To the author's knowledge there exists no established explanation on the mechanism of the erosion of the bricks used in the equipments of bottom casting for producing conventional carbon steel with basic open-hearth furnace, and also with converter. Moreover, while it is generally assumed that the occurence of aluminous sand is very likely due to the erosion of the bricks by molten steel, in particular to the reaction of the reducing SiO₂ of fire-clay bricks by Mn of molten steel, whose concentration is closely related to the deoxidizing reaction, the effective method of preventing the sand has not been known.
From the results of the previous investigations the author concluded that the erosion of the bricks is mainly due to the oxides of slaggy matter contained in flowing molten steel, and also the occurence of aluminous sand is likely due to another causes. This paper contains the results of the mathematical-theoretical as well as the experimental studies carried out to prove more clearly the author's conception.

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The effects of the flow of hard solder were investigated in relation to the stress in alumina-to-kovar seal used in the envelopes of electron tubes.
Melting point of the solder was 780°C. The ceramics and the metal were sealed together to form a bimetallic strip to measure the bending during heating or cooling.
When the sample was cooled from the temperature higher than the melting point of the soldet bending occured rather sharply at arround that point, and the curvature of the strip was approximately proportional to the contraction difference between the ceramics and the metal. More detailed examination on the relations of temperature vs. bending during repeated cooling showed some kind of hysteresis phenomena near the melting point of the solder.
Assuming that these were caused by the flow of the solder, by which some of the stress in the seal is released, the hysteresis phenomena could be explained quantitatively with a result that the equivalent setting point of the seal was found to be about 20°C lower than the melting point of the solder.

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The tablets consisting of chemically purest Mg(OH)₂ and 0-1.5wt. per cent Fe₂O₃ were fired at 1000°-1550°C to examine the appearance after the firing as well as the microstructure.
The firing shrinkage and the bulk density began to increase markedly from 1000° to 1200°C (Figs. 1-4). At 1200°C the coloured regions, which had developed by the diffusion of iron from Fe₂O₃ grains, began to spread abruptly with the remarkable growth of periclase crystals. From the results mentioned above, it may be inferred that the sintering of Mg(OH)₂ occurs in two successive stages; (1) up to 1200°C the periclase crystals formed by the decomposition of Mg(OH)₂ come into intimate contact each other showing the remarkable shrinkage of the specimens, and (2) in the second stage during which the growth of periclase crystals takes place with the rapid diffusion of iron from Fe₂O₃ through the contact points between periclase grains.
The mechanism of the reaction of Fe₂O₃ and MgO examined by poralization microscope and X-ray diffraction may be interpreted clearly with the aid of the phase diagram of the binary system MgO and Fe₂O₃ (B. Phillips, S. Somiya, and A. Muan, J. Am. Ceram. Soc., 44, 169 (1961)).
The reaction is a kind of the counter diffusion processes. MgO diffuses into Fe₂O₃ grains to form magnesioferrite. With the elevation of temperature, Fe₃O₄ content of the magnesioferrite becomes higher until it changes to very dark colour. On the other hand, Fe₂O₃ is reduced into ferrous state which duffuses into MgO to form a solid solution, magnesiowüstite. With increasing temperature the content of ferrous iron increases up to the saturation limit with a result that the further introduction of iron oxide to the periclase phase gives rise to the formation of magnesioferrite.
The acicular hematite crystals are exsoluted from the magnesioferrite during cooling, which distribute between the grains of magnesioferrite, as the solid solution limit of Fe₃O₄ decreases with decreasing temperature. Also magnesioferrite is exsoluted from magnesiowüstite and spread throughout the periclase phase, as the solid solution limit of FeO in periclase decreases grately with decreasing temperature.
The results of the experiments mentioned above suggest that the following conditions should be held in order to maintain the higher FeO content of magnesia clinker: (1) In order to enlarge the area of the solid solution limits of FeO in periclase, and of Fe₃O₄ in magnesioferrite, it is desirable that the firing temperature is kept as high as possible. (2) To maintain the conditions in higher temperature the clinkers should be cooled quickly. (3) To accelerate the reactions between Fe₂O₃ and MgO the grain size should be reduced as far as possible. In practice the refractories can not be cooled rapid enough to prevent the exsolution of FeO. If we consider only this phenomenon, it seems to be inferred that the magnesia clinker mineralized with Fe₂O₃ is not suitable for the fired refractories, and if the clinker mineralized with Fe₂O₃ is used, unburned refractories seem to be prefered rather than the fired ones.
From the experimental results concerning the relation between the firing shrinkage and Fe₂O₃ contents, it is suggested that only a small amount of Fe₂O₃ would be sufficient for the mineralizer of magnesia clinker.
During the heating up the growth of periclase grains proceeds gradually together with the diffusion of iron from Fe₂O₃ grains. Pores between the periclase grains, and perhaps the oxygen releases by the reduction of

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The study of the phase diagram for the system YF₃-PbF₂ was made to use the mixed fused salt as a flux of oxides. By the differential thermal analysis and the X-ray diffraction, it was recognized that solid solutions existed over all ranges of composition in this binary system.
Pb²⁺ might be substituted by Y₃₊. At 40 mol% YF₃, the liquidus point was 930°C, and the solidus point 890°C. The lattice constants of solid solutions were obtained by the X-ray diffraction.

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