In distillation, reflux is defined as which of the following?

• A. The portion of overhead liquid product returned to the upper part of the column.
• B. The bottom product that leaves the column.
• C. The feed to the column.
• D. The gas leaving the top of the column.

Answer: (A)

Reflux is the portion of the overhead that is condensed and returned to the top of the column as liquid. After the vapor reaching the condenser is condensed, some of that condensate is fed back down the column to contact the rising vapors. This recycled liquid increases the number of effective contacting stages and helps sharpen the separation, while the rest of the condensate becomes the distillate overhead. The bottom product is the liquid collected at the bottom, the feed is what enters the column, and the gas leaving the top is the overhead vapor before condensation.