Solubility Measurement of the Solid Solution Containing the RbCl–CsCl–H2O System from T = 298.15 to 348.15 K

The solubility of the RbCl–CsCl–H2O ternary system has been investigated at the temperature range from 298.15 to 348.15 K by two different methods, namely, the Flow-Cloud-Point (FCP) method and the Isothermal Dissolve Equilibrium (IDE) method. The measured solubility for this ternary system at 298.15 K by FCP method is consistent with the reported result in literature. The measured solubility results for this ternary system at 323.15 K by the FCP and IDE, two different methods that are consistent with each other, which indicated the results are more reliable. Meanwhile, the measured liquid–wet solid–solid lines proved that the equilibrium solid phases are two types of solid solutions (Rb,Cs)Cl(ss) and (Cs,Rb)Cl(ss) rather than pure salts (RbCl and CsCl) reported in literature. For the first time, the solubility of the RbCl–CsCl–H2O ternary system at 308.15 and 348.15 K has been measured by IDE method. The measured results shown that the equilibrated solid phases in this ternary system at 308.15 and 348.15 K are two types of solid solution (Rb,Cs)Cl(ss) and (Cs,Rb)Cl(ss), at RbCl rich side and CsCl rich side, respectively.