Abstract: A device for treating aqueous solutions with magnetic lines of force includes a pipe through which the solution passes. An electromagnetic coil surrounds the pipe and a core consisting of endwise connected alternating short sections of magnetic and non-magnetic material is disposed coaxially with and spaced from the pipe. Located between the pipe and the core is a helical baffle. A housing is spaced from and surrounds the coil. Air circulation vents are located at the upper and lower ends of the housing. Annular cooling fins extend outwardly through the coil with their outer peripheries terminating in the gap between the coil and the housing. A plurality of apertures are formed in the exposed outer portions of each cooling fin with the apertures of one fin being staggered relative to the apertures of the adjacent fins.