Thermodynamic equilibrium diagram of CaCl₂-Ca(OH)₂-H₂O system

Abstract

The lg c-pH diagram of the CaCl₂-Ca(OH)₂-H₂O system and its two subsystems at 298.15 K are constructed according to the theory of thermodynamic equilibrium. The interaction characteristics between the solubility of CaCl₂ and Ca(OH)₂ can be found out from the diagrams. CaCl₂·6H₂O (s), Ca(OH)₂(s) and solution coexist when the pH value of solution is about 10.8. CaCl₂ with the minimum solubility of 1 682.4 g/L is in equilibrium with solution when the pH value is lower than 9.4, and Ca(OH)₂ with the minimum solubility of 2.749 g/L is in equilibrium with solution at the pH value over 12.1, which provides a theoretical basis for the treatment and reuse of calcium chloride mother liquor for collocating lime cream which is the precipitant in the process of synthesizing magnesium hydroxide.

Keywords

CaCl₂-Ca(OH)₂-H₂O system / solubility / lg c-pH diagram / thermodynamic equilibrium / magnesium hydroxide

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