A supercritical fluid is loosely defined as a fluid above, but not very far away from its critical point. Properties such as density or viscosity are intermediate between those of gas and liquid. Others, such as compressibility or thermal conductivity, may be very different from those of either gas or liquid. The structure of a supercritical fluid is unlike that of a gas or liquid. Near a critical point, long-range correlations extend far beyond the range of intermolecular forces.
Snapshots produced by molecular simulation reveal a sponge-like structure.
Widely used supercritical fluids are carbon dioxide and water, which are nontoxic, nonflammable and friendly to the environment. Tunable solvent properties and environmental compatibility make supercritical fluids desirable agents for extraction of food products and fragrances. They are used as carriers in chromatography, and as media for chemical and materials processing. Virtually all aspects of polymer processing may involve the use of supercritical fluids. I Refreshments will be served.