The relation between the change of infrared spectra in 450-550cm^-1 (22.2-18.2μ) and 900-1000cm^-1 (11.1-10.0μ), and the change of structure by rehydration of pyrophyllite, montmorillonite, illite, kaolinite, halloysite and muscovite were studied.
The samples were dehydrated by heating, respectively, at 250°, 600°, and 1050°C for an hour. Some of them were rehydrated by keeping in air or in water, and also by hydrothermal treatment (300°C, 85atm., 1-10hrs.).
The results obtained are as follows:
(1) The absorption in the wave numbers 520-540cm^-1 remained unaffected by the dehydration at 250°C, whereas it disappeared after the removal of lattice water by heating at a temperature higher than 600°C.
The spectra did not come into existence again by the rehydration by keeping in air, or in water, but appeared again by hydrothermal treatment (300°C, 85atm., 1-10hrs). It seems, therefore, that the absorption is closely related with the water of crystallization, and probably the water in the lattice is held strongly by hydrogen bond.
(2) The absorption in 900-1000cm^-1 (11.1-10.0μ) which disappeared by the removal of the water of crystallization did not appeared by rehydration by keeping in air, or in water, but appeared again by hydrothermal treatment.
It was confirmed by hydrothermal treatment that the spectra were based on the OH in lattice combining to Al in the octahedral layer of clay minerals.
(3) The absorption in 460-470cm^-1 (21.2-21.7μ), comming from Si-O bond, changed as the sliding down of the base line by the removal of lattice water, and recovered again by the hydrothermal treatment.

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Refractive indices and Abbe's numbers of borate glasses of binary and ternary systems containing the oxides of Li, Na, K, Be, Mg, Ca, Sr, Ba, Al, La, Ti, Zr, Th, Nb, Ta, and W were measured.
The relation of composition to refractive index, n_D and Abbe's number (Table 1) was able to be expressed by a formula which does not contain the values of specific gravity, viz.
n_D=1.455+Σia_ix_i+Σib_ix_i²,
v=(n_D-1)/(0.521+Σik_ix_i)n_D,
where a_i, b_i, k_i, are the component factors, x_i is the molar fraction of M_inO_m.
From the values of n_D and ν of borate glasses the component factors were calculated with a result that b_i on the network former is zero, and the values a_i/k_i of modifier is larger than those of network former. And the intermediated Al, Be, La, etc., do not fit in with above equations, which may be explained by the change from modifier to network former in conformity with external circumstances such as the kind or quantity of existing components.

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The thermal expansion of forsterite porcelain, which is one of the most important properties for use in electron tube, and the effect of different firing temperature, and of repeated heating were investigated. Based on the experimental results the relation between the microstructure and the thermal properties were discussed.
The coefficients of linear expansion along each axis of synthesized forsterite were measured by X-ray with a result; a-axis 10.47, b-axis 12.50, c-axis 11.05×10^-6, in the temperatures 20°-800°C. These values correspond to that of the forsterite porcelain containing much forsterite.
Referring to the data of Navias (J. Am. Ceram. Soc., 37 [8] 329 (1954)) it was pointed out that the elevation of the firing temperature of 25°C would accompany with the increase of the coefficient by 1.0×10^-6, and this is the figure being intorelably large for the vacuum sealing with metal.
To study this phenomenon many batches of forsterite porcelain were prepared, and fired at different temperatures. The specimen made from talc, sea-water magnesia and BaCO₃ showed the marked decrease of the coefficient (about 1×10^-6) with the elevation of firing temperature from 1400° to 1500°C. Under microscope was observed the increase of glassy phase with increasing firing temperature, which probably leads to the reduction of the expansion coefficient.
The coefficient of the specimens containing MgO and SiO₂ in various ratios have also beem measured. Forsterite porcelain having excess of SiO₂ (SiO₂ 47%) showed the increase of the coefficient of about 1.2×10^-6 by the elevation of firing temperature from 1400° to 1500°C, which, however, decreased with increasing MgO. The specimens containing excess MgO showed only a very small variation.
By microscopic observation of the specimens containing excess SiO₂, the forsterite crystal showed a marked aggregation by the elevation of firing temperature, causing the decrease of the coefficient, while in the forsterite containg excess of MgO the aggregation was scarecely recognized, and consequently gave the constant coefficient.
Moreover, for many kinds of forsterite porcelain, the variations of the coefficients of linear thermal expansion by the repeated heating were measured. They could be classified into two groups, i.e., one coefficients increased, and the other coefficient did not nearly or entirely increased with repeated heating. The former has more glassy substance than the latter, and it was concluded that such a glassy substance decreased the coefficient by the repeated heating.
The authors have confirmed that the composition of forsterite porcelain for use in electron tube should be in excess of MgO and the glassy substance should be reduced as far as possible.

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In the previous paper (J. Ceram. Assoc. Japan, 67 [4] 139 (1959)) the authors have reported that the titanium spinel pigments of the system, CoO-MgO-TiO₂, NiO-ZnO-TiO₂ gave clean and brilliant hues. In titanium spinels TiO₂ may partly or entirely be replaced by SnO₂, and in aluminium spinels Al₂O₃ may be replaced by Cr₂O₃. For the purpose of throwing the light on the properties of the pigments of quarternary, and multi component systems the combinations of CoO-MgO-TiO₂-SnO₂, NiO-ZnO-TiO₂-SnO₂, Coo-NiO-ZnO-TiO₂-SnO₂, and CoO-ZnO-Al₂O₃-Cr₂O₃ were investigated.
The components were mixed by wet process, calcined at 1350°C. The reflactance between 400-750mμ were measured by a self recording photo-electric spectrometer to represent the result by C. I. E. colour specification, and X-ray analysis was carried out to calculate the lattice constant.
The results are summarized as follows:
(1) Each sample gave not mixed but single spinel structure.
(2) In CoO-MgO-TiO₂-SnO₂ system there were a wide varaiety of pigments of clean and brilliant hues ranging from greenish blue or medium green to blue.
(3) NiO-ZnO-TiO₂-SnO₂ system gave light green hues.
(4) In CoO-NiO-ZnO-TiO₂-SnO₂ system colour changed from yellowish to bluish green with increasing content of SnO₂
(5) In CoO-ZnO-Al₂O₃-Cr₂O₃ system colour turned to green with increasing content of Cr₂O₃, and blue with increasing content of CoO.

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