Abstract: A spacer sheet for use together with another spacer sheet between adjacent membranes (17) in a fluid separation cell, for example an electroldilysis cell, has an open center (2), conduit passages (8 and 9) for the supply and withdrawal of fluid to the chamber formed by the open center (2) between the membranes (17), and slots consisting of an offset slot stem (13) and a narrow mouth (14) opening into either the open center (2) or the conduit passages (8 or 9). The slots of the 2 sheets of a spacer assembly cooperate to provide a passage for fluid between the conduit passage and the open center. Identical spacer assemblies may be used between membranes in adjacent cell pairs by positioning the mutually perpendicular. The new spacers are suitable for use in an electrodialysis cell for use in a new method in which ions are removed from a liquid mixture comprising water and water-miscible organic liquid. The deionized liqiud is concentrated and used dowhole, for example in the recovery of methane.