亜硫酸カルシウム四水和物の構造と安定性
1982 年 1982 巻 180 号 p. 217-223
詳細
1982 年 1982 巻 180 号 p. 217-223
In order to systematize the phase relationships in the CaSO3-H2O system, the present work was paid attention to calcium sulfite tetrahydrate (CaSO3·4H2O) which crystallographic data have not yet been published. Single crystal of the tetrahydrate was prepared by slow precipitation from diffusing 4N CaCl2 and 4N Na2SO3 solutions containing 0.05% Na3C6H5O7 at temperature of 5 to 10°C. The crystallographic data of the tetrahydrate and thermal stability on the transformation of tetrahydrate to a-hemihydrate were investigated by using X-ray diffraction, thermal analysis (TG-DTA) and scanning microscope.
The crystal was rhombohedral with space group R3c or R3c and had a unit cell with aR=11.48Å and α=58.40° from X-ray powder diffraction data. The difference between single crystal and polycrystal (powder) on the stability of the tetrahydrate were also studied. The tetrahydrate powders synthesized by the Ca (OH) 2-SO2 system reaction were stable at the temperature below 10°C and converted into a-hemihydrate instantly at room temperature. However the single crystal was fairly stable at room temperature and was found to be stable to heating at 70°C from TG-DTA curves. The dehydrated crystal was α-hemihydrate with particle size of 1-2 μm in skeleton structure of the tetrahydrate crystal.
