This research was carried out as a part of the study on synthesis of hexagonal boron nitride.
Orthoboric acid (B) and ammonium thiocyanate (N) were mixed as starting materials and then put in a porcelain vessel. The four steps heating method was used, namely, the first was held at 100°C for one hour, the second at 140°C for 2 hours, the third at 250°C for 2 hours and lastly at 800°C for 2 hours, as the better condition in a stream of nitrogen and ammonia.
The obtained white product was filtered off, washed with hot water and ethanol and dried. Then the composition and crystalline state of residual sample were examined by a chemical analysis, X-ray diffractometer and under a polarizing microscope. The yield of boron nitride was decided from its content in the product by chemical analysis.
In the mixture of N/B=1 in a nitrogen atmosphere, the yield was only about 25% by weight, but in N/B=2, about 57%, the higher yield.
On the other hand, in a flowing atmosphere of ammonia, the yield was about 83% by weight in the mixture of N/B=1, 94% in N/B=2 and 96% in N/B=5, and inclined to increase with N/B molar ratio.
It is remarkable that direct heating to 800°C in ammonia atmosphere was given the nearly same yield compared with that of the four steps heating method.

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The residual slag after the refineing of sand iron has several and valuable components, such as SiO₂, TiO₂, Al₂O₃, Fe₂O₃, CaO, MgO, V₂O₃ etc.. When the slag is in glassy state, it easily dissolves in most mineral acids.
In the present paper, the influence of seed on the formation of titanium oxide hydrates by the hydrolysis of titanium sulfate solution which is obtained by the sulfuric acid treatment of the slag and of SO₃ on the formation of rutile-type titanium dioxide by heating of the hydrates are studied.
The obtained results are as follow;
(1) An effective seed in the hydrolysis of titanium sulfate solution in sulfuric acid solution is anatase-type hydrate.
(2) The content of SO₃ in the hydrates is reduced by the use of anatase-type seed in the hydrolysis.
(3) Most of SO₃ in the hydrates is removed by the washing with NaOH solution and Na-citrate solution (alkalic with NaOH).
(4) In spite of the fact that the formation of oxygen vacancies in the oxygen structure of titanium dioxide accelerates the thermal transition of anatase to rutile, the hydrates containing SO₃ convert more easily to rutile in O₂ atmosphere than in air and N₂ atmosphere. From this experimental result it is suggested that the rapid reduction of SO₃ in titanium dioxide in O₂ atmosphere promotes the thermal transition of anatase to rutile.
(5) In the chromaticity coordinates, the whiteness of rutile-type titanium dioxide which was prepared from the slag in this study is approximately equal to that of a commercial rutile-type titanium dioxide.

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In order to improve the life of saggers, three kinds of material were studied as for the sagger bodies. The physical properties of trial manufactured saggers, thermal stress for saggers of large size, and temperature gradients between the outer and inner sides of saggers in the tunnel kiln were examined. The mechanical strengths, thermal expansion, specific heat, and thermal conductivity of saggers of chamotte, cordierite, or semi silicon carbide type were measured.
The suitable heating or cooling rate for saggers were found to be 1.5°C/min for chamotte type, and 6°C/min for cordierite or semi silicon carbide type saggers, from thermal stress analysis.

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The solid solubility of Ti or Mn in C₃S and alite was first of all investigated in the hypothetical systems, C₃S-3CaO⋅TiO₂, C₃S-3CaO⋅MnO₂, alite-3CaO⋅TiO₂ and alite-3CaO⋅MnO₂.
Synthesized samples preparared by heating at 1500°-1600°C were examined by means of chemical analysis, X-ray diffraction analysis, microscopic observation and electron probe microanalysis.
Hydration experiments were then made using the samples containing 0.07mol Ti or 0.05mol Mn in either C₃S or alite. The paste hydration was investigated by means of calorimetry, X-ray diffraction, chemical analysis and microscopic observation, and also the motar strength was tested.
The following results were obtained.
(1) Ti can substitute for 0.13mol Si at the maximum both in C₃S and alite, accompanied by slight expansion of their crystal lattice. Mn dissolves up to 0.06mol in C₃S and up to 0.08mol in alite and their crystal lattice contracts very slightly through its dissolution.
(2) The hydration characteristics of C₃S and alite are affected by the dissolution of Ti or Mn. In the case of Ti bearing solid solutions, the rate of hydration is lowest at the early stage, but it becomes highest and their mortar strength also becomes highest after 3 days-curing.
While, the degree of hydration and the motar strength of the Mn bearing solid solutions become higher in later stage. These results seem to be due to mainly the chemical compositions rather than the change in crystal forms of C₃S and alite.

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