In the course of industrial grinding, gypsum contained in cement is generally inverted to hemihydrate which sometimes causes to the false setting and other defects, while proper content of SO₃ improves the properties of hardened cement mortars, ie, strength, shrinkage and chemical resistivity. Therefore this research aimed to minimize the amount of gypsum within the scope that the normal initial setting would just take place, and at the same time, to make a further addition of insoluble anhydrite such as calcined gypsum, natural or byproduct anhydrite up to the optimum SO₃ content. Those results are summarised as follows:
(1) The determination of SO₃ concentration of extracted solution and the strength test led a conclusion that, for a normal portland cement of some Co., the optimum amount of SO₃ should be nearly 2-3%, regardless of the modification of gypsum, though its amount of SO₃ has been kept as 1.1-1.5% according to the current practice in this country.
(2) In order to still more improve the quality of a sample of commercial rapid hardening portland cement, further addition of insoluble anhydrite was advisable, because its amount of SO₃ seemed to be rather small.
(3) The extraction test to infere the optimum SO₃ content was likely to be successfully applied to the case of portland blastfurnace cement, as well as to portland cement.

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Characteristics in oxide composition of commercial borosilicate glasses for electronic tubes and lamps are explained. In the oxide composition region for these glasses, the lines of constant thermal expansion coefficient, the isothermal lines of softening point and transformation point and the lines of constant chemical durability are shown which are more accurate and detailed than the author's previous data.
The contradiction which is often encountered between high chemical durability and low transformation temperature, may be solved for some cases by introducing Al₂O₃ and PbO in these glasses.

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1. Apparatus with an absorption tube in which water to be absorbed under the pressure of nearly 3mm H₂O is preserved, is described, By the apparatus, contact absorption (A₁) immediately after the specimen is placed on the water, subsequent absorption (A₂) and evaporation (E) are measured.
2. According to the result of blank test with non-absorptive specimens (brass), A₁ and E showed mean errors of+0.22g and+0.31g respectively during the whole testing period of 168 hours.
3. Capillary absorption was measured of 1:3 cement mortars, aged 7 or 28 (or 29) days and stored in water or in moist air. Total absorption (A₁+Total A₂) of moist-cured specimen is larger than that of water-cured; and total absorption of 7 day watercured specimen is larger than that of 28 day water-cured; The vales of A₁ of moistcured samples are larger than those of water-cured.
4. Mean deviations of total absorption from the averages are ±3.6% with watercuring, 7 days, and ±2.8% with water-curing, 28 days, and ±4.5% with moist-curing, 7 days, and ±6.1% with moist-curing, 29 days.
5. It seems that effect of admixtures on the capillary absorption of the cement mortar can be determined by the apparatus.

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It is generally known that the percussion sound of the porcelain body reveals some of its qualities.
The “Magnachina” which was invented in Japan has very bad percussion sound despite of its very good whiteness and translucency.
The percussion sound of common porcelain, bone china and Magnachina bodies were studied quantitatively by measuring the Q values from the curves of damping oscillation by the brown tube and the oscilloscope.
Porcelain bodies with good percussion sound have Q value more than 500 and those with best clear percussion sound have Q value of 800-1300, but Magnachina has Q value of about 200.
It is suposed that the common porcelain and bone china bodies have good percussion sound because they are composed of mineral components with network structure such as feldspar, mullite or phosphates, but magnachina has bad percussion sound, because it is made up of non-network structure of magnesium silicate and therefore has large internal friction.

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