本研究分別對丙酸甲酯＋乙酸甲酯，丙酸＋丙酸甲酯、丙酸＋乙酸甲酯、乙酸+丙酸甲酯，以及丙酸異丙酯＋異丙醇等雙成分系統量測在恆壓 (760 mmHg) 下的汽液相平衡數據，所量取的汽液相平衡數據均通過熱力學一致性測試。觀察汽液相平衡的T-x-y曲線，相對於理想溶液而言，僅丙酸異丙酯＋異丙醇系統呈現負偏差，其餘系統均呈現正偏差。本研究之相平衡數據關聯分別採用三種汽相逸壓模式 - 理想氣體模式或保留兩項之維里方程式，其中之第二維里係數以Hayden-O’ Connell (HOC) 模式或Nothnagel (NTH) 模式估算，並結合液相活性係數模式(Wilson, NRTL, UNIQUAC )。所獲得的迴歸結果顯示對於不含酸類分子的雙成分系統，改變汽相逸壓模式獲得的迴歸結果均很相近；然而對於含有酸類分子的混合物系統，考慮汽相中酸類成分有結合效應的方法獲得較佳的成果。不論使用何種液相活性係數模式，對丙酸＋丙酸甲酯系統而言，以使用HOC之汽相逸壓模式可獲得較為良好的迴歸效果；同樣的對於丙酸＋乙酸甲酯與乙酸＋丙酸甲酯系統而言，使用HOC之汽相逸壓模式也獲得較佳的數據關聯結果。

Isobaric vapor-liquid phase equilibrium (VLE) data were measured for the binary systems of methyl propionate + methyl acetate, propionic acid + methyl propionate, propionic acid + methyl acetate, acetic acid + methyl propionate, and isopropyl propionate + isopropanol at 760 mmHg. All the binary VLE data passed the thermodynamic consistency test. While the system of isopropyl propionate + isopropanol exhibited negative deviation, the other four binary systems showed positive deviation. The VLE data were correlated with the Wilson, the NRTL, and the UNIQUAC models combining with ideal gas assumption or the two-term virial equation here the second virial coefficients were estimated from the Hayden–O’ Connell (HOC) or the Nothnagel (NTH) method. For the binary systems without containing organic acids, the correlated results were almost the same by using different vapor-fugacity calculation models. However, the correlated results were much better while the association effect in the vapor phase was considered for the systems containing organic acids. Regardless of the activity coefficient models to be used, estimation of the second virial coefficient from the HOC method is better for propionic acid + methyl propionate, propionic acid + methyl acetate and acetic acid + methyl propionate.

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