Infrared Absorption Spectra of α and β-Calcium Sulphate Hemihydrates


IN their recent communication concerning the application of infrared spectroscopy to the calcium sulphate–water system, Bensted and Prakash1 stated that they obtained no spectral differences between the α and β forms of the hemihydrate. I would like to report that I have found differences in the spectral range 1,200 to 1,000 cm−1 associated with the vibrations of the tetrahedral SO4 ion as shown in Table 1.

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  1. 1

    Bensted, J., and Prakash, S., Nature, 219, 60 (1968).

  2. 2

    Holdridge, D. A., Trans. Brit. Ceram. Soc, 64, 211 (1965).

  3. 3

    Holdridge, D. A., and Walker, E. G., Trans. Brit. Ceram. Soc., 66, 485 (1967).

  4. 4

    ASTM E 168–64T General Techniques of Infrared Quantitative Analysis, section 5e.

  5. 5

    Duyckaerts, G., The Analyst, 84, 201 (1959).

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BARTRAM, D. Infrared Absorption Spectra of α and β-Calcium Sulphate Hemihydrates. Nature 223, 494 (1969).

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