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A modified Martin–Hou (M–H) equation of state (EOS) for the accurate representation of thermodynamic property data of some pure substances in liquid phase is presented in this work. The improvement is achieved by substituting a new parameter η into the original M–H EOS. Eighteen pure substances are chosen to construct the dependency relationship of η on reduced temperature Tr and acentric factor ω. Furthermore, to verify the effectiveness and improvement of the modified M–H EOS, the calculated values of the saturated vapor and liquid molar volumes are compared with the literature data in the reduced temperature ranging from approximately 0.6 to 1.0. The results show that the modified M–H EOS perform a good prediction in gaseous phase for pure substances with the average absolute deviation (AAD) generally less than 1%, and more precise liquid molar volume values can be obtained with the modified equation. In liquid phase, the AAD of the modified M–H EOS is 3.71%, which is much lower than 6.16% of the original M–H EOS.

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In order to further improve the accuracy in liquid-phase state and get a simpler algorithm, the Martin-Hou Equation of State is modified after rigorous data analyses in different cases. A new revision factor h, a function of critical compression factor, is introduced into the novel M-H EOS. According to the derivation of the new EOS, only a few number of physical properties are needed to characterize a given substance, which greatly reduced the difficulty of the solution about the EOS. The novel M-H EOS is applied to argon, methane, nitrogen, propane, benzene and water to verify the applicability and the accuracy in liquid-phase state. The overall average deviation for the six substance is 1.29% by the novel M-H EOS; as a comparison, the overall average deviation is 2.51% by Hou's M-H EOS, the novel M-H EOS obviously reduces the deviation and can universally be applied to most kinds of substances.

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