For temperatures and pressures above the critical temperature and critical pressure, the properties of gases and liquids become indistinguishable. Both gases and liquids are called fluids. Substances in this region are called supercritical fluids.

Supercritical fluids [local] exhibit a pressure dependent dissolving power. As the pressure on the fluid is increased, so is the solubility of potential solutes. This property can be applied to purification, extraction, fractionation, and recrystallization of a wide host of materials.

At pressure levels below the critical pressure, the solubility of certain solutes is negligible. As the pressure is raised, the solubility increases to quite high levels. Commercial applications of this process include coffee and tea decaffeination as well as dry cleaning.