A simple method is described for determining the approximate positions of Li+, Mg2+ and Ca2+ in three montmorillonite samples saturated with these cations and subsequently dehydroxylated. The method depends only upon changes in the relative intensity of the three lowest order basal reflections, and its applicability to other problems is illustrated.

Dehydration curves have been obtained for vermiculite saturated with Mg2+, Ca2+, Sr2+, Ba2+ and Na2+. Three of the hydration phases of Mg-vermiculite give energies of hydration of −3·8±0·1, −5·5±0·1, and −18±3 K cal per mole of water. The heat of hydration of vermiculite has been found to vary with the saturating cation, and to decrease with decreasing energy of hydration of the cation. Values for the heats of hydration of vermiculite saturated with Mg2+, Ca2+, Sr2+, Ba2+ and Na+ are reported.

Complexes of vermiculite with neutral and ionic amines have been prepared and investigated by X-ray diffraction techniques. The results enable certain conclusions to be drawn regarding the structure of such complexes.

Delta alumina is a transition form obtained during the conversion of boehmite to corundum. Alternative methods have been found for preparing this alumina in a well crystallised condition, enabling detailed X-ray powder data to be compiled. The X-ray data are accounted for by a large tetragonal structure cell of which the axial ratio is 1·47, or 3/2 times the axial ratio of the spinel-like pseudo-cell of Saalfeld. The lattice parameters are a0=7·96 Å and c0=11·70 Å. This large cell provides an integral number of vacancies, contrasting with the 2⅔ vacancies of the pseudo-cell, and allows the atomic arrangement to be ordered.

X-ray powder diffraction data were used to determine the mineralogical composition of the fine suspended material present in nine English rivers. The mineralogy of these solids is discussed in relation to the geological formations through which the rivers flow.

A new method for estimating the sulphide content of samples of impermeable rocks is described. It is based on the oxidation of reducing substances by nitric acid and titration with permanganate of the nitrous oxides absorbed by potash.