Vortical motion of liquids in tubes, for the purpose of mixing or evaporation in small‐scale chemical process streams, is produced by a magnetically coupled digital drive mechanism. The latter consists of an eight‐pole stator, to which a continuously commutating magnetization is applied, one pole at a time, and a rotor consisting of a magnetically soft steel ring surrounding and fixed to the liquid‐containing tube. The power to the stator windings is controlled by MOSFET transistors driven directly by a CMOS counter decoder. The clock signal is derived from the 60‐Hz ac line, eliminating the need for a filtered power supply.