Letter | Published:

Similarity between “Chukhrovite” and the Octahedral Crystals found in Gypsum in the Manufacture of Phosphoric Acid

Nature volume 212, page 392 (22 October 1966) | Download Citation



THE presence of minute colourless octahedral crystals has long been noticed in gypsum made during the manufacture of phosphoric acid from phosphate rock and sulphuric acid. They normally occur at a concentration of 0.1 weight per cent or less of the gypsum and, therefore, separation for analysis is extremely difficult. The use of selective dissolution, density separation, and sedimentation to produce a sufficient quantity for chemical analysis yielded material contaminated with silica and calcium fluoride. In 1959, however, using X-ray powder and single-crystal diffraction techniques, we determined their unit cell to be cubic, of parameter 16.75 ± 0.05 Å, and probable space-group Th-Fd3.

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  1. Department of Chemistry, Fisons Fertilizers, Ltd., Levington Research Station, Levington, Suffolk.

    • R. V. COATES
    •  & G. D. WOODARD


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