The binary subsystems of the quaternary system Na₂SO₄–K₂SO₄–MgSO₄–CaSO₄ were thermodynamically assessed using the available experimental information including own thermochemical and structure measurements. Phase equilibria and thermodynamic properties of all six binary systems were properly considered. The modified associate species model was successfully applied for the description of the liquid phase while the mutual solubility between various sulphates in the solid state was treated with appropriate multi-sublattice models. The resulting new databank being compatible with the general oxide database was used for the representation of the thermodynamic properties in the binary systems including phase equilibria, activity and mixing data. The calculations are in good agreement with the experimental data.

四元体系的二元子系统Na ₂ SO ₄ –K ₂ SO ₄ –MgSO ₄ –CaSO ₄使用可获得的实验信息，包括自身的热化学和结构测量，对它们进行热力学评估。适当考虑了所有六个二元系统的相平衡和热力学性质。改进的缔合物种模型已成功地用于液相描述，而固态中各种硫酸盐之间的互溶性则通过适当的多亚晶格模型进行了处理。得到的与通用氧化物数据库兼容的新数据库用于表示二元系统中的热力学性质，包括相平衡，活性和混合数据。计算结果与实验数据吻合良好。