Potential difference across the

It should be noted that the capacity as given by C, = a/E, where a is obtained from the current flow at the dropping electrode or from Eq. V-49, is an integral capacity (E is the potential relative to the electrocapillary maximum (ecm), and an assumption is involved here in identifying this with the potential difference across the interface). The differential capacity C given by Eq. V-50 is also then given by... 

The potential difference across the mobile part of the diffuse-charge layer is frequently called the zeta potential, = E(0) — E(oo). Its value depends on the composition of the electrolytic solution as well as on the nature of the particle-hquid interface. 

FIGURE 10.2 The passive diffusion of a charged species across a membrane depends upon the concentration and also on the charge of the particle, Z, and the electrical potential difference across the membrane, Ai/<. 

Consider a phospholipid vesicle containing 10 mMNa ions. The vesicle is bathed in a solution that contains 52 mMNa ions, and the electrical potential difference across the vesicle membrane Ai/t = i/toutskie / inside = —30 mV. What is the electrochemical potential at 25°C for Na ions ... 

The potential difference across the electric double layer A. This cannot be determined in absolute terms but must be defined with reference to another charged interface, i.e. a reference electrode. In the case of a corroding metal the potential is the corrosion potential which arises from the mutual polarisation of the anodic and cathodic reactions constituting the overall corrosion reaction see Section 1.4). 

The net electrochemical driving force is determined by two factors, the electrical potential difference across the cell membrane and the concentration gradient of the permeant ion across the membrane. Changing either one can change the net driving force. The membrane potential of a cell is defined as the inside potential minus the outside, i.e. the potential difference across the cell membrane. It results from the separation of charge across the cell membrane. 

If we add the two equations of (10) we obtain the potential difference across the double layer ... 

As the cell is discharged, Zn2+ ions are produced at the anode while Cu2+ ions are used up at the cathode. To maintain electrical neutrality, SO4- ions must migrate through the porous membrane,dd which serves to keep the two solutions from mixing. The result of this migration is a potential difference across the membrane. This junction potential works in opposition to the cell voltage E and affects the value obtained. Junction potentials are usually small, and in some cases, corrections can be made to E if the transference numbers of the ions are known as a function of concentration.ee It is difficult to accurately make these corrections, and, if possible, cells with transference should be avoided when using cell measurements to obtain thermodynamic data. 

The seminal part of this contribution is that there is a non-Faradaic catalysis, that the catalytic reaction of ethylene with oxygen occurs as well and that it depends on the potential difference across the electrode ... 

Complexes III and IV have Fe-porphyrin prosthetic groups (hemes), complex IV also contains copper atoms which are involved in electron transport. Complexes I, III, and IV use the energy of electron transport to pump protons out of the matrix so as to maintain a pH gradient and an electrical potential difference across the inner membrane required for ATP synthesis (see below and Appendix 3). It is important to remember that all dehydrogenations of metabolic substrates remove two protons as well as two electrons and that a corresponding number of protons are consumed in the final reduction of dioxygen (Figures 5, 6). 

Rona, J.P., Cornel, D., Gignon, C. Heller, R. (1982). The electrical potential difference across the tonoplast of Acer pseudoplantus cells. Physiologic Vegetale, 20, 459-63. 

Each of the respiratory chain complexes I, III, and IV (Figures 12-7 and 12-8) acts as a proton pump. The inner membrane is impermeable to ions in general but particularly to protons, which accumulate outside the membrane, creating an electrochemical potential difference across the membrane (A iH )-This consists of a chemical potential (difference in pH) and an electrical potential. 

Recent work has shown that bacteria, in common with chloroplasts and mitochondria, are able, through the membrane-bound electron transport chain aerobically, or the membrane-bound adenosine triphosphate (ATP) anerobically, to maintain a gradient of electrical potential and pH such that the interior of the bacterial cell is negahve and alkaline. This potential gradient and the electrical equivalent of the pH difference (1 pH unit = 58 mV at 37°C) give a potential difference across the membrane of 100-180 mV, with the inside negative. The membrane is impermeable to protons, whose extmsion creates the potential described. 

ATP levels and oxygen consumption [66]. Et3PAuCl treatment also reduced the potential difference across the inner mitochondrial membrane releasing sequestered calcium from mitochondria [66]. 

In initial ET rate measurements, both the NB and aqueous phases contained 0.1 M TEAP, enabling measurements to be made with a constant Galvani potential difference across the liquid junction. In these early studies, the concentration of Fc used in the organic phase (phase 2) was at least 50 times the concentration of the electroactive mediator in the aqueous phase which contained the probe UME (phase 1). This ensured that the interfacial process was not limited by mass transport in the organic phase, and that the simple constant-composition model, described briefly in Section IV, could be used. 

The same system has been studied previously by Boguslavsky et al. [29], who also used the drop weight method. While qualitatively the same behavior was observed over the broad concentration range up to the solubility limit, the data were fitted to a Frumkin isotherm, i.e., the ions were supposed to be specifically adsorbed as the interfacial ion pair [29]. The equation of the Frumkin-type isotherm was derived by Krylov et al. [31], on assuming that the electrolyte concentration in each phase is high, so that the potential difference across the diffuse double layer can be neglected. 

Monolayers of distearoylphosphatidylcholine spread on the water-1,2-dichloro-ethane interface were studied by Grandell et al. [52] in a novel type of Langmuir trough [53]. Isotherms of the lipid were measured at controlled potential difference across the interface. Electrocapillary curves derived from the isotherms agreed with those measured under the true thermodynamic equilibrium. Weak adsorption or a stable monolayer was found to be formed, when the potential of the aqueous phase was positive or negative respectively, with respect to the potential of the 1,2-dichloroethane phase [52]. This result... 

FIG. 8 Calculated potential differences, across the membrane boundary as a function of... 

FIG. 11 Simulated enhancement factor against electrol5de concentration in aqueous phase. The potential different across the water-1,2-DCE interface is/A"0 = 5 and the electrol5de concentration in the organic phase is c° = 10 mM and 50 mM. The phospholipid molecular area is 50 A. ... 

The applied potential, that is, the observed potential, E, is related to the potential difference across the O/W interface, A. by... 

As will be described in detail below, solute distribution in biphasic systems can be modulated by application of a Galvani potential difference across the interface, thereby leading to the transfer of species from one phase to the other. Therefore, in electrochemical terms, passive transfer simply means the partition across an interface, mediated by a potential-driven process. 

This time, the boundary line is independent of the Galvani potential difference across the interface, and the corresponding pH value can be regarded as the effective dissociation constant, pK eff, which appears experimentally due to the partitioning of the neutral species. For a monoprotic substance, pK eff can thus be defined as ... 

---