Chapter 4 - The Corresponding-States Parameters

Abstract

It is 125 years since Van der Waals discovered the corresponding states principle. Our understanding of the forces operating between molecules has developed rapidly since the emergence of a satisfactory quantum theory in 1926. Particularly important is the work of London on the attractive forces between molecules. This situation is in marked contrast to the extensive theoretical advances with respect to the thermodynamic properties of ideal gases. The Riedel parameter and Rowlinson theoretical work are discussed in this chapter, but the most generally useful method of prediction of the volumetric properties of fluids is the hypothesis of corresponding states from Van der Waals. As described in Sections 2.3 and 2.4, the two-parameter corresponding-states principle in terms of the critical parameters is: p/p=f(T/Tc, V/Vc), which is only applicable to monatomic molecules and may cause about 30% error when describing normal fluids. The Acentric factor, Aspherical factor, is covered in depth here. Also seen are the properties from the corresponding-states principle and the compressibility factor. Comparison of the vapor–pressure data with values calculated from the corresponding-mates theory of Pitzer. From the graphs, errors show that the predictions of the corresponding-mates principle for a strongly nonspherical molecule errors in various compounds. Enthalpy departure, fugacity, entropy departure, vapor pressure, density, heat capacity and viscosity, thermal conductivity, and surface tension relations are also seen lastly.