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

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

where $p$ is the pressure, $T$ is the temperature and $R$ is the molar gas constant. $T_{c}$ is the critical temperature and $P_{c}$ is the pressure at the critical point.

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)
2. Giorgio Soave "Equilibrium constants from a modified Redlich-Kwong equation of state", Chemical Engineering Science 27 pp. 1197-1203 (1972)