ABSTRACT
Barium is a silvery-white metal. It exists in nature only in ores containing mixtures of elements. The important combinations are the peroxide, chloride, sulphate, carbonate, nitrate, and chlorate. The pure metal oxidises readily and reacts with water emitting hydrogen. It combines with other chemicals such as sulphur or carbon and oxygen to form barium compounds. Barium compounds are used by the oil and gas industries to make drilling muds. Barium attacks most metals with the formation of alloys; iron is the most resistant to alloy formation. Barium forms alloys and intermetallic compounds with lead, potassium, platinum, magnesium, silicon, zinc, aluminium, and mercury. Barium compounds exhibit close relationships with the compounds of calcium and strontium, which are also alkaline earth metals. Twenty-ve barium isotopes have been identied, 138Ba being the most abundant, and the others are unstable isotopes with half-lives ranging from 12.8 days for 140Ba to 12 s for 143Ba. Two of these isotopes, 131Ba and 139Ba, are used in research as radioactive tracers. The general population is exposed to barium through air, drinking water, and food.
