is a silver-colored metal that is actually liquid at room temperature. In fact, it flows so easily and rapidly that it is sometimes called quicksilver. No one knows who discovered mercury, but the ancient Chinese, Egyptians, Greeks, Hindus, and Romans knew about the metal. It was named for the swift messenger of the gods in Roman mythology. Its chemical symbol comes from hydrargyrum, which is Latin for liquid silver.

Chemical Properties

Mercury is one of the Third Transition Metals. Its atomic weight is 200.59 and its atomic number is 80. It melts at -37.97º F. (-38.87º C) and boils at 673.84º F. (356.58º C).

Sources

Most of the mercury used today comes from an ore called cinnabar. To obtain pure mercury, refiners heat cinnabar in a flow of air. Oxygen in the air combines with sulfur in the ore, forming sulfur dioxide gas and leaving mercury behind.

Spain is one of the world's leading producers of mercury. Large deposits of cinnabar also occur in Chile, China, the Czech Republic, Iran, Italy, Japan, Mexico, Peru, the Philippines, Russia, Turkey, and the United States. Alaska, California, and Nevada have the largest cinnabar deposits in the United States.

Uses

Mercury has many properties that make it useful. For example, it expands and contracts evenly when heated or cooled. It also remains liquid over a wide range of temperatures. Mercury thermometers use these properties to indicate temperature.

Mercury conducts electricity and is used in some electric switches and relays to make them operate silently and efficiently. Industrial chemical manufacturers use mercury in electrolysis cells to change substances with electricity. Mercury vapor, used in flourescent lamps, gives off light when electricity passes through it.

Various alloys containing mercury have many uses. Mercury alloys are called amalgams. They include silver amalgam, which was once commonly used to fill cavities in teeth. Many dry cell batteries contain amalgams of zinc and cadmium to prevent impurities from shortening the life of the battery.

Compounds

Chemists divide mercury compounds into two groups -- mercurous or mercury (I) and mercuric or mercury (II).

Mercurous compounds include mercurous chloride, also called calomel, and mercurous sulfate. Calomel is an antiseptic used to kill bacteria. Mercurous sulfate is used to speed up certain tests on organic compounds.

Mercuric compounds include mercuric chloride, a powerful poison that surgeons once used to disinfect wounds. Most ammunition uses mercuric fulminate to set off its explosive. Paint manufacturers use mercuric sulfide in making a red pigment called vermilion. Mercury batteries contain mercuric oxide.

Several organic mercuric compounds have important medical uses. Some medicines called diuretics, which are used to treat kidney disease, contain such compounds. The antiseptic Mercurochrome is also a mercuric compound.

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