Thermodynamic Properties of Propane. I. <i>p−</i>ρ−<i>T</i> Behavior from (265 to 500) K with Pressures to 36 MPa

The p−ρ−T behavior of high-purity (99.999 %) propane was measured from (265 to 500) K with pressures to 36 MPa with a two-sinker densimeter. The measurements extend from low-density vapor to compressed-liquid states, and the extended critical region was studied extensively. Vapor pressures from (270 to 369) K were also measured. The expanded (k = 2) uncertainty in density is (56·10−6·ρ + 0.0013 kg·m−3) at near-ambient conditions, increasing to (170·10−6·ρ + 0.0013 kg·m−3) at 500 K and 36 MPa. The uncertainties in temperature and pressure are 0.004 K and (51·10−6·p + 2.0 kPa), respectively. The analysis for density accounts for the force transmission error in the magnetic suspension coupling of the densimeter and includes corrections for vertical density gradients in the measuring cell. These data, together with other new data and carefully selected literature data, have been used to develop an equation of state covering the entire fluid region from the triple-point temperature to 650 K with pressures to 1000 MPa. New measurements of the isochoric heat capacity and speed of sound and the equation of state are described in companion papers.