an ion - permeable spacer is provided for an electrochemical apparatus . the spacer comprises a perforated or ion - permeable , relatively - thin , synthetic plastic material sheet having two opposed faces and having a plurality of magnets completely embedded in both opposed faces thereof and including at least four vertically - upwardly slanting slits extending at an upwardly - sloping angle along each of the two opposed faces and also extending transversely through the spacer between the two opposed faces , the slits having a particularly defined width and disposed at a particular angle , thereby to provide greater combined flow and mixing of electrolyte through the spacer .