Concept
Version 8
Created by Boundless
Supercritical Fluids
A close look at supercritical carbon dioxide
A pressure vessel made of aluminum and acrylic is filled with pieces of dry ice. The dry ice melts under high pressure, and forms a liquid and gas phase. When the vessel is heated, the CO2 becomes supercritical -- meaning the liquid and gas phases merge together into a new phase that has properties of a gas, but the density of a liquid. Supercritical CO2 is a good solvent, and is used for decaffeinating coffee, dry cleaning clothes, and other situations where avoiding a hydrocarbon solvent is desirable for environmental or health reasons.