This paper discusses the hydration products in C₃A-CaSO₄.2H₂O-CaCra₄system. The mole ratio of gypsum to C₃A is 2/3 and the replacement mole ratio of CaCrO₄ to gypsum is ranged from 0 to 1.0. CrO_42- is fixed to AFm phase and the basal space of AFm is not changed until the replacement ratio of CaCrO₄ is 0.25. But, the basal space of AFm is increased and the XRD peak of AFm become broad with increasing of the replacement ratio of CaCrO₄. In CrO_42--AFm, the basal space changed from 0.98 into 1.02 nm depending on a synthetic condition and the drying conditions, and the water between layers in AFm in that case was presumed to be 12 and 14 moles.

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Lead-free glasses with a low melting point and good chemical durability are desirable for the sealing process in the ceramic and electronic fields. In this study, B₂O₃, ZnO, BaO, and TeO₂ or Bi₂O₃ were used to prepare lead-free sealing glasses with a low melting temperature. The glass forming region, glass transition temperature, softening temperature, thermal stability, thermal expansion property, and X-ray properties were investigated in detail in the ternary (B₂O₃-ZnO-BaO) and quaternary (B₂O₃-ZnO-BaO-TeO₂ or Bi₂O₃) systems. The dependencies of these properties on composition were quantitatively characterized. The ternary system glass (30 mass% B₂O₃-20 mass % ZnO-50 mass% BaO) had a low melting property, a high chemical stability (ΔT : 110°C), and an amorphous structure. Furthermore, the quaternary lead-free glass (10 mass% B₂O₃-6.7 mass% ZnO-16.7 mass% BaO-66.6 mass% TeO₂ or Bi₂O₃) showed even higher thermal stability (Δ T : more than 200°C) and good bonding and sealing properties. The quaternary glass also had a high water resistance compared to commercial lead glass. In a sealing test with a plane fluorescence lamp incorporated in a digital camera, perfect sealing was achieved. The prepared lead-free glass showed an excellent performance as a substitute for the commercial lead glass.

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Elution properties of Si⁴⁺ and Al³⁺ ions from pyrophyllite ores have been studied in associated with thermal alteration of pyrophyllite. Two kinds of pyrophyllite are designated A (80.2 mass%) and B (35.7 mass%) were examined.
Elution experiments were performed for raw and calcined pyrophyllite ores, leaching in 0.1N caustic soda solution at 25°C and 80°C. ICP technique was used for quantitative analysis of both Si⁴⁺ and Al³⁺ ions. Pyrophyllite are A consisting mainly of pyrophyllite showed high elution for Si⁴⁺ and Al³⁺ ions in 80°C leaching even for raw sample. On the other hand, pyrophyllite are B containing kaolinite and quartz showed a little elution in 80°C leaching for raw sample compared with pyrophyllite are A, but it showed high elution due to the decomposition of kaolinite when calcined at intermediate temperatures. It was revealed that pyrophyllite ores containing much amount of pyrophyllite might be used as an active filler in the geopolymeric monolith fabrications without calcination process.

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In order to increase amount of recovery of phosphorus furthermore in sewage, the methods of sludge treatment using polyaluminum chloride (PAC) which has an effect of phosphorus removal were investigated. The experiments recovering phosphorus from the incinerated ash of the sludge and aluminum of the flocculant added to remove phosphorus were carried out. When PAC was added 1.5 times mole as Al for PO₄-P into the sludge, 56% of PO₄-P was removed and the amount of elution of phosphorus and aluminum were increased by 50% and 40% respectively. When PAC was added 3.0 times mole, 95% of PO4-P was removed and the amount of elution of phosphorus and aluminum were increased by 80% and 80% respectively. It was found that more amount than the aluminum added to remove phosphorus could be recovered from incinerator ash.

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Calcium carbonate deposited on titanium substrate by electrochemical method has been investigated from view point of modification and shape. Electrolytic solution of calcium dihydrogencarbonate was prepared by bubbling carbon dioxide into calcium carbonate suspension. Calcium carbonate was deposited on the substrate electrode in the electrolytic solution of pH1.99-8.29. Main product obtained at lower pH region was calcite of rhombohedral shape and that obtained at higher pH region was vaterite of spherical aggregate of plate-like crystal. The larger the current density and the longer the electrolysis time were, the larger the deposition rate of vaterite became. The tendency was estimated to be related to the hydroxyl ion concentration on the substrate electrode surface.

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