Abstract: There is disclosed a bipolar electrolytic cell comprising a row of spaced-apart electrodes which include at least one bipolar intermediate electrode. There are an inlet for the supply of electrolyte liquid and an outlet for the discharge of treated liquid, the cell being such that liquid can flow from the inlet to the outlet via a path in which it passes in succession through all the spaces between the electrodes in the row, in each case across the faces of the two electrodes on opposite sides of the space. There is a coating of electrically insulating material on that external surface of each of the electrodes which is on the outside of the row, the insulating material for example being a plastics material such as nylon.