Solubility of Calcium Carbonate Hexahydrate.

Abstract

Calcium carbonate hexahydrate (CaCO3 . 6H2O) has been synthesized, and the procedure is reported. The crystals were characterized by means of optical microscopy, thermogravimetry and IR-spectroscopy. The solubility was found by recording the pH during the dissolution of the hexahydrate in water, preventing the entrance of carbon dioxide. The solubility product was calculated from the final constant pH value, taking all known calcium and carbonate species into account. Between 10 and 40-degrees-C the solubility product (or equilibrium constant), K(s)(CaCO3 . 6H2O), could be expressed by: - log K(s) = 7.1199 + 0.011 756t + 0.000 075 556t2 where t is in degrees-C. The solubility product decreases with increasing temperature, and is (5.7, 3.5 and 1.9) x 10(-8), at 10, 25 and 40-degrees-C, respectively.