Wikipedia
A separatory funnel, also known as separation funnel, separating funnel, or colloquially sep funnel, is a piece of laboratory glassware used in liquid-liquid extractions to separate (partition) the components of a mixture into two immiscible solvent phases of different densities. Typically, one of the phases will be aqueous, and the other a non-polar lipophilic organic solvent such as ether, MTBE, dichloromethane, chloroform, or ethyl acetate. All of these solvents form a clear delineation between the two liquids. The two layers formed are usually known as the organic and aqueous phases. Most organic solvents float on top of an aqueous phase, though important exceptions are most halogenated solvents. The organic solvent used for the extraction must not react with the substance to be extracted or with water. It should also have a low boiling point so it can be easily removed from the product.