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mercury

Heavy, silver-grey, metallic element, atomic number 80, relative atomic mass 200.59. Its symbol comes from the Latin hydrargyrum, derived from the Greek words for water and silver. It is a dense, mobile liquid with a low melting point (−38.87°C/−37.96°F). Its chief source is the mineral cinnabar, HgS, but it sometimes occurs in nature as a free metal.

Uses

Its alloys with other metals are called amalgams (a silver-mercury amalgam is used in dentistry for filling cavities in teeth). Industrial uses include drugs and chemicals, mercury-vapour lamps, arc rectifiers, power-control switches, barometers, and thermometers.

Hazards

Mercury is a cumulative poison that can contaminate the food chain, and cause intestinal disturbance, kidney and brain damage, and birth defects in humans. Where liquid mercury is handled, vapours are also a health risk. The World Health Organization's ‘safe’ limit for mercury is 0.5 milligrams of mercury per kilogram of muscle tissue. The US Environmental Protection Agency recommended a maximum safe level for mercury of 0.1 mg per kilogram of body weight in January 1998 (a fifth of that recommended by WHO).The discharge into the sea by industry of organic mercury compounds such as dimethylmercury was the chief cause of mercury poisoning in the latter half of the 20th century.

Between 1953 and 1975, 684 people in the Japanese fishing village of Minamata were poisoned (115 fatally) by organic mercury wastes that had been dumped into the bay and had accumulated in the bodies of fish and shellfish.

History

The element was known to the ancient Chinese and Hindus, and is found in Egyptian tombs of about 1500 BC. It was named by the alchemists after the fast-moving god, for its fluidity.

Use in mining Mercury forms an amalgam with gold and so is used in gold mining to extract gold from low-grade deposits. Each year 250-300 tonnes are used in the Amazon basin alone. In 1990 mercury concentrations in edible fish close to the mining sites were ten times greater than the WHO recommended limits for human consumption.

Mercury

Nickname of Joseph Haydn's symphony no. 43, in E flat major, composed c. 1771.

amalgam atmospheric pressure

barometer Fortin, Jean Nicolas

Mercury (astronomy) Mercury Prize

Mercury project Schirra, Walter (Marty)

Torricelli, Evangelista