The unit structure, space group symmetry and detailed atomic arrangement of -(bohmite) and -ScOOH have been determined. The unit structure is orthorhombic end-centered on (100) and the most probable space group is DjZ-Amam.Bohmite, -, has been found to exist in nature1•2 and may be prepared in the laboratory in a variety of ways.3-6 From the close similarity of the powder X-radiograms of bohmite and the mineral lepidocrocite, -FeOOH, it has been concluded that the structures are analogous.7•8 The existence of the closely related compound -ScOOH has clearly been established by X-ray diffraction and dehydration isobaric studies,9-11 but quantitative Xray studies have not been made.

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X-ray diffraction patterns and cation-exchange data are presented for centrifuged Wyoming bentonite to demonstrate the heterogeneous nature of montmorillonite. It has been shown that in the bentonite samples studied, the montmorillonite can be separated into at least two fractions. One phase consists of essentially a sodium montmorillonite while the other consists of essentially a calcium-magnesium montmorillonite. It is postulated that these differences occur because of differences in the isomorphous substitutions within the montmorillonite crystal lattice.

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Organophilic bentonites prepared by reacting various amounts of n-laurylamine hydrochloride and dimethyldioctadecyl ammonium chloride with bentonite have been studied by the method of Fourier transforms. The transform curves obtained from the x-ray diffraction patterns of these samples show how different numbers of organic layers between clay laminae are produced by different kinds and amounts of organic material added to the clay. It has been found that as the organic material reacts by base exchange with the clay surfaces, the number of organic layers between each two clay platelets increases in a regular and stepwise manner.