We present a detailed experimental study of the pressure and density of N-2-Ar mixtures at 0 degrees C, 25.0 degrees C and 50.0 degrees C with four different mixtures at each temperature. The pressures are measured with a dead-weight tester. The densities are determined from knowledge of the precise volume and weight measurement of the mixtures. Statistical analysis of the experimental data yielded very precise values for the second and third density virial coefficients. Finally experimentally determined virial coefficients are compared with those calculated on the basis of statistical mechanics. The maximum percentage deviation between experimental and theoretical second virial coefficients is about 10% and that between third virial coefficients is less than 1%.