Limitations of the Peng-Robinson equation of state

The predicted liquid phase densities for the Peng-Robinson (PR) equation of state (EOS) are not very accurate. We recommend that you use the API liquid density method as an alternative when liquid densities are important and the system in question falls within the applications of the API liquid density method.

The PR EOS does not give accurate predictions for systems of polar and nonpolar components; it approximates hydrogen phase behavior is approximated by modification of the acentric factor.