In distillation, what is reflux?

• A. The bottom product from the column.
• B. The portion of overhead liquid product returned to the upper part of the column.
• C. The overhead liquid that is dumped from the column.
• D. The feed to the column.

Answer: (B)

Reflux is the portion of condensed overhead liquid that is returned to the top of the distillation column. By returning this liquid, it flows downward inside the column while rising vapors contact it, creating more opportunities for vapor-liquid interaction and improving separation. The remainder of the overhead that leaves the column is the distillate product, bottom product is the residue, and the feed is what enters the column.