Magnesium

Category: alkaline earth metal Atomic number: 12 Colour: silvery white Melting point: 650°C (1,202°F) Boiling point: 1,090°C (1,994°F) First identified: 1755

Magnesium is the lightest metal that we can easily and safely use – lithium and sodium are both highly reactive, while beryllium is too toxic to be used without extreme precautions. It burns extremely brightly when ignited in air; a common science experiment in schools is to demonstrate this in the classroom, by lighting a ribbon of the metal.

Another element that is crucial for living organisms, magnesium plays an especially important role in photosynthesis as part of chlorophyll, the green plant pigment that does this job. You can spot a magnesium deficiency when plant leaves turn yellowy brown or develop unexpected dark red spots; the solution may be a leaf spray or the addition of calcium-magnesium carbonate to the soil.

Medicinal Magnesium

Epsom salts, which have been used since the seventeenth century to treat constipation, were discovered by a farmer who investigated why his cows (in Epsom in England) were ignoring a particular puddle during a drought; the puddle turned out to contain bitter-tasting crystals of magnesium sulphate, and the discovery inspired the medicine. Some readers will also be familiar with Milk of Magnesia, a suspension of magnesium oxide in water, used to treat indigestion and as a laxative.

We ingest magnesium from plants or other animals – especially from bran, chocolate, Brazil nuts, soya beans and almonds: it supports a range of bodily functions, including nerve and muscle functions, the regulation of blood sugar, and protein synthesis in the body. Some gastrointestinal diseases lead to magnesium deficiency, which can cause lethargy, depression and other more severe symptoms. It is also possible that a deficiency plays a role in Chronic Fatigue Syndrome (CFS)/myalgic encephalomyelitis (ME).

Joseph Black of Edinburgh recognized magnesium must be an element in 1755, following a careful comparison of magnesia (magnesium oxide) and lime (calcium oxide) extracted from the carbonate rocks, magnesite and limestone respectively. Humphry Davy isolated a tiny, pure amount of the metal in 1808 through the electrolysis of magnesium oxide.

Historically, magnesium was used to make meerschaum pipes (in the form of magnesium silicate), and its fierce flames were exploited in early flashlight bulbs and in the Second World War’s terrifying magnesium bombs, which could cause huge conflagrations and firestorms – it is hard to ignite solid magnesium, so these bombs required a thermite reaction to ignite them. Happily, there are some more positive uses. The metal can safely be used, especially in alloys with aluminium and other light metals, to reduce the weight of metal components in cars and aeroplanes. It is also being used to create lightweight mobile phones and laptop computers.