关键词: 水盐体系, 共晶点, 温度, 相

Abstract:

For the quaternary salt-water systems, such as the homo-ion system K⁺//Cl^-, SO₄^2-, NO₃^--H₂O and interaction system Na⁺, K⁺//SO₄^2-, NO₃^--H₂O, as well as their six ternary subsystems, the freezing points, eutectic points and the crystallization regularities of salts were studied by cooling method. According to experimental data, the eutectic point temperature-liquid composition diagrams for these systems were plotted. The results were as follows: (1) The crystallization regularity of salts and the eutectic point temperatures can be obtained by measuring the time-temperature curves for multicomponent salt-water systems during cooling process; (2) In these systems above, 3K₂SO₄·Na₂SO₄ existing under normal temperature did not appear at the eutectic point temperature. As a result, the phase relationships in these systems were simplified; (3) The prism can be used to describe the relationships among the phases, freezing points or eutectic points and the compositions of liquids for the ternary systems, the quaternary homo-ion systems and interaction systems concisely and visually; (4) In the eutectic point temperature-liquid composition diagrams, for ternary systems without double-salts, there were two eutectic curves with single salt and ice, one eutectic point with two salts and ice, and one ice crystallizing region. For the quaternary homo-ion systems and interaction systems, there were three and four eutectic regions with single salt and ice, three and five eutectic curves with two salts and ice, and one and two eutectic points with three salts and ice, respectively.

Key words: salt-water system, eutectic point, temperature, phase