Project Details Calcium sulfate in water

Project No.:
Start Date:
01 May 2016
End Date:


*IUPAC-NIST Solubility Data Series

This project will compile and evaluate all available solubilities of calcium sulfate in water. Three solid phases are recognized, gypsum (CaSO4•2H2O), bassanite (CaSO4•½H2O), and anhydrite (CaSO4). Solubility data for all three will be examined over the range of temperatures studied. The results will be prepared in the standard format of the IUPAC-NIST Solubility Data Series for publication in the Journal of Physical and Chemical Reference Data. Thermodynamic evaluations and implications for minerals in the associated network will be published in Geochimica et Cosmochimica Acta. This project will provide the basis for subsequent evaluations of calcium sulfate solubilities in multicomponent systems.


The volume will compile, review, and evaluate the solubilities of gypsum, anhydrite, and bassanite in water over the entire temperature range up to the critical point of water. It will include reports from the 19th century up to the current time and only original reports and measurements with methods descriptions will be considered. Evaluations will be based on review of the experimental technique, especially the analytical method, and consistency with density and conductivity data where possible.


Feb 2021 update – A paper on the temperature dependence of the calcium sulfate neutral ion pair and gypsum solubility thermodynamics has been prepared for publication. An inconsistency in the thermodynamic relations has been uncovered and is being resolved. A second paper is nearly completed on temperature-dependence of activity coefficients which must be consistent with the first paper and is awaiting resolution.

Page last updated 17 April 2021