Anhydrous barium chloride is marketed as a white, crystalline powder. It tastes bitter and is toxic when eaten or inhaled. When crystallized from an aqueous solution, the dihydrate is obtained in colorless, flat sheets. When heated above 120 °C, the dihydrate releases its water of crystallization.
Barium chloride, like barium and all its salts, has a green flame coloration, is highly soluble in water and, like all soluble barium compounds, is toxic.
Barium chloride usually occurs in combination with two molecules of water of crystallization as barium chloride dihydrate. Anhydrous barium chloride is obtained by removing the water from barium chloride dihydrate through heat (dehydration). Barium chloride dihydrate is also a white, crystalline powder.
Commercially, barium chloride is synthesized by reacting barium sulfide with hydrochloric acid to form hydrosulfuric acid:
BaS + 2HCl → BaCl2 + H2S ↑
Barium chloride is used as an indicator for sulphate ions, since barium sulphate precipitates as a white solid when reacting with sulphate ions (see reactions). This precipitation reaction can also be used to purify sodium chloride from sulphates.
Barium chloride is also used for hardening steel, in pyrotechnics because of its green flame colouring and for the production of the dyes barium sulphate (see reactions) and barium chromate (see reactions).
During the Second World War, the Red Army used greenish glowing barium chloride tracer bullets to make aiming easier for the shooter, while the Wehrmacht used yellowish glowing phosphorus bullets. These projectiles were used in the LMGs and machine guns of the tanks. These projectiles also helped other soldiers because they could see where the shooter was aiming.
Barium chloride is slightly hazardous to water. Barium chloride is toxic if inhaled or swallowed. In case of accident or indisposition due to this substance, a doctor must be consulted immediately. Keep barium chloride under lock and key and out of the reach of children. In the past, barium chloride was used as rat poison.
Barium inactivates the passive potassium channels in the membrane of muscle cells. Potassium can thus no longer leave the muscle cells. Since the sodium-potassium ATPase continues to pump potassium into the cells, the potassium levels in the blood drop. The symptoms are hypermotility of the gastrointestinal tract, loss of muscle reflexes (areflexia), flaccid muscle paralysis and respiratory paralysis. A blood test reveals severe hypokalemia.
As a first aid measure, the intake of sodium or potassium sulphate solution is recommended, as sulphate ions precipitate the barium ions and form insoluble and therefore non-toxic barium sulphate. Barium can be removed in hospital by dialysis.