LXI. On virial coefficients and the born-green theory of fluids

Summary The validity of the superposition approximation used in the Born-Green theory of classical fluids is examined by obtaining a virial expansion of the pressure in powers of the density. It is found that the second and third virial coefficients are given correctly, but that the fourth is not. The discrepancy is illustrated numerically by considering explicitly the case of a gas of rigid spheres. The corresponding equations for a two-component mixture are aIso considered and it is shown that the equations are mutually consistent only when linearized.