Barium - Ba

Barium — chemical properties and water context

Barium is a soft, silvery alkaline-earth metal. In natural waters and treatment systems, the relevant form is usually dissolved barium ion (Ba²⁺) or a barium-bearing mineral or particle, rather than the reactive metal.

Atomic number	56
Standard atomic weight	137.327 g/mol
Density	3.62 g/cm³
Melting point	727 °C
Boiling point	1845 °C
Electron configuration	[Xe] 6s²

Chemical properties

Barium is in Group 2 and Period 6 and commonly forms Ba²⁺. The metal reacts with water and rapidly tarnishes in air. Barium occurs in minerals such as barite (barium sulfate) and witherite (barium carbonate). Solubility varies substantially among barium compounds: barium sulfate is sparingly soluble, while several other salts are more soluble.

Uses and applications

Barite is used as a weighting material in drilling fluids. Barium compounds are also used in glass, ceramics and other specialized products. The properties and hazards of a barium material depend on its chemical form; insoluble barium sulfate should not be treated as equivalent to soluble barium salts.

Barium in water treatment

Barium can occur in groundwater because of local geology or industrial activity. Health Canada identifies lime softening and ion-exchange softening as effective removal options; reverse osmosis and nanofiltration can also remove barium. Conventional coagulation alone is not considered an effective removal method. Selection and monitoring depend on source-water chemistry, scaling risk and the applicable drinking-water requirements.

Environmental and health context

The health significance of barium depends on concentration and chemical form. For drinking-water assessment, laboratories measure total barium, including dissolved and particulate fractions. Apply the drinking-water guideline or regulation relevant to the site and jurisdiction rather than assuming a single universal limit.