Vigreux distillation column

A Vigreux column is a modification of the air condenser. It is usually used as a fractionating column for fractional distillations. Unlike straight-walled columns, a Vigreux column has a series of downward-pointing indentations on the inside wall which serve to dramatically increase the surface area without increasing the length of the condenser. Because of their added complexity, Vigreux columns also tend to be considerably more expensive than traditional straight-walled designs. They are named after Henri Vigreux. [Condenser (laboratory). Wikipedia]