For representative samples of pottery stone from Amakusa, Izushi, Kawaai, and Matsumae, Japan, the constituent minerals were separated by centrifugation using Thoulet's solution, and burning tests, measurements of refractive indices, chemical, thermal, and X-ray analysis were carried out. The variation of the refractive indices of quartz crystals in each sample of pottery stone, if it existed, disappeared almost entirely after the burning at 1300°C. By the X-ray analysis, it was found that the sericites thus separated from Matsumae and Izushi pottery stones, especially the former, are accompanied with some amount of kaolinite, but those from Amakusa pottery stone are accompanied with no minerals; from Kawaai pottery stone a small amount of illite, besides the kaolinite, was found. The differences of these experimental results and the charactristic property of each pottery stone seem to be caused by the presence and quantity of kaolinite and illite, and in addition, by the type of pottery stone deposit.

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Experiments with alternating torsional stresses on clay bars are described. The stress-strain hysteresis loops so obtained show that repeated cycles produce not only a softening but also a hardening of them which are apparently analogus to the thixotropy, dilatancy, and rheopexy which occur in clay slips. The “backlash” phenomenon is also discussed in detail, and some notices in working on jiggering are mentioned.

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The authors collected some samples of disintegrated residue from calcium suicide manufacturing plants, and their main chemical component was determined to be nearly dicalcium silicate 2CaO⋅SiO₂, having main compositions SiO₂: 30-32% and CaO: 59-60%. So that, these samples and other synthesized samples of dicalcium silicate from pure chemicals were mixed with 2-5% magnesia or alumina containing compounds with or without 0.5-1% K₂O, P₂O₅ or Cr₂O₃ as the third addition agents for the purpose to prohibit the disintegration of dicalcium silicate α-2CaO⋅SiO₂→α′-2CaO⋅SiO₂→γ-2CaO⋅SiO₂, or α-2CaO⋅SiO₂→α′-2CaO⋅SiO₂→β-2CaO⋅SiO₂. These powdered materials were mixed homogeneously in the wet state, dried to the state containing about 5% water, moulded under high pressure 200kg/cm², and then fired at 1400-1500°C for 6 hours. These fired test pieces were tested on their several physical properties, e.g., firing shrinkage, water absorption, apparent and volume densities, compressive strength, refractoriness, expansion on heating, softening under load, etc.. The crushed pieces were, on the one side, further powdered, and separated by heavy liquid to several portions for X-ray analysis, and on the other side, polished and etched by several reagents for reflective microscopic test to study the mineralogical structures.

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CaO-MgO-SiO₂ and CaO-MgO-Al₂O₃ Systems containing CaO and MgO at the same molecular ratio were studied. The results obtained are as follows:
1) It was comfirmed by X-ray analysis and chemical analysis that binary and ternary compounds containing MgO are formed in the system CaO-MgO-SiO₂ (CaO/MgO=1) when CaO/SiO₂ ratio is below 2. But above 2, these compounds are not formed and MgO exists as free MgO, and also when CaO/SiO₂ ratio is 1, CaO⋅MgO⋅SiO₂ is formed.
2) In the system CaO-MgO-Al₂O₃ (CaO/MgO=1) the binary compounds MgO⋅Al₂O₃ is formed only when CaO/Al₂O₃ ratio is below 1.66. These results are different from those reported by H. E. Schwiete and H. zur Strassen concluding that the combination of MgO and Al₂O₃ was found only when CaO/Al₂O₃ is below 1.

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