NOVELTY - The spacer (4) comprises first and second portions (6,8) comprising respective ion conductive materials, anion conductive material or cation conductive material. The spacer portions are provided with openings (16) that extend substantially in one direction, and in use, the spacer portions are provided such that the openings of adjacent spacer portions extend substantially perpendicular to each other. The spacer is provided with an open structure that is open for more than 50%, preferably more than 70%, and most preferably more than 75%.    USE - Spacer for separating two adjacent membranes in cell used for ion-exchanging process (both claimed) such as electro dialysis, electro de-ionization and reverse electro dialysis.    ADVANTAGE - The overall performance of the ion-exchanging processes can be improved using the membranes, and the overall resistance of a stack of membranes with spacers can be improved. The ion exchanging area of the membrane is increased as the ions may transfer through the ion exchanging material of the spacer. The use of ion exchanging material in one portion of the spacer improves the conductivity in the volume between two adjacent membranes. The contact area between the spacer and the membrane can be improved, thereby reducing the resistance and increasing the overall stability of the cell. The thickness of the membranes that are used in the cell can be reduced, so that the sizes of the stack of membranes can be reduced and/or the use of more membranes can be enabled without increasing the volume of the stack.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) cell for ion-exchanging process;    (2) method for carrying out ion exchange process using spacer and/or cell; and    (3) method for providing membrane connected to corresponding spacer portion.    DESCRIPTION OF DRAWING(S) - The drawing shows the exploded perspective view of the cell with a spacer comprising two portions.    Cell (2)    Spacer (4)    Spacer portions (6,8)    Gasket (10)    Opening (16)