Barium

Chemical Formula

Background

Barium was discovered as an element in 1808 by Sir Humphrey Davy. In its elemental form it is soft and silvery white resembling lead. It belongs to the alkaline earth group and is chemically similar to calcium.

In nature it is found in combination with other elements, namely in barite or heavy spar (BaSO₄) and witherite (BaCO₃) and is obtained by electrolysis of the chloride (BaCl₂). However, in the pure metal form oxidation occurs very easily therefore making it difficult to obtain the pure metal. It should be kept under petroleum or other suitable oxygen-free liquids to exclude air. It is decomposed by water and alcohol and is explosive in the powder/granular form when in contact with carbon tetrachloride fluoro-chloromethanes, and other halogenated hydrocarbons.

Applications

The pure metal is used as a “getter” in vacuum tubes and is introduced to lead bearing metals via electrolysis to harden the lead.

However the most extensive use of barium is in the form of its compounds of which the most important are the peroxide (BaO₂), chloride (BaCl₂), sulphate (BaSO₄), carbonate (BaCO₃), nitrate (Ba(NO₃)₂), chlorate (Ba(ClO₃)₂.H₂O), and hydride (BaH₂).

· The sulphate is used in pigments and glassmaking, and the insoluble non-toxic form is used in radiography.

· The carbonate is used as a rat poison.

· The nitrate and chlorate produce colours in pyrotechnics.

· Impure sulphide phosphoresces upon exposure to light.

· Barium heat-treated to 200°C (392°F) in a hydrogen gas it forms barium hydride (BaH₂), a grey powder that decomposes on contact with water and can be used as a source of nascent hydrogen for life rafts.

· Barium is also a key element in the production of ceramic superconductors.