Sublimation apparatus is a piece of laboratory glassware use in the technique of sublimation usually used by chemists to purify compounds. Typically a solid is placed in a vessel which is then heated under vacuum. Under this reduced pressure the solid volatilizes and condenses as a purified compound on a cooled surface, leaving the non-volatile residue impurities behind. This cooled surface often take the form of a cold finger. Once heating ceases and the vacuum is released, the sublimed compound can be collected from the cooled surface.