Electrochemical cells

An electrochemical cell in which an inner cylindrical electrode extends coaxially within a tube of ion-permeable material that is mounted coaxially within a hollow, cylindrical outer electrode to define inner and outer annular passageways between the respective electrodes and said tube for liquid-flow lengthwise of them from one to the other of cup-shape fittings at either end of the cell, each cup-shape fitting having two inlet/outlet ports that communicate with the inner and outer passageways respectively, wherein each cup-shape fitting defines a cylindrical cavity which has an open-mouth that is of a diameter to receive a respective end of the outer electrode for liquid-tight sealing therewith, said tube projects at each end of the cell from within the outer electrode into said cavity of the fitting at that end and has an annular rim for engagement with an internal cylindrical wall of the cavity for liquid-tight sealing therewith to separate the inner and outer passageways from one another within the fitting, and the inner electrode projects at each end of the cell from said tube into the cavity of the fitting at that end.