Barium chloride is an inorganic compound with the formula BaCl2. It is one of the most common water-soluble salts of barium. Like most other water-soluble barium salts, it is white, highly toxic, and imparts a yellow-green coloration to a flame. It is also hygroscopic, converting first to the dihydrate BaCl2(H2O)2. It has limited use in the laboratory and industry.
== Structure and properties ==
BaCl2 crystallizes in two forms (polymorphs). One form has the cubic fluorite (CaF2) structure and the other the orthorhombic cotunnite (PbCl2) structure. Both polymorphs accommodate the preference of the large Ba2+ ion for coordination numbers greater than six. The coordination of Ba2+ is 8 in the fluorite structure and 9 in the cotunnite structure. When cotunnite-structure BaCl2 is subjected to pressures of 7–10 GPa, it transforms to a third structure, a monoclinic post-cotunnite phase. The coordination number of Ba2+ increases from 9 to 10.In aqueous solution BaCl2 behaves as a simple salt; in water it is a 1:2 electrolyte and the solution exhibits a neutral pH. Its solutions react with sulfate ion to produce a thick white precipitate of barium sulfate.
Ba2+ + SO2−4 → BaSO4Oxalate effects a similar reaction:
Ba2+ + C2O2−4 → BaC2O4When it is mixed with sodium hydroxide, it gives the dihydroxide, which is moderately soluble in water.
== Preparation ==
On an industrial scale, it is prepared via a two step process from barite (barium sulfate):
BaSO4 + 4 C → BaS + 4 COThis first step requires high temperatures.
BaS + 2 HCl → BaCl2 + H2SIn place of HCl, chlorine can be used.Barium chloride can in principle be prepared from barium hydroxide or barium carbonate. These basic salts react with hydrochloric acid to give hydrated barium chloride.
== Uses ==
Although inexpensive, barium chloride finds limited applications in the laboratory and industry. In industry, barium chloride is mainly used in the purification of brine solution in caustic chlorine plants and also in the manufacture of heat treatment salts, case hardening of steel.
It is also used to make red pigments such as Lithol red and Red Lake C. Its toxicity limits its applicability.
== Safety ==
Barium chloride, along with other water-soluble barium salts, is highly toxic. Sodium sulfate and magnesium sulfate are potential antidotes because they form barium sulfate BaSO4, which is relatively non-toxic because of its insolubility.
== References ==
== External links ==
International Chemical Safety Card 0614. (anhydrous)
International Chemical Safety Card 0615. (dihydrate)
Barium chloride's use in industry.
ChemSub Online: Barium chloride.