We determine the surface tension of aqueous electrolyte solutions in contact with non-polar dielectric media using a thermomechanical approach, which involves deriving the stress tensor from the thermodynamic potential of an inhomogeneous fluid. To obtain the surface tension, we calculate both the normal and tangential pressures using the components of the stress tensor, recently derived by us [Y. A. Budkov and P. E. Brandyshev, J. Chem. Phys. 159, 174103 (2023)] within the framework of Wang’s variational field theory. Using this approach, we derive an analytical expression for the surface tension in the linear approximation. At low ionic concentrations, this expression represents the classical Onsager–Samaras limiting law. By utilizing only one fitting parameter, which is related to the affinity of anions to the dielectric boundary, we successfully approximated experimental data on the surface tension of several aqueous electrolyte solutions. This approximation applies to both the solution–air and solution–dodecane interfaces, covering a wide range of electrolyte concentrations.

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电解质水溶液的表面张力。热机械方法

我们使用热机械方法确定与非极性介电介质接触的电解质水溶液的表面张力，该方法涉及从非均匀流体的热力学势导出应力张量。为了获得表面张力，我们使用最近由我们导出的应力张量的分量来计算法向压力和切向压力[YA Budkov 和 PE Brandyshev，J. Chem.物理。 159, 174103 (2023)]在王变分场理论的框架内。使用这种方法，我们推导出线性近似中的表面张力的解析表达式。在低离子浓度下，该表达式代表经典的 Onsager-Samaras 极限定律。通过仅利用一个与阴离子对介电边界的亲和力相关的拟合参数，我们成功地近似了几种电解质水溶液的表面张力的实验数据。这种近似适用于溶液-空气和溶液-十二烷界面，涵盖了广泛的电解质浓度范围。