Using X-ray techniques, the orientation distributions of crystal planes in laboratory prepared and naturally occurring aggregates were measured. A small specimen was mounted on the axis of a goniometer and the diffracted intensity measured as the specimen was rotated. Mo radiation was used to reduce the absorption effects. A mathematical relation between the distribution of particles and the distribution of crystal planes was derived for platy and fibrous particles in flake-like and rod-shaped specimens.

When diffracted intensities of the 001 reflection of several different kaolinites were corrected for the degree of orientation in the respective specimens, a constant value was obtained. This would enable quantitative diffraction analyses to be made without the large errors that can be introduced by orientation effects. The degree of particle orientation achieved appeared to be more dependent on particle morphology than on the method of sample preparation or formation.

Urea was observed to become protonated in H-, Fe-, and Al-montmorillonite films and to form hemisalts when urea was present in excess of the number of available protons. The fully protonated urea disappeared upon dehydration, then the original protonated condition was re-established by rehydration. This completely reversible reaction indicates the importance of water in the protonated form. Indications were that urea will coordinate through the carbonyl group to the metal ion in Cu (II), Mn (II), and Ni (II) montmorillonite. Urea may be bonded to the metal ion in Mg-, Ca-, Li-, Na-, and K-montmorillonite by coordination and possibly by ionization of the N-H bond. The importance of ion-dipole interaction in urea complexes with montmorillonite is suggested. Decomposition of urea to ammonium ions was observed mainly in the Cumontmorillonite system.

Cretaceous and Eocene bentonites from Azerbaijan have been studied from the standpoint of their occurrence, mode of formation, and mineralogy. The bentonites are shown to be derived from the vitroclastic products of volcanic eruption by transformation in a marine environment.

Differential thermal analysis curves were obtained for a series of diamine and glycol complexes with natural and copper substituted montmorillonite, in air and in an inert atmosphere. Thermobalance curves of the diamine-clay systems were also determined. The exothermic peaks observed in air are characteristic for any particular system and reflect the nature and binding of the interlamellar material; no direct correlation was, however, observed with pyrolysis and oxidation processes in the clay. Organic matter is frequently liberated from the clay before oxidation, which then occurs within the reaction cell but outside the clay phase. The extent to which oxidation is completed at any particular temperature depends upon the supply of oxygen and the amount of organic material present.

The clay mineral composition is one of the factors that affect the physical properties of soils, and a knowledge of it is required to promote a fuller understanding of the origin of these properties. The relationships between the clay content and the plastic and liquid limits of natural montmorillonitic and kaolinitic soils and of artificial mixtures have been examined and compared. Factors affecting the relationships are discussed, and illustrated by the effect of particle aggregation on the measurement of the liquid limit of tropical red clays and on the sedimentation analysis of the Keuper Marl. The effect of muscovite and of silt-sized material on the position of soils on the Casagrande classification chart has also been examined.

Calcareous volcanic ashes (pumice–tuffs) occur among Ordovician rocks in Snowdonia, North Wales. The clays of these rocks and of the ecologically important soils derived from them are found to be almost mono-mineralic and to consist of chlorites. Chemical, differential thermal and X-ray analyses are given and discussed with particular reference to a clay-size chlorite from weathered pumice–tuff. There is no evidence for pedogenetic clay mineral transformations in the range of soils studied.

The surface properties of wet-ground muscovite were studied by thermodynamics of water adsorption. The surface appears to be covered by contaminating material, probably organic, which is strongly held; it was not removed at 350° C and under a vacuum of 10−4 torr. Attention is directed to the difficulty of maintaining freshly made silicate surfaces without contamination and to the importance of surface conditions in the interpretation of silicate properties which involve surface phenomena.

The water gained by two micas during a wet-grinding process (extra-water) has been evaluated. It was found to be proportional to the surface area and the amount was about 29 µmoles/m2 for a fluorphlogopite and about 16 µmoles/m2 for a muscovite. This estimation was made possible by eliminating the physically adsorbed water. The material contaminating the surfaces and the constitution water of muscovite were taken into account by the comparison of the two minerals and by the use of infrared spectroscopy in addition to thermovolumetric data. It is thought that the extra-water is related to a disordered and chemically modified surface layer of the particles. The bearing of these results on the nature of illite is indicated.