Water activities of the CuCl₂−MCl₂−H₂O (M = Mg, Ca) ternary systems and their sub-binary systems have been measured by the isopiestic method at 298.15 K. The maximum concentrations of the CuCl₂−H₂O, MgCl₂−H₂O and CaCl₂−H₂O binary systems are 5.28 mol•kg⁻¹, 5.25 mol•kg⁻¹ and 6.61 mol•kg⁻¹, respectively. The concentrations of mixture solution rang from 0.91 mol•kg⁻¹ to 5.69 mol•kg⁻¹ for CuCl₂−MgCl₂−H₂O system, and 1.29 mol•kg⁻¹ to 6.87 mol•kg⁻¹ for CuCl₂−CaCl₂−H₂O system. The measured water activities of the sub-binary systems are consistent with the experimental results reported in literature. The measured equal water activities in the ternary systems strongly deviate from the Zdanovskii-Stokes-Robinson (ZSR) lines. The Pitzer model, Pitzer-Simonson-Clegg (PSC) model and Reaction model were selected to correlate and predict the water activity obtained in this work and the solubility reported in literature for the CuCl₂−MCl₂−H₂O (M = Mg, Ca) ternary systems at 298.15 K. It was found that, the Pitzer model and PSC model cannot consistently represent these thermodynamic properties, with the binary and mixing parameters that already reported or fitted in this work. However, the Reaction model, representing the different competition association ability of common-anions and water molecules with different cations, can successfully predictethe water activity and solubility isotherms in these ternary systems at 298.15 K with binary parameters only. Applying the Reaction model, some examples of the Cu-bearing species distribution as a function of MgCl₂ (CaCl₂) molalities are given and used to account for how the structure variation of a electrolyte solution influences its macroproperties.

CuCl ₂ -MCl ₂ -H ₂ O（M  = Mg，Ca）三元体系及其亚二元体系的水活度已通过等值方法在298.15 K下进行了测量。CuCl ₂ -H ₂ O的最大浓度，氯化镁₂ -H ₂ O和氯化钙₂ -H ₂ O二进制文件系统是5.28摩尔•千克^-1，5.25摩尔•千克^-1和6.61摩尔•千克^-1，分别。对于CuCl ₂ -MgCl ₂ -H ，混合溶液的浓度范围为0.91 mol•kg ^-1至5.69 mol•kg ^-1₂ O系统，对于CuCl ₂ -CaCl ₂ -H ₂ O系统为1.29 mol•kg ^-1至6.87 mol•kg ^-1。次二元系统测得的水活度与文献报道的实验结果一致。三元系统中测得的相等水活度大大偏离Zdanovskii-Stokes-Robinson（ZSR）线。选择Pitzer模型，Pitzer-Simonson-Clegg（PSC）模型和反应模型来关联和预测在这项工作中获得的水活度以及文献中报道的CuCl ₂ -MCl ₂ -H ₂ O（M = Mg，Ca）三元体系在298.15K。发现Pitzer模型和PSC模型不能始终如一地表示这些热力学性质，二元和混合参数已在这项工作中报告或得到拟合。但是，反应模型代表了普通阴离子和具有不同阳离子的水分子的不同竞争缔合能力，仅用二元参数就能成功地预测这些三元体系在298.15 K下的水活度和溶解度等温线。应用反应模型，给出了作为MgCl ₂（CaCl ₂）摩尔浓度函数的含Cu物种分布的一些示例，并用于说明电解质溶液的结构变化如何影响其宏观性能。