Solvent extraction, also known as Liquid–liquid extraction or partitioning, is a method to separate a compound based on the solubility of its parts. This is done using two liquids that don’t mix, for example water and an organic solvent. Solvent extraction is used in the processing of perfumes, vegetable oil, or biodiesel. It is also used to recover plutonium from irradiated nuclear fuel, a process which is usually called nuclear reprocessing. The recovered plutonium can then be re-used as nuclear fuel. In this process one of the components of a mixture dissolves in a particular liquid and the other component is separated as a residue by filtration.