The authors have studied the effect on the rate of melting and refinning, the chemical durability, the viscosity at high temperature, softening temperature and devitrification temperature, of making small substitutions in a general glass formula suitable for the manufacture of sheet glass by the automatic drawing process. In particular a study was made of the most suitable ratio of CaO: MgO and the effect also of substituting, within the total range of 1.5%, Na₂O by Al₂O₃, SiO₂, B₂O₃, and ZnO respectively. The results are presented in a series of tables and curves.

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The authors collected many samples of clayey substances of high alumina content for the purpose of extraction of pure alumina by the special wet method, which had been already reported in the other paper (Journ. of Chem. Ind., Japan, 1936, 39, 183, 549). The chemical compositions and specific gravities of these samples were fully collected and discussed their mutual relations in the present paper. The main points are briefly abstracted, as following:
(1) 35 samples of high alumina content were collected from Korea, Manchoakuo and North China. 12 samples of diaspore were also collected in Japan proper and Korea. For comparison to these samples of diaspore origin, 5 samples of kyanite (or cyanite) and 4 samples of bauxite were collected from India.
(2) The specific gravities of these 52 samples were determined in two ways, i.e., (1) true specific gravity by powder and (2) apparent specific gravity by lump sample.
(3) The chemical compositions of these samples were also determined by the total analysis. Avoiding the diffuseness of indicating the total results of these chemical analyses and specific gravities, some typical samples were tabulated in the following table.
Table 1. Chemical Compositions and Specific Gravities of Typical Samples of High Alumina n Content and Chemical Compositions.
From these results, the following points are clearly observed and discussed, (1) The higher the specific gravity is, the larger the content of alumina and the smaller the content of silica, in both samples of diaspore and diaspore-clay, (2) The contents of TiO₂ and Fe₂O₃ are greater in diaspore-clay than in diaspore, so that the specific gravity of the former is larger about 0.10 than that of the latter, by comparing both samples of nearly equal content of alumina, (3) The content of combined water or the amount of loss on ignition of all samples of diaspore and diaspore-clay is nearly 14-15%, which is the quite powerful evidence to discuss these samples being the intimate mixture of diaspore Al₂O₃⋅H₂O(H₂O:14.99%) and kaolinite Al₂O₃⋅2SiO₂⋅2H₂O(H₂O:13.96%), i.e., xAl₂O₃⋅H₂O(1-x) Al₂O₃⋅2SiO₂⋅2H₂O. This point was already discussed by many experiments in the other reports of studies (loc. cit.), (4) kyanite Al₂O₃⋅SiO₂ and bauxite Al₂O₃⋅xH₂O are quite different high aluminous samples from these diaspore origins, so that their spiclfis gravities and chemical compositions are quite different from those of diaspore origins, etc.
(4) The proportionality of specific gravity and content of alumina or silica of samples of diaspore origin was fully discussed by the specially designed graphical method, and the simple method of estimation of contents of diaspore and kaolinite parts and amounts of alumina of diaspore base was proposed by the present authors.
(5) By using these high aluminous samples of diaspore origin, the present authors are now further studying on the special method of extraction of alumina, which will be hereafter reported.

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The effect of alkalies on the resistivity of the MgO-Al₂O₃-SiO₂ system was determined.
The composition of bodies is shown in Table 1 and Table 2.
Table 1. The Composition of Bodies
Table 2. The Amount of Alkalies in Bodies.
The resistivity of the MgO-Al₂O₃-SiO₂ system is very much lowered by the presence of alkalies. By the increase of alkali content from 0.45 to 0.55%, the resistivity of the bodies becomes about 1/2 and to 0.85%, about 1/10-1/15. On the other hand, the effect of the variation of MgO: Al₂O₃: SiO₂ on the resistivity of the bodies is comparatively small, compared with that of alkalies. When the content of alkalies is constant, the ratio of the resistivity of A22 series to that of A28 series is the range of 2.5 to 3, while the percentage of MgO increases 23 to 45.

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