Rotary vacuum evaporators are used in the laboratory to remove solvent from samples by evaporation. The evaporator consists of a heated bath, a rotating flask, and a condenser. The sample is placed in the flask and heated in the bath. As the flask rotates, the solvent is forced to the walls of the flask and evaporates. The vapors are then captured by the condenser and cooled, resulting in the collection of the concentrated sample.