NOVELTY - Oxygen is separated from an oxygen-containing gas in an electrolytic cell stack in which anode and cathode seals are radially offset such that the seals do not overlap on opposite sides of the electrolyte plate.    USE - For the separation of oxygen from oxygen-containing gases, e.g. for the production of high-purity oxygen from air and in the removal of residual oxygen from inert gases such as argon or nitrogen, e.g. in fuel cells and gas analysis and monitoring.    ADVANTAGE - Anode seal failure is eliminated, as the anode and cathode seals are radially offset, such that the seals do not overlap on opposite sides of the electrolyte plate. The electrolyte potential in the seal region is modified or regulated such that current flow through the anode seal is minimized.    DETAILED DESCRIPTION - Separating oxygen from an oxygen-containing gas comprises:    (a) contacting the oxygen-containing gas with a first surface of a planar solid electrolyte capable of transporting oxygen ions;    (b) supplying electrons to the surface of the planar solid electrolyte by a cathode in electrical contact with a portion of the surface;    (c) electrochemically reducing oxygen in the oxygen-containing gas by consuming electrons to produce oxygen ions;    (d) transporting the resulting oxygen ions as current through the solid electrolyte by imposing an electrical potential across the solid electrolyte;    (e) producing oxygen at a second surface of the solid electrolyte by consuming oxygen ions and producing electrons;    (f) conducting the electrons of (e) from the second surface by an anode in electrical contact with a portion of the second surface;    (g) conducting the electrons of (f) from the anode by a gas impermeable electrically conducting interconnect which is in electrical contact with the anode;    (h) collecting the oxygen in a cavity bounded at least in part by the second surface of the solid electrolyte, the gas impermeable electrically conducting interconnect, and a gas-tight anode seal between a portion of the second surface and an opposing portion of the electrically conducting interconnect;    (i) withdrawing oxygen from the cavity;    (j) withdrawing an oxygen-depleted gas from contact with the first surface of the planar solid electrolyte; and    (k) maintaining the 24-hour anode seal power density below ca. 1.5 microW/cm2.    DESCRIPTION OF DRAWING(S) - The figure shows an exploded sectional view of a single electrolytic cell.