A column used in liquid–liquid extraction in which two immiscible liquids enter the column in the same direction. A reciprocating-type pump causes sharp pulsations in the direction of the flow, causing the liquids to disperse in one another, allowing intimate mixing of the liquids, and encouraging mass transfer. The dispersion is encouraged in columns that may contain perforated distribution plates, packing, or horizontal discs to prevent coalescence. Pulsed columns have found many applications, particularly in the nuclear-reprocessing industry for the separation of radioactive waste materials.