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Out of the oceans and on to faster bicycles

Molecule of the month: magnesium: John Emsley examines new benefits of the metal that helps to make our planet green

In a recent edition of The Lancet Dr Mike Campbell of Southampton University suggested magnesium as a treatment for chronic fatigue syndrome, also known as ME or myalgic encephalomyelitis. In a test lasting six weeks, 15 patients were given injections of a gram of magnesium sulphate while 17 others were given onty distilled water. Twelve of the 15 on magnesium responded positively, compared with only three of the 17 on water. Patients on magnesium therapy reported having more energy, feeling betler and coping more easily with pain.

The research is being followed up to see if those trealed continue to improve. Liz Morris, Dr Campbell's research student, has been checking the original patients, and those given the placebo injections. Most of the latter opted for a course of magnesium when the original trials were over.

Magnesium is an essential element for all living things. It is at the heart of the chlorophyll molecule that plants need to trap the sun's energy to make sugar and starch molecules. Our planet is green because magnesium-chlorophyll abstracts the blue and red of sunlight and reflects the green. Plants take their magnesium from the soil, and we take our magnesium directly from plants or indirectly by eating animals that feed on them.

Our daily intake is between a third and half a gram (about one-fiftieth of an ounce). Adults have 25 grams (nearly an ounce) spread throughout their body, with most in their bones which act as a store for magnesium. The metal has three functions: it regulates movement through membranes; it is part of the enzymes that release energy from our food; and it is needed for building proteins. We rarely need to worry about getting enough magnesium, but a deficiency manifests itself as lethargy, irritation, depression and even personality changes.

A normal diet provides enough magnesium, although spirits, soft drinks, sugar and fats contain virlually nőne. Magnesium is not easily absorbed by our bodies and too much acts as a mild laxative, as we discover when we take Epsom salts (magnesium sulphate) or Milk of Magnesia (magnesium hydroxide). Rhubarb and spinach prevent magnesium being absorbed because the oxalic acid they contain forms a compound with it which we cannot absorb. Cooking does not affect magnesium, although if you throw away the water in which greens are boiled you discard more than half their magnesium.

The rising popularity of certain Yorkshire bitters will also boost the magnesium intake of those who drink it. Dr Tom Coultate, of the South Bank Polytechnic in London, comments in his book Food that Webster's Yorkshire Bitter may owe some of its unique taste to the high levels of magnesium sulphate in the water used to brew it. Magnesium salts taste bitter.

Magnesium is the fourth most abundant metal on earth, and there are vast deposits of ores such as dolomite (magnesium calcium carbonate) and carnallite (magnesium calcium chloride). Magnesium salts are leached from the land by rivers and carried to the sea where they remain soluble. This explains why there is 0.12 per cent magnesium in seawater; the oceans hold a trillion trillion tons of it. Production now exeeeds 300,000 tons, about half coming from the sea.

The Norwegian company Norsk Hydro extracts magnesium from seawater. According to Charles Duff, the company's UK corporate development manager, most magnesium is used in steel refining to remove sulphur, and to strengthen aluminium, but there is an expanding market for magnesium metal itself. Although it is remembered for its historical role in incendiary bombs and flash bulbs, it does not burn as a bulk metal and magnesium tubes and rods can be welded.

Cyclists are among the first to benefit from this new trend. Last year Phil Anderson, the leader of the Dutch cycle team, rode bicycles with pure magnesium frames in the Tour de France and other racex. Frank Kirk, the frame's designer, believes that magnesium gives a better combination of strength and lightness than other metals. A steel frame is nearly five times heavier than a magnesium one, and even aluminium is one and a half times as heavy.

Mr Kirk has shown that if the complete frame is cast as a single component from molten magnesium this avoids welded joints while maximising lightness and strength. His firm, Kirk Precision of Chelmsford, has the world's largest pressure die-casting machine for magnesium components, capable of producing 250,000 cycle frames a year. These are being made for Japanese Muddy Fox mountain bikes and the UK the cycle maker Dawes.

Magnesium is already used for luggage frames, disc drives and camera parts, where lightness is important. By the end of the century, production of this versatile metal is expected to exceed 500,000 tons a year as car makers discover the environmental benefits of magnesium for lighter and longer-lasting vehicles. Mercedes already uses it for seat frames and Porsche for wheels. Reducing the weight of a car not only cuts the amount of fuel it consumes, it alsa rcduces its power to kill in road accidents. And at the end of the vehicle's life, the magnesium can be recycled at little cost.

John Emsley is science writer in residence at the Chemistry Department of Imperial College London and author of 'The Elements'.

(The Independent, 29.4.91.)

 

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