Basic Cobaltous Carbonates

Several of these have been described, although it may well be that many of them are not really separate chemical entities. The three following substances were described by early workers.

By the action of finely divided aragonite upon concentrated aqueous solutions of cobaltous nitrate, 2CoCO₃.3Co(OH)₂ H₂O is obtained as a lilac precipitate, which is stable up to 80.85° C., but loses a molecule of water at 95° C. Treatment of more dilute solutions of cobaltous nitrate with aragonite yields CoCO₃.2Co(OH)₂, also a lilac precipitate. CoCO₃.3Co(OH)₂ is obtained as a blue precipitate by the addition of calcite to concentrated cobaltous nitrate. A pink potassium cobalt carbonate, K₂CO₃.CoCO₃.4H₂O, has been prepared. Its solution becomes blue on boiling, returning to its pink colour on cooling. It apparently yields a complex negative ion, Co(CO₃)₂''.