Plasticity of ceramic bodies, mixture of Gairome, Kibushi or Murakami clay and Kamado feldspar, were examined by Pfefferkorn and Atterberg method. The resultswere,
(1) In any clay-feldspar systems, Atterberg plastic limit showed minimum value at the clay content of 40%. Liquid limit and Pfefferkorn plasticity index were increased with the increase of clay content. These behavior were explained approximately by the concept of binary-particle packing.
(2) In this experiment, the Pfefferkorn plasticity indices (PV) were situated approximatelyat the mean values of Atterberg liquid limit (WL') and plastic limit (Wp'), which were measured on the basis of wet weight instead of usual values based on dry weight. By assuming the generality of this relation (PV=(WL'+Wp')/2), empirical equations (WL'=(B-7.88)/A, Wp'=(-B+32.12)/A) were presented to derive Atterberg liquid limitand plastic limit from the data by Pfefferkorn method.
(3) According to the above relation between Pfefferkorn plasticity index and Atterberg limits, Bowmaker's plasticity factor was qualitatively related to the plasticitychart.

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Thermal transformations of a fluorine bearing phlogopite and synthetic fluor micas were studied mainly by X-ray diffraction method and thermogravimetry.
Two phlogopites transformed to forsterite, leucite and glass; tetrasilicic potassium fluor mica to forsterite and glass; tetrasilicic sodium fluor mica first to fluormagnesiorichterite and enstatite, and then to enstatite, forsterite and glass.
The phase transformations mentioned above were discussed by means of the phase assemblage expected from the phase diagrams of oxides whose end members are derived from the chemical compositions of the micas.
The difference of the decomposition temperature between phlogopites and tetrasilicic micas was discussed on the basis of the crystal structures of the micas. It is considered that higher thermal resistivity of phlogopites might be attributable to their crystal structures in which the dimensions of tetrahedral layer are larger than those of tetrasilicic micas.

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Changes on the lattice constants of fluorine bearing phlogopite occurring on heating were studied by X-ray diffraction method, and were discussed from the structural point of view.
The phlogopite shows a prominent loss in weight between 1000°C and 1200°C, and a contraction of the lattice is observed for the phlogopite heated at temperatures higher than 900°C. The contraction of the lattice for the phlogopite heated in air is larger than that for the phlogopite heated in argon. Structural parameters of Suzorite mica and those of Suzorite mica heated at 1000°C are predicted from their chemical compositions and lattice constants. As is obvious from the predicted structural parameters mentioned above, the flattening of the octahedral sheet is occurred by the oxidation of the transition elements in the octahedra on heating. The contraction of the lattice, therefore, might be attributable to the oxidation of the transition elements in the octahedra.

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Various members in the talc-willemseite series were obtained by hydrothermal synthesis under the conditions of 550°C, 500kg/cm² (water vapour pressure) and 10 days. The products were examined by infrared absorption spectroscopy, X-ray diffraction technique, thermal analysis, heat treatment and electron microscopy.
Nickel contents of the products calculated from the intensities of the absorption bands in the OH stretching vibration region were in good agreement with those of starting materials.
Their DTA curves were characterized by the very large endotherm in the temperature range of 800-1000°C. The peak temperature shifted gradually to higher temperature from 862°C for talc to 945°C for willemseite with increasing nickel content, indicating that nickel rich members are thermally more stable than magnesium rich members. This behaviour was also confirmed by the results of the heat treatment.

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