Complexing Electrolytes

Given the crucial roles complexes play in modeling solution behavior, it is quite 

---

COMPUTER SIMULATION OF DYNAMIC PROCESSES IN COMPLEX ELECTROLYTIC MEDIA... 

Figure 6. Concentration of the complexing cations MEP1 (A) and MEM1 (0) in the complex electrolyte phase during one total charge-discharge cycle of a model zinc-flow battery. Taken from Ref. [90],...

MIC depends on the complex structure of corrosion products and passive films on metal surfaces as well as on the structure of the biofilm. Unfortunately, electrochemical methods have sometimes been used in complex electrolytes, such as microbiological culture media, where the characteristics and properties of passive films and MIC deposits are quite active and not fully understood. It must be kept in mind that microbial colonization of passive metals can drastically change their resistance to film breakdown by causing localized changes in the type, concentration, and thickness of anions, pH, oxygen gradients, and inhibitor levels at the metal surface during the course of a... 

FIG. 12 Cyclic voltammogram for Au electrode modified with el6S-tl9-T12Fc ternary complex. Electrolyte solution, aqueous 0.1 M KCl scan rate 25 mV s temperature, 5°C electrode area, 0.02 cm (geometrical). 

Very few references are available regarding the study of this redox couple. Gorbachev and co-workers64,65 reported from polarization curves that in citrate and chloride complex electrolytes, the oxidant and reductant reduce to the metal state. 

Fig. 19. Pfeiffer complexes. Influence of the central atom on the oxygen activity of the Pfeiffer complexes. (Electrolyte Carbonate/bicarbonate buffer solution)...

This book was written to provide readers with some knowledge of electrochemistry in non-aqueous solutions, from its fundamentals to the latest developments, including the current situation concerning hazardous solvents. The book is divided into two parts. Part I (Chapters 1 to 4) contains a discussion of solvent properties and then deals with solvent effects on chemical processes such as ion solvation, ion complexation, electrolyte dissociation, acid-base reactions and redox reactions. Such solvent effects are of fundamental importance in understanding chem-... 

The ZPC in complex electrolytes may become completely unrelated to the identity of the solid phase, the ZPC being several pH units removed from the IEP(s). The best example of complete loss of influence by the solid phase is the successful measurement of correct IEP(s) values for proteins adsorbed onto quartz (I, 53). 

This equation is approximate since it assumes that the solvent is a structureless continuum, and so cannot interact with the reactants and the activated complex. Electrolyte solution studies demonstrate conclusively that this is not the case. In... 

Ionization of the oxide/water interface and the resultant electrical double layer have been studied intensively by a variety of techniques within the last decade. Although many electrical double layer and adsorption models have been proposed, few are sufficiently general to consider surface equilibria in complex electrolyte solutions. Recently we proposed a comprehensive adsorption model for the oxide/water interface which can simultaneously estimate adsorption density, surface charge, and electro-kinetic potential in a self-consistent manner (jL, 2, 3). One advantage of the model was that it could be incorporated within the computer program, MINEQL ( ), by adding charge and mass-balance equations for the surface. 

In this paper we examine the assumptions of our previous modeling approach and present new model calculations which consider alternative assumptions. In addition, we discuss the physicochemical factors which affect the formation of surface complexes at the oxide/water interface, in particular the effect of decreasing dielectric strength of the solvent. Finally, to demonstrate the general applicability of the model we present modeling results for a complex electrolyte system, where adsorption of a metal-ligand complex must be considered. 

Pharmaceutical colloids are rarely simple systems. The influence of additives including simple and complex electrolytes has to be considered. Electrolyte concentration and valence (z) are accounted for in the term (Zc,z ) in equation (7.3) and thus in equations (7.4) and (7.5). Figure 7.5 gives an example of the influence of electrolyte concentration on the electrostatic repulsive force. In this example, a = 10 cm, A = 10 J, and xpQ = RT/F 26.5 mV. As the electrolyte concentration is increased, k increases due to compression of the double layer with consequent decrease in 1/k. 

The possibility of using electroless deposition to superfill sub-micrometer features has also been explored[347-349] successful filling was recently reported for an alkaline EDTA-complexed electrolyte containing SPS and PEG as additives [349]. However, the tilted sidewalls in the lower half of the features, combined with the absence of kinetic data, make a mechanistic assessment of feature filling difficult. 

As a measure of the concentration of a complex electrolyte solution, ionic strength is better than the simple sum of molar concentrations, as it accounts for the effect of charge of multivalent ions. 

Chemical composition of the electrolyte is a particularly important parameter in PEC systems based on complex electrolytes snch as polysnlphide or ferro/ ferricyanide. In the latter redox conple, as shown in Fig. 10.8, replacement of one of the hexacyano ligands strongly changes the photoelectrochemical response of illnminated n-CdSe dne to a combination of electrochemical and spectroscopic effects (Licht, 1995), and addition of the KCN to the electrolyte can increase n-CdSe and n-CdTe photovoltages by 200 mV (Licht and Peramnnage, 1990). 

Kanungo, S.B., Adsorption of cations on hydrous oxides of iron. III. Adsorption of Mn, Co, Ni, and Zn on p-FeOOII from simple electrolyte solutions as well as from a complex electrolyte solution resembling seawater in major ion content, J. Colloid Interf. Sci.. 162, 103, 1994. 

The above equations for a 1-1 electrolyte are easily extended to a more complex electrolyte MaXb. Dissociation of this electrolyte give cations M " and anions X ... 

The above analysis shows how the GAI is applied to the simplest polarizable interface in contact with a 11 electrolyte. Other more complicated situations have been analyzed for systems with more complex electrolytes and molecular solutes. More details can be found in reviews by Mohilner [1] and Parsons [G4]. The essential feature of these analyses is that an equation is derived which relates the change in interfacial tension to the change in the potential of the polarizable electrode with respect to that of a non-polarizable electrode, and to the chemical potentials of the components of the solution. 

Y. Shi and J. S. Fritz, Separation of metal ions by capillary electrophoresis with a complexing electrolyte,. 1. Chromatogr., 640, 473,1993. 

From this very basic and elementary discussion it should be abundantly clear that the solvent plays a crucial role in the behaviour of electrolyte solutions, quite apart from its role as a dielectric reducing the forces of interaction between ions. Such considerations are of vital importance in physical chemistry and have only been tackled rigorously in the past three decades or so. Where complex electrolytes such as are encountered in biological chemistry are concerned, they are of crucial importance and may well dominate the behaviom of such solutions. 

But as has been hinted at above, there is one important limitation to this when considering large complex electrolytes such as are found in aqueous solutions of biological materials. Here the central ion is non-spherical. An ion which is not spherically symmetrical may impose a non-spherically symmetrical distribution of charge around it, and this ought to be taken care of, but is not, in the theory. The Debye-Hiickel theory can thus only be approximate for non-spherical ions. 

A generalization of the classical result of Lax and Mengert (53) to the case of multicharge ions and combined systems demonstrates that just because of the long-range Coulomb forces between ions, the conductance fluctuation level in dilute simple electrolytes must be normalized to the total number of ions regardless of the electrolyte type and ion mobility difference (45). However, this condition does not hold for complex electrolytes or electrolyte mixtures that contain more than one type of cation or anion. If the mobilities of different types of ions of the same sign are not equal, the fluctuation level would increase so that normalization to the total number of ions in the sample would fail. 

---