Starting from the state equation reported by Hirn in 1863 and the experimental studies of Andrews (1863), plus over a century and twenty years of efforts on the van der Waals classical theory, the search for a predictive equation of state led to reexamination of the work of eight Nobel Laureates and revised value of van der Waals’ gas constant for the Silberberg constant. The use of the Silberberg constant provides a better basis in theory for the development of the predictive equation of state than the purely empirical definitions used by earlier investigators. The perceived confusion of the van der Waals gas constant, which hitherto has been assumed to be synonymous to the constant of the gas laws, has also been resolved with the Silberberg constant.
The question of why van der Waals theory of the cubic equation of state was in error is an intriguing one, and its answer provides dramatic proof of the human side of science. This paper uncovers the source of the error and pin-points the Nobel speech of van der Waals as the fruitful source of resolving the two oversights of his earlier works. A reformed van der Waals equation of state is used to demonstrate the solution for two important and often puzzling areas of active research: improvement of the predictive power of the equation of state for complex hydrocarbon molecules and the prediction of critical points of disparate molecules from their constituent components.