Extended Thermodynamic Scaling from a Generalized Parametric Form

A generalization of the parametric representation for thermodynamic scaling is proposed, introducing a new critical exponent ε. Expansions about the critical point are deduced for the fluids, and to lowest order the asymptotic power-low forms are recovered. An exponent 1-α^' is obtained for the diameter of the coexistence curve. Experimental data are shown to support the predicted forms.