Equilibria Involving a Supercritical Fluid

Temperature-presstire diagram for a pure substance and the region of SCE. 

The earliest indication of this property of SCF is to be found in the work of J.B. Hannay and J. Hogarth (1879), who reported that an increase in pressure of supercritical ethanol caused increased dissolution of certain inorganic salts such as potassium iodide, while conversely a relaxation in pressure resulted in the precipitation of the salts as a white snow.  

This early work was followed intermittently by a flurry of activity that intensified diuing the 1970s and 1980s, partly as a result of environmental concerns over the use of conventional solvents. Major commercial processes currently in use are the SCE of caffeine from coffee and tea, the SCE of spice aromas, and the fractionation and purification of polymers. Processes under investigation include the treatment of wastewaters, activated carbon regeneration, and the SCE of edible oils and therapeutic agents from plant materials. 

Comparison of diffusivities in supercritical carbon dioxide and normal liquids. (From McHugh, M. and Krrrkonis, V. Supercritical Fluid Extraction, 2nd ed., Butterworth-Heinemann, Boston, 1994. With permission.) 

Comparison of diffusivities in supercritical carbon dioxide and normal liquids. 

Mass Transfer and Separation Processes Principles and Applications 

Extraction vessel used in Maxwell House Coffee Company supercritical COj decaffeination plant in Houston, Texas. 

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