The phase equilibrium data of the ternary system Na₂SO₃–Na₂SO₄–H₂O at 293.15, 313.15, and 353.15 K were determined by the isothermal dissolution method. There are one invariant point, two univariant isothermal dissolution curves, and three crystallization regions at each temperature. As the temperature increases from 293.15 to 313.15 K, the solubilities of both Na₂SO₄ and Na₂SO₃ increase. The single crystallization region of Na₂SO₄ decreases, while the single crystallization region of Na₂SO₃ increases. When the temperature increases from 313.15 to 353.15 K, the solubilities of both Na₂SO₄ and Na₂SO₃ decrease. The single crystallization region of Na₂SO₄ decreases, and the single crystallization region of Na₂SO₃ is basically unchanged. Furthermore, based on the solubility data, the Pitzer ion interaction model was used to calculate the relevant Pitzer parameters and then to calculate the solubilities of Na₂SO₃ and Na₂SO₄ theoretically. The calculated Na₂SO₃ and Na₂SO₄ solubilities basically agree with the experimental values. The data obtained in this work have important implications for the design and optimization of the Na₂SO₃ crystallization process from resorcinol production wastewater.

中文翻译：

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三元体系 Na2SO3–Na2SO4–H2O 在 293.15、313.15 和 353.15 K 时的相平衡

三元体系Na ₂ SO ₃ -Na ₂ SO ₄ -H ₂ O在293.15、313.15和353.15 K的相平衡数据采用等温溶解法测定。每个温度下有一个不变量点、两条单变量等温溶解曲线和三个结晶区。随着温度从 293.15 增加到 313.15 K，Na ₂ SO ₄和 Na ₂ SO ₃的溶解度都增加。Na ₂ SO ₄单晶区减少，而Na ₂ SO _{3单晶区减少}增加。当温度从 313.15 升高到 353.15 K 时，Na ₂ SO ₄和 Na ₂ SO ₃的溶解度均降低。Na ₂ SO ₄单晶区减少，Na ₂ SO ₃单晶区基本不变。此外，基于溶解度数据，利用Pitzer离子相互作用模型计算了相关Pitzer参数，进而从理论上计算了Na ₂ SO ₃和Na ₂ SO _{4的溶解度。}计算出的 Na ₂ SO ₃和 Na₂ SO ₄溶解度与实验值基本一致。这项工作中获得的数据对间苯二酚生产废水中Na ₂ SO _{3结晶工艺的设计和优化具有重要意义。}