Fig. 4. Difference in cation transparency for a sequence of large and narrow slits with apertures a₂ and a₁, respectively (Eq. [12]). The graphs were calculated for different ratios of the Debye length to the aperture of the narrow slit (/a₁) and for a value of ₁ potential of 0.1 V. The difference in cation transparency strongly increases when a₂/a₁ is in the region between 3 and 30. Lower graphs, corresponding to a narrow slit with an aperture 1000 and 10000 times larger than the Debye length, can be attributed to saturated cells (Fig. 1a and 1b). Upper graphs, corresponding to a narrow slit with an aperture 10 and 100 times larger than the Debye length, can be attributed to unsaturated cells (Fig. 1c–1f).