Magnesium

Notable characteristics

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 alkaline metals, storage in an oxygen free environment is unnecessary because magnesium is protected by a thin layer of oxide which is fairly impermeable and hard to remove. Like its lower carbon).

Magnesium, when it burns in air, produces a brilliant white light. This was used in the early days of photography when magnesium powder was used as a source of illumination (flash powder). Later, magnesium ribbon was used in electrically ignited flash bulbs. Magnesium powder is still used in the manufacture of fireworks and marine flares where a brilliant white light is required.

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

Applications

As the metal

Magnesium is the third most commonly used structural metal, following steel and aluminium.

Magnesium compounds, primarily 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.

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 "calcium.^[1] New alloy development and lower costs, which are becoming competitive to aluminium, will further the number of automotive applications.  

The second application field of magnesium is electronic devices. Due to low weight, good mechanical and electrical properties, magnesium is widely used for manufacturing of mobile phones, laptop computers, cameras, and other electronic components.

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

  Other uses include:

• Removal of sulfur from iron and steel.
• Production of titanium
• Photoengraved plates in the printing industry.
• Combined in alloys, this metal is essential for airplane and missile construction.
• When used as an alloying agent, this metal improves the mechanical, fabrication and welding characteristics of aluminium.
• Additive agent for conventional propellants and used in producing nodular graphite in cast iron.
• Reducing agent for the production of pure salts.
• Magnesium turnings or ribbon are used to prepare organic synthesis
• Easily reacting with water, it can serve as a desiccant
• Magnesium is also flammable, burning at a temperature of approximately 2500 K (2200 °C, 4000 °F).
• The autoignition temperature of magnesium is approximately 744 K (473 °C, 883 °F).
• The extremely high temperature at which magnesium burns makes it a handy tool for starting emergency fires during outdoor recreation.
• Other uses include flashlight photography, flares, pyrotechnics, sparklers, and incendiary bombs.

In magnesium compounds

• The magnesium ion is necessary for all life (see magnesium in biological systems), so magnesium salts are an additive for foods, fertilizers (Mg is a component of chlorophyll), and culture media.
• Magnesium's hydroxide is used in milk of magnesia, its Epsom salts) for various purposes in medicine, and elsewhere.
• Epsom salt (magnesium sulfate) is used to treat aches and sore throats.
• Dead-burned magnesite is used for refractory purposes such as brick and liners in furnaces and converters.
• CO₃) powder is also used by athletes, such as gymnasts and weightlifters, to improve the grip on objects – the apparatus or lifting bar.
• 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 borate, magnesium salicylate and magnesium sulfate are used as antiseptics to kill germs.
• Magnesium bromide is used as a mild sedative.
• Magnesium in the forms of magnesium oxide and magnesium gluconate are used in dietary supplement tablets. These have been shown to be an effective therapy for some individuals who suffer from Restless Leg Syndrome (RLS).
• Magnesium sulfite is used in the manufacture of paper.
• Magnesium phosphate is used to fireproof wood for construction.
• Magnesium hexafluorosilicate is used in mothproofing of textiles.
• Magnesium is even used to make some higher end yo-yos such as the Duncan Freehand Mg.

History

The name originates from the Greek word for a district in Thessaly called Magnesia. It is related to manganese for this history.

Magnesium is the eighth most abundant element in the earth's crust. It is found in large deposits of Epsom salts spread. Eventually they were recognized to be hydrated magnesium sulphate, MgSO₄.

Sir O, and A. A. B. Bussy prepared it in coherent form in 1831. Davy's first suggestion for a name was magnium, but the name magnesium is now used.

Sources

Although magnesium is found in over 60 olivine are of commercial importance.

In the United States this metal is principally obtained by sea water:

e^- → Mg

gas) + 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.^[2] 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 Pidgeon process (the reduction of the oxide at high temperatures with silicon).

Magnesium from sea water

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, magnesium carbonate precipitate.

MgCl₂ + CaCO₃ → MgCO₃ + CaCl₂

magnesium chloride.

MgCO₃ + 2HCl → MgCl₂ + CO₂ + H₂O

From magnesium chloride, electrolysis produces magnesium.

See also:

Biology

Main article: Magnesium in biology

Magnesium ions are essential to the basic limestone to the soil.

Magnesium is a vital component of a healthy human diet and deficiency has been implicated in a number of human diseases. Magnesium is readily available in many common foods but studies indicate that many Americans are magnesium deficient. Excess magnesium in the blood is freely filterd at the kidneys, and for this reason it is very difficult to overdose on magnesium from dietary sources alone ^[3]. However, there are a number of magnesium supplements available which make overdose possible, particularly in people with poor renal function.

Isotopes

Magnesium has three stable isotopes: ²⁴Mg, ²⁵Mg, 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 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.

Precautions

 

Magnesium metal and alloys are highly flammable in their pure form when molten, as a powder, or in ribbon form. Burning or molten magnesium metal reacts violently with water. Magnesium powder is an explosive hazard. One should wear safety glasses while working with magnesium, and if burning it, these should include a heavy U.V. filter, similar to welding eye protection. The bright white light (including ultraviolet) produced by burning magnesium can permanently damage the retinas of the eyes, similar to welding arc burns.^[4]

Water should not be used to extinguish magnesium fires, because it can produce hydrogen which will feed the fire, according to the reaction:^[5]

Mg _(s) + 2 H₂O _(g) → Mg(OH)_{2 (s)} + H_{2 (g)}

or in words:

Magnesium _(solid) + steam → Magnesium hydroxide _(solid) + Hydrogen _(gas)

Carbon dioxide fire extinguishers should not be used either, because magnesium can burn in carbon dioxide (forming carbon).^[6] A Class D dry chemical fire extinguisher should be used if available, or else the fire should be covered with sand or magnesium foundry flux. An easy way to put out small metal fires is to place a polyethylene bag filled with dry sand on top of the fire. The heat of the fire will melt the bag and the sand will flow out onto the fire.

See also

• Magnesium minerals
• Magnesium compounds

References