Speed of Sound in (Carbon Dioxide + Propane) and Derived Sound Speed of Pure Carbon Dioxide at Temperatures between (248 and 373) K and at Pressures up to 200 MPa

The speed of sound in (carbon dioxide + propane) mixtures, with mole fractions of carbon dioxide between 0.938 and 0.998, has been measured at temperatures from (248 to 373) K and at pressures between (8 and 200) MPa. We find that the addition of propane to carbon dioxide is highly effective in catalyzing vibration-translation energy transfer and reduces the sound absorption coefficient sufficiently to permit sensitive measurements of the speed of sound at frequencies in the low-MHz range. In this work, a 2 MHz ultrasonic cell based on the double-path pulse-echo method was used. The cell was calibrated with degassed ultrapure water at T = 298.15 K and p = 1 MPa, making use of the speed of sound computed from the International Association for Properties of Water and Steam equation of state (IAPWS-95). The estimated overall standard relative uncertainty of the speeds of sound measured in this study are 0.035 %. The speed of sound in pure carbon dioxide was obtained by extrapolation of the sound-speed data w...