摘要:
Solid-liquid equilibria of a reciprocal quaternary system (Na+, K+ // SO42-, H2PO4-- H2O) at 298.15K were studied with isothermal solution saturation method. Solubility and physical properties (nD, η, ρ) of the equilibrium quaternary system were measured, and corresponding phase diagram, water diagram and physical property (ρ, η, nD) diagram were produced based on the data measured. The experimental results show that the phase diagram at 298.15 K contains four invariant points, nine univariant curves and six single salt crystallization fields which are K2SO4, Gla (3K2SO4·Na2SO4), Na2SO4·10H2O, KH2PO4, Na2SO4,NaH2PO4·2H2O, respectively. The Gla crystallization field occupies the largest part, which indicates it is easier to crystallize in the mixing solution. Gla (3K2SO4·Na2SO4) and crystalline hydrate (Na2SO4·10H2O,NaH2PO4·2H2O) are proven to co-exist in the quaternary system, whereas no solid solution is found at the investigated temperature, which means the reciprocal quaternary system is a complex eutectic type. Physical properties (nD, η, ρ) change regularly with the change of J(SO42-) composition in the saturated solution.%采用等温溶解法研究298.15 K下交互四元体系(Na+,K+//SO42-,H2PO4--H2O)的固液相平衡关系.测定了平衡溶液的溶解度数据及物理性质,包括密度,黏度,折光率.根据实验数据,绘制了相应的干盐相图,水图及物理性质-组成图.实验结果表明:在298.15 K下,该交互四元体系相图包括四个共饱和点,九条单变曲线及六个单盐结晶区域,分别为K2SO4,Gla(3K2SO4·Na2SO4),Na2SO4·10H2O,KH2PO4,Na2SO4,NaH2PO4·2H2O,其中Gla的结晶区域最大,最容易从混合溶液中结晶析出.该体系中存在复盐钾芒硝Gla(3K2SO4.Na2SO4),结晶水合物(Na2SO4.10H2O,NaH2PO4.2H2O),没有固溶体存在,是一个复杂的共饱和型体系.物理性质(黏度,密度,折光率)随饱和溶液中J(SO42-)的变化呈现相似规律.