Cobalt(II) phosphate

Cobalt phosphate is the inorganic compound with the formula Co3(PO4)2. It is a violet solid that is insoluble in water.

Structure According to X-ray crystallography, the anhydrous Co3(PO4)2 consists of discrete phosphate () anions that link centres. The cobalt ions occupy both octahedral (six-coordinate) and pentacoordinate sites in a 1:2 ratio.

Preparation The tetrahydrate Co3(PO4)2•4H2O precipitates as a solid upon mixing aqueous solutions of cobalt(II) and phosphate salts. Upon heating, the tetrahydrate converts to the anhydrous material.

Uses Thin films of this material are water oxidation catalysts.

It is also a commercial inorganic pigment known as cobalt violet (PV14).Hugo Müller, Wolfgang Müller, Manfred Wehner, Heike Liewald "Artists' Colors" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim.

The color of Cobalt Phosphate differentiates depending on its hydration state. Three different compounds are usually reported including, violet anhydrous cobalt phosphate, a tetrahydrate described as violet-pink or deep violet, and the pink octahydrate.Corbeil, Marie-Claude, et al. “The characterization of cobalt violet pigments.” Studies in Conservation, vol. 47, no. 4, Dec. 2002, pp. 237–249, https://doi.org/10.1179/sic.2002.47.4.237.

See also List of inorganic pigments

References