Berthelot equation of state

$RT=\left(p+{\frac {a}{Tv^{2}}}\right)\left(v-b\right)$

where

$a={\frac {27}{64}}R{\frac {T_{c}^{3}}{P_{c}}}$

and

$b={\frac {RT_{c}}{8P_{c}}}$

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. D. J. Berthelot "", J. Phys., 8 pp. 263- (1899)