Dependence on electrolyte concentration

The electrochemical equivalent of 3860 Ah/kg is the highest among all metal anodes and the open-circuit voltage of 2.7-2.8 V (depending on electrolyte concentration) is rather high too. 

Another important and fundamental consequence of Figure 2.9 is that the Helmholtz theory cannot cope with a concentration dependence of the differential capacitance nor can it be modified in such a way as to incorporate a minimum in (derM/d V) at low concentrations of electrolyte. Instead, a second theory must be invoked, having a dependence on electrolyte concentration but in such a way that it is only important at low concentration. A first step... 

The capacity of the Stern layer (Cj = CIS) does not depend on electrolyte concentration except in so far as C is affected. In the case of the silver iodide-aqueous electrolyte interface, Stern layer capacities of c. 0.1 to 0.2 F m 2 have been calculated taking 8- 5 x 10 10 m, this corresponds to a dielectric constant in the Stern layer of c. 5-10, which, compared with the normal value of c. 80 for water, suggests considerable ordering of water molecules close to the surface. 

The two principal defects of this model are first that it neglects interactions that occur further from the electrode than the first layer of adsorbed species, and secondly that it does not take into account any dependence on electrolyte concentration. 

The degree of adsorption depends on electrolyte concentration. The degree of coverage of a surface by specific adsorption of ions can be described by monolayer adsorption isotherms (Fig. 3.11). Three types of isotherm are generally considered ... 

More precise verification of the theory was achieved with films studied by the microinterferometric technique. Though performed a long time ago (1960), these experiments deserve attention, since they represent the first quantitative proof of the DLVO-theory conducted on a model system (foam film) which still hold true. Independent studies were performed of the X ei(k) and Vlvw(h) as well as of their joint action at various electrolyte concentrations. At very low Cei equilibrium films of large thickness formed in which the electrostatic interaction was prevailing and their behaviour could be described completely with this interaction. At such film thickness Y vw was still very low so that the equilibrium film state was reached at equal electrostatic disjoining and capillary pressure (n, = p ). Fig. 3.15 depicts the equilibrium thickness dependence on electrolyte concentration for saponin microscopic foam films. 

Hottenliuis et al. studied Ag (100) surface. They made a comparison between ex situ images and in situ images. " To interpret their results they postulated a resolution increase in dependence on electrolyte concentration and its limitation to the Gouy-Chapman layer thickness. 

Representative plots of as a function of concentration are shown in fig. 4.10. The principal feature depending on electrolyte concentration is the initial slope which is called the dielectric decrement. In addition all plots are curved, suggesting that a limiting permittivity is reached at high electrolyte concentration. The dependence of on electrolyte concentration c. has been examined by Friedman [30], who derived the following relationship ... 

It should be mentioned that the value of 5f, calculated using the above simple equation shows a dependence on electrolyte concentration, and hence the method carmot be used in a straightforward manner. Cohen-Stuart et al. [36] showed that the measured electrophoretic thickness approaches Sf, only at low electrolyte concentrations. Thus, in order to obtain Sf, from electrophoretic mobihty measurements, results should be obtained at various electrolyte concentrations and 5 plotted versus the Debye length (l/xr) to obtain the limiting value at high (1/xr) (i.e., low electrolyte concentration) which now corresponds to 5f,. 

The double-layer extension depends on electrolyte concentration and valency of the counterions,... 

Under some conditions (depending on electrolyte concentration and particle size), flocculation into the secondary minimum may occur, although such flocculation is weak and reversible. On increasing the electrolyte concentration decreases until, at a given concentration, it vanishes and particle coagulation occurs. This is illustrated in Figure 7.10, which shows the variation of with h at various electrolyte concentrations. 

The decrease in thickness of foam and emulsion films may result in a metastable equilibrium described by the II = - pa condition (Fig. VII-10, point A). In this case film thickness depends on electrolyte concentration the increase in the latter results in a decrease of electrostatic component of... 

It follows from eqs. (VII.23) and (VII.24) that values of n and A depend on electrolyte concentration. Concequently, the electrolyte concentration defines the height as well as position of potential barrier (see Fig. VII-10), which characterize film stability. The addition of electrolyte to colloidal system results in compression of electrical double layer, and, hence, in compression of the region of the effective action of electrostatic repulsion... 

Figure 3.5 Variation of electrical potential with distance from the surface and its dependence on electrolyte concentration (i) low, (ii) medium,...

For mixed solutions, hindered diffusivity becomes more significant. The rejection depends on electrolyte concentration and the membrane charge increases with salt concentration. This indicates colon adsorption on the membrane, and, in fact the effective membrane charge was described as a Freundlich isotherm as a function of bulk concentration by Bowen and Mukhtar (1996). 

Similar to diffusion coefficient, the molar electroconductivity exponentially increases with temperature. It also depends on electrolyte concentration, decreasing with concentration increase. 

The dependence of colloid stability on the size of the particles formed and its dependence on electrolyte concentration can be discussed simplistically in the following way [71], Assuming, (1) that the particles formed are spherical, (2) each polymer chain has the same molar mass, M, (3) each chain has two charged end-groups and (4) all the end-groups are anchored at the surface of the particle, it follows that the number of polymer chains per particle, Nc is given by... 

The study of the membrane-electrolyte interfaces occurring in collodion membranes was focused on the corresponding complex power spectrum. The membrane-electrolyte interface power spectrum is not a simple 1/v noise but depends on electrolyte concentration. At infinite dilution of the electrolyte this power spectrum reverts to white noise. 

Ionophores are substances that already exist as ionic crystals in their pure state, such as alkali metal halides. When dissolved in a solvent, ionophores are initially completely dissociated in the solution and their ions are solvated. However, association to ion pairs and higher ion aggregates with and without inclusion of solvent molecules may occur in many solvents depending on electrolyte concentration and solvent permittivity. Equation (1) shows the ionic species in an aqueous CdS04 solution—solvated ions and ion pairs—which can be detected by appropriate methods and which determine the physical properties of this solution ... 

When two droplets approach to a distance h that is smaller than the double layer extension, double layer overlap occurs and this leads to repulsion (the double layers cannot be fully developed) [5]. The double layer extension depends on electrolyte concentration and valency (the lower the electrolyte concentration and the lower the valency the more extended the double layer is). 

The magnitude of the energy minima and the energy maximum depends on electrolyte concentration and valency. This is illustrated in Figure 11.35 for a 1 1 electrolyte (e.g. NaCl) at various concentrations. 

The above expression shows that Gei decreases exponentially with increasing h and the rate of this decrease depends on electrolyte concentration. 

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