The prediction of the thermodynamic properties of fluids and fluid mixtures-I The principle of corresponding states and its extensions

Abstract The principle of corresponding states is a sound but limited principle from which to predict the thermodynamic properties of pure fluids. We describe formal extensions of the principle to cover wide classes of fluids and their mixtures. These extensions are made in a general form, from which most previous schemes can be obtained as special cases. One of these, which we call van der Waals's approximation, is discussed in detail both for the usual one-fluid model of a mixture, and for a new two-fluid model. Application of these methods, and the testing of the two-fluid model, are to be made in later papers.