Definitions

covering power

Barium

[bair-ee-uhm, bar-]
Barium 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.

Characteristics

Barium is a metallic element that is chemically similar to calcium and strontium, 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:

History

Barium (Greek bary, 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 crystallized barium sulfate. 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

BaSO4 + 2CBaS + 2CO2

The barium sulfide is then hydrolyzed or reacted 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) Isolation (* follow):

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

Compounds

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

Isotopes

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 taken orally because it is highly insoluble in water, and is eliminated completely from the digestive tract. Unlike other heavy metals, barium does not bioaccumulate. However, inhaled dust containing barium compounds can accumulate in the lungs, causing 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

External links

Search another word or see covering poweron Dictionary | Thesaurus |Spanish
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature
FAVORITES
RECENT

;