AN EMPIRICAL-EQUATION OF STATE FOR LIQUIDS

An empirical four-parameter equation is presented. It has been applied to 104 compounds in the liquid state, and it allows experimental specific volumes of liquids up to 300 MPa to be interpolated quite well at least in the temperature domain approximately ranging from melting to boiling at atmospheric pressure. In particular, results for saturated hydrocarbons, alcohols, esters, glycols, and alkyl halides have been considered. In each family of compounds, the four parameters were found not to vary much. It was then possible to characterize each family by mean values of two parameters. Using these two parameters together with two volume data determined at atmospheric pressure, it was possible to predict specific volumes of liquids up to 300 MPa with a 1% accuracy for the last four families quoted above. The results for saturated hydrocarbons are more scattered (in the 2% range), but this extrapolating method is surely a useful one when high-pressure data are lacking.