(a) The bentonite, sp. gr. of it was 2.674 (25°/4°). This value can be taken to represent the true value very closely.
(b) It was confirmed that there are good linear relations between conc. and sp. gr., sp. vol. or ref. index of hydrosols or hydrogels (25.0°)
d=0.9971+0.00650 X
v=1.0029-0.006503 x
nD=1.3324+0.0009594 X
here, X and x are the concs. expressed in g per 100cc and g per 100g of sol respectively, and nD is the ref. index of Na-light. Moreover, it has been found that the above mentioned three relations could be applied up to X=31 or x=26.
(c) Through the Du Nouy's pull ring method, statical surface tensions of hydrosols of the clay have been measured. It seems there is a slight, below 1%, surface tension drop. But the average values are practically constant independent of the sol concs.

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The purpose of the study is to find out the influence of differences in raw materials and manufacturing method of magnesite refractories upon their modulus of elasticity and also the relation between the modulus and their spalling tendency, and thereby to obtain the refractories low in the modulus and rich in thermal endurance. In this first report, descriptions and discussions are given on the formulae on the relation between the resistance of refractories to spalling and their other physical properties given by Winkelmann and Schott, F. H. Norton, F. W. Preston, H. White, and R. A. Heindl as well as on theories on the mechanism of spalling. Thereafter, an authors' apparatus for accurate measurement of the modulus of elasticity is described.

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In continuing the previous studies (This Journal, 1934, 42, 273, 628, 688; 1935, 43, 215, 572; 1936, 44, 22, etc.), the authors report the results of further studies on high siliceous mixed Portland cements. The principal points of the present report were abstracted from the original Japanese paper, as following:
(1) Many samples of siliceous admixtures were analysed by both methods of ordinary total analysis and special soluble analysis. The latter method is the treatment of sample with 10% NaOH solution and then with 5% HCl solution to separate soluble components, and its result of amount of soluble parts, especially soluble silica, is the most important point to discuss the suitableness of the admixture. The results are shown in the following table 1.
Table 1-Results of Soluble Analysis of Various Siliceous Admixtures
From these results it is seen that the siliceous admixtures of highest grade containing large amount of soluble silica and medium grade can be used for the mixed Portland cement, but the admixtures of low and lowest grades containing small amount of soluble silica can not be used with good result. For the comparison two samples of blast furnace slag after water granulation were analysed, which were nearly completely soluble and different from siliceous admixtures by containing large amount of lime.
Table 2-Results of Comparative Tests of Physical Properties and Chemical Compositions of Various Samples of Common and Mixed Portland Cements
(2) Many series of samples of mixed Portland cements were prepared from these admixtures and cement or its clinker in the proportion of 30-45 parts of admixture and 70-55 parts of cement or clinker, by grinding with small amount of gypsum in a small test ball mill. These samples were systematically compared on their physical properties and chemical compositions to discuss the suitableness of admixtures above classified. Some results of these tests are shown in the above table 2.
It is seen from these results, that (1) All mixed Portland cements have smaller specific gravities and slower setting times than common Portland cements, (2) Chemical compositions of mixed Portland cements differ quitely from common Portland cements, especially large amounts of silica and insoluble residue and small amount of lime, (3) Blast furnace slag cements differ from other kinds of siliceous mixed Portland cements, in the smaller amounts of silica and insoluble residue, larger amount of alumina and lime, and some amounts of sulphide, sulphur and manganese oxide, etc., (4) Two samples of alumina cement imported are quitely different from these common and mixed Portland cement, in their large content of alumina, (5) Some samples of mixed Portland cements, i.e., No. 299, No. 300, No. 310, No. 427 and No. 429, are special mixed Portland cements obtained by mixing and grinding clinker or cement with admixture and slaked lime or calcined (about at 900°C for 2 hours) mixture of admixture and limestone, and these special mixed Portland cements have quick setting time as that of common Portland cement, owing to the content of some amount of free lime added.
(3) These cement samples were tested on their mortar strengths by both methods of (a) dry or non-plastic mortar of Japanese Engineering Standards for Portland cement (JES 28) and blast furnace slag cement (JES 29) and (b) wet or plastic mortar newly prposed by Prof. R_??_s in Switzerland and by Dr. Haegermann in Germany. High siliceous mixed Portland cements, i.e., No. 282, No. 298, No. 299, etc., have remarkably high strengths by the nonplastic mortar, which are greater than those of alumina cements, early high strength Portland cements, etc., but their strengths by plastic mortars are smaller than those of common Portland cement.
(4) These cement samples were tested their expansions or contractions and corrosions of prismatic test pieces (4×4×16cm) of plastic mortar during the curing in

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X-ray analyses ware made of 12 different clinkers manufactured by 9 Japanese portland cement plants. Of these clinkers 6 were made by dry process and 6 by wet. The results can be abridged as follows:
(1) All clinkers showed almost same structure although some differences in the amounts of constituent minerals and in the degree of their crystal development were observable.
(2) The chief constituent of these clinkers was similar to the tricalcium silicate reported in “The Study of Calcium Silicates” (S. Kondo & T. Yamauchi, Jour. Jap. Ceram. Assoc., 1934, Vol. 42, 479). Also some dicalcium silicate was found. No other constituents could be distinctly detected.
(3) The authors' results agree well with those reported by A. Guttmann & F. Gille of centrifuged Alite portions and also those obtained by K. Koyanagi of Alite portion of a particular clinker whose chemical composition was very near to that of Alite.
(4) Strictly speaking, there were some slight differences between the wet process and dry process clinkers.
Chemical and mineralogical compositions, diffraction patterns, and interplaner distances are given.

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