КОБАЛЬТ гидроксид (II)

The addition of alkali metal hydroxides to solutions of cobalt(II) salts results in the precipitation of cobalt(II) hydroxide in either a blue or pink form depending upon the conditions. The pink form is the more stable of the two and is obtained when a suspension of the blue form is allowed to stand or is warmed. Cobalt(II) hydroxide is amphoteric, dissolving in alkalis to form blue solutions of the [Co(OH)4]2- ions. In the presence of alkali, suspensions of Co(OH) are oxidized by air to the brown CoO(OH), this oxidation being brought about rapidly by oxidants such as hypochlorite, bromine water or hydrogen peroxide. The pink Co(OH)2 (density 3.597) has the brucite (Mg(OH)2) structure in which the cobalt atoms are surrounded by six hydroxides. The blue form is more disordered, but its structure is not known for certain.

Rose-red powder.Soluble in acids and ammonium salt solutions; insoluble in water and alkalies.

Cobalt(II) hydroxide is used as a drying agent for paints and varnishes. It acts as an aid to dry the lithographic inks and catalyst in the preparation of battery electrode impregnating solutions. It is also involved in the synthesis of other cobalt compounds.