A preliminary set of ‘rules’ for acid-catalysis by ion-exchanged montmorillonites has been derived from the reaction of alkenes, alcohols and alicyclic acids over such catalysts. It has been shown that: 1. Cr(III) and Fe(III) are the most active interlayer cations. Although Al is also active, the exact procedures used for the ion-exchange and washing steps appear to be critical for giving catalysts of reproducible activity. 2. Below 100°C, the reactions proceed provided they involve tertiary or allylic carbocation intermediates, whereas at 150–180°C reactions involving primary and secondary carbocations are possible. 3. Reactions of carbocations with unsaturated hydrocarbons take place overwhelmingly in the interlayer region of the clay, where the hydrocarbon double bond can be effectively polarized. Reactions of carbocations with polar, oxygenated, species can take place on the surface of the clay particles as well as in the interlayer space. 4. When the acid-catalysed reactions are performed in the liquid phase and involve tertiary carbocations, the most suitable solvents are those which provide miscibility; 1,4-dioxan is especially good. However, when more acid conditions are required for the formation of primary and secondary carbocations a non-polar solvent is more efficacious.

Chemical and crystallochemical properties of natural dioctahedral Fe-rich smectites formed by weathering of basaltic rocks in the Berici-Euganei Area, northern Italy, were investigated. It was found that: (i) the b-dimension could be correlated both to Fe3+/Σ ratio (Σ = octahedral occupancy) and to dehydroxylation peak temperature in the range 400–600°C; (ii) it is not correct to impose a total octahedral occupancy strictly equal to 2 for dioctahedral smectites; (iii) in the smectite group there is not a continuous isomorphous series as would appear on the basis of chemical features only.

Water-sorption isotherms and interlamellar spacings were measured for Ca montmorillonite (from Redhill. UK) over the relative pressure range 1 > P/P0 > 0. By taking account of the change in interlamellar volume with relative pressure, it is shown that internal and external surfaces can be calculated by a modified t-plot analysis. The results also show that sorption on the external surfaces of the montmorillonite is quantitatively similar to that on reference oxide surfaces. Desorption-sorption hysteresis occurred and was apparently caused by an ageing process in which the interlamellar volume increased at the expense of the external surfaces.

Clay mineral and trace element data indicate that sediments in the vicinity of the North Mid-Atlantic Ridge derive from material of both Icelandic and Canadian origin. These sources agree with the marine and atmospheric circulation patterns observed in this area.

Both aluminium substitution and poor crystallinity reduce the magnetic hyperfine field of goethite. Mössbauer spectra taken at 4·2 K show that the effect of poor crystallinity is similar to that of Al substitution, i.e. it reduces the saturation hyperfine field. A multiple correlation was found to exist between the magnetic hyperfine field at 4·2 K as a dependent variable vs Al substitution and crystallinity as independent variables. If a hyperfine field is to be interpreted with respect to either Al substitution or crystallinity, it is therefore necessary to have knowledge of the other variable.

A series of phlogopite and biotite samples were examined by wide-line NMR spectroscopy. Monitoring of the fluorine signal revealed the presence of homogeneous fluorine domains. The importance of these domains increased with increase in F and Fe contents. A model for the distribution of anions and cations in the octahedral sheet of micas is presented and discussed.

Ion-exchanged montmorillonites behave as solid acid catalysts and are effective and selective catalysts for the hydration of ethylene. The reaction proceeds predominantly in the interlamellar environment of the clay catalyst. Ethylene conversions were found to be markedly dependent on the choice of exchangeable cation, with Al being the best of those examined.

Weathering products of a serpentinized Iherzolite were investigated using optical microscopy, X-ray diffraction, infrared spectroscopy, and electron microprobe and wet-chemical analysis methods. The original mineral assemblage of the rock was chrysotile-enstatite-diopside-picotite-magnetite-calcite. Rock porosity governed the types of chemical microsystems from which the clay minerals were derived. These microsystems were grouped into three types. (1) Grain microcracks and grain boundaries. These were the earliest manifestations of weathering. Only pyroxenes were affected and transformed into talc + iron oxides. (2) Plasma zones in which the rock structure was preserved. The talc + oxide and chrysotile were both altered into a saponitic mineral. Picotite was oxidized to oxipicotite. (3) Fissure zones. In the argillized zones the rock was restructured. Saponite was altered to nontronite + magnesium silicate gel. Talc was also transformed to the same gel. Fissures were often filled with clay cutans and some were edged with iron oxides. Mineral facies in the different zones have been plotted in Si-R2-R3 coordinates.

Wyoming bentonite, exchanged with cations of high charge density, is an efficient and selective catalyst for the production of ethyl acetate, in a single step, from ethylene and acetic acid. The reaction occurs in the interlamellar space of the clay where it is proposed that strong Brönsted acid sites on the clay coupled with highly polarized intercalated reactants produce a reaction which is otherwise difficult to carry out.

The translatory and rotatory diffusion coefficients, electrophoretic mobility, permanent dipole moment, electrical polarizability and optical anisotropy factor for a crocidolite sol have all been measured in a single optical apparatus. Electrophoretic light-scattering and electrically-induced birefringence were the methods used, these being rapid and well-suited to particles in the micron and sub-micron size-range, where conventional electrophoresis is difficult. Electric birefringence offers a fast means of sizing mineral particles in suspension and the electrical polarizability and electrophoretic mobility have a common origin in such sols. This is discussed in terms of the surface-charge and electric double-layer characteristics of the particles.

Le spectre de réflexion diffuse de pâtes de kaolinite obtenues pour des teneurs en eau croissantes a été étudié en séparant la part due au phénomène d'absorption de celle due à d'autres phénomènes comme la diffusion. On montre que l'intensité des bandes d'absorption varie linéairement avec la teneur en eau jusqu'à ce que le point d'entrée d'air dans le système soit atteint. Au-delà du point d'entrée d'air, quand le système est saturé en eau, l'intensité des bandes d'absorption semble tendre vers une limite. On montre de même que l'intensité réfléchie-diffusée en dehors des bandes d'absorption tend elle aussi vers une limite quand le système est saturé en eau. Il en résulte: (i) que la détermination des teneurs en eau à partir des données de réflexion diffuse est possible grâce à l'existence de courbes d'étalonnage linéaires dans le domaine d'hydratation pour lequel le système n'est pas saturé en eau, (ii) que l'analyse quantitative des données de réflexion diffuse est plus facile lorsque le milieu est saturé en eau. Les résultats obtenus montrent en outre que la relation générale proposée par P. F. Low: J = J0eα/θ; où où J est une propriété de l'eau associée avec l'argile, J0 une même propriété pour l'eau liquide, θ; la teneur en eau et α un coefficient, ne s'applique que sur un domaine limité de teneurs en eau.

Basal X-ray peaks from normal and ethylene glycol-saturated tarasovite have been measured to 0.0.36 and 0.0.38, respectively; the mean basal spacings were 43·73 ± 0·44 and 46·05 ± 0·33 Å, with CV values of 1·31 and 0·97. The spacings indicate a near approach to a 3 : 1 illite-smectite but the CV values indicate a greater variability than is normally consistent with the allocation of a special name. Comparison of the observed spacings with those for illite showed that the more deviant values were always adjacent to positions of illite reflections. A modified Mering treatment of diffraction by mixed-layer sequences was used to estimate the proportion of illite layers; the average result was 79·9 ± 2·0%. The mineral is considered to have 3 : 1 illite-smectite units with randomly added illite layers, bringing the ratio from 75% for the ideally ordered sequence to near 80%.

Some uses of clay-supported reagents in fine organic synthesis are discussed, in particular the catalysis of the phase-transfer preparation of formaldehyde acetals by quaternary ammonium montmorillonites. The preparation and some applications of clay-supported ferric nitrate, a new reagent which oxidizes alcohols into carbonyl derivatives, couples thiols into disulphides, nitrates phenols, and oxidatively couples pyrrole and benzaldehyde into tetra-phenylporphyrin, are also described

During the reaction of solutions of the leuco dyes crystal violet lactone and N-benzoyl leuco methylene blue with acid-treated montmarillonite (as occurs with carbonless copying papers), most of the offered dye is intercalated within the interlayers of the montmorillonite structure remaining after acid attack. This phenomenon was demonstrated by XRD and also by high-resolution transmission electron microscopy. During acid treatment, octahedral cations are dissolved from exposed edges of the montmorillonite lamellae and amorphous silica builds up in these areas. As a result, the BET(N2) specific surface area increases from ∼60 m2/g to ∼300 m2/g and, consequently, the theoretical reactivity towards leuco dyes. Nevertheless, only small quantities of the dye molecules are adsorbed onto the amorphous silica. The excellent colour intensity and, in particular, the resistance to fading in the light of the montmorillonite dye complexes may be explained by the protected position of the dye molecules within the interlayers of the montmorillonite.