on the reduction of sodium hydroxide was developed in 1886.[32]
Sodium is now produced commercially through the electrolysis of molten sodium chloride, based on a process patented in 1924.[35][36] This is done in a Downs Cell in which the NaCl is mixed with calcium chloride to lower the melting point below 700 °C. As calcium is less electropositive than sodium, no calcium will be formed at the anodeSony VAIO VPCF217HG/BI battery. This method is less expensive than the previous Castner process of electrolyzing sodium hydroxide.
Reagent-grade sodium in tonne quantities sold for about US$3.30/kg in 2009; lower purity metal sells for considerably less. The market for sodium is volatile due to the difficulty in its storage and shipping; it must be stored under a dry inert gas atmosphere or anhydrous mineral oil to prevent the formation of a surface layer of sodium oxide or sodium superoxideSony VAIO VPCF217HG battery. These oxides can react violently in the presence of organic materials. Sodium will also burn violently when heated in air.[37] Smaller quantities of sodium cost far more, in the range of US$165/kg; the high cost is partially due to the expense of shipping hazardous material.[38]
[edit]Applications
Though metallic sodium has some important uses, the major applications of sodium use it in its many compounds; millions of tons of the chloride, hydroxide, and carbonate are produced annuallySony VAIO VPCF14ZHJ battery.
[edit]Free element
Metallic sodium is mainly used for the production of sodium borohydride, sodium azide, indigo, and triphenylphosphine. Previous uses were for the making of tetraethyllead and titanium metal; because applications for these chemicals were discontinued, the production of sodium declined after 1970.[14] Sodium is also used as an alloying metal, an anti-scaling agentSony VAIO VPCF14AHJ battery,[39] and as a reducing agent for metals when other materials are ineffective. Sodium vapor lamps are often used for street lighting in cities and give colours ranging from yellow-orange to peach as the pressure increases.[40] By itself or with potassium, sodium is a desiccant; it gives an intense blue colouration with benzophenone when the desiccate is dry.[41] In organic synthesisSony VAIO VPCF14AGJ battery, sodium is used in various reactions such as the Birch reduction, and the sodium fusion test is conducted to qualitatively analyse compounds.[42] Lasers emitting light at the D line, utilising sodium, are used to create artificial laser guide stars that assist in the adaptive optics for land-based visible light telescopes. Sony VAIO VPCF14AFJ battery
[edit]Heat transfer
Liquid sodium is used as a heat transfer fluid in some fast reactors,[44] due to its high thermal conductivity and low neutron absorption cross section, which is required to achieve a high neutron flux; the high boiling point allows the reactor to operate at ambient pressure. Drawbacks of using sodium include its opacity, which hinders visual maintenanceSony VAIO VPCF149FJ/BI battery, and its explosive properties. Radioactive sodium-24 may be formed by neutron activation during operation, posing a slight radiation hazard; the radioactivity stops within a few days after removal from the reactor. If a reactor needs to be frequently shut down, NaK is used; due to it being liquid at room temperature, cooling pipes do not freeze. In this case, the pyrophoricity of potassium means extra precautions against leaks need to be takenSony VAIO VPCF148FJ/B battery. Another heat transfer application is in high-performance internal combustion engines with poppet valves, where valve stems partially filled with sodium are used as a heat pipe to cool the valves.
[edit]Compounds
Two equivalent images of the chemical structure of sodium stearate, a typical soap.
Most soaps are sodium salts of fatty acids. Sodium soaps are harder (higher melting) soaps than potassium soaps.[15] Sodium chloride is extensively used for anti-icing and de-icing and as a preservative; sodium bicarbonate is mainly used for cookingSony VAIO VPCF13ZHJ battery. Along with potassium, many important medicines have sodium added to improve their bioavailability; although in most cases potassium is the better ion, sodium is selected for its lower price and atomic weight.[45] Sodium hydride is used as a base for various reactions (such as the aldol reaction) in organic chemistry, and as a reducing agent in inorganic chemistry. Sony VAIO VPCF13Z0E/B battery
[edit]Biological role
Main article: Sodium in biology
Sodium is an essential nutrient that regulates blood volume, blood pressure, osmotic equilibrium and pH; the minimum physiological requirement for sodium is 500 milligrams per day.[47] Sodium chloride is the principal source of sodium in the diet, and is used as seasoning and preservative, such as for pickling and jerky; most of it comes from processed foodsSony VAIO VPCF13M8E/B battery.[48] The DRI for sodium is 2.3 grams per day,[49] but on average people in the United States consume 3.4 grams per day,[50] the minimum amount that promotes hypertension;[51] this in turn causes 7.6 million premature deaths worldwide.[52]
The renin-angiotensin system regulates the amount of fluids and sodium in the body. Reduction of blood pressure and sodium concentration in the kidney result in the production of renin, which in turn produces aldosterone and angiotensinSony VAIO VPCF13AHJ battery, retaining sodium in the urine. Because of the increase in sodium concentration, the production of renin decreases, and the sodium concentration returns to normal.[53] Sodium is also important in neuron function and osmoregulation between cells and the extracellular fluid, their distribution mediated in all animals by Na+/K+-ATPase;[54] hence, sodium is the most prominent cation in extracellular fluidSony VAIO VPCF13AGJ battery.[55]
In C4 plants, sodium is a micronutrient that aids in metabolism, specifically in regeneration of phosphoenolpyruvate and synthesis of chlorophyll.[56] In others, it substitutes for potassium in several roles, such as maintaining turgor pressure and aiding in the opening and closing of stomata.[57] Excess sodium in the soil limits the uptake of water due to decreased water potentialSony VAIO VPCF13AFJ battery, which may result in wilting; similar concentrations in the cytoplasm can lead to enzyme inhibition, which in turn causes necrosis and chlorosis.[58] To avoid these problems, plants developed mechanisms that limit sodium uptake by roots, store them in cell vacuoles, and control them over long distances;[59] excess sodium may also be stored in old plant tissue, limiting the damage to new growthSony VAIO VPCF138FJ/BI battery.
[edit]Precautions
Care is required in handling elemental sodium, as it is potentially explosive and generates flammable hydrogen and caustic sodium hydroxide upon contact with water; powdered sodium may combust spontaneously in air or oxygen.[60] Excess sodium can be safely removed by hydrolysis in a ventilated cabinet; this is typically done by sequential treatment with isopropanolSony VAIO VPCF138FJ/B battery, ethanol and water. Isopropanol reacts very slowly, generating the corresponding alkoxide and hydrogen.[61] Fire extinguishers based on water accelerate sodium fires; those based on carbon dioxide and bromochlorodifluoromethane lose their effectiveness when they dissipate. An effective extinguishing agent is Met-L-X, which comprises approximately 5% Saran in sodium chloride together with flow agentsSony VAIO VPCF138FC/BI battery; it is most commonly hand-applied with a scoop. Other materials include Lith+, which has graphite powder and an organophosphate flame retardant, and dry sand.
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 Sony VAIO VPCF135FG battery (behind iron, oxygen and silicon), 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 seawaterSony VAIO VPCF12AHJ battery.[5]
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 brineSony VAIO VPCF12AGJ battery. Commercially, 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, where they play a major role in manipulating important biological polyphosphate compounds like ATP, DNA, and RNASony VAIO VPCF12AFJ battery. Hundreds of enzymes thus require magnesium ions to function. Magnesium compounds are used medicinally as common laxatives, antacids (e.g., milk of magnesia), 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 watersSony VAIO VPCF129FJ/BI battery.
In vegetation magnesium is the metallic ion at the center of chlorophyll, and is thus a common additive to fertilizers.[6]
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 removeSony VAIO VPCF128FJ/B 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 rapidly. The reaction will occur faster with higher temperatures (see precautions) Sony VAIO VPCF127FJ/W battery. 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 gasSony VAIO VPCF11ZHJ 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) Sony VAIO VPCF11AHJ 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 photographySony VAIO VPCF11AGJ 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) Sony VAIO VPCF11AFJ 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 (common name: Epsom salt) is sometimes used for this purposeSony VAIO VPCF118FJ battery. 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 effectSony VAIO VPCF117FJ 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 timesSony VAIO VGN-CS33H 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 meteorites. The anomalous abundance of 26Mg is attributed to the decay of its parent 26Al in the inclusionsSony VAIO VGN-CS33H/Z battery. 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 reservoirSony VAIO VGN-CS33H/B battery.
[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 megakelvins.
[edit]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 precipitateSony VAIO VGN-CS31Z/Q 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 metalSony VAIO VGN-CS31S/W 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 Magcorp. Sony VAIO VGN-CS31S/V battery
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). Sony VAIO VGN-CS31S/T 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 history.
Magnesium is the seventh most abundant element in the Earth's crust by mass or molarity.[2] It is found in large deposits of magnesiteSony VAIO VGN-CS31S/R battery, 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 there. 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, MgSO4Sony VAIO VGN-CS31S/P battery.
The metal itself was first produced by Sir Humphry Davy in England in 1808 using electrolysis of a mixture of magnesia and mercuric oxide.[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 usedSony VAIO VGN-CS28 battery.
[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 Videos.[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 processSony VAIO VGN-CS28/Q battery.[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 components. Specialty, high-grade car wheels of magnesium alloy are called "mag wheels", although the term is often more broadly misapplied to include aluminum wheelsSony VAIO VGN-CS27 battery. 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 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 historySony VAIO VGN-CS27/W battery, 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 hpSony VAIO VGN-CS27/R battery. 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 AJ62ASony VAIO VGN-CS27/P battery. 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 boundariesSony VAIO VGN-CS27/C battery, for example by adding mischmetal or calcium.[15] New alloy development and lower costs, 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 componentsSony VAIO VGN-CS26T/W 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 fireSony VAIO VGN-CS26T/V 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 continues, notably Elektron 21Sony VAIO VGN-CS26T/T battery, 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),[7] and the autoignition temperature of magnesium ribbon is approximately 473 °C (746 K; 883 °F). Sony VAIO VGN-CS26T/R battery 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 shavingsSony VAIO VGN-CS26T/Q battery
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 heatersSony VAIO VGN-CS26T/P battery.
Alloyed with zinc to produce the zinc sheet used in photoengraving plates in the printing industry, dry-cell battery walls, and roofing.[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 cementSony VAIO VGN-CS26T/C 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 mediaSony VAIO VGN-CS25H 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. Oral magnesium supplements have been claimed to be therapeutic for some individuals who suffer from Restless Leg Syndrome (RLS). Sony VAIO VGN-CS25H/W battery
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).
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 Sony VAIO VGN-CS25H/R battery (i.e., when the tablet's substance is pressed into tablet form).
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 textilesSony VAIO VGN-CS25H/Q 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, including all enzymes utilizing or synthesizing ATP, or those that use other nucleotides to synthesize DNA and RNASony VAIO VGN-CS25H/P battery. 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 soilSony VAIO VGN-CS25H/C battery.
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, diabetesSony VAIO VGN-CS23T/W battery, and osteoporosis.[19] Taken in the proper amount magnesium plays a role in preventing both stroke and heart attack. The symptoms of people with fibromyalgia, migraines, and girls going through their premenstrual syndrome are less severe and magnesium can shorten the length of the migraine symptoms. Sony VAIO VGN-CS23T/Q battery
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, although no known mechanism maintains a homeostatic level in the blood other than renal excretion of high blood levelsSony VAIO VGN-CS23H battery.
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, and other factors such as phosphate, phytate, and fat affect absorptionSony VAIO VGN-CS23H/S battery. Absorbed dietary magnesium is largely excreted through the urine, although most magnesium "administered orally" is excreted through the feces.[22] 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 peopleSony VAIO VGN-CS23H/B battery.[23] In these tests, magnesium is injected intravenously; a retention of 20% or more indicates deficiency.[24] Other nutrient deficiencies are identified through biomarkers, but none are established for magnesium.[25]
Spices, nuts, cereals, coffee, cocoa, tea, and vegetables are rich sources of magnesium[26]. Green leafy vegetables such as spinach are also rich in magnesium as they contain chlorophyllSony VAIO VGN-CS23G battery. 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.[22]
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.[27][28] Magnesium citrate has been reported as more bioavailable than oxide or amino-acid chelate (glycinate) formsSony VAIO VGN-CS23G/W battery.[29]
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, severe hypermagnesemia has been reported to occur even without renal dysfunction.[30] Alcoholism can produce a magnesium deficiencySony VAIO VGN-CS23G/Q battery, which is easily reversed by oral or parenteral administration, depending on the degree of deficiency.[31]
[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. 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 mothersSony VAIO VGN-CS23G/P battery.[32]
[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. Brain magnesium has been found low in TRD using phosphorus nuclear magnetic resonance spectroscopySony VAIO VGN-CS21Z/Q battery, an accurate means for measuring brain magnesium. Blood and CSF magnesium do not appear well-correlated with major depression.[33] 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. Sony VAIO VGN-CS21S/W battery
[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.
[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 magnesiumSony VAIO VGN-CS21S/V battery, 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.[35]
Magnesium is capable of reducing water to the highly flammable hydrogen gas:[36]
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 surfacesSony VAIO VGN-CS21S/T 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.[37]
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 sourceSony VAIO VGN-CS21S/R battery.
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