Passivation Nernst equation

Maintenance of unequal concentrations of ions across membranes is a fundamental property of living cells. In most cells, the concentration of K+ inside the cells is about 30 times that in the extracellular fluids, while sodium ions are present in much higher concentration outside the cells than inside. These concentration gradients are maintained by the Na+-K+-ATPase by means of the expenditure of cellular energy. Since the plasma membrane is more permeable to K+ than to other ions, a K+ diffusion potential maintains membrane potentials which are usually in the range of -30 to -90 mV. H+ ions do not behave in a manner different from that of other ions. If passively distributed across the plasma membrane, then the equilibrium intracellular H+ concentration can be calculated from the Nernst equation via... 

A difference in chemical potential of species j across a membrane causes the ratio of the passive flux densities to differ from 1 (Fig. 3-12), a conclusion that follows directly from Equation 3.26. When fi° is equal to fip the influx balances the efflux, so no net passive flux density of species j occurs across the membrane (Jj = JJ1 - J°ut by Eq. 3.16). This condition (fi° = fij) is also described by Equation 3.5, which was used to derive the Nernst equation (Eq. 3.6). In fact, the electrical potential difference across a membrane when... 

The Nernst equation predicts that because of the cell electronegativity, passive facilitated diffusion should allow a concentration ratio cell water/external medium approximating 10 to 15 at steady state. In isolated unperfused proximal tubules from rabbits, ratios exceeding 100 for TEA, have been measured [44] and one can wonder if another mechanism exists, for example a cation exchanger, as demonstrated in rabbits (mechanism 2), but which has generally not been observed in rats and dogs [44], which might be implicated in basolateral uptake. However, as reported for anions. 

Nernst equation (13.3) nickel-cadmium battery (13.5) nickel-metal-hydride battery (13.5) oxidation (13.2) oxidation-reduction (13.2) passivation (corrosion) (13.8)... 

The comparison of the obtained results gives evidence that with the increase in the concentration of the cerium ions in 0.1 N H2SO4 solution the equilibrium oxidation-reduction potential of the system Ce / Ce is shifted in positive direction (Fig.lO and Table 4), in correspondence with the equation of Nernst, whereupon at all the studied concentrations it is located in the zone of potentials, characteristic of the passive state of steel (Fig. 7). Thereupon the corrosion potentials of the steel are more negative than the equilibrium oxidation-reduction potentials of the system Ce4+/Ce . At the same time, the juxtaposition of the corrosion currents for the steel in the presence of cerium ions with the exchange currents for the system Ce /Ce on Pt, at comparable concentration levels of the cerium ions, shows that they have quite close values. 

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