“…For instance, for mixtures of non-polar fluids the overall average absolute deviation (AAD) obtained with the model of [15] was 0.11 percent for densities, 0.55 percent for isobaric heat capacities and 0.20 percent for speeds of sound. Thence the rationale for the models of [1,2]: the Helmholtz energy can be given by the contribution of two terms, one is an ECS term and the other is a supplemental contribution due to different intermolecular forces between unlike species. Given that ECS models are in fact Helmholtz energy models, the desired effect is that the ECS term responds for an accurate approximation to the Helmholtz energy and thus the formulation of the correction term is arguably much simpler.…”