Distillery

Distillation is a method of separation of substances based on differences in their vapour pressures. more...

Known since antiquity, the concentration of alcohol by the application of heat to a fermented liquid solution is perhaps the oldest form of distillation, in the course of producing distilled beverages. However, the technique is now widely used for a variety of liquids in the chemical industry and in the production of petroleum products, among other fields.

The liquid solution evaporates, such that the vapor has a composition determined by the chemical properties of the solution. Distillation of a given component is possible, if the vapor has a higher proportion of the given component than the solution. This is caused by the given component having a higher vapor pressure — and thus a lower boiling point — than the other components.

However, interactions between the components of the solution can create properties unique to the solution. Such interactions can result in an azeotrope. At an azeotrope, the solution contains the given component in the same proportion as the vapor, so that evaporation does not change the purity, and distillation does not effect separation. For example, ethyl alcohol and water form an azeotrope of 95% at 78.2°C.

By the nature of the process, it is theoretically impossible to completely purify the components using distillation, as distillation only tends to purity, never reaching it. This is comparable to dilution, which never reaches purity. If ultra-pure products are the goal, then further chemical separation must be used.

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