35112-53-9

White, crystalline powder.Slightly soluble in water; insoluble in alcohol.

Barium thiosulfate has the molecular formula of BaS₂O₃ and the molecular weight of 249.4602 g/mol. It can be prepared by the reaction of sodium thiosulfate in water with the chloride of barium:
BaCl2+Na2S2O3 ? BaS2O3+2NaCl
It is not very soluble in water (0.25 g/100 ml at 15°C) so that the solution does not need to be evaporated at a low temperature to crystallize the product. A monohydrate is the result. BaS₂O₃·H₂O has the CAS number of 35112-53-9. It is insoluble in ethanol. It is a white, crystalline, water-insoluble, poisonous solid. It loses the water of hydration at 110°C and decomposes at 228°C to form the sulfate, sulfur and SO₂.
BaS₂O₃·H₂O is used chiefly in the manufacture of explosives, matches, paints, and varnishes. However,the demand for this chemical is not substantial and it is classified as a “rare” chemical.

It is very slightly soluble in water and is washed repeatedly with chilled water and dried in air at 40o.