Redlich-Kwong equation of state

$\left[P+{\frac {a}{T^{1/2}v(v+b)}}\right](v-b)=RT$

where

$a=0.4278{\frac {R^{2}T_{c}^{2.5}}{P_{c}}}$

and

$b=0.0867{\frac {RT_{c}}{P_{c}}}$

References

1. Otto Redlich and J. N. S. Kwong "On the Thermodynamics of Solutions. V. An Equation of State. Fugacities of Gaseous Solutions", Chemical Reviews 44 pp. 233 - 244 (1949)