A laboratory procedure in which a solid product in a mixture is separated from liquid impurities (such as washes or reagents), using a vacuum to evaporate the volatile liquid (since liquids boil when there is no vapor pressure to keep the substance in liquid form) and leave the pure solid product. In this procedure, the product was washed with benzene to separate it into an organic layer, and in vacuo concentration allowed the solid to be collected after the volatile liquid benzene was evaporated (the boiling point of benzene is 80 ° C) 4 .