Resonance Raman spectroscopy has been used to observe the formation of cation radicals in the adsorption of N,N,N',N'-tetramethylbenzidine (TMBD), benzidine, N,Ndimethylaniline (DMA) and aniline on Na-, Cu- and Fe-montmorillonites. Cation radicals of benzidine and TMBD, and their dications were formed at acid sites on the montmorillonite surface, or through the reduction of Cu or Fe interlayer ions, and were adsorbed in the interlayer. Their structures are represented by biphenoquinone type structure, where the inter-ring CC bond and the ring C-N bond have double bond characters. It was demonstrated from Raman spectra that DMA and aniline adsorbed on Cu-montmorillonite from the vapour phase dimerize to form TMBD and benzidine dications.

A comprehensive Mössbauer spectroscopic and X-ray diffraction study of six purified glauconites is presented. The Mössbauer spectra were computer-fitted with three Fe3+ and three Fe2+ doublets, both Fe species occupying the trans-OH and two cis-OH octahedral sites. In addition, a seventh smaller doublet is assigned to Fe3+ in tetrahedral coordination. It has been shown that an increasing IVFe3+ content directs VIFe3+ substitution to the cis-OH octahedrally coordinated sites. A correlation between the d(060) reflection and elemental composition is demonstrated.

Intercalated compounds of montmorillonite and poly-6-amide were prepared by heating mixtures of ɛ-caprolactam and 5, 10, 15 and 30 wt% of montmorillonite, cation-exchanged with NH3+(CH2)11COOH, at 250°C in a nitrogen atmosphere, and examined by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), gel permeation chromatography (GPC) and elemental analysis. ɛ-caprolactam was polymerized to poly-6-amide by the heat treatment. The mean number-average molecular weight decreased from 3·6 × 104 to 0·8 × 104 with increasing montmorillonite content. TEM showed that considerable swelling had taken place subsequent to polymerization and that the clay layers were uniformly distributed in the final clay/poly-6-amide products. Both XRD and TEM showed that the basal spacing of the compound increased from 51 Å to 210 Å with increasing polyamide content. The driving force for the swelling was considered to be a combination of the polymerization energy of ɛ-caprolactam and the attractive interaction between the interlayer cation and ɛ-caprolactam.

The study of 13C NMR spectra of polystyrene thermally obtained on clays shows that thermal polymerization of styrene on these minerals proceeds by two parallel reaction mechanisms: the radical mechanism due to the thermal effect, and the cationic mechanism in which the initiatory cation H+ is provided by the clay. The latter mechanism, accelerated by increase in temperature, becomes more important as the clay content increases in the reaction medium. Otherwise, the thermal polymerization on clays is accompanied by the hydrogenation of some α carbons of the polystyrene molecule and the oxidation of certain aromatic carbons.

The study of M and Mg ion exchange (M = Co, Ni, Cu, Zn), between silicate gels SiO2.q(M, Mg)O.nH2O and amino acid (glycine) saline aqueous solutions (M, Mg)SO4, shows that the introduction of the complexing agent completely upsets the original distribution equilibria of M and Mg between the two types of phases. The values of the measured bulk distribution coefficient

are lowered considerably relative to the inorganic reference distribution coefficients. The lowering of D may be accounted for by calculating the contents of the different species, MA, MA+, M2+, under which the metallic element M is present in the solutions. The values of

resulting from the calculated M2+ contents are identical to the values of Dref, determined in systems without a complexing agent.

Conductimetric curves based on dissolution in dilute HF of a series of metakaolinite samples prepared by thermal dehydroxylation of kaolinite in air from 500°C to 987°C, have been interpreted in terms of (i) short-time conductivity variation, and (ii) specific initial dissolution rate (rsi). The first parameter has been correlated with a disorganization factor (Fd, equal to unity for an entirely amorphous silica-alumina mix) which does not exceed 0·52 for metakaolinite and, like rsi, reaches a maximum for samples prepared at about 720–750°C. These results, which agree with other data obtained by calorimetry and infrared spectroscopy, show that metakaolinite is never entirely amorphous and has a degree of disorder which varies with the conditions of preparation, and increases for samples which have been mechanically treated by grinding.

Minerals studied by an equilibrium model with a single mineral are similar to those studied in solid-solution models with q end-members. After discussing solid-solution models with q end-members where the limits of this kind of models are specified, the mathematical relations between the two kinds of models are developed. These relations show that the equilibrium model with a single mineral is compatible with the geochemical assumption of solid-solution. A method for estimation of equilibrium between a single mineral and a homogeneous set of aqueous solutions is proposed.

A montmorillonite clay and an X-ray amorphous Fe(II)-silicate were suspended in a synthetic groundwater solution under oxic and anoxic conditions at 23 and 70°C for 200 days. The clay samples were then analysed for total Fe, Fe(II), dithionite- and oxalate-extractable Fe (Fed and Feo), cation exchange capacity (CEC), and examined by X-ray diffraction (XRD) and diffuse reflectance spectrometry (DRS). The total iron content and Fe(II)/Fe(III) ratio of the clay increased with an increase in temperature and both were greater under anoxic than oxic conditions, as were the amounts of Fed and Feo. The CEC of the clay was lower in the presence of the Fe-silicate, suggesting that Fe-hydroxide had precipitated at the edges of the clay blocking some cation-exchange sites. No changes in the clay were detected by XRD or DRS after contact with the Fe-silicate, nor was there any evidence for Fe-hydroxide material in the interlayer region of the clay. However, it is shown that the amount and nature of iron associated with clay can be significantly altered and certain properties of the clay, such as CEC, can be affected when the clay is in contact with Fe(II)-containing materials.

The clay-mineralogical assemblages of Purbeckian carbonate sediments of the Swiss and French Jura Mountains are often composed of illite and interstratified illite-smectite. These illitic minerals occur mainly in thin layers of green marls which show evidence of subaerial exposure and mark the top of shallowing-upward sequences. X-ray diffraction, chemical and thermal analyses coupled with transmission electron microscopy suggest that the Purbeckian illitic minerals replaced smectite in intermediate continental-marine environments. The transition from smectite to illite and interstratified illite-smectite probably resulted from repeated cycles of wetting by marine waters and subsequent drying in hypersaline environments, under a hot Purbeckian climate.