A new analysis method for improving collection of vapor-liquid equilibrium (VLE) data of binary mixtures using differential scanning calorimetry (DSC)

The method specified in ASTM E1782-14 for using differential scanning calorimetry (DSC) to measure vapor pressure of liquid samples can be extended to binary mixtures to gather vapor-liquid equilibrium (VLE data). In previous studies, the main uncertainty was in determining the transition temperature due to evaporation of the liquid sample prior to its actual boiling point. Using lids with a pinhole on the sample pan can only mitigate the adverse effect of pre-boiling. Present work shows evaluating the second derivative of temperature difference between the sample and reference temperature instead of the heat-flow curve eliminates the aforementioned drawback in the result analysis. The results obtained using the proposed method were benchmarked against published data and excellent agreement with published data indicates that this technique can be reliably used for experimental measurement of binary VLE data. Also, the results showed to be reproducible and thermodynamically consistent.