Cubic equation of state as a quartic in disguise

•Novel quartic equation of state (QEOS) presented as improvement over cubic.•Quartic term is practically negligible making behavior similar to CEOS.•EOS can be treated as QEOS for theoretical analysis.•EOS can be treated as CEOS for practical calculations. A six parameter Quartic equation of state (QEOS) is presented in this work to explore the scope of a non-cubic equation of state for the prediction of thermodynamic properties and analyze its improvement over the commonly used cubic equations of state. The QEOS uses 4 compound specific parameters in addition to the critical constants. The QEOS predicted results for various thermodynamic properties are compared with experimental data and with results obtained from Ghoderao-Dalvi-Narayan (4PGDN1) equation of state. The QEOS fits data best when it most resembles a Cubic EOS (CEOS) obtained by setting one compound specific parameter e to nearly zero. This presents an opportunity to use the CEOS for practical calculations while using the theoretically more correct QEOS for theoretical analysis. [Display omitted]