Reaction mechanism between hydroxide ion (OH^-) and pore region of nano-ball allophane was analyzed by molecular orbital method (MOPAC-PM3) with a model cluster including the pore. Many Siatoms with silanol groups (Si-OH) are exposed as broken edge at the pore region, and nucleophilic OH^- may attack the positively charged Si atoms. When Na⁺, as a counter ion of OH^-, was held on the silanol group by cation exchange reaction (Si-ONa), calculated positive charge of the Si atom increased from that of Si-O^-. This may promote nucleophilic attack and adsorption of OH^- toward the Si atom. In model cluster with an OH^- adsorbed on the Si atom to form five-fold coordination, decreases in calculated bond orders, bond strengths, of some Si-O and Al-O bondings were observed near the OH^-adsorption site. This bond weakening will lead to dissolution of one Si and three Al atoms from the pore region of fundamental allophane structure, which is consistent with experimental observation. The increase in positive charge on Si atom and decrease in bond order of Si-O and Al-O bondings were also observed in calculations with one to six water molecules added to simulate reactions in aqueous system.

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The weathering process of the Pan African granitic rock of Batie was mineralogically investigated by means of Microprobe analysis (EPMA), X-ray diffraction (XRD), X-ray fluorescent (XRF), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The porphyritic granite is composed of biotite, feldspar and quartz as main minerals, whereas epidote, chlorite, kaolinite and mica clay mineral are secondary products. Mica clay mineral and kaolinite are main constituent clay minerals in the granite saprolite (weathered granite). Mica clay mineral predominantly occurs at the lower part of the investigated profile associating with a small amount of kaolinite. The granite saprolite at the top part of the profile consists mainly of platy kaolinite with a small amount of lath shape mica clay mineral. Mica clay mineral was formed in the hydrothermal clay veins occurring in the weathering profile. It is inferred that mica clay mineral occurred in the altered granite was formed by hydrothermal activity.
Detailed observations of morphological variation by TEM with X-ray analysis revealed that crystal size and shape reasonably explain the transformation sequence of kaolinite as weathering proceeds. Close relationship between crystal size and morphology is obtained.
Etch pits developed on quartz and K-feldspar grains are commonly observed. However, shape and size of the etch pits are quite complicated suggesting none monotonous micro-weathering condition. Etch pits found in the upper part are much rougher than those of the lower part.
Based on the results obtained, weathering condition of the Batie granite was discussed mainly from the standpoint of clay mineralogy.

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Hectorite containing Ni²⁺ instead of Mg²⁺ in the trioctahedral sheets has been synthesized at 300°C for 12 h under autogenous water vapor pressure by hydrothermal reaction of four kinds of starting slurry with the initial molar ratios Na: Ni: Li: Si=0.7: 5.4: 0.6: 8.0, 1.4: 5.4: 1.2: 8.0, 1.4: 4.8: 1.2: 8.0 and 1.4: 4.8: 1.2: 7.5 made from Ni-Si homogeneous precipitates, lithium fluoride and sodium hydroxide. The resulting Ni-hectorite has been characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrophotometry (FT-IR), thermogravimetry and differential thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry. The Ni-hectorite is relatively large massive plate-like particles with a characteristic tint of green and has similar structure to other hectorites, a smaller cation exchange capacity (CEC) and lower adsorptive ability of methylene blue (MB) compared to a commercial Mg-hectorite and a synthetic Znhectorite as reference. It has also been clarified that the Ni-hectorite modified electrode shows a redox reaction Ni²⁺ to Ni³⁺ and Ni³⁺ to Ni²⁺ in cyclic voltammetry.

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Layered double hydroxide (LDH) has an anion exchange property, and the intercalation of various organic molecules into LDH has been investigated in recent years. We have reported the intercalation of non-ionized guests such as pentose, hexose and cyclodextrin, into Mg-Al LDH by the calcinationrehydration reaction. In this paper, the intercalation behavior of non-ionized guests, various straight chain polyhydric alcohols (carbon number 3-5), into Mg-Al LDH by the same reaction has been examined. According to the XRD patterns and FT-IR spectra, the solid product was found to contain polyhydric alcohol and to show the restorable LDH structures. The amount of polyhydric alcohols intercalated was as follows: glycerin (C3)<erythritol (C4)<ribitol (C5)<arabitol (C5)<xylitol (C5) and greatly influenced by the conformation of C5 polyhydric alcohol isomers. It was confirmed that these polyhydric alcohols were intercalated into the LDH interlayer space by the formation of hydrogen bond between hydroxyl groups of guest polyhydric alcohols and the host LDH basal layer.

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