Alkali Metal Barium

barium

Dictionary: bar·i·um (bâr'ē-əm, băr'-)

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n. (Symbol Ba)
A soft, silvery-white alkaline-earth metal, used to deoxidize copper and in various alloys. Atomic number 56; atomic weight 137.33; melting point 725°C; boiling point 1,140°C; specific gravity 3.50; valence 2.

[BAR(YTA) + -IUM.]

baric bar'ic (-ĭk) adj.

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Britannica Concise Encyclopedia: barium

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barium

Chemical element, one of the alkaline earth metals, chemical symbol Ba, atomic number 56. It is very reactive and in compounds always has valence 2. In nature it is found chiefly as the minerals barite (barium sulfate) and witherite (barium carbonate). The element is used in metallurgy, and its compounds are used in fireworks, petroleum mining, and radiology and as pigments and reagents. All soluble barium compounds are toxic. Barium sulfate, one of the most insoluble salts known, is given in a "barium meal" as a contrast medium for X-ray examination of the gastrointestinal tract.

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Sci-Tech Encyclopedia: Barium

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A chemical element, Ba, with atomic number 56 and atomic weight of 137.34. Barium is eighteenth in abundance in the Earth's crust, where it is found to the extent of 0.04%, making it intermediate in amount between calcium and strontium, the other alkaline-earth metals. Barium compounds are obtained from the mining and conversion of two barium minerals. Barite, barium sulfate, is the principal ore and contains 65.79% barium oxide. Witherite, sometimes called heavy spar, is barium carbonate and is 72% barium oxide. See also Periodic table.

The metal was first isolated by Sir Humphry Davy in 1808 by electrolysis. Industrially, only small amounts are prepared by aluminum reduction of barium oxide in large retorts. These are used in barium-nickel alloys for spark-plug wire (the barium increases the emissivity of the alloy) and in frary metal, which is an alloy of lead, barium, and calcium used in place of babbitt metal because it can be cast.

The metal reacts with water more readily than do strontium and calcium, but less readily than sodium; it oxidizes quickly in air to form a surface film that inhibits further reaction, but in moist air it may inflame. The metal is sufficiently active chemically to react with most nonmetals. Freshly cut pieces have a lustrous gray-white appearance, and the metal is both ductile and malleable. The physical properties of the elementary form are given in the table.