Effect of Calcium Salt on Crystal Growth of Ca (OH) 2 in Aqueous Solution

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Studies of preparation of crystalline Ca (OH) 2 particles with large and equal size were carried out by hydration of CaO in the aqueous solutions of organic acids, inorganic acids and their calcium salts. The plate-shaped single crystals of Ca (OH) 2 with 3μm across and 0.2 μm thick were obtained after the slurries of CaO (10g) and a 1wt% solution (100 ml) of highly soluble calcium salts such as Ca (CH3COO)2 were allowed to stand at 25°C for one day. The grown Ca (OH) 2 crystals were well-formed and surrounded by (001) and (101) faces and the hexagonal lattice constants, a0=3.592 (Å), c0=4.908 (å), were equel to those of pure one. On growth mechanism, it is assumed that Ca (OH) 2 crystals were grown by the reversible reaction of eq. (1). Namely, small Ca (OH) 2 particles acting as nutrients were dissolved by the reaction toward Ca (CH3COO) 2+2H2O_??_2CH3COOH+Ca (OH) 2 …(1) left and Ca (OH) 2 was separated on the surface of growing crystal by the reaction toward right.
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