Abstract: Ordinarily Redlich-Kister equation and SSF equation are used for correlating excess enthalpies.Both equations are multinomials in which the number of parameters is undetermined.The equation with three parameters proposed by Liu Guojie has a fixed form, but besides three undetermined parameters, the molar volume of the solution needs to be known.A model with three parameters that does not have this demand was proposed by the present author, but the composition of solution is shown by mol fraction, so it is difficult to reflect the special effect of difference in molecular sizes.In this paper, a modified model for correlating the excess enthalpies of binary systems is developed in which the macro-composition of solution is shown with volume fraction to emphasize the special mutual effect of molecules caused by different molecular sizes.Tests with experimental data of more than 100 non-symmetrical binary systems in which the components have different molecular sizes, shapes and structures,show that for non-symmetrical binary systems the modified model is of an apparent advantage over the former one in accuracy, and is still tenable in the limiting condition of φ→0 and φ→1.

Key words: 超额焓, 分子热力学模型, 体积分数, 非对称体系

摘要： 在已提出的二元体系超额焓分子热力学模型基础上，用体积分数表征溶液宏观组成以校正由于分子尺寸不同引起的分子之间特殊交互效应，推导出关联二元溶液超额焓的三参数改进模型.用近10年发表的有代表性的上百个二元非对称体系实验数据，主要是含不同分子尺寸、形状、结构组分的复杂体系实验数据，对所提超额焓改进模型进行了检验.结果表明，对含不同分子尺寸、形状、结构组分的非对称体系，改进模型的关联精度明显优于原模型.同时，在φ→0 或φ→1的极限条件下，改进模型同样成立.

关键词: 超额焓, 分子热力学模型, 体积分数, 非对称体系