Limiting (or infinite dilution) activity coefficients are of particular interest both in their fundamental and practical applications. As will be shown, the log limiting activity coefficient for solute i infinitely dilute in solvent j is proportional to the transfer free energy of i from a solution of pure i to pure j (in which it is infinitely dilute). Therefore fundamentally, the limiting activity coefficient sheds insight into how favorable the interactions of i with j are relative to i with itself. This fundamental molecular-level understanding provides the framework that directly impacts design schemes for chemical processes .