Thermodynamic properties of a mixture of He and N2 at high pressures determined from speeds of sound

The equation of state and heat capacity of a mixture of He and N2 of equal composition have been determined at temperatures from 156.15 to 298.15 K and at pressures from 200 to 1000 MPa using a recently developed computational method. This is based on stepwise construction of T isobars starting from an experimental reference p isotherm and using the previously reported sound speed data of the mixture as a function of pressure and temperature. The derived p T data have been fitted to a new empirical equation of state for the mixture with a r.m.s. deviation of 0.02%.