Speeds of sound in (0.95 N2 + 0.05 CO and 0.9 N2 + 0.1 CO) gas mixtures at T = (273 and 325) K and pressure up to 10 MPa

•Experimental speeds of sound for two mixtures are reported.•A spherical resonator is used for the measurements.•Heat capacities are calculated from the speeds of sound.

The measurements of speed of sound for two mixtures of (N2 + CO) are reported. The data have been obtained using a spherical resonator for two isotherms T = (273.15 and 325.15) K and pressures up to 10 MPa. The uncertainty study is detailed and the total uncertainty of the speed of sound is not worse than 0.016%. The results have been compared with the GERG-2008 equation of state.