Physicochemical aspects of fluid extraction

The present review considers some physicochemical properties of fluid mixtures that are important for fluid extraction, supercritical fluid chromatography (SFC) and other applications.

Firstly, the most important types of phase diagrams involving liquid-gas, liquid-liquid and gas-gas equilibria are treated. Specific examples are given of binary mixtures of a highly volatile component I (e.g. CO₂, C₂H₆, N₂) with a relatively involatile component II of very different molecular size, shape, structure and/ or polarity (e.g. long-chained hydrocarbons, alcohols). It is also shown how the rather complicated types of phase diagrams can be calculated and correlated.

Some important thermodynamic and transport properties of such fluid mixtures are shortly discussed e.g. density, viscosity, diffusion coefficient etc. Here it is of interest for many effects (e.g. mass transfer) that unusually low viscosities and large diffusion coefficients are found.

Finally some important applications are shortly reviewed. Most of these applications will be treated in detail in the following papers of this Meeting.