The hydrothermal reactions were carried out at 190°-300°C with mixtures of lime slurry and amorphous silica in the CaO/SiO₂ mole ratio 1.35:1. The products were crystalline foshagite (4CaO⋅3SiO₂⋅H₂O) or near-gel calcium silicate hydrate. The properties of products were studied by means of X-ray diffraction analyses, differential thermal analyses, electron microscopic observations and specific surface area measurements.
The results obtained were summarized as follows.
1) The synthetic foshagite was formed at the saturated steam pressure of the temperature above 200°C for over 5hrs. Our result indicated that foshagite is formed at the temperature which is about 60°C lower than that of Speakman's result. Also, the X-ray diffraction analyses showed that the formation of foshagite had proceeded through the intermediate stages of CSH gel or C-S-H (I) in the initial reaction.
2) According to the X-ray diffraction analyses, the d-spacings and the intensities of our synthetic foshagite coincided closely with that of natural one.
3) The crystals of synthetic foshagite had a characteristic lath-like appearance under an electron microscope. The cleavage habits of crystal were (001) and (100). While, the products of intermediate stages formed fibrous aggregates with elongation pararell to the b-axis
4) The specific surface area of synthetic foshagite was about 60m²/g

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A sintering characteristics of three kinds of alumina is studied in connection with repeated pressing of the powders. These powders used are of two kinds of alumina decomposed from aluminum sulfate and that by the Bayer process. The two kinds of alumina particles derived from aluminum sulfate had different mechanical strength. Results are as follows;
1) The repeated pressing of the Bayer alumina had a little effect on its particle shape as well as change in sinterability.
2) For aluminas obtained from aluminum sulfate, the number of broken secondary particles in compacts increased with the repeat of pressing and the sinterability of powders were improved. Especially, compacts containing secondary particles with weaker strength showed good sintering characteristics. It appears that the relation between distribution of the size of secondary particle in compacts and their sinterability is nearly proportional.
3) The slopes of log-log plot for shrinkage isotherm vs. times were unity for aluminas obtained from the salt, and 0.8 for the Bayer alumina in initial sintering stage. These results seem to show that “rearrangement” of powders is carried out in the initial stage of sintering.
4) Unbroken secondary particles in compacts caused poor sinterability by following reasons. Firstly, the particles prevent the rearrangement because of their large size and flat shape. Secondly, in the neighborhood two or so large particles which apt to cause a void in compacts, relatively large pores which hardly vanish during sintering are formed.
5) The main effect of repeated pressing on the sinterability of each alumina powder was exhibited in the rearrangement process which occurred during a very short time in initial sintering stage.

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弗化カルシウムの焼結において, 原料粉末に吸着している水分の影響を調べた. 単にアルゴン中で焼結した場合と, 水分を除去しつつ減圧下で焼結した場合とを比較した. この結果, 水の存在は, 焼結組織および焼結体のイオン伝導度に大きな影響を及ぼしていることが認められた. 酸素をドープした単結晶の伝導度との比較から, 水は弗化カルシウムと反応し, 弗素空孔を生じていると結論された.

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SrO⋅(6-x)Fe₂O₃⋅xAl₂O₃ solid solution crystals were grown from two series of melts of compositions expressed as 0.85(SrO⋅B₂O₃)-0.15 [SrO⋅(6-y₁)Fe₂O₃⋅y₁Al₂O₃] and 0.875(1.5SrO⋅B₂O₃)-0.125[SrO⋅(6-y₂)Fe₂O₃⋅y₂Al₂O₃], where 0<y₁, y₂<6. The melts were cooled at the rate of 50°-6°C/hr from 1300° to 1100°C. No crystals came out of the melts of y₂ series with y₂ value more than 4.5. From the melt of y₁ series, the solid solution crystals could be obtaind for all y₁ values. The concentration ratio of aluminium to iron of the crystals grown from a melt of y₂ series was considerably smaller than the same concentration ratio in the melt from which the crystals was grown. Crystals with the x values of 0.82, 1.51, 3.54, 5.25 were obtained from the melts with the y₁ value 2, 3, 4, 5, respectively. These results suggest that the molar ratio SrO/Al₂O₃ of melts should be less than 1.5 to get crystals with high Al content.
Most of the crystals were hexagonal thin plate with 1cm-0.1mm across. The higher the Al content in the crystals, the smaller the crystal size. Other crystalline phase did not precipitate for all composition and temperature range in the present experiment. Lattice parameter and Curie temperature were also measured for the solid solution crystals.

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Stress relaxation of glasses in the systems As-S and As-Se was measured by the torsional method near the transition temperature (relaxation modulus of 10¹⁰-10⁸dyne/cm²). Time-temperature superpositions of each run for all samples were successful in this range. And so, at the fixed temperature (the temperature of isoviscosity, η=2×10¹³poise) we could draw master curves for all samples as shown in Fig. 5, 6 and 7. As to the shift factor, a_T, the plots of loga_T vs. 1/T give essentially a straight line for each sample as shown in Fig. 9 and 10. Therefore, for the stress relaxation of glass, the apparent activation energy can be calculated by the following equation, ΔE=Rd(loga_T)/d(1/T), where R is the gas constant. The results are shown in Fig. 11. In the As-S system, the activation energy is high at As₂S₃ and goes through an unusual maximum around As₂S₈. In the As-Se system, the activation energy is high at As₂Se₃ and decreases with increasing Se content. But it increases again with Se contents above 80 atomic per cent.
The distribution of relaxation time can be expressed approximately as follows, H(τ)=-{G_r(t)⋅dlogG_r(t)/dlogt}_t=τ. The results are shown in Fig. 12, 13 and 14. The distribution curves for all the samples go through the maximum. The peak appears at the longest period for As₂S₃ and As₂Se₃ glasses in As-S and As-Se systems, respectively, and shifts from long time to short time with increasing S and Se contents. The relaxation moduli at t=0 are shown in Fig. 15 and are the largest for As₂S₃ and As₂Se₃ glasses in the systems As-S and As-Se, respectively.

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This study was concerned with the formation, color development and application for colored glazes of the spinel solid solution in CoO-MgO-Cr₂O₃-TiO₂-SnO₂ system.
Specimens were prepared by calcining the oxide mixtures at 1400°C for 1hr. Concerning each specimens, the formation of spinel solid solution was investigated by X-ray diffraction, the color was discussed by means of spectral reflectance and the stability for various glazes was tested. The results were summarized as follows.
1. A formation of continuous solid solution and an obedience to Vegard's law were confirmed by X-ray analysis.
2. In MgO-Cr₂O₃-TiO₂-SnO₂ system, as the amount of Cr³⁺ increased, color ranged from yellow green through leaf to grayish leaf, and the absorption of Cr³⁺ shifted towards violet region.
3. Colors which developed in CoO-MgO-Cr₂O₃-SnO₂ system ranged from blue to bluish green, and the absorption of Cr³⁺ shifted towards violet region with increasing amount of Cr³⁺.
4. As the amount of Cr³⁺ increased, colors obtained in CoO-MgO-Cr₂O₃-TiO₂ system, ranged from bluish green through green to bluish green, and the absorption of Co²⁺ and Cr³⁺ shifted towards violet region.
5. CoO-MgO-TiO₂-SnO₂ system revealed the colors ranging from blue to bluish green, and the absorption of Co²⁺ shifted towards red region as the amount of Ti⁴⁺ increased.
6. Colors ranging from bluish green to green developed in CoO-MgO-Cr₂O₃-TiO₂-SnO₂ system.
7. According to the results of the colored glaze tests, the specimens with the composition in Cr³⁺ rich region were appreciated to be stable as a glaze stain.

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It is ascertained without a contradiction that CaSO₄⋅2/3H₂O composition corresponds to the primary peak at 75°C of D. T. A. curve.
The preparation of CaSO₄⋅2/3H₂O sample is rather more difficult in the electric furnace installed with the thermostat apparatus than in collecting by the co-operation of thermal balance and D. T. A. equipment. Accordingly the author preferred to make use of the latter thermal analysis method.
The initial decisive assertion of existence about CaSO₄⋅2/3H₂O thermal transformation was proposed by M. Sekiya. The fundamental notes relating to CaSO₄⋅2/3H₂O amongs such as J. S. Dunn, C. W. Bunn, and A. Debuisson are discussed by K. Inô with his original comparative interpretation. The transformation such as hemihydrate and anhydrite (α-type, β-type) was reported by S. Yamanouchi et al., or P. Gay. The general description on CaSO₄…CaSO₄⋅2H₂O system was realized by Flörke. Also, McConnell discussed the reactive mechanics as follows: CaSO₄⋅1/2H₂O=CaSO₄(β-soluble anhydrite)+1/2H₂O.
Several observations on this study are performed employing the methods such as D. T. A., powder X-ray diffraction, infrared absorption and far-infrared absorption. The results from these experiments inform us that the lattice character of CaSO₄⋅2/3H₂O belongs to a hexagonal system P6mm(C_6v¹) with consulting international tables for X-ray crystallography (Henry et al.).

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Four series of photochromic glasses were prepared by heating a glass having the batch composition SiO₂ 59.5, B₂O₃ 20.6, Al₂O₃ 8.9, Na₂O 4.7, Li₂O 4.3, Cl 1.5, Ag 0.5, CuO 0.015% in wt. at 570°C for 3hr, at 580°C for 3hr, at 580°C for 8hr and at 580°C for 31hr. The samples of different thicknesses ranging from 0.19mm to 2.73mm obtained from each series were subjected to optical measurements of darkening and fading. The following results were obtained.
1. The degree of U. V.-induced darkening increased as the sample thickness increased for all series as expected. However, the features of the curves correlating the degree of darkening with the sample thickness varied with the series, namely, with the conditions of high temperature heat treatment required for precipitation of AgCl particles; the rate of increase in the degree of darkening with increasing thickness of the sample decreased more rapidly as the thickness increased for a series having a large light scattering factor than for a series having a small one. A large scattering factor was caused by large AgCl particles that was produced by prolonged heat treatment. On the other hand, the degree of darkening of very thin samples did not undergo the effect of the light scattering, but depended only upon the light absorption characteristics of the sample.
2. The rate of fading of U. V.-darkened glasses varied with the thickness of the sample; in general, thinner samples exhibited higher fading rate than thicker ones for glasses subjected to the same heat treatment for AgCl precipitation.
3. No general relation was found between the degree of darkening and the rate of fading.

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