The most abundant clay mineral group in Iowa soils is montmorillonite, most commonly calcium-saturated (Hanway et al. 1960). The calcium montmorillonite-water system was therefore selected for detailed X-ray study. Montmorillonite is unusual among minerals in that it has an expansible lattice in the c direction. That is, upon wetting with water, the individual silicate layers separate to allow entry of water, and the mineral expands. Characteristics of expansion are readily studied by means of X-ray diffraction: the X-ray diffraction angle gives the average layer-to-layer "d001" spacing for any given moisture condition; the sharpness of the diffraction peak is a measure of uniformity of the d001 spacing; and the intensity of the peak relates to uniformity of the d001 spacing and in addition to the electron density distribution within the repeating elements. The latter is embodied in the "structure factor". The variation of d001 structure factor caused by montmorillonite expansion is the subject of this paper.
Proceedings of the Iowa Academy of Science
©1966 Iowa Academy of Science, Inc.
Senich, Donald; Demirel, T.; and Handy, R. L.
"Effect of Ca-Montmorilionite Expansion on X-ray Diffraction lntensities,"
Proceedings of the Iowa Academy of Science, 73(1), 212-218.
Available at: https://scholarworks.uni.edu/pias/vol73/iss1/33