Raschig rings are generally used in distillation units. Distillation columns are used for greater separation or to
accelerate the process. The disadvantage of a more or less considerable holdup, which formerly required large quantities of substance in order to achieve effective fractionation, has been
largely overcome by the development of modern columns. As a
makeshift device, a 60-cm.-long column packed with metal or
glass Raschig rings, and insulated by a glass jacket, can be used
(Fig. 75).
