An extraction process that uses pressures and temperatures above the critical point of the extracting solvent. Carbon dioxide is a popular solvent on account of its low critical point (31.4^ºC and 72 bar). The extraction process involves compressing the carbon dioxide and heating it. The supercritical carbon dioxide has the density of a liquid but properties of a gas, which aids diffusion and helps solubility. The solvent and dissolved extract is then transferred to a separator tank and the pressure reduced precipitating the extract. The carbon dioxide is recycled into the extractor via a condenser. A small amount of make-up is required to allow for losses. Examples of SFE using carbon dioxide include the decaffeination of tea and coffee, flavour extraction from hops, the removal of pesticides from rice, and the dry cleaning of cloths. Other solvents used in supercritical fluid extraction include nitrous oxide, propane, and water.