The mineralogical constitution of the alumina cements of various composition (Table 1) were investigated by comparing the peaks of the X-ray patterns with those of the mixture of the synthetic minerals, CA, C₅A₃, C₃A₅, C₂AS and glassy substance (Fig. 1, Table 2).
The samples, except C and D (Table 1) were produced by an electric furnace. They, therefore, contained a small amount of FeO. The following results were obtained:
(1) CA was found to be the principal mineral of the cement.
(2) The samples with more than 35% CaO and less than 56% Al₂O₃ contained C₅A₃.
(3) The samples with more than 57% Al₂O₃ and less than 34% CaO contained C₃A₅.
(4) All samples contained C₂AS. The samples with more than 35% CaO contained a small amount of C₂AS together with β-C₂S.
(5) Fairly large crystals of C₂AS were found in the samples with more than 5.2% SiO₂, while no such large crystals did not exist in the samples with less than 5% SiO₂.
(6) The residue insoluble in N/2 HCl was CaTiO₃. Also C₃A₅ was slightly soluble in N/2 HCl (Fig. 2).
Shrinkage on heating the castable refractories prepared from these cement and usual or light weight chamotte was tested.
At 1200°C the component of the cement acted upon the cristoballite of the chamotte to form C₂AS, while above 1300° CAS₂ was formed together with glassy substance. The more the CaO content of the cement the more was the amount of CAS₂ thus formed.
When 72 parts of the chamotte and 28 parts of the CaO rich (37-39% CaO) cement were used the refractories swelled in the case of usual chamotte, or shrinked slightly in the case of light weight chamotte. However, such cement caused the softening of the refractories at lower temperature. When the refractories were heated under small load, i.e. 110-190g/cm², those prepared with CaO rich cement deformed easily.

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High permittivity ceramics containing PbO have many useful characteristics for electrical application, for example, PbTiO₃-PbZrO₃ for electro-acoustic transducer, BaTiO₃-PbSnO₃ for non linear element of electric circuit and so on. But as the firing of these ceramics is generally accompanied by the evaporation of PbO, it was difficult to get a dense ceramic body, the fact which has prevented the practical application of these materials.
The author has investigated systematically the evaporation of PbO from the ceramics having various compositions as the functions of both temperature and time using the thermobalance with strain meter. It was confirmed that the rate of the evaporation of PbO from the specimen was affected by the factors such as the composition and moulding pressure, etc.
Resting on the results of the investigation the author has set up an industrial method which gives a dense body containing PbO without using such precious metal as platinum. The electrical characteristics of the products were measured with the results which proved that they have excellent, uniform and reproducible properties.

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Calcium sulfite acts as a retarder for the setting of normal Portland cement, high early strength cement, and blast furnace slag cement. If used with gypsum it is possible to prevent the false setting under the federal test. The mortar strength test for the cement mixed with calcium sulfite and gypsum gave the better results.
The specimens showed the general trend of giving higher bending strength. The cements mixed with calcium sulfite gave a larger expansion and a smaller shrinkage under water than those mixed with gypsum, the specimens showed the larger trend of returning to the original size even after the repeated expansion and shrinkage.

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