Mischungswärmen und Verbindungsbildung in binären flüssigen Systemen

Abstract

The heats of mixing of binary liquid systems with strong specific interactions are treated by means of simple equilibrium models based on the concept of the ideal associated solution. In this paper unsymmetrical heat-of-mixing curves Hᴍ = f(NA0) are analysed in terms of two different twostep equilibrium models, i . e . A+2 B ⇄ AB2 (I), and A+B2 ⇄ AB+B (II). Iterative calculation methods for determining the four equilibrium parameters from experimental data are given, including approximative methods for obtaining an initial set of these parameters. The method is applied to new experimental data on the systems (1) tetrahydrofurane-chloroform, (2) methyl isobutyl ketone-sulphuric acid, and (3) pyridine-chloroform, obtained at 25° by a continuous enthalpy titration method. It is shown that the data of the systems (1) and (2) can be very well fitted by the equations of model (I), whilst model (II) is valid for the system (3). Complete thermodynamic data for all three systems are given, and the reasons why these systems fulfil the assumptions of the two-step equilibrium models are discussed.