Barium Fluoride, BaF₂

Barium Fluoride, BaF₂, may be obtained either by the action of a large excess of hydrofluoric acid on barium carbonate or oxide and calcination of the acid fluoride, or by precipitation of a soluble barium salt with an alkali fluoride. If the latter method is employed in dilute boiling solution, a crystalline precipitate is formed. Fine octahedral crystals may be obtained by fusing barium chloride with acid potassium fluoride, and washing with water. Crystals may also be produced by heating the fluoride with dilute hydrochloric or nitric acid in a closed tube at 230°-240° C., or by slow evaporation of the aqueous solution. Barium fluoride is also formed by the action of hydrofluoric acid gas on barium oxide or chloride.

The heat of formation of barium fluoride is 226.68 Cal. The density of the precipitated and calcined fluoride is 4.828.The melting point is 1289° C.

Barium fluoride is not very soluble in water, although more so than the calcium salt. At 18° C. a saturated solution contains 18.3 milli-equivalents per litre. The heat of solution is -1.9 Cal. It is somewhat more soluble in acids and in a finely divided form is decomposed by hydrochloric and nitric acids under pressure at 230° C.