Cobalt(III) hydroxide explained

Cobalt(III) hydroxide or cobaltic hydroxide is a chemical compound with formula or . It is an ionic compound, with trivalent cobalt cations and hydroxyl anions .

The compound is known in two structurally different forms, "brownish-black" and "green". The brownish-black form is a stable solid and can be prepared by reaction of water solutions of cobalt(II) chloride and sodium hydroxide, followed by oxidation with ozone.^[1]

The green form, formerly thought to be cobalt(II) peroxide, apparently requires carbon dioxide as a catalyst. It can be prepared by adding hydrogen peroxide to a solution of cobalt(II) chloride in 96% ethanol at –30 to –35°C, then adding a 15% solution of sodium carbonate in water with intense stirring. The resulting dark green powder is fairly stable at liquid nitrogen temperature, but at room temperature it turns dark brown within a few days.^[2]

Natural occurrence

As of 2020, Cobalt(III) hydroxide is unknown among the known mineral species. However, heterogenite, CoO(OH), is known.^{[3] [4]}

Notes and References

1. Pankratov, D.A., Veligzhanin, A.A., and Zubavichus, Y.V. (2013): "Structural Features of Green Cobalt(III) Hydroxide". Russian Journal of Inorganic Chemistry, volume 58, issue 1, pages 67–73.
2. Pankratov, D.A., Portachenko, T.A., and Perfil’ev, Y.D. (2008): "Emission Mössbauer Study of 'Cobalt Peroxide'". Moscow University Chemical Bulletin, volume 63, issue 5, pages 292–296.
3. Web site: Heterogenite .
4. Web site: List of Minerals . 21 March 2011 .