Cobalt(II) hydroxide

The pure compound, often called the "beta form" (β-Co(OH)2) is a pink solid insoluble in water.

[2][3] The name is also applied to a related compound, often called "alpha" or "blue" form (α-Co(OH)2), which incorporates other anions in its molecular structure.

[4] For example, The compound can be prepared by reacting cobalt(II) nitrate in water with a solution of triethylamine N(C2H5)3 as both the base and a complexing agent.

It also reacts with strong bases to form solutions with dark blue cobaltate(II) anions, [Co(OH)4]2− and [Co(OH)6]4−.

[3] It is usually obtained as a blue precipitate when a base like sodium hydroxide is added to a solution of a cobalt(II) salt.

NFPA 704 four-colored diamond Health 1: Exposure would cause irritation but only minor residual injury. E.g. turpentine Flammability 0: Will not burn. E.g. water Instability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorus Special hazards (white): no code
Alpha Cobalt (II) Hydroxide
Cobalt hydroxide nanotubes. Scale bars: (a,b) 500 nm, inset 200  nm; (c,e) 50 nm; (d) 100  nm.