1 Introduction · continued

The previously mentioned nitromethane/pentanol system is particularly suitable for this task: within the measured range of its ultrasound spectrum, no additional relaxations due to molecular processes occur. Consequently, the critical absorption processes associated with the liquid–liquid phase transition are not obscured by elementary chemical processes.

Binary liquid systems are of particular interest not only because of critical fluctuations but also because they open up a broad field of research. Intermolecular behaviour is studied both in computer simulations—for example using soft-SAFT¹ theory [1–3]—and in microgravity environments. An especially interesting experiment was carried out by NASA in 1997. A space-compatible light-scattering apparatus was developed to investigate the demixing behaviour of binary systems under reduced gravity [4].

The chemical industry likewise hopes that research on binary liquid mixtures will lead to new separation and filtration methods. Finally, many findings from research into binary systems also find applications in biophysics.

¹ SAFT: Statistical Associating Fluid Theory.