Abstract: The P-V-T relations for polar substances are studied by using a partition function. The attraction effects are divided into polar and nonpolar term, and a polar partition expression with intermolecular potential function is derived, to modify Van der Waals equation of state and obtain a correlation for attraction parameter"a". Polar substances are correlated with critical compressibility factor as well as reduced dipole moment. The calculated vapor pressure and heat of vaporization of 45 kinds of polar substances are satisfactory. A modified, SRK equation is developed with improved accuracy.

摘要： 本文把引力项对配分函数的贡献分成极性项和非极性项,由分子位能函数推导出极性项配分函数表达式.由此得出了VdW方程引力参数“a”的极性项关联式.并提出用临界压缩因子和对比偶极矩共同关联极性物质.所推导出的“a”的表达式改进了SRK方程的计算精度.对45种极性物质的饱和蒸汽压和汽化热进行了计算,获得良好的结果.