The stability of smectite separated from a Houston Black clay soil was studied by solubility methods in an acid environment. High Silicon levels (supersaturated with respect to amorphous Si) probably were due to dissolution of the smectite and slow precipitation of amorphous Silicon. Also, mica and vermiculite impurities may have contributed to high solution Si values. Solubility data from equilibrium solutions of various treatments and chemical structural analyses permitted the formulation of a solubility equation. The ΔG°f for the Houston Black smectite computed from pK values was —2433.9 ± 0.8 kcal/mole. The stability of this clay could then be determined by calculations for any desired solution environment. It was found that under some conditions this soil smectite could be more stable than Belle Fourche and Aberdeen montmorillonites. Therefore, it appears that this soil clay has the required stability area in which it can form in nature.

Micas are described from the kaolin type Tertiary weathering crusts formed on granites and gneisses of Lower Silesia, Poland. In the weathering crust, large scale processes of transformation of micas (muscovite, biotite) take place. Weathering of micas is a gradual transformation of their structures by removal of the mobile cations Mg2+ Fe2+ Fe3+ and finally K +. Muscovite transforms into kaolinite through the intergrowths of two phases, mica and kaolinite. A degradation series, muscovite → mica/montmorillonite → montmorillonite → kaolinite also is observed. Biotite passes directly into kaolinite, but at higher concentrations of K and Al one observes the following sequence of biotite degradation: biotite → dioctahedral mica rich in Fe → dioctahedral mica poor in Fe → kaolinite. This process involves the exchange of Mg2+ and then Fe2+ of octahedral layers by Al3+ less mobile under weathering conditions. In the next stage of degradation, K + removal and kaolinite formation takes place. The micas representing different stages of this transformation, dark green, light-green, and silver-white, have been separated and investigated.

An electrooptic birefringence technique was employed to study the effect of particle size, saturating cation, and clay type on the rotational diffusion coefficient (a measure of the rate at which the particles rotate or relax within the solution) from a preferred orientation. These studies help elucidate the nature of the cation—water environment near the clay particles.

Previous work has shown that some clay particles orient at both low and high voltages due to a permanent dipole and an induced dipole, respectively, whereas other clays under similar short-duration pulses orient only at high voltages. The permanent dipole was attributed to the iron in the octahedral layer of the clay mineral, whereas the induced dipole was probably due to a redistribution of the diffuse double-layer cations. This study shows that smaller clay particles orient more readily at low voltages and have greater rotational diffusion coefficients at high voltages. The higher the rotational diffusion coefficient, the faster the particles move in their surrounding water-cation environment. The effect of the saturating cation on the rotational diffusion coefficients was Na > Li > K for the permanent dipole and K > Li > Na > Ca > Mg for the induced dipole orientation. Previous results (Schepers and Miller, 1974) are interpreted to mean that a particle in dilute suspension can rotate independently of its environment only when the salt concentration in the surrounding medium approaches zero. At higher salt concentrations, or if the particle environment is perturbed by an electric field, the particle rotates with a water shell. As the concentration of salt or strength of the electric field increases further, either the viscosity of the surrounding solution increases or the size of the rotating shell is greatly increased. Thus, the water around clay particles appears to be structurally different than normal, and this condition is probably caused by the nature of the clay—cation interaction.

The extent of protonation of organic bases in clay—water systems depends upon the adsorptive properties of the organo-clay species involved, and upon the structure and degree of hydration of the clay system. Organic molecules that can disperse cationic charge over two or more condensed aromatic rings give rise to greater surface-induced protonation than do single-ring organic molecules with similar solution pKa. Protonation in clay suspensions is frequently far in excess of that predicted on the basis of electrolytic suspension pH and solution pKa of the organic base. For a given organic base, protonation in a clay film exceeds that in the suspended clay system. Protonation in an organo-clay film increases as the film moisture content decreases. The extent of protonation in organo—clay systems varies with cationic species, cationic saturation, and clay type.

Highly significant differences are observed between the methyl derivatives of attapulgite, produced when this mineral is reacted with (CH3)2Si(OC2H5)2, in the presence or in absence of HCl. In the first case, the corresponding infrared spectra show characteristic absorption bands due to the Si(CH3)2 radicals at 1260, 850 and 800 cm−1 as well as a shoulder at 960 cm−1, the latter assigned to silanol groups. The 850 cm−1 frequency which is usually exhibited by trimethylsilicon compounds is also detected when —O—Si(CH3)2 radicals are grafted in the silicates, but only if HCl is present in the reaction. Neither this band nor the 960 cm−1 shoulder appear in the spectrum of the derivative synthetized in absence of HCl. A comparative study by both i.r. spectroscopy and X-ray diffraction does not reveal structural modifications in attapulgite after it has been methylated in absence of HCl. However, although the i.r. spectra of the HCl-methylated derivatives, prepared at different periods, do not indicate substantial structural perturbations, X-ray diffraction patterns show a gradual weakening of the peaks due to attapulgite, as reaction time increases; the intensity of the (110) order reflection is drastically reduced after a 165 hr attack. The most viable mechanism for the grafting of the dimethylsiloxy units in attapulgite is through the HCl induced silanol sites. When the reaction is taking place in anh. benzene medium (absence of HCl), dimethyldiethoxysilane may be hydrolyzed by a fraction of water contained in attapulgite; the hydrolysis products which do incorporate on the surface of the silicate are identified by i.r. spectroscopy.

A IIb orthochlorite (brunsvigite), from the chloritic metabasalt in the Middletown Valley of Maryland, was altered to a regularly interstratified chlorite—vermiculite after four months reaction in saturated bromine water on the steambath. The artificial weathering product resembles the regularly interstratified chlorite—vermiculite in a soil in Adams County, Pennsylvania, that has developed in greenstone similar to the chloritic metabasalt in the Middletown Valley of Maryland. The results of this and previous investigations on artificial and natural weathering of chlorites indicate that oxidation of structural Fe2+ is an important reaction in the alteration of chlorites into vermiculitic products. The results also show that IIb orthochlorites, apparently structurally similar but having different Fe2+ contents may react differently under the same weathering conditions. For example the acid oxidation treatment altered a IIb chlorite (diabantite) directly into a vermiculite, whereas the same treatment altered another IIb chlorite (brunsvigite) into a regularly interstratified chlorite—vermiculite. Detailed investigations of the chlorite structures are probably necessary to determine whether or not these alteration processes are structurally controlled.

The i.r. spectra of mixtures of different Na-montmorillonites were determined at several water contents between 2 and 22 g of water/g of montmorillonite. It was found that Si—O absorption is represented by four closely-spaced bands, one of which is pleochroic. The pleochroic band appeared only at higher water contents. All of these bands, excepting that with the highest wave number, shifted in frequency with increasing isomorphous substitution. None of them shifted in frequency with increasing water content.

The absorption coefficient for the principal Si—O absorption decreased with increasing isomorphous substitution but increased with increasing water content. Niether isomorphous substitution nor water content appeared to have any significant effect on absorption due to O—H stretching or H—O—H bending in the interlayer water.

At a critical water content for each montmorillonite, an abrupt change occurred in the absorption coefficient for the principal Si—O absorption. This change was ascribed to a sudden rearrangement of the particles.

The hydrothermal aging of pure silica—alumina gels in presence of 10 ml of 0.1 N sodium hydroxide solution at 175, 150 and 130°C for 8–30 days led to the synthesis of zeolites and the phyllosilicates, beidellite and kaolinite. The solution was neutralized by a partial hydrolysis of the gel which readily reorganized into a prezeolitic material. At pH values ⩾ 9, with 300 or 600 mg of gel, it evolved towards the crystalline zeolites P and S, with low surface area (7–100 m2/g) but high exchange capacity (300–475 m-equiv./100 g). With gel amounts of 600–2400 mg, and pH values of 8–5.5, the prezeolitic material provided rows of O—Si—O—Al—OH which recombined to form the phyllosilicate structures. Surface area increased (170–325 m2/g) but exchange capacity decreased (100–250m-equiv./100 g). The results obtained by various techniques (XRD, DTA, IR) indicated a moderate degree of crystallinity of these phyllosilicates; in addition, X-ray powder diffraction suggested that hk bands were the first to develop.

The positive results obtained with a 0.40 ratio Al2O3 gel compared with the negative results obtained with 0.30 or 0.50 Al2O3 gels indicate that the gel composition is very important for the formation of phyllosilicates under the experimental conditions.