Fluid brought by a combination of heat and
pressure to the point at which, as a near
vapour, it combines the properties of a gas
and a liquid. Supercritical fluids are used
as solvents in chemical processes, such as
the extraction of lubricating oil from
refinery residues or the decaffeination of
coffee, because they avoid the
energy-expensive need for phase changes (from
liquid to gas and back again) required in
conventional distillation processes.