Galvani potential.

Fig. V-15. Volta potentials Galvani potentials 0, and surface potential jumps x in a two-phase system. (From Ref. 187.)...

Thus Pi, surface potential jump X, the chemical potential p, and the Galvani potential difference between two phases A0 = are not. While jl, is defined, there is a practical dif-... 

This internal potential, cj), is not directly measurable it is temied the Galvani potential, and is the target of most of tire modellmg discussed below. Clearly we have = A j x +... 

Figure A2.4.9. Components of the Galvani potential differenee at a metal-solution interfaee. From [16], A2.4.5.2 INTERFACIAL THERMODYNAMICS OF THE DIFFUSE LAYER...

In addition to the case of a metal in contact with its ions in solution there are other cases in which a Galvani potential difference between two phases may be found. One case is the innnersion of an inert electrode, such as platinum metal, into an electrolyte solution containing a substance S that can exist m either an oxidized or reduced fomi tlirough the loss or gain of electrons from the electrode. In the sunplest case, we have... 

Figure A2.4.12 shows the two possibilities that can exist, m which the Galvani potential of the solution, (jig, lies between ( )(I) and ( )(n) and in which it lies below (or, equivalently, above) the Galvani potentials of the metals. It should be emphasized that figure A2.4.12 is highly schematic in reality the potential near the phase boundary in the solution changes initially linearly and then exponentially with distance away from the electrode surface, as we saw above. The other point is that we have assumed that (jig is a constant in the region between the two electrodes. This will only be true provided the two electrodes are iimnersed in the same solution and that no current is passing.

In practice, since the Galvani potential of no single electrode is known the method adopted is to arbitrarily... 

Once current passes tluough the interface, the Galvani potential difference will differ from that expected from the Nemst equation above the magnitude of the difference is temied the overpotential, which is defined heiiristically as... 

Of fundamental importance in understanding the electrochemistry of ion-selective membranes and also of biomembranes is the research in the field of voltammetry at ITIES mainly pioneered by Koryta and coworkers 99 101 . Koryta also demonstrated convincingly that a treatment like corroding metal electrodes is possible 102). For the latter, the description in the form of an Evans-diagram is most appropriate Fig. 4 shows schematically some mixed potentials, which are likely to arise at cation-selective membranes if interfering ions disturb an ideal Nernstian behavior82. Here, the vertical axis describes the galvani potential differences (absolute po-... 

According to the exact position of the equilibrium galvani potential for Ca2+-ions on the voltage axis, stimulation or inhibition of the Na+—K+ exchange can be understood. The effect of anions (e.g., MgATP2-) may be similiar as shown in Fig. 4. 

The surface science approach (Eq. 5.14) has the important advantage that both d>and are measurable quantities. This is not the case for the electrochemical approach (Eq. 5.15) since neither the chemical potential p nor the Galvani potential tp are measurable quantities. Only changes in tp are measurable. 

As already noted the electrochemical potential of electrons in a metal, jl, is related to the Galvani potential q> via ... 

Gadolinia-ceria, solid electrolyte, 93, 526 Galvani potential, 203, 215 Gauss law, 214 Gold... 

The Volta potential, in contradiction to the Galvani potential, has the advantage of being measurable but also the disadvantage that it is not determined only by the chemical nature of the phases that create the interface, but also by the state at their surfaces, represented by the surface potentials, Eqs. (1) and (2). 

In principle, the distribution of ions and dipoles at the M/s interface is different from that at the free M and s surfaces. Therefore the Galvani potential may also be written, in the absence of specific adsorption, as the sum of the charge and dipole components ... 

It is clear that the Galvani potential, A (p, which is an electrostatic quantity, cannot be identified with the thermodynamic term called the electrode potential. 

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