Equilibria ionic, factors affecting

Most metals of practical importance are actually mixtures of two or more metals. Recall from Section 1.1.3 that these intimate mixtures of metals are called alloys, and when the bond between the metals is partially ionic, they are termed intermetallics. For the purposes of this chapter, and especially this section, we will not need to distinguish between an intermetallic and an alloy, except to note that when a compound is indicated on a phase diagram (e.g., CuAb), it indicates an intermetallic compound. We are concerned only with the thermodynamics that describe the intimate mixing of two species under equilibrium conditions. The factors affecting how two metal atoms mix has already been described in Section 1.1.3. Recall that the solubility of one element in another depends on the relative atomic radii, the electronegativity difference between the two elements, the similarity in crystal structures, and the valencies of the two elements. Thermodynamics does not yet allow us to translate these properties of atoms directly into free energies, but these factors are what contribute to the free energy of... 

Different di- and trihydroxy bile salts and drugs that differ in lipophilicity, basicity, and structure have been compared in order to examine solvatochromic equilibria. The principle exploited in the determination of thermodynamic equilibrium constants is the indirect measurement of the capacity factor affected by the tenside concentration (in this case, the bile acid concentration). A pronounced shift in the migration times and thus effective ionic mobility... 

The B-Z equilibrium is almost independent of temperature but depends on ionic strength. But the major factor affecting the equilibrium is DNA superhelicity (see chapter 4.5). 

The third factor that strongly affects the equilibrium between hexa- and heptacoordinated complexes (85) is the nature of the second, outer-sphere cations. Increasing the ionic radii of the cations causes the equilibrium in Equation (85) to shift to the left, forming mostly hexacoordinated complexes MeF6 The mechanism of interionic equilibrium in fluoride melts can be presented schematically as follows ... 

Oxidation-reduction reactions may affect the mobility of metal ions by changing the oxidation state. The environmental factors of pH and Eh (oxidation-reduction potential) strongly affect all the processes discussed above. For example, the type and number of molecular and ionic species of metals change with a change in pH (see Figures 20.5-20.7). A number of metals and nonmetals (As, Be, Cr, Cu, Fe, Ni, Se, V, Zn) are more mobile under anaerobic conditions than aerobic conditions, all other factors being equal.104 Additionally, the high salinity of deep-well injection zones increases the complexity of the equilibrium chemistry of heavy metals.106... 

Because our main concern is the composition of the ionic population of the polymerising solutions, we need to consider the principal factors which affect it, namely the polarity of the solvent and the ionic concentration with particular reference to the formation of ionic aggregates. The simplest of these are the ion-pairs, and we will not consider any higher aggregates because the ionic concentrations are usually far too low for their formation to be significant. This means that we are concerned with the equilibrium (11) ... 

Hydrogels are characterized, first by their capacity to absorb water or aqueous solutions. The water content in the swelling equilibrium of a hydrogel is affected, fundamentally, by the nature of the monomer or monomers that make it up, by the type and density of the cross-link, and by other factors such as temperature, ionic strength, and pH of the hydration medium. 

Nonspecific interference can be encountered as a result of changes in temperature, ionic strength, and pH, or as a result of the presence of hemolysis or excessive quantities of bilirubin, heparin, and urea. Any of these factors can alter the composition of the incubation medium and affect the kinetics or equilibrium of the antigen-antibody reaction. Nonspecific interference contributes to assay variability and results in a decrease in sensitivity. This is particularly prevalent in early enzyme IA applications. Assay sensitivity can be greatly improved with increased assay specificity. 

For nonideal solutions, the concentration ratio in Eq. 11.6 is replaced with the ratio of thermodynamic activities. Since, for biological compounds, the equilibrium solubility, C, is affected by a number of thermodynamic factors (e.g., anti-solvent concentration, ionic strength, pH) studies of their effect on growth rate can be used to test the relative usefulness of Eq. 11.4 versus Eq. 

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