The apparatus for this technique consists of a distilling flask containing the combined liquid
solution, a distillation column consisting of a thermometer and a condenser, and a receiving flask
to collect the distillate. The setup is the same as that shown in Figure 12.3, sans the vacuum
adaptor. Sometimes an additional piece of equipment, such as a boiling chip, ebulliator, or
magnetic stirrer, will be introduced to break surface tension and prevent superheating.
Superheating occurs when a liquid is heated to a temperature above its boiling point without
vaporization. Superheating situations occur when gas bubbles within a liquid are unable to
overcome the combination of atmospheric pressure and surface tension.
Figure 12.3. Vacuum Distillation
The initial solution is placed in the heated distilling flask, where the components of the solution with
the lowest boiling points will vaporize first. The vapor then condenses in the water-cooled condenser,
and this distillate drips into the receiving flask.VACUUM DISTILLATION
We use vacuum distillation whenever we want to distill a liquid with a boiling point over 150°C. By
using a vacuum, we lower the ambient pressure, thereby decreasing the temperature that the liquid
must reach in order to have sufficient vapor pressure to boil. This allows us to distill compounds
with higher boiling points at lower temperatures so that we do not have to worry about degrading
the product. The apparatus for vacuum distillation is shown in Figure 12.3.