The two faces of the Redlich–Kister equation and the limiting partial molar volume of water in 1-aminopropan-2-ol

The properties of the Redlich–Kister equation when expressed in power series of x1 − x2 are related to its alternative expression in terms of power series of x2 − x1, where x1 and x2 are mole fractions of the components 1 and 2 of a binary liquid mixture. The simple relationship between both sets of coefficients is derived and shown to conceal pitfalls while using Redlich–Kister coefficients to estimate partial molar properties of the components. The zero-powered terms, which are the same for the alternative expansions, are shown to yield four-fold the excess molar property for the equimolar mixture. Literature data for the partial molar volume of water at infinite dilution in 15 neat aminoalkanols at different temperatures are collected and tabulated. These data generally show a positive dependence of that limiting value on the temperature, the only apparent exception being in the case of 1-aminopropan-2-ol. It is demonstrated that the recently published data for this aminoalkanol [S. Mokraoui, A. Valtz, C. Coquelet, D. Richon, Thermochim. Acta 440 (2006) 122–128] were ill-treated and recalculated limiting values are given, which increase with increasing temperature.