Chemical Fact Sheet


Chemical Abstract Number (CAS #) 7440-39-3
Synonyms Bario-(Spanish);Baryum-(French)
Analytical Methods 200.7 - 200.8 - 6010 - 6020
Atomic Symbol Ba

Synopsis from the CRC Handbook of Chemistry and Physics 92nd Edition 2011-2013

Barium — (Gr. barys, heavy), Ba; at. wt. 137.327(7), at. no. 56; m.p. 727 °C; b.p. 1897 °C; sp. gr. 3.62 (20 °C); valence 2. Baryta was distinguished from lime by Scheele in 1774; the element was discovered by Sir Humphrey Davy in 1808. It is found only in combination with other elements, chiefly in barite or heavy spar (sulfate) and witherite (carbonate) and is prepared by electrolysis of the chloride. Large deposits of barite are found in China, Germany, India, Morocco, and in the U.S. Barium is a metallic element, soft, and when pure is silvery white like lead; it belongs to the alkaline earth group, resembling calcium chemically. The metal oxidizes very easily and should be kept under petroleum or other suitable oxygen-free liquids to exclude air. It is decomposed by water or alcohol. The metal is used as a “getter” in vacuum tubes. The most important compounds are the peroxide (BaO2), chloride, sulfate, carbonate, nitrate, and chlorate. Lithopone, a pigment containing barium sulfate and zinc sulfide, has good covering power, and does not darken in the presence of sulfides. The sulfate, as permanent white or blanc fixe, is also used in paint, in X-ray diagnostic work, and in glassmaking. Barite is extensively used as a weighting agent in oilwell drilling fluids, and also in making rubber. The carbonate has been used as a rat poison, while the nitrate and chlorate give green colors in pyrotechny. The impure sulfide phosphoresces after exposure to the light. The compounds and the metal are not expensive. Barium metal (99.2 + % pure) costs about $3/g. All barium compounds that are water or acid soluble are poisonous. Naturally occurring barium is a mixture of seven stable isotopes. Thirty-six other radioactive isotopes and isomers are known to exist.


In urban air, the avg concn of barium was 5 (range 0-1500) ng/cu m in 18 USA cities.

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