How to Purify by Simple Distillation at Atmospheric Pressure

How it works: To separate two or more liquids by simple distillation, they are first heated in a flask. The more volatile liquid (the liquid with the lower boiling point) will typically vaporize first and the vapor will pass into a condensing column, where it can revert to liquid phase (condense) on the cool glass walls and then drip into a collection vessel.

A procedure to carry out a simple distillation is provided below.

1. To a round bottom flask equipped with a stir bar, add the organic mixture to be purified.
2. Set up a simple distillation apparatus as shown below.

   

   Things to Note:

   • Position of the thermometer should be at the intersection of the “Y” piece.
   • The flask and collection flask should both be secured with clamps to the back of the fume hood.
   • Cold water should travel from bottom to top of the condenser.
   • It is usually a good idea to keep the system under nitrogen to avoid decomposition or reactions with oxygen since the material will be heated.
   • Keck clamps should be placed on joints to avoid pieces from disconnecting.
   • If you are distilling a very low-boiling compound (around 25 ^oC), you can place the receiving flask in an ice bath.

3. Use a heating mantle/block or oil bath to heat the organic liquid.
   • The temperature of the heating element typically needs to be at least 30^oC above the boiling point of the liquid for it to distill.

4. Distillation will commence once the flask reaches the desired temperature and the vapor begins condensing in the cooling channel.
   • After the first few drops of liquid start to fall down the condenser, the temperature should remain nearly constant.
   • To obtain the optimal distillation, the distillation rate must be constant and relatively slow.
   • This is the temperature that should be recorded as the boiling point of the compound.
   • If the distillation is occurring very slowly, wrap the column with aluminum foil or glass wool to protect it from cold drafts.

5. Once the distillation is complete, transfer the pure organic compound to a clean, labeled vial for safekeeping.