Nickel Carbonate, NiCO₃

When solutions of nickel salts are treated with potassium or sodium carbonate, basic Nickel Carbonate, NiCO₃ are precipitated, their compositions varying according to circumstances. The normal hexahydrated carbonate, NiCO₃. 6H₂O, is obtained when a solution of sodium hydrogen carbonate saturated with carbon dioxide is added to one of nickel nitrate and allowed to stand at a low temperature. It separates in monoclinic crystals, which lose water on warming. The trihydrate, NiCO₃.3H₂O, is also known. The anhydrous salt results when nickel chloride solution is heated with calcium carbonate to 150° C. It crystallises in pale green rhombohedra. Double carbonates have been prepared.