Iron Thioarsenates

Both ferrous and ferric salts,' when treated with a solution of sodium orthothioarsenate, yield brown precipitates which are soluble in excess of the reagent. The ferric salt is stable in air and may be heated to fusion without decomposition; at a higher temperature sulphur is expelled. The ferrous salt decomposes on drying in the air, ferric hydroxide and thioarsenate being formed. Ferrous sulphide dissolves in an aqueous solution of an alkali thioarsenate.