The theory of non-electrolyte solutions: an historical review

Starting with the work of van der Waals in 1873, a historical review is given of theories of non-electrolyte mixtures that are based on a well-defined Hamiltonian, and thus can be tested against molecular simulation, as well as experiment. Most of the first 100 years covered here were devoted to attempts to find a successful theory of simple mixtures, culminating in the van der Waals 1-fluid theory of conformal solutions, and perturbation theories based on a hard-sphere reference fluid. The last 40 years has seen the more rapid development of theories for fluids of more complex molecules, including strongly polar liquids, chain molecules and liquids in which molecular association is important.