Critical properties for binary mixtures of ethane containing low concentrations of n-alkane

The critical temperature and pressure for binary mixtures of ethane contain ing n-alkanes (Cs to C-10) at low concentrations (up to 5.2 mol %) have bee n 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 m easurements of the mixture critical temperature and pressure were +/-2 K an d +/-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 t heory of conformal solutions and a dilute-mixture Soave-Redlich-Kwong (SRK) equation of state approach. Both methods correlated the critical mixture t emperature to an absolute error of within 3 K. However, the mixture critica l 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 s tate, respectively.