Trimethylsilylated (TMS) magadiite and kenyaite were treated thermally and the influence of trimethylsilyl groups on the surface areas of the heat-treated products was investigated. The basal spacings of the TMS-magadiites treated up to 300°C were constant. When TMS-kenyaite was heat-treated, the basal spacing was kept at a constant value until 400°C. The specific surface areas of the products increased up to those temperatures. After the organic groups were burned, the interlayer spaces of the heat-treated TMS-magadiite and TMS-kenyaite were still expanded possibly by the presence of oxidized silyl groups in the interlayer spaces.

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The interaction between the talc layers is studied for a model system of two tetrahedral sheets. The upper sheet is a unit cell of tetrahedral sheet, [Si₄0₁₀] ^4- and the lower sheet an infinite hexagonal network of [Sio₄] ^4-. Using the electrostatic and Lennard-Jones equations, the energy for the interlayer interaction is calculated under the periodic boundary conditions. It is concluded that the interaction between the above two silicate sheets is attractive. The most stable configuration is predicted to be that the Si atom in the upper sheet is located nearly in the middle of the hexagonal hole in the lower sheet.

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The adsorption of various odorous vapors (adsorbates) by sepiolite, which adsorbed water previously, was studied by comparison with that of ammonia. Experiments were carried out at 25°C in ambient atmosphere or under the reduced pressure without air nor water. The amounts of adsorbates, adsorbed on sepiolite in the air having 30% relative humidity, were found to be rather large. They were about 0.15, 0.011, and 0.0042mmol/g, for ammonia, pyridine, and acetaldehyde, respectively, under the relative vapor pressure of these adsorbates, P/P₀, of 10^-5 at 25°C. And they were also about 0.73, 0.04 and 0.0045mmol/g, for acetone, toluene, and styrene, respectively, under the relative pressure, P/P₀, of 10^-3 at 25°C. The amounts of the adsorbates were found to be closely related to the hydrophilic properties such as pK_a, hydrogen bonding, and solubility in water. The adsorption is thought to be made through a water molecular layer on the sepiolite. The amounts of the adsorbates, adsorbed on sepiolite under a reduced pressure without air nor water, were about 6.0, 2.0, 1.5, 1.0 and 0.8mmol/g, for ammonia, pyridine, ethyl acetate, styrene and hexane, respectively, under the relative pressure, P/P₀, of 10^-1 at 25°C. On the other hand, the amounts of the adsorbates, adsorbed on coconut-shell active carbon in the air of 30% relative humidity, were about 0.015, 0.011 and 0.008mmol/g, for pyridine, acetaldehyde and ammonia, respectively, under the P/P₀ of 10^-5 at 25°C, and were about 0.9, 0.4 and 0.06 mmol/g, for acetone, toluene and styrene, respectively, under the P/P₀ of 10^-3 at 25°C. On the carbon surface, however, a close relation was not observed between the amount of adsorbates and the hydrophilic property. The amounts of the adsorbates having the hydrophilic properties such as acetone, pyridine, acetaldehyde, and ammonia plotted as a function of the relative vapor pressure, fell on the line extrapolated from those of these other adsorbates. The adsorption on the carbon takes place mainly on its naked surface and partly through the water molecular layer.

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Ab initio Hartree-Fock molecular orbital (MO) calculations are carried out for a system of linked [SiO₄] ^4- and [Al0₄] ^5-tetrahedra (denoted by a cluster). The system is regarded as a model of the tetrahedral sheet of a clay. The effective charges from the Mulliken population analyses are almost constant when the number of tetrahedra in a cluster increases from 1 to 6. The MO calculation is extended for the system of a point positive charge located over the surface of a cluster. The obtained potential curves of the point positive charge coincide well with the electrostatic potentials due to the effective charges on the atoms of the cluster. The binding energy of a metal complex ion, [M (phen) ₃] ²⁺ (phen=1, 10-phenanthroline), with a cluster, {[SiO₄] ^4-} ₉₇₁/{[Al0₄] ^5-}, is estimated in terms of the electrostatic and van der Waals energies for the atomic pairs. The orientation of the chelate at the minimum energy is compared with the recent experimental results for an adduct of the chelate with montmorillonite clay.

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An imnrovement in the “crystallinity” of an industrially synthesized Nafluortaeniolite was performed by hydrothermal annealing with pure water or NaOH solutions. The temperatures and pressure applied were 300, 450 and 600°C, and 100MPa, respectively. The run duration was 7 days. By hydrothermal annealing, the particles of Na-fluortaeniolite less than about 21Lm disappeared and others grew to have the euhedral shape common to micas. The improvements in the size, form and perfection of crystals resulted from a pure water treatments, especially that at 600°C. The hydrothermal annealing with NaOH solution showed a similar effect but produced some second phases.

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