Abstract: The phase equilibrium in the ternary system of MeSO4-(NH4)2SO4-H2O at 298 K was studied by isothermal equilibrium method and many significant experimental results were obtained. In the ternary system of MnSO4-(NH4)2SO4-H2O, there were 3 saturation curves given by MnSO4×H2O, (NH4)2Mn(SO4)2×6H2O and (NH4)2SO4, respectively. There were 2 co-saturation points, A having the composition of MnSO4×H2O and (NH4)2Mn(SO4)2×6H2O, and B given by (NH4)2Mn(SO4)2×6H2O and (NH4)2SO4. There were 3 purification crystallization areas given by (NH4)2Mn(SO4)2×6H2O, MnSO4×H2O and (NH4)2SO4, respectively. In the ternary system of ZnSO4-(NH4)2SO4-H2O, there were 3 saturation curves given by (NH4)2Zn(SO4)2×6H2O, ZnSO4×7H2O and (NH4)2SO4, respectively. There were 2 co-saturation points, C having the composition of (NH4)2Zn(SO4)2×6H2O and ZnSO4×7H2O, and D given by (NH4)2SO4 and (NH4)2Zn(SO4)2×6H2O, respectively. There were 3 purification crystallization areas given by (NH4)2Zn(SO4)2·6H2O, ZnSO4×7H2O and (NH4)2SO4, respectively. In the ternary system of FeSO4-(NH4)2SO4-H2O, there were 3 saturation curves given by (NH4)2Fe(SO4)2·6H2O, FeSO4×7H2O and (NH4)2SO4, respectively. There were 2 co-saturation points, E having the composition of (NH4)2Fe(SO4)2×6H2O and FeSO4×7H2O, and F given by (NH4)2Fe(SO4)2×6H2O and (NH4)2SO4, respectively. There were 3 purification crystallization areas of FeSO4×7H2O, (NH4)2Fe(SO4)2×6H2O and (NH4)2SO4, respectively. These experimental results gained above not only give theoretical guidance for the double-salt precipitation deep purification of such solutions containing Fe2+, Mn2+ and Zn2+, etc., but also establish foundation for study on the quarternary system consisting of Fe2+, Mn2+, Zn2+ and NH4+/SO42--H2O.

Key words: solubility, salt-water system, phase equilibrium

摘要： 用等温溶解平衡法研究了298 K时MeSO4-(NH4)2SO4-H2O三元体系的溶解度，并绘制了平衡相图. 结果表明，在MnSO4-(NH4)2SO4-H2O体系中，有MnSO4×H2O, (NH4)2Mn(SO4)2×6H2O和(NH4)2SO4 3条饱和曲线，组成为MnSO4×H2O和(NH4)2Mn(SO4)2×6H2O及(NH4)2Mn(SO4)2×6H2O和(NH4)2SO4的2个共饱和点，以及平衡固相为(NH4)2SO4, (NH4)2Mn(SO4)2×6H2O和MnSO4×H2O的3个纯盐结晶区. 在ZnSO4-(NH4)2SO4-H2O体系中，有(NH4)2Zn(SO4)2×6H2O, ZnSO4×7H2O与(NH4)2SO4 3条饱和曲线，组成为(NH4)2Zn(SO4)2×6H2O和ZnSO4×7H2O及(NH4)2SO4和(NH4)2Zn(SO4)2×6H2O的2个共饱和点，以及平衡固相为(NH4)2Zn(SO4)2×6H2O, ZnSO4×7H2O和(NH4)2SO4的3个纯盐结晶区. 在(NH4)2SO4-FeSO4-H2O体系中，有(NH4)2Fe(SO4)2×6H2O, FeSO4×7H2O和(NH4)2SO4的3条饱和曲线，组成为(NH4)2Fe(SO4)2×6H2O和FeSO4×7H2O及(NH4)2Fe(SO4)2×6H2O和(NH4)2SO4的2个共饱和点，以及平衡固相为(NH4)2Fe(SO4)2×6H2O, FeSO4×7H2O和(NH4)2SO4的3个纯盐结晶区. 研究结果既为含Fe2+, Mn2+和Zn2+溶液的复盐沉淀深度净化提供了理论指导，同时也为四元体系的研究奠定了基础.

关键词: 溶解度, 水盐体系, 相平衡