三元体系CsCl+MgCl2+H2O298K介稳相平衡研究

摘要

The metastable phase equilibrium of the ternary system CsCl + MgCl2 + H2O at 298 K was studied by isothermal evaporation method.Results show that the phase diagram consists of two invariant points,three univariant curves,and three crystalline regions corresponding to two single salts CsCl,MgCl2 · 6H2O and a double salt CsCl · MgCl2 · 6H2O.The ternary system belongs to a complex type,with a double salt cesium carnallite (CsCl · MgCl2 · 6H2O) formed.From the phase diagram we can see,double salt cesium carnallite,whose double salt ray (CW) through its own solubility curve (E1E2) in the phase diagram,belongs to congruent double salt.The two invariant points (E1 and E2) are saturated by two salts and an equilibrated solution,and the cosaturated salts for two invariant points are MgCl2 · 6H2 O + CsCl · MgCl2 · 6H2O and CsCl + CsCl · MgCl2 · 6H2O,respectively.The invariant points E1 and E2 are located in the triangle which constructed by its component points and both belong to the commensurate invariant points.The salt crystal regions are in the following order:CsCl ·MgCl2 · 6H2O ＞ CsCl ＞ MgCl2 · 6H2O.The crystallization zone of double salt CsCl · MgCl2 · 6H2O is the largest,which means that the double salt CsCl · MgCl2 · 6H2O is easy to be separated from solution.%采用等温蒸发法研究三元体系CsCl+MgCl2+H2O 298 K的介稳相平衡.结果发现,相图包含2个共饱点,3条溶解度曲线和3个结晶相区.3个结晶区分别为单盐CsCl,MgCl2·6H2O和复盐CsCl· MgCl2·6H2O的结晶区.此体系有复盐铯光卤石形成,为复杂三元体系.由相图可知,铯光卤石CsCl· MgCl2·6H2O的复盐射线(CW)通过其溶解度曲线(E1E2),属同成分复盐.随着复盐的形成,相图中出现2个共饱点,在共饱点处,均有2种盐和一种平衡溶液达到共饱和.2个共饱点对应的饱和盐分别为MgCl2·6H2O+CsCl·MgCl2·6H2O和CsCl+CsCl·MgCl2· 6H2O,且2个共饱点均位于其相应组分点构成的三角形之内,均属于相称共饱点.3种盐结晶区大小按以下顺序排列:CsCl·MgCl2·6H2O＞CsCl＞MgCl2·6H2O,其中CsCl· MgCl2·6H2O结晶区最大,意味着复盐CsCl·MgCl2·6H2O比其他盐更容易析出.