Ferrous phosphate

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A hygroscopic, blue-gray powder that occurs naturally as the mineral Vivianite. Vivianite was described after discovery in the St. Agnes mine in Cornwall in 1817. It has been called 'blue ocher' and has been found in Roman paint residues. Ferrous phosphate is used as a colorant in ceramics.



Synonyms and Related Terms

iron phosphate; vivianite; blue ochre; blue ocher; ocre de fer (Fr.)


  • Slowly decomposes and darkens in light and air.
  • NIH: Safety sheet

Physical and Chemical Properties

  • Soluble in mineral acids. Insoluble in water.
  • Euhedral crystals with strong pleochroism from colorless to lilac blue.
  • Strongly birefringent under crossed polars.
Composition Fe3(PO4)2.8H2O
CAS 14940-41-1
Density 2.58-2.68 g/ml
Molecular Weight mol. wt. = 357.48
Refractive Index 1.60; 1.63; 1.65


Characteristics of Common Blue Pigments

Resources and Citations

  • Nicholas Eastaugh, Valentine Walsh, Tracey Chaplin, Ruth Siddall, Pigment Compendium, Elsevier Butterworth-Heinemann, Oxford, 2004
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • R.D. Harley, Artists' Pigments c. 1600-1835, Butterworth Scientific, London, 1982
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 4101

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