The Equation of State of Isobutane: An Interim Assessment

摘要

New and very accurate measurements of the vapor pressure and two PVT isotherms of isobutane below critical are presented. The vapor pressure data have been correlated to within parts per 10,000 using a scaled vapor pressure equation. The Beattie data in the critical region has been correlated using a scaling law approach. This required a shift in the critical temperature of 0.3 K from that published by Beattie. The significance of this shift in an overall correlation is not yet clear. The two PV isotherms are compared with literature data and the results of Sage and Lacy shown to be inaccurate. Those of Connolly appear to be sufficiently accurate for including in future correlations. Two correlations of Starling et al. and that of Das et al. are intercompared and are compared with these new results. As might be expected, these correlations, being based on inaccurate data, are not of sufficient accuracy for use as representations of the properties of isobutane. A program is presented for the completion of a correlation of the properties of isobutane to engineering accuracy.