The separation of the constituents of a liquid by contact with another insoluble liquid. If the constituents distribute themselves differently between the two liquids, a certain degree of separation will result. The separation can be enhanced further by multiple contacts. An example is the separation of plutonium and uranium isotopes dissolved in nitric acid, which can be extracted to differing extents using odourless kerosene as the solvent. Since the two liquids are immiscible in one another, the two liquids are agitated in such a way as to increase the surface area contact and to promote the rate of separation. The extract is the solvent-rich product stream while the raffinate is the residual liquid stream from which the solute has been removed. It is also known as liquid-liquid extraction.