While the research and industrial communities are wholehartedly embracing the use of supercritical fluid extraction (SFE) technology, little has been written about it in undergraduate texts or in educational journals such as the Journal of Chemical Education . The supercritical phenomenon of fluids was first discovered in the early 1800's by the Frenchman Baron Charles Cagniard de la Tour, but the significance and practical application of his discovery have only recently been recognized and achieved. This article presents a general overview of the principles of SFE and describes the instrumentation necessary to carry out an extraction using a supercirtical fluid. The reader will also gain insight into the types of research currently being conducted using supercritical fluids as either processing solvents or as reaction constituents and matrices. Because carbon dioxide is the supercritical fluid of choice for many procedures, its use and modification for specific solutes is covered in some detail.

The equilibrium between the keto and enol tautomers of acetylacetone, triÑuoroacetylacetone and hexaÑuoroacetylacetone in the neat liquid state and dissolved in supercritical Ñuid carbon dioxide have been studied, as a function of pressure and temperature, by 1H NMR. This allows determination of the thermodynamic parameters, *H and *S, for the ketoÈenol equilibrium. The observed trends are well correlated with extraction results for this class of compounds.

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