Boynton and Bramley equation of state

The Boynton and Bramley equation of state is given by

\[\left( p + \frac{a}{V^2}\right) (V-b) = \frac{RT}{\left(1+ \frac{\psi^2}{T^2}\right)}\]

where \(\psi\) is a characteristic temperature. and where:

• \( p \) is the pressure,
• \( V \) is the volume,
• \( T \) is the absolute temperature,
• \( R \) is the molar gas constant; \( R = N_A k_B \), with \( N_A \) being the Avogadro constant and \(k_B\) being the Boltzmann constant.
• \(a\) and \(b\) are constants that introduce the effects of attraction and volume respectively and depend on the substance in question.

For this equation at the critical point one has

\[\frac{RT_c}{p_cV_c} = \frac{8}{3}\left( 1 + \frac{\psi^2}{T_c^2}\right)\]