Second Virial Coefficient of Polar Gases

The theoretical expressions for the second virial coefficient, B(T), are derived for the (18–6‐3) Stockmayer potential $$\text{Φ(r)=4ε}\left[{\left(\frac{\sigma }{r}\right)}^{18}-{\left(\frac{\sigma }{r}\right)}^6\right]-\frac{{\mu }^2}{r^3}{\mathrm{g(\theta }}_1{\mathrm{,\theta }}_2\mathrm{,\phi )}$$ , where g(θ₁, θ₂, φ) = 2 cos θ₁ cos θ₂ − sin θ₁ sin θ₂ cos φ, and also according to the (28–7‐3) potential. Tables of the reduced virial coefficient are given as a function of the reduced temperature for the (18–6‐3) potential, and experimental B(T) data are interpreted for a number of gases. The potential parameters are reasonable and reproduce the B(T) data within the limits of experimental errors. The point dipole polarizable model is also considered.