Solid–Liquid\nand Vapor–Liquid Equilibria,\nVolume Properties in Water–Calcium (Magnesium) Methanesulfonate:\nExperimental Data and Modeling with Pitzer and Pitzer–Simonson–Clegg\nFormalism

Water vapor pressure was determined by a static method\nat 298.15\nK and a dew point method at 323.15 K in the Ca(CH<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>–H<sub>2</sub>O and Mg(CH<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>–H<sub>2</sub>O systems. Equilibrium isothermal\nsolubility for Ca(CH<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>–H<sub>2</sub>O was determined from\n250.15 to 353.15 K,\nand from 250.15 to 318.15 K for Mg(CH<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>–H<sub>2</sub>O. A new hydrate was revealed in the\nsystem, Ca(CH<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>·4H<sub>2</sub>O. It melts incongruently at 282.4 K. Additional data for ice liquidus\nobtained using DSC in both systems are in good agreement with literature.\nBased on vapor–liquid (VLE) and solid–liquid (SLE) equilibria\ndata, parameters of the Pitzer–Simonson–Clegg and Pitzer\nmodels were obtained. Stability parameters of Mg(CH<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>·12H<sub>2</sub>O, Ca(CH<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>·4H<sub>2</sub>O and Ca(CH<sub>3</sub>SO<sub>3</sub>)<sub>2</sub> were estimated. Binary phase diagram fragments\nwere calculated. The eutectic point in Mg(CH<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>–H<sub>2</sub>O was estimated using the Tamman\nmethod and from phase diagram calculations is in good agreement. The\neutectic point in Ca(CH<sub>3</sub>SO<sub>3</sub>)<sub>2</sub>–H<sub>2</sub>O was not estimated by the Tamman method due to supercooling.\nBoth metastable and stable phase diagrams were calculated. Pitzer\nand PSC models were extended with a pressure dependence used to predict\nthe volume properties of the solutions. Densities of the solutions\nwere measured in both binary systems at 288.15, 298.15, and 308.15\nK.