Electrolytes dependence

Debye-Hiickel theory The activity coefficient of an electrolyte depends markedly upon concentration. Jn dilute solutions, due to the Coulombic forces of attraction and repulsion, the ions tend to surround themselves with an atmosphere of oppositely charged ions. Debye and Hiickel showed that it was possible to explain the abnormal activity coefficients at least for very dilute solutions of electrolytes. 

Before considering the principles of this method, it is useful to distinguish between anodic protection and cathodic protection (when the latter is produced by an external e.m.f.). Both these techniques, which may be used to reduce the corrosion of metals in contact with electrolytes, depend upon the electrochemical mechanisms that result from changing the potential of a metal. The appropriate potential-pH diagram for the Fe-H20 system (Section 1.4) indicates the magnitude and direction of the changes in the potential of iron immersed in water (pH about 7) necessary to make it either passive or immune in the former case the stability of the metal depends on the formation of a protective film of metal oxide (passivation), whereas in the latter the metal itself is thermodynamically stable and egress of metal ions from the lattice into the solution is thus prevented. 

This result demonstrates that the self-spreading dynamics are controllable by tuning the bilayer-substrate interactions. The above-mentioned electrolyte dependence is an example of this fact. Considering that there are many parameters that alter the bilayer-substrate interaction, a diverse approach can be proposed. For example, Nissen et al. investigated the spreading dynamics on the substrate coated with polymetic materials [48]. They found that insertion of a hydrophilic and inert polymer layer under the self-spreading lipid bilayer strongly attenuated the bilayer-substrate interaction. 

Diffusion and migration in solid crystalline electrolytes depend on the presence of defects in the crystal lattice (Fig. 2.16). Frenkel defects originate from some ions leaving the regular lattice positions and coming to interstitial positions. In this way empty sites (holes or vacancies) are formed, somewhat analogous to the holes appearing in the band theory of electronic conductors (see Section 2.4.1). 

From the preceding paragraphs it is clear that the capacity to calculate the properties of a variety of mixed electrolytes depends on an adequate theoretical structure within which the available experimental data can be organized. Thus the primary emphasis for the remainder of this paper will be the description of this structure of semi-empirical equations. The array of substances for which experimental data are available will be described in general terms but there is not sufficient space to list results in detail. Also a severe test of predictions for mixed electrolytes will be reported. 

M. Preuss and H.-J. Butt Direct Measurement of Particle-Bubble Interactions in Aqueous Electrolyte Dependence on Surfactant. Langmuir 14, 3164 (1998). 

A mathematical approach that attempts to explain how the solution behavior of electrolytes depends on their ionic charge and the overall ionic strength of the solution. This treatment allows one to estimate the mean activity coefficients that relate the analytical concentration of an electrolyte to its solution activity. We also can come to understand how the activity coefficient behaves as a function of ionic strength. 

The LB monolayers of dimethyldioctyadecylammonium ions on molecularly smooth muscovite mica surfaces were investigated. Direct measurements of the interaction between such surfaces were carried out using the surface force apparatus. A long-range attractive force considerably stronger than the expected van der Waals force was measured. Studies on the electrolyte dependence of this force indicate that it does not have an electrostatic origin but that the water molecules were involved in this. 

This same solvent and supporting electrolyte dependence effect is observed for C70 and for the higher fullerenes (see the following). 

The theory for cyclic voltammetry was developed by Nicholson and Shain [80]. The mid-peak potential of the anodic and cathodic peak potentials obtained under our experimental conditions defines an electrolyte-dependent formal electrode potential for the [Fe(CN)g] /[Fe(CN)g]" couple E°, whose meaning is close to the genuine thermodynamic, electrolyte-independent, electrode potential E° [79, 80]. For electrochemically reversible systems, the value of7i° (= ( pc- - pa)/2) remains constant upon varying the potential scan rate, while the peak potential separation provides information on the number of electrons involved in the electrochemical process (Epa - pc) = 59/n mV at 298 K [79, 80]. Another interesting relationship is provided by the variation of peak current on the potential scan rate for diffusion-controlled processes, tp becomes proportional to the square root of the potential scan rate, while in the case of reactants confined to the electrode surface, ip is proportional to V [79]. 

Pour 2 ml of the prepared colloidal iron hydroxide solution into each of several test tubes and add 2 ml of one of the following solutions of the same normality (0.1 N) to each of them sodium chloride, barium chloride, aluminium chloride, sodium sulphate, aluminium sulphate, or monosubstituted sodium orthophosphate. What do you observe How does the coagulating effect of an electrolyte depend on the sign and magnitude of the charge of its ions ... 

Fig. 1. Electrolyte-dependent EGA Generation in Acetone (16 ml) Containing 2 mmol of Electrolytes...

Electrolytes, depending upon their strength, dissociate to a greater or less extenl in polar solvents. The extent to which a weak electrolyte dissociates may be determined by electrical conductance, electromotive force, and freezing point depression methods. The electrical conductance method is the most used because of its accuracy and simplicity. Arrhenius proposed that the degree of dissociation, a. of a weak electrolyte at any concentration in solution could be found from the rutio of the equivalent conductance. A. of the electrolyte at the concentration in question to (he equivalent conductance at infinite dilution A0 of the electrolyte. Thus... 

Electrolyte Injected under the Lipid Film. There is a marked difference in the AV response of phosphatidyl choline films to the electrolyte, depending on whether the lipid film is spread onto the electrolyte solution or the electrolyte is injected under the lecithin film that was spread first onto distilled H20 (I). 

Solutions are usually classified as nonelectrolyte or electrolyte depending upon whether one or more of the components dissociates in the mixture. The two types of solutions are often treated differently. In electrolyte solutions properties like the activity coefficients and the osmotic coefficients are emphasized, with the dilute solution standard state chosen for the solute.c With nonelectrolyte solutions we often choose a Raoult s law standard state for both components, and we are more interested in the changes in the thermodynamic properties with mixing, AmjxZ. In this chapter, we will restrict our discussion to nonelectrolyte mixtures and use the change AmjxZ to help us understand the nature of the interactions that are occurring in the mixture. In the next chapter, we will describe the properties of electrolyte solutions. 

We start this chapter with electrocapillarity because it provides detailed information of the electric double layer. In a classical electrocapillary experiment the change of interfacial tension at a metal-electrolyte interface is determined upon variation of an applied potential (Fig. 5.1). It was known for a long time that the shape of a mercury drop which is in contact with an electrolyte depends on the electric potential. Lippmann1 examined this electrocapillary effect in 1875 for the first time [68], He succeeded in calculating the interfacial tension as a function of applied potential and he measured it with mercury. 

Figure 10.9 Conformation of a linear poly electrolyte depending on salt concentration. At high salt concentration they tend to from a dense random coil which changes to a more stretched conformation at low salt concentration. In addition, the conformation in the adsorbed state is indicated.

Typical materials for the electrolyte are YSZ, samaria doped ceria (SDC), and LaGaC>3. The intrinsic property of the thermal expansion behavior of an electrolyte depends only on the material species. However, the other mechanical properties (Young s modulus, Poisson s ratio, and strength) depend on the morphology through the manufacturing processes. Accordingly, the reported mechanical properties are not unique. The reported thermal expansion coefficient (TEC) and other mechanical properties for the electrolyte materials are listed in Table 10.1. 

Polycyclic aromatics with more than two aromatic rings, or more than one heteroatom are relatively easy to reduce and several reviews have summarized works on their electrochemical behavior. Bicyclic heteroaromatics with one heteroatom are reduced close to or beyond the decomposition of the electrolyte unless acidic solutions are used. Very few compounds of this kind have been preparatively reduced in neutral media. Their cathodic reduction could be carried out at mercury cathodes with TA A+ electrolytes. Depending on the heteroatom and the amount of charge transferred, hydrogenated and/or reductive cleavage products were obtained. 

Now, it will be recalled that the adsorption of a particular constituent of the electrolyte depends not only on its chemical nature (i.e., on the chemical part, AG°c, of its free energy of adsorption) but also upon the electrode charge (remember the parabolic 0org versus qu curves in Chapter 7). So the corrosion inhibitor must not only be highly adsorbable in a chemical sense, it must also adsorb in the range of potentials which includes the potential at which the corrosion reactions occur. Correspondingly,... 

The electrostatic contribution to the energy, in the presence of an electrolyte, depends on the behavior of the surface charge density, oe, when two surfaces approach each other. Assuming that the surface charge density remains constant, an excellent approximation for the electrostatic contribution to the energy is given by20... 

The activity coefficient of a strong electrolyte depends, therefore, on the concentration and valence of both, its own ions and that of all other ions present in the solutions. It. follows further from the last two equations that the activity coefficient of a given electrolyte is the same in any solution, if we assume that ionic strength is always the same. According to experimental results, this proposition is more oxactly valid with an increased dilution of the solutions. 

The way of connecting the current conductors to electrodes which remain permanently dipped into the solution of electrolytes depends on the material of the electrode (whether noninetallic, such as graphite, or metallic.) One possible method of connecting a graphite rod to the current conductor is schematically represented in Fig. 41. the upper end of the electrode has a small recess it is encompassed by a two-piece copper terminal which is connected to the current conductor. A terminal for connection of a plate shaped electrode to the current conductor is illustrated in Fig. 42. At first the upper edge of plate A is fitted... 

The stability of the perborate in the electrolyte depends on the presence of catalytioally active poisons and on the temperature and concentration of the solution. If the temperature is increased by 10°C, the rate of decomposition is more... 

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