Distillation

Distillation is a separative process which involves drying, evaporating or boiling a liquid, redirecting the vapor produced, and condensing the vapor back into a liquid. Because this process proceeds based on the specific boiling/condensing point of the material, it can be used to separate one material from another. It is often repeated with successive iteration having increasing control over the evaporation and condensation temperatures, resulting in successively purer distillates.

Vocabulary

Equipment

• The device the source material is evaporated from is called the boiling flask
• The device which condenses the vapors is called the condenser
• The device which collects the drops of distillate is called the receiver.
• A device above the boiling container which directs the vapors upward is called the column
• The device which diverts the vapors at the top of the column into the condenser is called the stillhead. This device often includes a thermometer.
• Sometimes the boiling flask and condenser are combined into one piece of equipment. This device is called an alembic.
• Sometimes the column and the condenser are combined into a single device, often with multiple trays which redirect the fluids condensed at different temperatures to different receivers.

Materials

• The source material to be wholly or partly evaporated is sometimes referred to as the mother liquor
• The condensed material is called the distillate, or sometimes the condensate
• When the process is finished, any material not evaporated, remaining in the heating container, is called the residue

Variations

• Sometimes the pressure in the distillation apparatus is intentionally lowered below the ambient pressure. This is inaccurately called vacuum distillation regardless of the actual pressure within the apparatus.
• Sometimes multiple stillheads or trays are employed to fractionate the mother liquor into several distillates (with different boiling points) simultaneously.

See Also

• Drying