High-temperature Debye-Huckel correlated solubilities of calcium sulfate in aqueous sodium perchlorate solutions

Abstract

The solubilities of CaSO4·2H2O at 298 K and of CaSO4 at 423 and 523 K have been determined in aqueous solutions of sodium perchlorate having molalities from 0 to 6 mol kg-1 of NaClO4. When the results were treated with an extended Debye-Hückel equation, substantial agreement with theory was observed to moderate ionic strengths at all three temperatures. The results therefore support previous observations of aqueous electrolyte behavior adhering to a Debye-Hückel treatment to high temperatures. However, at high ionic strengths (1 to 6 mol kg-1) of supporting salt the solubilities of CaSO4·2H2O and of CaSO4 were sharply lower than the corresponding solubilities in aqueous sodium chloride, sodium nitrate, and lithium nitrate solutions. Several attempts to explain these differences in solubility are presented. In addition, the activity coefficient behavior of calcium sulfate in the aqueous sodium perchlorate solutions is given. © 1973 Academic Press Inc. (London) Ltd. All rights reserved.