Cobalt Violet

Artificial inorganic pigment

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Composition and Properties of Cobalt Violet

Cobalt violet is either cobalt phosphate Co3(PO4)2 either anhydrous or crystallized with different numbers of water molecules. The second possibility is cobalt arsenate Co3(AsO4)2. The newer samples may contain cobalt ammonium phosphate CoNH4PO4 and also lithium cobalt phosphate LiCoPO4.

References

(1) Marie-Claude Corbeil, Jean-Pierre Charland and Elizabeth A. Moffatt, The Characterization of Cobalt Violet Pigments Studies in Conservation, Vol. 47, No. 4 (2002), pp. 237-249

cobalt-violet-crystals

Pigment

cobalt-violet-painted-swatch

Painted swatch

Names 

Alternative names

Color Index

PV 14, CI 77630

Word origin

From the German word Kobold meaning evil house spirit. The name was originated by medieval miners who believed, that cobalt ores made it difficult to extract silver from silver ore.

Spain Flag

Cobaltviolet

German

Spain Flag

Violet de cobalt

French

Spain Flag

Violetto di cobalto

Italian

Spain Flag

Violeta de cobalto

Spanish

Preparation of Cobalt Violet

Attention: Cobalt compounds are highly toxic and should not be handled by people not trained to do so.

Preparation of cobalt phosphate in the lab

Cobalt (II) phosphate can be prepared by the reaction of a solution of cobalt (II) chloride with a solution of sodium hydrogenphosphate. 2 g cobalt (II) chloride CoCl2 and 1,3 g of sodium hydrogenphosphate Na2HPO4 are each separately dissolved in 20 mL of deionized water.

cobalt-violet-synthesis-1

cobalt-violet-synthesis-2

 

The solutions are then poured together and the resulting precipitation of cobalt (II) phosphate is then filtered, dried and homogenized in a mortar.

cobalt-violet-synthesis-3

cobalt-violet-synthesis-4

Video: 'Preparation of cobalt phosphate' by The Alchemical Arts

Video: 'Arsenic-based pigments (cobalt arsenate)' by Hegelrast

History of Use 

This pigment was discovered in 1859 by Salvétat and was used since this time in all its variations until the present.

Examples of use

Claude Monet, Bathing at La Grenouillère, 1869

Monet_-_Bathers_at_La_Grenouillère-600b

 

7 Mauve colored flowers on the left: cobalt violet mixed with other pigments.

Monet_-_Bathers_at_La_Grenouillère-pigments-7

 

Identification

Fiber Optics Reflectance Spectra (FORS)
Raman Spectrum

(2) F. Casadio, A. Bezúr, I. Fiedler, K. Muir T. Trad and S. Maccagnola, Pablo Picasso to Jasper Johns: a Raman study of cobalt-based synthetic inorganic pigments, Special Issue: Raman spectroscopy in art and archaeology, Volume 43, Issue 11, pages 1761–1771, November 2012.

X-Ray Fluorescence Spektrum (XRF)

XRF Spectrum in the Free XRF Spectroscopy Database of Pigments Checker, CHSOS website.

References

(1) Marie-Claude Corbeil, Jean-Pierre Charland and Elizabeth A. Moffatt, The Characterization of Cobalt Violet Pigments Studies in Conservation, Vol. 47, No. 4 (2002), pp. 237-249

cobalt-violet-microphotograph

Microphotograph

image © Volker Emrath

Further Reading

References

(1) Marie-Claude Corbeil, Jean-Pierre Charland, and Elizabeth A. Moffatt, The Characterization of Cobalt Violet Pigments Studies in Conservation, Vol. 47, No. 4 (2002), pp. 237-249.

(2) F. Casadio, A. Bezúr, I. Fiedler, K. Muir T. Trad and S. Maccagnola, Pablo Picasso to Jasper Johns: a Raman study of cobalt-based synthetic inorganic pigments, Special Issue: Raman spectroscopy in art and archaeology, Volume 43, Issue 11, pages 1761–1771, November 2012.

(3) S. Muntwyler, J. Lipscher, HP. Schneider, Das Farbenbuch, 2nd. Ed., 2023, alataverlag Elsau, pp. 94-95.