Ionic fraction

Da en the ionic fraction of species A in the resin is very small and Dg when the ionic fraction of A in the resin approaches unity, indicating that the ion present in smaller concentration has the stronger effect on the local interdiffusion rate. 

The drermodynamic data for CuaS-FeS (Krivsky and Schuhmann, 1957) show that drese sulphides mix to form approximately ideal ionic liquids. These are molten salts in which the heat of mixing is essentially zero, and die entropy of mixing is related to the ionic fractions of die cations and anions. In the present case die ionic fractions yield values for the activities of the two sulphides... 

While the mole fraction is a natural measure of composition for solutions of metallic elements or alloys, the mole fraction of each molecule is chosen as the measure of composition in the case of solid or liquid mixtures of molecules.1 In ionic solutions cations and anions are not randomly mixed but occupy different sub-lattices. The mole fractions of the atoms are thus an inconvenient measure of composition for ionic substances. Since cations are mixed with cations and anions are mixed with anions, it is convenient for such materials to define composition in terms of ionic fractions rather than mole fractions. In a mixture of the salts AB and AC, where A is a cation and B and C are anions, the ionic fractions of B and C are defined through... 

In a binary solution AB-AC, the ionic fractions of B and C are identical to the mole fractions of AB and AC. It may therefore seem unnecessary to use the ionic fractions. However, in the case of multi-component systems the advantage of ionic fractions is evident, as will be shown in Chapter 9. 

A ternary reciprocal system is a system containing four components, but where these components are related through a reciprocal reaction. One example is the system LiCl-LiF-KCl-KF. Solid LiCl, LiF, KC1 and KF are highly ionic materials and take the rock salt crystal structure, in which the cations and anions are located on separate sub-lattices. It is therefore convenient to introduce ionic fractions (Xj) for each sub-lattice as discussed briefly in Section 3.1. The ionic fractions of the anions and cations are not independent since electron neutrality must be fulfilled ... 

Both the ternary systems are simple eutectic ones and the composition of the system is represented by the ionic fraction of one of the cations and one of the anions. In Figure 4.21 the ionic fraction of Li+ is varied along the X-axis, while the ionic fraction of F is varied along the 7-axis. 

The equations for the regular solution model for a binary mixture with two sublattices are quite similar to the equations derived for a regular solution with a single lattice only. The main difference is that the mole fractions have been replaced by ionic fractions, and that while the pair interaction is between nearest neighbours in the single lattice case, it is between next nearest neighbours in the case of a two sub-lattice solution. 

Crystalline salts of many organic acids and bases often have a maximum solubility in a mixture of water and water-miscible solvents. The ionic part of snch a molecule requires a strongly polar solvent, snch as water, to initiate dissociation. A mixture of water-miscible solvents hydrates and dissociates the ionic fraction of pollutants at a higher concentration than wonld either solvent alone. Therefore, from a practical point of view, the deliberate nse of a water-soluble solvent as a cosolvent in the formnlation of toxic organic chemicals can lead to an increased solnbility of hydrophobic organic contaminants in the aqueous phase and, conse-qnently, to a potential increase in their transport from land surface to groundwater. 

Cations Ionic Fractions on a Four-Oxygens Basis ... 

Table 5.17 lists analyses of several types of natural garnet, after Deer et al. (1983). The calculation of ionic fractions on the basis of 24 oxygens shows elfec-tive diadochy of Al on Si in tetrahedral site Z, whereas Ti" and Fe appear to be stabilized in octahedral site Y. Deviation from ideal closure in sites Y and X (6 and 4, respectively) may be attributed in some instances to erroneous estimation of ferric iron (samples 4, 5, and 6), but in others it is difficult to interpret (samples 1, 2, and 3). 

Consideration of the actual extension of miscibility gaps in natural systems led Will and Powell (1992) to establish systematic relationships between the actual free energy of pure components and their Active potentials in the phases of interest, as listed in table 5.51. Note that, amphiboles being multisite phases, their ideal activity in a chemically complex phase is expressed in terms of multiple product of site ionic fractions (see section 3.8.7). For anthophyllite ( Mg2Mg3Mg2Si4Si4022(OH)2), for instance, we have... 

Table 5.55 Chemical analyses of natural micas (from Deer et al., 1983). Note that ionic fractions are retrieved on a 24-anion basis—i.e. double the canonical formula. (1) Muscovite from a low-grade metamorphic prasinite schist (2) glauconite from a sandstone (3) phlogopite from a marble (4) biotite from a quartz-bearing latite (5) lepidolite from a pegmatite. ...

By applying the ionic solution model, we may express the relationship between ionic fraction and activity in the garnet phase as... 

ED appears to be an inefficient method to recover free citric acid because of its low electric conductivity (Novalic et al., 1995). As it is converted into the monovalent (at pH ca. 3), divalent (at pH ca. 5), or trivalent (at pH about 7) citrate anion, there is a significant increase in the electric conductivity (%), the latter increasing from 0.95 to 2.18 and to 3.9 S/m, respectively, in the case of an aqueous solution containing 50 kg/m3 of citric acid equivalent (Moresi and Sappino, 1998). By increasing the pH from 3 to 7, e reduced about eight times, the solute flux (JB) practically doubled, while the overall water transport (/w) increased 3-4 times. The latter partly counterbalanced the greater effectiveness of the electrodialytic concentration of citric acid at pH 7 with respect to that at pH 3. Table XV presents a summary of the effect of current density ( j) on the main performance indicators of the electrodialytic recovery of the monovalent, divalent, or trivalent ionic fractions of citric acid (Moresi and Sappino, 1998). All the mean values or empirical correlations of the earlier indicators were useful to evaluate the economic feasibility of this separation technique (Moresi and Sappino, 2000). 

If only the non-ionic fraction can be absorbed via the respiratory surface, it follows that the fraction of chemical that is available for uptake is ... 

Ion-exchange equilibrium data are reported in the form of isotherms with the help of the equivalent ionic fraction in the solution (Figure 7.2) ... 

The atmospheric transport of sea-derived salts for hundreds of kilometers causes no ionic fractionation. 

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