Dictionary:

barium

  (bâr'ē-əm, băr'-)

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.]

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.

For the manufacture of barium compounds, soft (easily crushable) barite is preferred, but crystalline varieties may be used. Crude barite is crushed and then mixed with pulverized coal. The mixture is roasted in a rotary reduction furnace, and the barium sulfate is thus reduced to barium sulfide or black ash. Black ash is roughly 70% barium sulfide and is treated with hot water to make a solution used as the starting material for the manufacture of many compounds.

Lithopone, a white powder consisting of 20% barium sulfate, 30% zinc sulfide, and less than 3% zinc oxide, is widely used as a pigment in white paints. Blanc fixe is used in the manufacture of brilliant coloring compounds. It is the best grade of barium sulfate for paint pigments. Because of the large absorption of x-rays by barium, the sulfate is used to coat the alimentary tract for x-ray photographs in order to increase the contrast. Barium carbonate is useful in the ceramic industry to prevent efflorescence on claywares. It is used also as a pottery glaze, in optical glass, and in rat poisons. Barium chloride is used in purifying salt brines, in chlorine and sodium hydroxide manufacture, as a flux for magnesium alloys, as a water softener in boiler compounds, and in medicinal preparations. Barium nitrate, or the so-called baryta saltpeter, finds use in pyrotechnics and signal flares (to produce a green color), and to a small extent in medicinal preparations. Barium oxide, known as baryta or calcined baryta, finds use both as an industrial drying agent and in the case-hardening of steels. Barium peroxide is sometimes used as a bleaching agent. Barium chromate, lemon chrome or chrome yellow, is used in yellow pigments and safety matches. Barium chlorate finds use in the manufacture of pyrotechnics. Barium acetate and cyanide are used industrially as a chemical reagent and in metallurgy, respectively.

A metal of no known metabolic function, and hence not a dietary essential. Barium sulphate is opaque to X-rays and a suspension is used (a barium meal) to allow examination of the shape and movements of the stomach for diagnostic purposes, and as a barium enema for X-ray investigation of the lower intestinal tract.

A pale yellow, metallic element classified with the alkaline earths.

For more information on barium, visit Britannica.com.

A chemical element, atomic number 56, atomic weight 137.34, symbol Ba. Soluble salts, e.g. the chloride and the carbonate, are toxic.

• b. burger, barium meal — a mixture of barium and solid food, used as a contrast medium in radiographic studies of the esophagus, instead of liquid barium mixtures.
• b. chloride — used as a rodenticide. The baits are attractive to dogs. Clinical signs include salivation, convulsions and paralysis.
• b. deficiency — preliminary experiments showing that diets deficient in barium fed to rats and guinea pigs depress growth have been neither invalidated nor confirmed.
• b. enema — a dilute (5 to 20%) suspension of barium is introduced into a colon that has been emptied by starvation and previous enema.

  Barium enema. By permission from Ettinger SJ, Feldman E, Textbook of Veterinary Internal Medicine, Saunders, 2004

• b.-impregnated polyethylene spheres (BIPS) — radio-opaque markers used to demonstrate intestinal obstruction and motility disorders; the spheres are given orally and their movement can be tracked radiographically.
• b. meal — a strong (usually 100%) suspension of barium sulfate is administered to an animal which has been starved for at least 12 hours.
• b. study — x-ray examination using a barium mixture to help locate disorders in the esophagus, stomach, duodenum, and the small and large intestines. Called also barium test.
• b. sulfate — a water-insoluble salt used as an opaque contrast medium for x-ray examination of the digestive tract.
• b. swallow — a small amount of barium paste or liquid administered orally and observed radiographically or by fluoroscopy for examination of swallowing and esophageal function.
• b. test — barium study.

56 caesium ← barium → lanthanum Sr ↑ Ba ↓ Ra Periodic Table - Extended Periodic Table
General
Name, Symbol, Number	barium, Ba, 56
Chemical series	alkaline earth metals
Group, Period, Block	2, 6, s
Appearance	silvery white
Standard atomic weight	137.327(7)  g·mol−1
Electron configuration	[Xe] 6s2
Electrons per shell	2, 8, 18, 18, 8, 2
Physical properties
Phase	solid
Density (near r.t.)	3.51  g·cm−3
Liquid density at m.p.	3.338  g·cm−3
Melting point	1000 K (727 °C, 1341 °F)
Boiling point	2170 K (1897 °C, 3447 °F)
Heat of fusion	7.12  kJ·mol−1
Heat of vaporization	140.3  kJ·mol−1
Heat capacity	(25 °C) 28.07  J·mol−1·K−1
Vapor pressure P(Pa) 1 10 100 1 k 10 k 100 k at T(K) 911 1038 1185 1388 1686 2170
Atomic properties
Crystal structure	cubic body centered
Oxidation states	2 (strongly basic oxide)
Electronegativity	0.89 (scale Pauling)
Ionization energies	1st: 502.9 kJ/mol
	2nd: 965.2 kJ/mol
	3rd: 3600 kJ/mol
Atomic radius	215  pm
Atomic radius (calc.)	253  pm
Covalent radius	198  pm
Miscellaneous
Magnetic ordering	paramagnetic
Electrical resistivity	(20 °C) 332 n Ω·m
Thermal conductivity	(300 K) 18.4  W·m−1·K−1
Thermal expansion	(25 °C) 20.6  µm·m−1·K−1
Speed of sound (thin rod)	(20 °C) 1620 m/s
Young's modulus	13  GPa
Shear modulus	4.9  GPa
Bulk modulus	9.6  GPa
Mohs hardness	1.25
CAS registry number	7440-39-3
Selected isotopes
Main article: Isotopes of barium iso NA half-life DM DE (MeV) DP 130Ba 0.106% Ba is stable with 74 neutrons 132Ba 0.101% Ba is stable with 76 neutrons 133Ba syn 10.51 y ε 0.517 133Cs 134Ba 2.417% Ba is stable with 78 neutrons 135Ba 6.592% Ba is stable with 79 neutrons 136Ba 7.854% Ba is stable with 80 neutrons 137Ba 11.23% Ba is stable with 81 neutrons 138Ba 71.7% Ba is stable with 82 neutrons
References

Barium (IPA: /ˈbɛːɹiəm/) is a chemical element. It has the symbol Ba, and atomic number 56. Barium is a soft silvery metallic alkaline earth metal. It is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with water and carbon dioxide and is not found as a mineral. The most common naturally occurring minerals are the very insoluble barium sulfate, BaSO₄ (barite), and barium carbonate, BaCO₃ (witherite). Benitoite is a rare gem containing barium.

Notable characteristics

Barium is a metallic element that is chemically similar to calcium but more reactive. This metal oxidizes very easily when exposed to air and is highly reactive with water or alcohol, producing hydrogen gas. Burning in air or oxygen produces not just barium oxide (BaO) but also the peroxide. Simple compounds of this heavy element are notable for their high specific gravity. This is true of the most common barium-bearing mineral, its sulfate barite BaSO₄, also called 'heavy spar' due to the high density (4.5 g/cm³).

Applications

Barium has some medical and many industrial uses:

• Barium compounds, and especially barite (BaSO₄), are extremely important to the petroleum industry. Barite is used in drilling mud, a weighting agent in drilling new oil wells.
• Barium sulfate is radioopaque (x-ray absorbant), used in X-ray diagnostic work for obtaining images of the digestive system ("barium meals" and "barium enemas").
• Barium carbonate is a useful rat poison and can also be used in making bricks. Unlike the sulfate, the carbonate dissolves in stomach acid, allowing it to be poisonous.
• An alloy with nickel is used in spark plug wire.
• Barium oxide is used in a coating for the electrodes of fluorescent lamps, which facilitates the release of electrons.
• The metal is a "getter" in vacuum tubes, to remove the last traces of oxygen.
• Barium carbonate is used in glassmaking. Being a heavy element, barium increases the refractive index and luster of the glass.
• Barite is used extensively in rubber production.
• Barium nitrate and chlorate give green colors in fireworks.
• Impure barium sulfide phosphoresces after exposure to the light.
• Lithopone, a pigment that contains barium sulfate and zinc sulfide, is a permanent white that has good covering power, and does not darken in when exposed to sulfides.
• Barium peroxide can be used as a catalyst to start an aluminothermic reaction when welding rail tracks together. It can also be used in green tracer ammunition.
• Barium titanate was proposed in 2007[1] to be used in next generation battery technology for electric cars.
• Barium Fluoride is used in infrared applications.
• Barium is a key element in YBCO superconductors.

History

Barium (Greek "barys" meaning "heavy") was first identified in 1774 by Carl Scheele and extracted in 1808 by Sir Humphry Davy in England. The oxide was at first called barote, by Guyton de Morveau, which was changed by Antoine Lavoisier to baryta, from which "barium" was derived to describe the metal.

Occurrence

Because barium quickly becomes oxidized in air, it is difficult to obtain this metal in its pure form. It is primarily found in and extracted from the mineral barite which is crystalized barium sulfate. Barium is commercially produced through the electrolysis of molten barium chloride (BaCl₂) Isolation (* follow):

(cathode) Ba²⁺* + 2e^- → Ba (anode) Cl^-* → ½Cl₂ (g) + e^-

See also barium minerals.

Compounds

The most important compounds are barium peroxide, barium chloride, sulfate, carbonate, nitrate, and chlorate.

See also barium compounds.

Isotopes

Main article: isotopes of barium

Naturally occurring barium is a mix of seven stable isotopes. There are twenty-two isotopes known, but most of these are highly radioactive and have half-lives in the several millisecond to several minute range. The only notable exceptions are ¹³³Ba which has a half-life of 10.51 years, and ^137mBa (2.55 minutes).

Precautions

All water or acid soluble barium compounds are extremely poisonous. At low doses, barium acts as a muscle stimulant, while higher doses affect the nervous system, causing cardiac irregularities, tremors, weakness, anxiety, dyspnea and paralysis. This may be due to its ability to block potassium ion channels which are critical to the proper function of the nervous system.

Barium sulfate can be used in medicine only because it does not dissolve, and is eliminated completely from the digestive tract. Unlike other heavy metals, barium does not bioaccumulate.^[1] However, inhaled barium dust can accumulate in the lungs, a benign condition called baritosis.

Oxidation occurs very easily and, to remain pure, barium should be kept under a petroleum-based fluid (such as kerosene) or other suitable oxygen-free liquids that exclude air.

Barium acetate could lead to death in high doses. Marie Robards poisoned her father with the substance in Texas in 1993. She was tried and convicted in 1996.

References

1. ^ http://www.epa.gov/region5/superfund/ecology/html/toxprofiles.htm#ba

External links

Wikimedia Commons has media related to:

Barium

• WebElements.com – Barium
• Elementymology & Elements Multidict

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - barium

Nederlands (Dutch)
barium(sulfaat)

Français (French)
n. - baryum, (Méd) sulfate de baryum

Deutsch (German)
n. - (chem.) Barium

Ελληνική (Greek)
n. - βάριο

Italiano (Italian)
bario

Português (Portuguese)
n. - bário (m) (Quím.)

Русский (Russian)
барий

Español (Spanish)
n. - bario

Svenska (Swedish)
n. - barium

中文（简体） (Chinese (Simplified))
钡

中文（繁體） (Chinese (Traditional))
n. - 鋇

한국어 (Korean)
n. - 바륨(금속원소의 하나)

日本語 (Japanese)
n. - バリウム

العربيه (Arabic)
‏(الاسم) مادة الباريوم‏

עברית (Hebrew)
n. - ‮בריום (מתכת)‬

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