Among fundamental properties of ceramic raw materials, particle size distribution, hygroscopicity, colloid, content, etc. were measured directly; surface factor and total surface area were calculated from these data, and discussed the relations among them.
The effects of treating methods of clays, e.g. water-washing hydrogen peroxide treatment, egeing in water, etc. upon dispersion of clays were also studied and discussed.

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An apparatus for determining thermal conductivity by an absolute (calorimetric) method of steady-state hea tflow through small cylindrical (20 or 30mmφ) or prismatic (22mm square) samples is described (Fig. 1). Some estimate of the accuracy and precision obtained is evidenced by comparing the values with that calculated from a comparative method experiment which the apparatus can also afford to perform with the aid of long silver rod beneath the sample. The results of the study are as follows;
(1) It has been shown that if proper precautions are taken, linear heat flow and low heat loss can be so easily attained by the absolute method using a water flow calorimeter as to obtain reliable values on the high-conductivity materials.
(2) An experimental results (Fig. 2) has shown that, unless the specimen is not soldered, interfacial temperature drop will grow so high that it can not be neglected in determining the thermal conductivity of these high-conductivity materials.
(3) Measurements on electrolytic lead (>99.997%) have given data in good agreement with previous values reported for melting-point lead in literatures. Reproducibility obtained by using lead samples of various size and shape has also proved to be satisfactory (Table 1 and Fig. 4).
(4) Two series of experiments were conducted in which the temperature of guard ring was made too high or too low relative to that of the sample, and the effect of these temperature gap on conductivity values obtained were examined. Examples obtained on lead are shown (Fig. 4).
(5) It is very difficult to prepare accurate cylindrical samples of hard ceramic materials and to drill thermocouple holes. The difficulties were removed by preparing prismatic samples with narrow but deep groove on a vertical side face (Photo. 2 & 3). The holes for thermocouples were drilled into insulating material filled in the groove. The new method of sample preparation has been proved correct through the experiments made with lead (as well as with SiC brick) (Fig. 4, P).
(5) The thermal conductivity of Carbofrax brick decreases from 0.052 at 100°C to 0.033 (cal. sec^-1. cm^-2. °C^-1. cm.) at 750°C. The result is in good agreement with that of F. Holler for clay-bonded SiC bricks, but it is somewhat higher and has negative gradient to the contrary of the data given in the manufacturer's catalogue. The same is true on a domestic SiC brick (Fig. 5).

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In his previous paper, the writer has reported a quantitative investigation on the behaviours of dissolution of coarse quartz gains into feldspathic fusions, one of the most important reactions occurring in porcelain bodies during firing (this Journal 63 [712] 432 (1955)). The present one gives the results of a study on the same subject from a microstructural point of view.
By firing the small tablets consisting of 97% fine ground potash-, or soda-feldspar and 3% coarse quartz grains (Table 1), one fired at 1150°-1450°C, with heating rates of 60°, 120°C, and 180°C per hr., and the other with 0.5-4 hrs. soaking at 1300°, 1350°, or 1400°C. They were studied with aid of polarization microscope, and occasionally by means of X-ray.
The results obtained were summarized as follows:
(1) The reaction between quartz and feldspar started from a little lower temperatures than 1150°C, with the formation of very thin reaction layers between them.
(2) Refractive index distributions of glasses formed in the fired bodies were measured. From the results obtained, it is inferred that the uniformity of the melting phases formed in the bodies of quartz-potash-feldspar system were raised with the increase of firing temperatures and holding times (Fig. 4), and that in the case of the bodies of quartz-soda-feldspar system, unhomogeneity of the phases was, on the contrary, rather increased with their SiO₂ content being also gradually increased with temperature and time (Fig. 5). These differences were mostly due to the difference of diffusion velocity of SiO₂ which entered into the melting phases accompanied with dissolution of quartz grains.
(3) In soda-feldspar fusions, the diffusion layers formed around the quartz grains temporarily showed double construction layers (Fig. 1-9), and, with soaking time, these layers gradually changed into continuous ones with the increase of their thickness. The temporary formation of these double diffusion layers was due to the fusion of soda-feldspar itself, whose fusion behaviour showed a marked change at a certain temperature range.
(4) Quartz grains kept their phases metastablly until they dissolved at 1150°-1450°C., and converted to neither cristobalite nor tridymite, though a weak pseudo biaxial interferrence figures which were perhaps owing to the stresses formed with rapid cooling, were observed (Table 2). In the diffusin layers and the glassy phases, cristobalite or tridymite were also not found.

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