Abstract: The solubilities of the quinary system Na⁺,K⁺,Mg²⁺//Cl,NO₃^--H₂O and its two quaternary subsystems, Na⁺,K⁺,Mg²⁺//NO₃^--H₂O and K⁺,Mg²⁺//Cl,NO₃^--H₂O,were studied by isothermal method at 25℃ and their phase diagrams were plotted.In the equilibrium phase diagram of quaternary system Na⁺,K⁺,Mg²⁺//NO₃^--H₂O, there are one invariant point,three univariant curves and three regions of crystallization with one salt:NaNO₃, KNO₃ and Mg(NO₃)2·6H₂O.In the equilibrium phase diagram of quaternary system K⁺,Mg²⁺//Cl,NO₃^--H₂O,there are three invariant points,seven univariant curves and five regions of crystallization with one salt:KNO₃,KCl, Mg(NO₃)2·6H₂O,MgCl₂·6H₂O and KCl·MgCl₂·6H₂O.In the equilibrium phase diagram of the quinary system Na⁺, K⁺,Mg²⁺//Cl,NO₃^--H₂O,there are four invariant points,and seven regions of crystallization with one salt:NaCl, KCl,NaNO₃,KCl·MgCl₂·6H₂O,KNO₃,MgCl₂·6H₂O and Mg(NO₃)2·6H₂O.

Key words: quinary system, phase equilibrium, nitrate, solubility

摘要： The solubilities of the quinary system Na⁺,K⁺,Mg²⁺//Cl,NO₃^--H₂O and its two quaternary subsystems, Na⁺,K⁺,Mg²⁺//NO₃^--H₂O and K⁺,Mg²⁺//Cl,NO₃^--H₂O,were studied by isothermal method at 25℃ and their phase diagrams were plotted.In the equilibrium phase diagram of quaternary system Na⁺,K⁺,Mg²⁺//NO₃^--H₂O, there are one invariant point,three univariant curves and three regions of crystallization with one salt:NaNO₃, KNO₃ and Mg(NO₃)2·6H₂O.In the equilibrium phase diagram of quaternary system K⁺,Mg²⁺//Cl,NO₃^--H₂O,there are three invariant points,seven univariant curves and five regions of crystallization with one salt:KNO₃,KCl, Mg(NO₃)2·6H₂O,MgCl₂·6H₂O and KCl·MgCl₂·6H₂O.In the equilibrium phase diagram of the quinary system Na⁺, K⁺,Mg²⁺//Cl,NO₃^--H₂O,there are four invariant points,and seven regions of crystallization with one salt:NaCl, KCl,NaNO₃,KCl·MgCl₂·6H₂O,KNO₃,MgCl₂·6H₂O and Mg(NO₃)2·6H₂O.

关键词: quinary system, phase equilibrium, nitrate, solubility