AbstractThe behaviour of potassium chloride solutions in a continuously operated electrodialysis cell using ion‐exchange membranes is described. The cell contained 25 desalting compartments and 25 concentrating compartments each 1.58 mm. thick. The membranes were supported by perforated separators carrying grooves for the passage of liquid, and turbulent flow was induced by forced recirculation. The dependence of current efficiency on the ion concentration in the desalting compartments was assessed and the effect of a number of design factors was investigated. Theoretical expressions have been derived for the current efficiency of the desalting proces