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采用等温溶解平衡法研究了三元体系MgCl2+NH4Cl+H2O 298.15 K的稳定相平衡,测定了平衡时各组分的溶解度及平衡液相的密度、折光率等物化性质。该三元体系在298.15 K时的稳定相图含有2个共饱点E1,E2,3条单变量曲线AE1,E1E2,E2B,3个结晶区。3个结晶区分别对应MgCl2.6H2O,NH4Cl及复盐铵光卤石(NH4Cl.MgCl2.6H2O)。2个共饱点中,E1为不相称共饱点,对应的平衡固相为NH4Cl.MgCl2.6H2O+NH4Cl,平衡液相组成为w(NH4Cl)=7.79%,w(MgCl2)=21.90%;E2为相称共饱点,对应的平衡固相为NH4Cl.MgCl2.6H2O+MgCl2.6H2O,平衡液相组成为w(NH4Cl)=0.21%,w(MgCl2)=32.27%。研究结果表明:该三元体系为复杂三元体系,有不相称复盐NH4Cl.MgCl2.6H2O生成。MgCl2对NH4Cl有强烈的盐析作用。平衡液相的密度和折光率随着溶液中MgCl2质量分数的增加而增大。采用经验公式对密度和折光率进行计算,计算值与实验值吻合度较好,相对偏差小于0.012。
The equilibrium phase equilibrium of the ternary system MgCl2 + NH4Cl + H2O 298.15 K was studied by isothermal dissolution equilibrium method. The solubility of each component and the density, refractive index and other physicochemical properties of the equilibrium liquid phase were determined. The stable phase diagram of the ternary system at 298.15 K contains two eutectic E1, E2, three univariate curves AE1, E1E2, E2B, and three crystallization zones. The three crystallization zones correspond to MgCl2.6H2O, NH4Cl and double-salt ammonium carnallite (NH4Cl.MgCl2.6H2O) respectively. In the two co-flooding sites, E1 is the disproportional co-flooding point, and the corresponding equilibrium solid phase is NH4Cl.MgCl2.6H2O + NH4Cl. The equilibrium liquid phase composition is w (NH4Cl) = 7.79% and w (MgCl2) = 21.90% E2 is symmetric point, the corresponding equilibrium solid phase is NH4Cl.MgCl2.6H2O + MgCl2.6H2O, the equilibrium liquid phase composition is w (NH4Cl) = 0.21%, w (MgCl2) = 32.27%. The results show that: the ternary system is a complex ternary system, there is an asymmetric double salt NH4Cl.MgCl2.6H2O generation. MgCl2 has a strong salting-out effect on NH4Cl. The density and refractive index of the equilibrium liquid phase increase as the mass fraction of MgCl2 in solution increases. The empirical formula is used to calculate the density and refractive index. The calculated values are in good agreement with the experimental values, and the relative deviation is less than 0.012.