Barium Gobaltite, BaO.2CoO₂

When a mixture of cobalt sesquioxide, barium oxide, and barium chloride or bromide is heated to redness, or about 800° C., and the product washed with hot water and then with acetic acid, brilliant black hexagonal plates of the Barium Gobaltite, BaO.2CoO₂ are formed. When this compound is treated with concentrated hydrochloric acid, chlorine is evolved. At higher temperatures, 1000°-1100° C., a monocobaltite, in large iridescent black prisms, is formed.