A Discussion of the Water Content of Vermiculite

Cambridge University Press (CUP) - 1958
William Bradley1
1Illinois Geological Survey, Urbana, USA

Tóm tắt

AbstractSelected chemical and diffraction analyses from the literature, supplemented by thermal and thermogravimetric analyses and infrared absorption observations, are utilized to construct a rational model of the water arrangement in natural vermiculites.A super cell is arranged by simple modification of the Hendricks water nets to accommodate the somewhat higher water contents, indicated by weight loss analyses, and the exchangeable cations.A three-cell unit (15.6 × 9 Å) contains two Mg2+·6H2O octahedra centered at the corners and face centers and four 4H2O squares centered about ±5.2 Å along a between the octahedra. The arrangement affords twenty hydrogen bonds near 2.75 Å, twelve between silicate and water layers and eight between water layers, and thirty-two hydrogen bonds near 3.0 Å within water layers. The remaining four hydrogens are not active in the bonding system. The environment of each water molecule is a distorted tetrahedron.A broad infrared absorption band shows maxima at about 3600, 3450 and 3350 cm−1 at normal incidence, with increased activity in the highest and lowest energies when a flake is tilted. It is concluded that OH axes in the shortest bonds are more inclined to the cleavage planes than are the intermediate length axes.

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Tài liệu tham khảo

10.1021/j150568a003

Barshad, 1948, Vermiculite and its relation to biotite as revealed by base exchange reactions, x-ray analyses, differential thermal curves, and water content, Amer. Min., 33, 655

Gruner, 1934, The structures of vermiculites and their collapse by dehydration, Amer. Min., 19, 557

Hendricks, 1938, Crystal structure of vermiculites and mixed vermiculite-chlorites, Amer. Min., 23, 851

Grudemo, A. (1954) x-Ray examination of the structure of vermiculite: Swedish Cement and Concrete Res. Inst. Proc., no. 22, 56 pp.

Mathieson, 1954, Crystal structure of magnesium- vermiculite, Amer. Min., 39, 231

Bradley, 1958, Clays and Clay Minerals, 566, 348

Weaver, 1958, The effects and geologic significance of potassium “ fixation “ by expandable clay minerals derived from muscovite, biotite, chlorite, and volcanic material, Amer. Min., 43, 839

Brindley, 1953, Ferrous chamosite and ferric chamosite, Min. Mag., 30, 57

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Cambridge University Press (CUP)

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