(p, ρ, T, x) properties for CO2/isobutane binary mixtures at T = (280 to 440) K and (3 to 200) MPa

Highlights: → The pρTx properties for CO2/isobutane were measured in the compressed liquid phase. → A total of 283 points data were obtained from T = (280 to 440) K and (3 to 200) MPa. → The data were compared with the available equation of state. → The excess molar volumes were calculated and plotted as a function of T and P. - Abstract: The (p, ρ, T, x) properties for binary mixtures of CO2 (volume fraction purity 0.99999) and isobutane (mole fraction purity 0.99988) {x1 CO2 + x2 isobutane (x1 = 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, vmE, of the mixtures were calculated and plotted as a function of temperature and pressure.