Reflux and distillation are two chemistry lab techniques which involve boiling and condensing of a solution. Reflux helps complete a reaction and distillation separates components of a mixture.
In distillation, a liquid is heated until it is boiling. The vapor which is produced is condensed and collected in a separate flask. In reflux, the liquid is boiled, but the vapor is allowed to condense and flow back into the original flask.
Collecting the condensed vapor in a second flask, allows you to separate out the individual components of a mixture by distillation. Allowing the condensed vapor to flow back into the original reaction flask, allows you to dissolve hard to dissolve compounds by reflux. This continual recycling of the solvent, helps drive the reaction to completion.
Separation by distillation works because each liquid has a different boiling point. The liquid with the lowest boiling point will vaporize and condense first.
A reflux set up includes a round bottom flask connected directly to a condenser, whereas in a distillation, the round bottom flask is connected to a y-adapter. The side arm of the y-adapter connects to the condenser. The condenser connects to a receiving flask via a vacuum adapter.
The rate of heating during reflux should be adjusted so that the condensation point in the condenser is no higher than half the distance to the top.