Although for a long time considerable attention has been paid to correlating the apparent molar volumes of electrolytes using the Pitzer ion-interaction approach in aqueous solutions, no attempt has, so far, been made to describe the volumetric data of electrolytes in mixed solvent media. This is due to the lack of experimental data on the pressure dependence of the dielectric constant in mixed solvent media. These data are essential to obtain the Debye–Hückel limiting law slopes for volumes that, in turn, are required to analyze the apparent molar volume vs. molality data of electrolytes in the light of the Pitzer ion-interaction approach. Here, we develop a convenient method which helped correlate the apparent molar volumes of electrolytes and estimate the Pitzer ion-interaction parameters for volume along with the Debye–Hückel limiting law slope for volumes. In particular, we have applied this approach to the literature apparent molar volume data of a number of uni-univalent electrolytes (viz., lithium chloride, sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, and potassium iodide) in methanol–water mixed solvent media at different temperatures. The parameters (namely, the apparent molar volume of the electrolyte at infinite dilution, $$V_{{\phi {\text{,MX}}}}^{\infty }$$ V ϕ ,MX ∞ , the second virial coefficient $$B_{{{\text{MX}}}}^{V}$$ B MX V , and the third virial coefficient, $$C_{{{\text{MX}}}}^{V}$$ C MX V ) obtained here satisfactorily describe the molality dependence of apparent molar volumes of the investigated electrolyte solutions. The present correlation indicates that the electrolytes exist essentially as free ions in methanol–water mixed solvent media in conformity with what inferred earlier from conductivity measurements.

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甲醇-水混合溶剂介质中单价电解质体积特性的相关性：Pitzer 离子相互作用方法

尽管很长一段时间以来，人们一直在关注使用 Pitzer 离子相互作用方法在水溶液中关联电解质的表观摩尔体积，但到目前为止，还没有尝试描述混合溶剂介质中电解质的体积数据。这是由于缺乏关于混合溶剂介质中介电常数的压力依赖性的实验数据。这些数据对于获得体积的 Debye-Hückel 极限定律斜率至关重要，反过来，根据 Pitzer 离子相互作用方法分析电解质的表观摩尔体积与摩尔浓度数据需要这些数据。这里，我们开发了一种方便的方法，该方法有助于关联电解质的表观摩尔体积，并估计体积的 Pitzer 离子相互作用参数以及体积的 Debye-Hückel 极限定律斜率。特别是，我们已将此方法应用于许多单价电解质（即氯化锂、氯化钠、氯化钾、溴化钠、溴化钾、碘化钠和碘化钾）的文献表观摩尔体积数据。不同温度下的甲醇-水混合溶剂介质。参数（即无限稀释时电解质的表观摩尔体积，$$V_{{\phi {\text{,MX}}}}^{\infty }$$ V ϕ ,MX ∞ ，第二维里系数$$B_{{{\text{MX}}}}^{V}$$ B MX V ，以及第三维里系数，$$C_{{{\text{MX}}}}^{V}$$ C MX V ）令人满意地描述了所研究电解质溶液的表观摩尔体积的摩尔浓度依赖性。目前的相关性表明，电解质基本上以游离离子形式存在于甲醇-水混合溶剂介质中，与之前从电导率测量中推断出的结果一致。