Dephlegmator

A condenser set above the column. It condenses the heavier part, sends it back down, and lets only the vapour richer in ethanol pass. Without it the column would be an ordinary pipe — the dephlegmator is what makes anything purify inside it.

The liquid running back down is called phlegm, which is where the name comes from: literally "the thing that makes phlegm".

The ratio of what goes back to what you draw off is the reflux ratio. You control it with the flow of cooling water through the dephlegmator, and in practice it is the main dial of the whole process. More water — more vapour returns, cleaner distillate, slower drip. Less water — faster, but weaker and dirtier.

A dephlegmator is easily confused with a condenser, since both cool. The difference is where the condensed liquid goes: the dephlegmator returns it to the column, the condenser sends the finished distillate to the receiver.