1. <astronomy> The first planet in order from the sun. It has no known natural satellites. It is one of the four inner or terrestrial planets of the solar system. It is the planet nearest the sun, from which its mean distance is about 36,000,000 miles. Its period is 88 days, and its diameter 3,000 miles.

2. <chemistry> A metallic element mostly obtained by reduction from cinnabar, one of its ores. It is a heavy, opaque, glistening liquid (commonly called quicksilver), and is used in barometers, thermometers, ect. Specific gravity 13.6. Symbol Hg (Hydrargyrum). Atomic weight 199.8. Mercury has a molecule which consists of only one atom. It was named by the alchemists after the god Mercury, and designated by his symbol, <su:mercury/.

Mercury forms alloys, called amalgams, with many metals, and is thus used in applying tin foil to the backs of mirrors, and in extracting gold and silver from their ores. It is poisonous, and is used in medicine in the free state as in blue pill, and in its compounds as calomel, corrosive sublimate, etc. It is the only metal which is liquid at ordinary temperatures, and it solidifies at about -39 deg Centigrade to a soft, malleable, ductile metal.

3. Sprightly or mercurial quality; spirit; mutability; fickleness. "He was so full of mercury that he could not fix long in any friendship, or to any design." (Bp. Burnet)

6. <botany> A plant (Mercurialis annua), of the Spurge family, the leaves of which are sometimes used for spinach, in Europe. The name is also applied, in the United States, to certain climbing plants, some of which are poisonous to the skin, especially. To the Rhus Toxicodendron, or poison ivy.

Origin: L. Mercurius; akin to merx wares.

(25 Jun 1999)