( p, ρ, T, x) properties for CO 2/isobutane binary mixtures at T = (280 to 440) K and (3 to 200) MPa

Abstract

The ( p, ρ, T, x) properties for binary mixtures of CO 2 (volume fraction purity 0.99999) and isobutane (mole fraction purity 0.99988) { x 1 CO 2 + x 2 isobutane ( x 1 = 0.2482, 0.4718, and 0.7506)} were measured in the compressed liquid phase using a metal-bellows variable volumometer. Measurements were conducted from T = (280 to 440) K and (3 to 200) MPa. The expanded uncertainties ( k = 2) were estimated to be: temperature, <3 mK; pressure, 1.5 kPa ( p ⩽ 7 MPa), 0.06% (7 MPa < p ⩽ 50 MPa), 0.1% (50 MPa < p ⩽ 150 MPa), 0.2% ( p > 150 MPa); density, 0.10%; and composition, 4.4 · 10 −4. At >100 MPa and T = (280 or 440) K, the uncertainties in the density measurements increased to 0.14% and 0.22%, respectively. The data are compared with the available equation of state. The excess molar volumes, v m E , of the mixtures were calculated and plotted as a function of temperature and pressure.