Magnesium

Scottish chemist Joseph Black recognized magnesium as an element in 1755. He showed by experiment that it differed from calcium, which it had previously been thought to be. Black wrote, "We have already shewn by experiment, that magnesia alba [magnesium carbonate] is a compound of a peculiar earth and fixed air." ⁽¹⁾ By peculiar, Black meant a new earth metal.

Magnesium was first isolated in England by Sir Humphrey Davy in 1808. Davy had built an enormous 600 plate battery with which he passed electricity through salts. In doing so, Davy discovered or isolated for the first time many alkali and alkali earth metals, such as potassium, sodium, barium, calcium and strontium. In magnesium's case, Davy mixed magnesium oxide to a paste with mercury sulfide. He made a depression in the paste and placed mercury metal there to act as an electrode. Platinum was used as a counter electrode. When electricity was passed through the paste, a magnesium-mercury amalgam formed at the mercury electrode. The mercury was then removed by heating to leave magnesium metal. ⁽²⁾

The name originates from the Greek word Magnesia, a district of Thessaly.

Magnesium powder is an explosive hazard.

The bright white light plus ultraviolet from burning magnesium can cause permanent eye damage.

Magnesium is a silvery-white, low density, reasonably strong metal that tarnishes in air to form a thin oxide coating. Magnesium and its alloys have very good corrosion resistance and good high temperature mechanical properties.

The metal reacts with water to produce hydrogen gas.

When it burns in air, magnesium produces a brilliant white light.

The brilliant light it produces when ignited is made use of in photography, flares, pyrotechnics and incendiary bombs.

With a density of only two-thirds that of aluminum, and just over one-fifth that of iron, magnesium alloys are used in aircraft, car engine casings, and missile construction.

The metal is widely used in the manufacturing of mobile phones, laptop computers, cameras, and other electronic components.

Organic magnesium compounds (Grignard reagents) are important in the synthesis of organic molecules.

Magnesium compounds such as the hydroxide (milk of magnesia, Mg(OH₂)), sulfate (Epsom salts), chloride and citrate are used for medicinal purposes.

Magnesium is the second most important intracellular cation and is involved in a variety of metabolic processes including glucose metabolism, ion channel translocation, stimulus-contraction coupling, stimulus secretion coupling, peptide hormone receptor signal transduction. ⁽³⁾

Magnesium is the eighth most abundant element in the Earth's crust and the sixth most abundant metal. Magnesium is obtained commercially by the 'Pidgeon' process. This high temperature method uses silicon as a reducing agent to extract magnesium from minerals such as dolomite (MgCa(CO ₃)₂) or magnesite (MgCO ₃) or saltwater.

Magnesium has 15 isotopes whose half-lives are known with mass ranges from 20 to 34. Of these 3 are stable, ²⁴Mg, ²⁵Mg and ²⁶Mg. Isotope ²⁴Mg is the most abundant (79%).

References
1. Joseph Black, Experiments upon Magnesia Alba, Quick-Lime, and some other Alkaline Substances (1756)
2. Mark A. Shand, The Chemistry and Technology of Magnesia., (2006) p2. Wiley-Interscience.
3. Nancy E. Bernhardt, Artur M. Kasko, Nutrition for the Middle Aged and Elderly., (2008) p333. Nova Science Publishers