Flask Logo Organic Chemistry at CU Boulder

Vacuum Distillation Set-Up

A vacuum distillation set-up differs from a simple distillation by the inclusion of a securely attached round bottom flask as the receiving flask (in the picture, it is clamped with a small three-pronged clamp) and a vacuum line connected to the vacuum adaptor. The vacuum line in this particular set-up is connected to a "water trap", which is a side-arm flask. The water trap is connected to a water aspirator (not shown), which is serving as the vacuum source. Preferrably, you would connect the vacuum line from the vacuum adaptor to a mechanical vacuum system instead. Be sure to check the round bottom flasks for star cracks before beginning the distillation.

Vacuum Distillation Set-Up

Instead of a boiling chip, use a stir bar inside the round bottom flask. A boiling chip cannot be used in vacuum distillation, since the reduced pressure sucks the trapped air from boiling chips and thus they do not work to prevent bumping. A rapidly spinning stir bar does prevent bumping. Place a stir motor under the heating source for the round bottom flask.

Vacuum Distillation Set-Up with Stir Bar

Back to Distillation