Barium is a chemical element with symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Its hydroxide, known in pre-modern history as baryta, does not occur as a mineral, but can be prepared by heating barium carbonate.
The most common naturally occurring minerals of barium are barite (barium sulfate, BaSO4) and witherite (barium carbonate, BaCO3), both insoluble in water. The barium name originates from the alchemical derivative “baryta”, from Greek βαρύς (barys), meaning “heavy.” Baric is the adjective form of barium. Barium was identified as a new element in 1774, but not reduced to a metal until 1808 with the advent of electrolysis.
Barium has few commercial uses. Barium salts are used in drilling mud due to high specific gravity of barium solutions, and as pure barium sulfate to enhance X-ray imaging. Barium is also used in making fireworks and occasionally as a getter for high vacuum applications.
Barium has high affinity for cation resins and can be readily removed along with other hardness ions such as calcium and magnesium. Care must be taken during regeneration to limit barium sulfate precipitation or leakage of suspended barium sulfate will occur. Regeneration of weak acid cation resin with hydrochloric acid followed by neutralization with caustic is one way to avoid the precipitation issues.