Study On The Solid-liquid Equilibrium Of The Quaternary System And Its Subsystems Of Na⁺,Ca²⁺//Cl^-,H₂PO₂^-,H₂O

Calcium hypophosphite has been widely used as an anti-corrosive agent, flame retardant, assistant for Ni-electroless plating, and animal nutrition supplement. High-purity calcium hypophosphite can be synthesized via the replacement reaction of sodium hypophosphite and calcium chloride. At present, the phase equilibrium of Na , Ca2+ // Cl-,H2PO2--H2O interaction quaternary system is studied in this laboratory, and phase diagrams of 298.15K and 323.15K have been obtained. In order to further improve the phase diagram of the system. In this work,the (solid + liquid) phase diagrams of (Ca(H2PO2)2 + H2O)binary system from freezing to boiling point at ambient pressure,and (Ca(H2PO2)2+ CaCl2+H2O),(Ca(H2PO2)2+ NaH2PO2+ H2O) ternary systems at 273.15K were experimentally determined via the classical isothermal solubility equilibrium method, it was found that:One anhydrous salt of Ca(H2PO2)2 occurs in (Ca(H2PO2)2 + H2O) binary systems within full temperature region from freezing to boiling points, And the temperature has little effect on the solubility of calcium hypophosphite.The study of ternary phase diagram found: the system of CaCl2-Ca(H2PO2)2-H2O have two solid phase area and a invariant point of two salt .The solid salt is CaC12·6H2O,Ca(H2PO2)2, which belongs to the simple ternary system. Solid phase area of calcium hypophosphite is larger; Ca (H2PO2) 2-NaH2PO2-H2O system is complex ternary system.There are there solid phase area and two invariant point of two salt. The solid salt are Ca(H2PO2)2?NaH2PO2?H20?NaCa(H2PO2)3 respectively. NaCa(H2PO2)3 is a double salt,Which is unstable. The solid-phase area of double salts is larger.The research of the quaternary system also adopted isothermal method. The study found: the system of Na+,Ca2+//Cl-,H2PO2 -H2O have five solid phase area,seven two salt invariant curve,three invariant point of there salt and.There is not double salt in the system.The Solid phase area of calcium hypophosphite is the largest. The Solid phase area of sodium hypophosphite is the smallest.The invariant line of NaCl+Ca(H2PO2)2 show this method is feasible to produce calcium hypophosphite. The presence the invariant line of NaCl+NaCa(H2PO2)3 and Ca(H2PO2)2+NaCa(H2PO2)3. Indicating that the presence of double salts will have an impact on the yield and purity of calcium hypophosphite products.