Vacuum distillation

Vacuum distillation is a method of distillation performed under reduced pressure, which lowers the boiling point of most liquids. As with distillation, this technique separates compounds based on differences in boiling points. This technique is used when the boiling point of the desired compound is difficult to achieve, will cause the compound to decompose or simply to save energy in heating. A reduced pressure decreases the boiling point of compounds. The reduction in boiling point can be calculated using a temperature-pressure nomograph using the Clausius–Clapeyron relation.A simple short path vacuum distillation apparatusKugelrohr – a short path vacuum distillation apparatusPerkin triangle – for air-sensitive vacuum distillationVacuum distillation apparatus Vacuum distillation is a method of distillation performed under reduced pressure, which lowers the boiling point of most liquids. As with distillation, this technique separates compounds based on differences in boiling points. This technique is used when the boiling point of the desired compound is difficult to achieve, will cause the compound to decompose or simply to save energy in heating. A reduced pressure decreases the boiling point of compounds. The reduction in boiling point can be calculated using a temperature-pressure nomograph using the Clausius–Clapeyron relation. Vacuum distillation often improves efficiency, and vacuum distillation of ocean water is considered one of the most efficient ways of desalination. In the laboratory vacuum distillation is used to purify compounds or remove solvent. This is generally done by applying a vacuum line to a sealed apparatus, lowering the pressure. Lowering the pressure causes most liquids to have a lower boiling point, and so less intense heat is required to boil them out of a solution. This allows for a more efficient separation process using lower temperature. To avoid the evaporated liquid entering the vacuum pump there is usually a condenser installed on the vacuum line in order to chill and condense the vapor before the vacuum pump. This allows for recovery of the liquid being removed and to avoid feeding any corrosive liquids into the vacuum pump or releasing them to the environment. Distillation is used to separate compounds based on differences in boiling point. Vacuum distillation allows for this purification technique to be used on compounds with high boiling points, or those which are air-sensitive. Compounds with a boiling point lower than 150oC can typically be distilled without reduced pressure. Using a fractionating column in the set-up improves the separation of mixtures, and can allow separation of compounds with similar boiling points. With the apparatus under reduced pressure, exposure to the atmosphere is minimised and the apparatus can be filled with inert atmosphere when the distillation is complete.