A new method for measuring the glost-warpage of refractory coating caused by the internal stress developing during the heating was described. The apparatus was designed so that it satisfies the following three conditions:
(1) Easy and stable setting of the specimen,
(2) Preventive measure against the oxidation during the heating,
(3) Accurate measurement of slight strain.
The specimen was prepared by applying the coating to one side of a piece of a Steel plate (0.8×20×80mm). It was inserted into the silica tube of the heating furnace to rest horizontally on the saddles of silica glass (Fig. 3). To avoid the oxidation nitrogen or argon was introduced from one end of the silica tube to which a small hole was provided at a proper position as a gas-outlet. For easy setting of the specimen the upper part of the furnace was cut off to form a longitudinal groove of 5mm in width. The deflection was measured by the displacement of the thin silica tube standing vertically at the middle point of the specimen.
Transition point, P_t, and softening point, P_s, of the thin coated layer could easily be evaluated from the deflection-temperature curve. A linear relation between P_t, P_s, and the content of alumina in mill addition was confirmed when the specimen was fired in nitrogen atmosphere. Moreover, the possibilities of evaluating the expansivity of coating layer and the internal stress developed in it were discussed making use of the examples of the actual deflection curves.
Deflection of warpage, δ, can be expressed by
δ=K⋅Δα⋅Δθ⋅l²/h
K=3pq(1+2p)/(4pq+1),
p²<<1, q<1,
where, Δα stands for the difference of the thermal expansion coefficients between the coating layer and the base metal. Δθ the temperature difference, l the span, and h the total thickness of the specimen, p=h_c/h_s and q=E_c/E_s, where h_c, E_s and E_c are respectively, the thickness and the elastic constant of the base metal, that of the coating layer as indicated in Fig. 8.
It was established experimentally that the relation between the coefficients of glost-warpage and the thickness of coating is expressed by a non-linear function.

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The chemical and mineralogical changes in silica brick used in a zebra roof was given in the previous paper, V. The present paper contains the results of a study on the changes observed in an unburned chrome-magnesia brick and its cladsteel plate coming into contact with a silica brick. The specimen was divided into seven zones according to their colors, chrome-bearing spinel grain and silicate matrix were separated using the heavy liquid method. The mineralogical constitution of spinel solid solutions and silicate matrix of each zone were calculated from the results of chemical analysis.
The results obtained may be summarized as follows: On the chrome-bearing spinel grain; (a) A large excess of sesqui-oxides of iron and chromium were found in the spinel in the zones exposed to highest temperatures. (b) Excess (8-13%) of magnesia was present in the spinel contained in the lower temperature zones. (c) The amount of MgO⋅Al₂O₃ decreased in a marked degree, from 25% to about 8%, according to the increase of temperature to which the zones were exposed. (d) In the spinel embedded in the silicious glass matrix formed by the diffusion from silica brick, MgO⋅Al₂O₃ was absent, and texture of spinel grains in this area was turned into a porous substance composed from separated small pieces, which suggests that the selective dissolution of MgO⋅Al₂O₃.
On the matrix; (a) In the surface layer of the chrome-magnesia brick coming in contact with silica brick and exposed to the highest temperature silicious glass penetrated into the brick up to about 10mm from the surface, and the dendrites of magnetite and cristobalite were present in the glass phase. Considering from the phase-equilibrium data it is highly probable that the formation of fayalite (m.p. 1250°C) from magnetite (m.p. 1590°C) by changing from oxidizing to reducing atmosphere gave more unfavourable influence on the refractoriness of the brick than the formation of monticellite (m.p. 1500°C) by the increase of lime content in the matrix. (b) The main constitutional mineral in the matrix in the middle zone was monticellite. (c) The conversion of chlorite to olivine in the original brick took place at the temperatures ranging from about 1100 to 1300°C.

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The preliminary experiments on the possibility of producing the “bone ash-magnesia porcelain” obtained by firing the mixture composed of bone ash, talc and quartzite were carried out. The properties investigated were the softening point, softening range, shrinkage, absorption, and the strength of the fired bodies.
From the results it was found out that the bodies composed of 60-30% bone ash, 30-60% talc, and 10-20% quartzite are promissing. For example, the specimen No. 9 containing 50% bone ash, 40% talc, and 10% quartzite fired to cone 8 showed the particularly low dielectric loss together with the large expansion coefficient (Table 4).
The investigations of the mineralogical constitution of the fired bodies by optical and X-ray methods revealed that β-tricalcium phosphate, diopside, and free silica (cristobalite and tridymite) were the principal minerals existing with a small amount of rhombic enstatite (proto-?) and glass matrix.
The properties of the specimens containing kaolinite were also given.

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A study on the static dehydration of various ionic kaolinites in vacuum at the temperatures up to 1000°C was carried out, concentrating the attention to the difference of (1) the rate of removal of the water of hydration of adsorbed monovalent rations, and (2) the rate of dehydration of lattice water at constant temperatures.
Using Zettlitz and Kampaku (Japanese origin) kaolin, both being high degree of crystallinity, as samples hydrogen kaolinite was prepared by electrodialysis. The single ionic (Li, Na, K, NH₄, Cs) kaolinite were obtained by neutralizing the acid clay with the respective bases. The processed samples were dried in vacuum of 10^-3 mmHg at 28°C for 12 hours. They were heated successively to 70°, 100°, 150°, 190°, 265°, 300°, 400°, 600° and 1000°C and the water came out by dehydration was determined by volumetric method.
The results obtained are summarized as follows:
(1) Water of hydration of the adsorbed cations was removed at the temperatures lower than 150-200°C. The maximum rate of dehydration was observed in H⁺, and the amount of dehydrated water except the case NH₄⁺ was in close correlation with the lyotropic series of the ions.
(2) It was confirmed that the lattice water came out at the temperature as low as 300°C.
(3) The adsorbed cations seemed to play some role in the dehydration process of lattice water, and the highest rate of dehydration was observed in H-kaolinite.

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Thermal conductivity of 15 Japanese fireclays of Kibushi brand mined from Aichi and Gifu prefecture was measured by an absolute method. The specimens of 2.7cm in diameter were prepared by pressing the pure clay mass and then fired at SK 9 and SK 14 respectively. The relation between the particle size distribution of grog and the thermal conductivity of the body prepared from it was also studied using the Shidare Kibushi clay.
The results obtained are as follows:
(1) The thermal conductivity increased with increasing firing temperature.
(2) At lower temperatures the thermal conductivity increased in direct proportion to the forming pressure, at higher temperature, 400° to 800°C there exist no such simple relation and the fluctuation of the measured values was observed.
(3) The conductivity of the clays containing kaolinite as the main component increased with the decreasing amount of mica, but decreased with the increasing free silica, especially at high temperature. It was thus cofirmed that the thermal conductivity was strongly influenced by the mineralogical composition of clays.
(4) There was no simple relation between the porosity and the thermal conductivity of the specimens.
(5) Fairly constant values of thermal conductivity were obtained at the temperatures ranging from room temperature to 600°C.

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