Cobalt(II) iodide

Cobalt(II) iodide crystallizes in two polymorphs, the α- and β-forms.

The α-polymorph consists of black hexagonal crystals, which turn dark green when exposed to air.

Under a vacuum at 500 °C, samples of α-CoI2 sublime, yielding the β-polymorph as a yellow crystals.

The hexaaquo salt consists of separated [Co(H2O)6]2+ and iodide ions as verified crystallographically.

[3][4] Anhydrous cobalt(II) iodide is sometimes used to test for the presence of water in various solvents.

NFPA 704 four-colored diamond Health 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gas Flammability 0: Will not burn. E.g. water Instability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calcium Special hazards (white): no code