A fluid becomes supercritical when compressed to a pressure and elevated to a temperature greater than that of its critical point (see figure 1). Although a supercritical fluid (SCF) is at single phase, it exhibits properties of both a liquid and a gas. A SCF has a relatively high liquid-like density. Solubility increases with density and pressure, thus, SCFs have a high absorption capacity (at high pressures, solubility increases with temperature as well). The gas-like properties of high diffusivity and low viscosity allow for high mass transfer rates between a solute and a SCF. Fluids in their supercritical states, having a high rate of absorbtion, are widely used in organic contaminant extraction from soil, water and precipitates.