Important Barium Compound
Barium carbonate: (BaCO₃), molecular weight: 197.34 g/mol , density: 4.286 g/cm3 , melting point: 811 °C . It is a white insoluble salt that occurs naturally as the mineral witherite. Barium carbonate can be readily precipitated by adding an alkali carbonate to a barium salt solution. On heating it decomposes reversibly with the formation of the oxide and carbon dioxide:
BaCO₃⇋BaO + CO₂
It is used as a rat poison.
Barium chloride (BaCl₂) molecular weight: 208.23 g/mol , density: 3.856 g/cm3 , melting point: 962 °C . It is a white solid that can be prepared by dissolving barium carbonate in hydrochloric acid and crystallizing out the dihydrate (BaCl₂.2H₂O). Barium chloride is used as the electrolyte in the extraction of barium, as a rat poison, and in the leather industry.
Barium hydrogencarbonate (barium bicarbonate; Ba(HCO₃)₂) A compound that occurs only in aqueous solution. It is formed by the action of cold water containing carbon dioxide on barium carbonate, to which it reverts on heating:
BaCO₃ + CO₂ + H₂O → Ba(HCO₃)₂
Barium hydroxide (baryta; Ba(OH)₂) , molecular weight: 171.34 g/mol , density: 3.743 g/cm3 , melting point: 78 °C . It is a white solid usually obtained as the octahydrate, Ba(OH)₂.8H₂O. Barium hydroxide is the most soluble of the group 2 hydroxides and can be used in volumetric analysis for the estimation of weak acids using phenolphthalein as an indicator.
Barium oxide (BaO), molecular weight: 153.326 g/mol , density: 5.72 g/cm3 , melting point: 1,923 °C . It is white powder prepared by heating barium in oxygen or by thermal decomposition of barium carbonate. It has been used in the manufacture of lubricating-oil additives.
barium peroxide (BaO₂) A dense offwhite powder that can be prepared by carefully heating barium oxide in oxygen. Barium peroxide is used for bleaching straw and silk and in the laboratory preparation of hydrogen peroxide.
Barium sulfate (BaSO₄), molecular weight: 233.38 g/mol , density: 4.49 g/cm3 , melting point: 1,580 °C . It is white solid that occurs naturally as the mineral barytes. Barium sulfate is very insoluble in water and can be prepared easily as a precipitate by adding sulfuric acid to barium chloride. Barium sulfate is an important industrial chemical. Under the name of ‘blanc fixe’ it is used as a pigment extender in surface coating compositions. It is also used in the glass and rubber industries and medically (taken orally) to allow radiographs to be taken of the digestive system.
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