Boynton and Bramley equation of state
The Boynton and Bramley equation of state is given by 
where is a characteristic temperature. and where:
- is the pressure,
- is the volume,
- is the absolute temperature,
- is the molar gas constant; , with being the Avogadro constant and being the Boltzmann constant.
- and 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