<P> Naphthalene, an organic compound commonly found in pesticide such as mothball also sublimes . It sublimes easily because it is made of non-polar molecules that are held together only by van der Waals intermolecular forces . Naphthalene is a solid that sublimes at standard atmospheric temperature with the sublimation point at around 80 _̊ C or 176 _̊ F. At low temperature, its vapour pressure is high enough, 1 mmHg at 53 _̊ C, to make the solid form of naphthalene evaporate into gas . On the cool surface, the sublimated vapour will be solidified to form a needle - like crystal . </P> <P> Iodine produces fumes on gentle heating . It is possible to obtain liquid iodine at atmospheric pressure by controlling the temperature at just above the melting point of iodine . In forensic science, iodine vapor can reveal latent fingerprints on paper . Arsenic can also sublime at high temperatures . </P> <P> Sublimation is a technique used by chemists to purify compounds . A solid is typically placed in a sublimation apparatus and heated under vacuum . Under this reduced pressure, the solid volatilizes and condenses as a purified compound on a cooled surface (cold finger), leaving a non-volatile residue of impurities behind . Once heating ceases and the vacuum is removed, the purified compound may be collected from the cooling surface . For even higher purification efficiencies a temperature gradient is applied, which also allows for the separation of different fractions . Typical setups use an evacuated glass tube that is gradually heated in a controlled manner . The material flow is from the hot end, where the initial material is placed, to the cold end that is connected to a pump stand . By controlling temperatures along the length of the tube the operator can control the zones of recondensation, with very volatile compounds being pumped out of the system completely (or caught by a separate cold trap), moderately volatile compounds recondensating along the tube according to their different volatilities, and non-volatile compounds remaining in the hot end . Vacuum sublimation of this type is also the method of choice for purification of organic compounds for the use in the organic electronics industry, where very high purities (often> 99.99%) are needed to satisfy the standards for consumer electronics and other applications . </P> <P> In ancient alchemy, a protoscience that contributed to the development of modern chemistry and medicine, alchemists developed a structure of basic laboratory techniques, theory, terminology, and experimental methods . Sublimation was used to refer to the process in which a substance is heated to a vapor, then immediately collects as sediment on the upper portion and neck of the heating medium (typically a retort or alembic), but can also be used to describe other similar non-laboratory transitions . It is mentioned by alchemical authors such as Basil Valentine and George Ripley, and in the Rosarium philosophorum, as a process necessary for the completion of the magnum opus . Here, the word sublimation is used to describe an exchange of "bodies" and "spirits" similar to laboratory phase transition between solids and gases . Valentine, in his Triumphal Chariot of Antimony (published 1678) makes a comparison to spagyrics in which a vegetable sublimation can be used to separate the spirits in wine and beer . Ripley uses language more indicative of the mystical implications of sublimation, indicating that the process has a double aspect in the spiritualization of the body and the corporalizing of the spirit . He writes: </P>

When can sublimation be applied as a process of separation