Sound velocity and refractive index of pure N2 fluid and of equimolar N2–CO2 fluid mixture up to 15 GPa

Abstract

The sound velocity and refractive index of pure N2 and of the equimolar N2–CO2 mixture are measured up to 15 GPa and 700 K in a resistive heating diamond anvil cell. The refractive index vs pressure is obtained by an interferometric method. The adiabatic sound velocity is then determined from the measurement of the Brillouin frequency shift in the backscattering geometry and the refractive index data. No phase separation of the N2–CO2 fluid mixture is observed. The fluid mixture properties are discussed in terms of ideal mixing.