KH_2PO_4-KNO_3-H_2O三元水盐体系在313.15 K条件下相图的测定和研究

采用等温溶解平衡法测定KH_2PO_4-KNO_3-H_2O三元水盐体系在313.15 K条件下的溶解度,并利用湿渣法和XRD对平衡固相进行分析和验证。根据实验数据绘制相图,相图结果表明,KH_2PO_4-KNO_3-H_2O体系的溶解度等温线有一个三元共饱和点,两条分支,将相图划分为4个区域:不饱和区、KH_2PO_4结晶区、KNO_3结晶区和KH_2PO_4-KNO_3的混合结晶区。313.15 K下的共饱和点组成为w(KH_2PO_4)7.76%、w(KNO_3)33.24%。同时,测定溶液的密度,画出三元体系溶液密度与KNO_3含量的关系图,并将实验测定的密度值与密度模型计算的密度值进行比较,验证了该密度模型的可靠性。

Study on phase equilibrium in KH2PO4-KNO3-H2O ternary system at 313.15 K

The solubility of KH2PO4-KNO3-H2O ternary system at 313.15 K is measured by the method of isothermal solution saturation,and the components of equilibrium solids are detected and verified by the Schreinemaker's method of wet residues and X-ray diffraction (XRD).According to the experimental data,the phase diagram is plotted.The results of the phase diagram show that there are a invariant point and two solubility branches,which divide the diagram into four regions,including the unsaturated region,KH2PO4 crystallization region,KNO3 crystallization region and the mixed crystallization region of KH2PO4-KNO3.The composition of invariant points is of w(KH2PO4)7.76％,w(KNO3)33.24％ at 313.15 K.At the same time,the density of the system is investigated and the relational graph of density and the content of KNO3 is plotted.The density of saturated solution according to the model of density is compared with the experimental data,which tests the reliability of the model.