Critical Properties for Binary Mixtures of Ethane Containing Low Concentrations of n-Alkane

The critical temperature and pressure for binary mixtures of ethane containing n -alkanes (C 5 to C 10 ) at low concentrations (up to 5.2 mol %) have been determined. A visual technique was used where the observation of mixture critical opalescence followed by the appearance of a vapor−liquid meniscus in a constant volume sight gauge was observed. The absolute errors in the measurements of the mixture critical temperature and pressure were ±2 K and ±0.5 bar, respectively, with an estimated relative error of ±1.5% for the composition of the organic compounds used. The binary mixture critical temperature and pressure were estimated using a correlation based on the theory of conformal solutions and a dilute-mixture Soave−Redlich−Kwong (SRK) equation of state approach. Both methods correlated the critical mixture temperature to an absolute error of within 3 K. However, the mixture critical pressure was correlated to an absolute error of within 10 and 4 bar using the conformal solutions correlation and a dilute-mixture SRK equation of state, respectively.