<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> 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>
when can sublimation be applied as a process of separation
when can sublimation be applied as a process of separation
to purify compounds
to purify compounds