An experimental study of the pressure-volume-temperature-composition (PVTx) properties in the gas phase for the R290 + R13I1 system was performed with an isochoric method. The measurements of R290 + R13I1 mixtures were conducted in the range of temperatures from 283.37 K to 353.29 K, pressures from 242.2 kPa to 1065.0 kPa, densities from 0.1091 mol dm(-3) to 0.4133 mol dm(-3), and compositions from 0.4502 to 0.8524 mol fraction of propane. The uncertainties in the present work were estimated to be within +/- 10 mK for temperature, +/- 2.4 kPa for pressure, +/- 0.1 mol% for mole composition and +/- 0.16% for density, respectively. On the basis of the experimental PVTx property data, a truncated virial equation of state was developed for the R290 + R13I1 system. This equation reproduces the experimental data in gas phase with relative deviation within +/- 0.23% in pressure and within +/- 0.25% in density. (C) 2019 Elsevier B.V. All rights reserved.