Water activities for the MgCl 2 –RbCl–H 2 O ternary system and its sub-binary MgCl 2 –H 2 O and RbCl–H 2 O systems at 298.15 K have been measured using the isopiestic method. The measured results for the binary systems agree well with literature data. The measured equal water activity lines for the MgCl 2 –RbCl–H 2 O ternary system deviate from Zdanovskii’s rule. The solubilities for the MgCl 2 –RbCl–H 2 O ternary system also have been measured using a isothermal visual first/last crystal method, and the results are consistent with one reported set of solubility data. Pitzer’s model was selected to correlate the measured water activity and solubility data and the parameters reported in the literature are re-examined by comparing the model-calculated equal water activity lines and solubilities with experimental values measured in this work. New and reasonable parameters are obtained by fitting the water activity and solubility data measured in this work and those reported in the literature. The water activities and solubilities were simulated with the new parameters and the results show that the Pitzer model can successfully represent the thermodynamic properties and be used to calculate the solubility isotherms.
The water activities of the MgCl 2 –RbCl–H 2 O ternary system and its sub-binary systems have been measured with the isopiestic method at 323.15 K. The measured water activities for the MgCl 2 –H 2 O and RbCl–H 2 O sub-binary systems agree well with the results reported in literature. The measured equal water activity lines of the MgCl 2 –RbCl–H 2 O ternary system are not straight lines, which means the mixing behavior of the solutions do not obey Zdanovskii’s rule. The solubility of the MgCl 2 –RbCl–H 2 O ternary system has been determined with the Flow-Cloud-Point method at 323.15 K, and the measured results are roughly consistent with values reported in the literature. The Pitzer model was selected to correlate the water activity and solubility data measured in this work. The predicted water activities and solubility isotherm for the MgCl 2 –RbCl–H 2 O ternary system at 323.15 K, with binary solution parameters only, both deviated from the experiment values. The ternary solution Pitzer model parameters were obtained by fitting the measured water activities in the ternary system. The water activities and solubility isotherms of the MgCl 2 –RbCl–H 2 O ternary system at 323.15 K were calculated including both binary and ternary solution parameters. The calculated water activities are consistent with the experimental values. The calculated solubility isotherms are roughly consistent with experiment values, except they deviate somewhat in the RbCl crystallization region.
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