Analysis of dipolarity/polarisability parameter, π*, for a range of supercritical fluids

The dipolarity/polarisability parameter, pi*, of Kamlet and Taft can be used to characterise the solvent properties of supercritical fluids and hence its correlation to more readily available parameters is important for predictive purposes. Almost perfect correlations are demonstrated between the pi* parameter and the cohesive energy density parameter, delta (2)(H), as a function of solvent type, temperature and pressure. Correlation is also observed between pi* and solvent dipole moment at constant reduced density. It is shown that the Gibbs energy of dissociation data can be modelled using delta (2)(H) and pi* parameters.