Abstract
GRUNER1 has shown that vermiculite consists of talc-like layers, 9·26 A. high, alternating with water layers (4·95 A.), the total water content of the mineral being in the region of 20 per cent. Theories2,3 as to the nature of the water layers have found difficulty in explaining the observation1,2,3 that, when vermiculite is heated at 110° C., about half the water is removed without apparently affecting the diffraction pattern. It can be shown, however, that a change in the structure does, in fact, take place during this treatment ; but that the rapid rehydration which occurs on contact with normal atmospheric conditions tends to obscure it. Thus, while the diffraction patterns of unheated and rehydrated samples are identical, a powder specimen heated at 110° C, and sealed in a thin glass tube before rehydration can occur does not give the usual 14·2 A. basal reflexion of vermiculite but one at 11·8 A. corresponding to a water-layer thickness of 2·54 A., which is about half the original value. A single flake similarly treated shows the 11·8 A. reflexion to be associated with a regular sequence of higher orders ; that is to say, it represents a real spacing and is not a diffraction effect from intimately mixed layers of different sizes4. It is clear, therefore, that removal of half the water is accompanied by replacement of an original double water-layer by a single layer.
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References
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Hendricks, S. B., and Jefferson, M. E., Amer. Min., 23, 863 (1938).
Hendricks, S. B., and Teller, E., J. Chem. Phys., 10, 147 (1942).
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WALKER, G. Water Layers in Vermiculite. Nature 163, 726–727 (1949). https://doi.org/10.1038/163726a0
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DOI: https://doi.org/10.1038/163726a0
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