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barium

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

Properties of barium

Property

Value

Atomic number

56

Atomic weight

137.34

Isotopes (stable)

130, 132, 134, 135, 136, 137, 138

Atomic volume

36.2 cm3/g-atom

Crystal structure

Face-centered cubic

Electron configuration

2 8 18 18 8 2

Valence

2+

Ionic radius (A)

1.35

Boiling point, °C

1140(?)

Melting point, °C

850(?)

Density

3.75 g/cm3 at 20°C

Latent heat of vaporization at boiling point, kj/g-atom

374

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.


 
Food and Nutrition: barium
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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.

 
Dental Dictionary: barium
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(ber′ē-əm)
n
Ba

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

 

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.

For more information on barium, visit Britannica.com.

 
barium (bâr'ēəm) [Gr.,=heavy], metallic chemical element; symbol Ba; at. no. 56; at. wt. 137.33; m.p. 725°C; b.p. 1,640°C; sp. gr. 3.5 at 20°C; valence +2. Barium is a soft, silver-white, chemically active, poisonous metal with a face-centered cubic crystalline structure. It is an alkaline-earth metal in Group 2 of the periodic table. Its principal ore is barite (barium sulfate); it also occurs in the mineral witherite (barium carbonate). The pure metal is obtained by the electrolysis of fused barium salts or, industrially, by the reduction of barium oxide with aluminum. Barium is often used in barium-nickel alloys for spark-plug electrodes and in vacuum tubes as a drying and oxygen-removing agent. Barium oxidizes in air, and it reacts vigorously with water to form the hydroxide, liberating hydrogen. In moist air it may spontaneously ignite. It burns in air to form the peroxide, which produces hydrogen peroxide when treated with water. Barium reacts with almost all of the nonmetals; all of its water-soluble and acid-soluble compounds are poisonous. Barium carbonate is used in glass, as a pottery glaze, and as a rat poison. Chrome yellow (barium chromate) is used as a paint pigment and in safety matches. The chlorate and nitrate are used in pyrotechnics to provide a green color. Barium oxide strongly absorbs carbon dioxide and water; it is used as a drying agent. Barium chloride is used in medicinal preparations and as a water softener. Barium sulfide phosphoresces after exposure to light; it is sometimes used as a paint pigment. Barite, the sulfate ore, has many industrial uses. Because barium sulfate is virtually insoluble in water and acids, it can be used to coat the alimentary tract to increase the contrast for X-ray photography without being absorbed by the body and poisoning the subject. Barium salts give a characteristic green color in the flame test. Barium metal was first isolated in 1808 by Sir Humphry Davy by electrolysis.


 

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.
 
Wikipedia: Barium
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56 caesiumbariumlanthanum
Sr

Ba

Ra
Barium in the periodic table of the elements
General
Name, symbol, number barium, Ba, 56
Element category alkaline earth metals
Group, period, block 26, s
Appearance silvery white
Standard atomic weight 137.33g·mol−1
Electron configuration [Xe] 6s2
Electrons per shell 2, 8, 18, 18, 8, 2 (Image)
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
Specific 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 body centered cubic
Oxidation states 2
(strongly basic oxide)
Electronegativity 0.89 (Pauling scale)
Ionization energies 1st: 502.9 kJ·mol−1
2nd: 965.2 kJ·mol−1
3rd: 3600 kJ·mol−1
Atomic radius 222 pm
Covalent radius 215±11 pm
Miscellaneous
Magnetic ordering paramagnetic
Electrical resistivity (20 °C) 332 nΩ·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
Most stable isotopes
Main article: Isotopes of barium
iso NA half-life DM DE (MeV) DP
130Ba 0.106% 130Ba is stable with 74 neutrons
132Ba 0.101% 132Ba is stable with 76 neutrons
133Ba syn 10.51 y ε 0.517 133Cs
134Ba 2.417% 134Ba is stable with 78 neutrons
135Ba 6.592% 135Ba is stable with 79 neutrons
136Ba 7.854% 136Ba is stable with 80 neutrons
137Ba 11.23% 137Ba is stable with 81 neutrons
138Ba 71.7% 138Ba is stable with 82 neutrons
References

Barium (pronounced /ˈbæriəm/) 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.

Metallic barium has few industrial uses, but has been historically used to scavenge air in electronic vacuum tubes. Barium compounds impart a green color to flames and have been used in fireworks. Barium sulfate is used for its heaviness, insolubility, and X-ray opacity. It is used as an insoluble heavy mud-like paste when drilling oil wells, and in purer form, as an X-ray radiocontrast agent for imaging the human gastrointestinal tract. Soluble barium compounds are poisonous due to release of the soluble barium ion, and have been used as rodenticides. New uses for barium continue to be found: it is an essential ingredient in "high temperature" YBCO superconductors.

Contents

Characteristics

Physical

Barium is a soft and ductile metal. Its simple compounds are notable for their relatively high (for an alkaline earth element) 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).

Chemical

Barium reacts exothermically with oxygen at room temperature to form barium oxide and peroxide. The reaction is violent if barium is powdered. It also reacts violently with dilute acids, alcohol and water

Ba + 2 H2O → Ba(OH)2 + H2 (g)

At elevated temperatures, barium combines with chlorine, nitrogen and hydrogen to produce BaCl2, Ba3N2 and BaH2, respectively. Barium reduces oxides, chlorides and sulfides of less reactive metals. For example:

Ba + CdO → BaO + Cd
Ba + ZnCl2 → BaCl2 + Zn
3 Ba + Al2S3 → 3 BaS + 2 Al

When heated with nitrogen and carbon, it forms the cyanide:

Ba + N2 + 2 C → Ba(CN)2

Barium combines with several metals, including aluminium, zinc, led and tin, forming intermetallic compounds and alloys.[1]

Isotopes

Naturally occurring barium is a mix of seven stable isotopes, the most abundant being 138Ba (71.7 %). There are twenty-two isotopes known, but most of these are highly radioactive and have half-lives in the several millisecond to several day range. The only notable exceptions are 133Ba which has a half-life of 10.51 years, and 137mBa (2.55 minutes).[2]

History

Name barium originates from Greek bary, meaning "heavy". Alchemists in the early Middle Ages knew about some barium minerals. Smooth pebble-like stones of mineral barite found in Bologna, Italy were known as "Bologna stones". After exposed to light they would glow for years that attracted them to witches and alchemists.[3]

Carl Scheele identified barite in 1774, but did not isolate barium. Barium was isolated, as ions in solution, in 1808 by Sir Humphry Davy in England. The oxidized barium 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.[3]

Occurrence and production

Barite
Trend in world production of barite

The abundance of barium is 0.0425 % in the Earth's crust and 13 µg/L in sea water. It occurs in the minerals barite (as the sulfate) and witherite (as the carbonate).[1] Large deposits of barite are found in China, Germany, India, Morocco, and in the US.[4]

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 barite. Because barite is so insoluble, it cannot be used directly for the preparation of other barium compounds. Instead, the ore is heated with carbon to reduce it to barium sulfide:[5]

BaSO4 + 2 C → BaS + 2 CO2

The barium sulfide is then hydrolyzed or treated with acids to form other barium compounds, such as the chloride, nitrate, and carbonate.

Barium is commercially produced through the electrolysis of molten barium chloride (BaCl2):

(cathode) Ba2+ + 2 e → Ba
(anode) 2 Cl → Cl2 (g) + 2 e

Barium metal is also obtained by the reduction of barium oxide with finely divided aluminum at temperatures between 1100 and 1200 °C:

4 BaO + 2 Al → BaO·Al2O3 + 3 Ba (g)

The barium vapor is cooled by means of a water jacket and condensed into the solid metal. The solid block may be cast into rods or extruded into wires. Being a flammable solid, it is packaged under argon in steel containers or plastic bags. [1]

Applications

Amoebiasis as seen in radiograph of barium-filled colon
Green barium fireworks

The most important use of elemental barium is as a scavenger removing last traces of oxygen and other gases in television and other electronic tubes. Besides, an isotope of barium, 133Ba, is routinely used as a standard source in the calibration of gamma-ray detectors in nuclear physics studies.[1]

Barium is an important component of YBCO superconductors. An alloy of barium 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.

Barium compounds, and especially barite (BaSO4), are extremely important to the petroleum industry. Besides,

Precautions

Barium powder is pyrophoric - it can explode in contact with air or oxidizing gases. it is likely to explode when combined with halogenated hydrocarbon solvents. It reacts violently with water. 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.[1]

Barium sulfate can be taken orally because it is highly insoluble in water, and is eliminated completely from the digestive tract.[1] Unlike other heavy metals, barium does not bioaccumulate.[11][12] However, inhaled dust containing barium compounds can accumulate in the lungs, causing a benign condition called baritosis.[13]

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.[14]

References

  1. ^ a b c d e f Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. pp. 77–78. ISBN 0070494398. http://books.google.com/books?id=Xqj-TTzkvTEC&pg=PA243. Retrieved on 2009-06-06. 
  2. ^ David R. Lide, Norman E. Holden (2005). "Section 11, Table of the Isotopes". CRC Handbook of Chemistry and Physics, 85th Edition. Boca Raton, Florida: CRC Press. 
  3. ^ a b Robert E. Krebs (2006). The history and use of our earth's chemical elements: a reference guide. Greenwood Publishing Group. p. 80. ISBN 0313334382. http://books.google.com/books?id=yb9xTj72vNAC&. 
  4. ^ a b c d C. R. Hammond (2000). The Elements, in Handbook of Chemistry and Physics 81th edition. CRC press. ISBN 0849304814. 
  5. ^ "Toxicological Profile for Barium and Barium Compounds. Agency for Toxic Substances and Disease Registry". CDC. 2007.. http://www.atsdr.cdc.gov/toxprofiles/tp24.pdf. 
  6. ^ Chris J. Jones, John Thornback (2007). Medicinal applications of coordination chemistry. Royal Society of Chemistry. p. 102. ISBN 0854045961. http://books.google.co.jp/books?id=uEJHsZWyO-EC&. 
  7. ^ Michael S. Russell, Kurt Svrcula (2008). Chemistry of Fireworks. Royal Society of Chemistry. p. 110. ISBN 0854041273. http://books.google.co.jp/books?id=yxRyOf8jFeQC&. 
  8. ^ Brent, G. F. (1995). "Surfactant coatings for the stabilization of barium peroxide and lead dioxide in pyrotechnic compositions". Propellants Explosives Pyrotechnics 20: 300. doi:10.1002/prep.19950200604. 
  9. ^ "Battery Breakthrough?". http://www.technologyreview.com/Biztech/18086/. Retrieved on 2009-06-06. 
  10. ^ "Crystran Ltd. Optical Component Materials". http://www.crystran.co.uk/products.asp?productid=75. Retrieved on 2009-06-06. 
  11. ^ "Toxicity Profiles, Ecological Risk Assessment". http://www.epa.gov/region5/superfund/ecology/html/toxprofiles.htm#ba. Retrieved on 2009-06-06. 
  12. ^ Moore, J. W. (1991). Inorganic Contaminants of Surface Waters, Research and Monitoring Priorities. New York: Springer-Verlag. 
  13. ^ Doig AT (February 1976). "Baritosis: a benign pneumoconiosis". Thorax 31 (1): 30–9. doi:10.1136/thx.31.1.30. PMID 1257935. 
  14. ^ "Boyfriend fight preceded Roanoke mom's slaying". http://www.buffalo.edu/news/pdf/October08/DallanMorningNewsEwingSlaying.pdf. Retrieved on 2009-06-06. 

External links


 
Translations: Barium
Top

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))

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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