Ionic constituents

Chromatographic separations are not limited to ionic constituents. For example, glucose [50-99-7] is separated from fmetose [57-48-7] ... 

Table 1. Common Ionic Constituents Contained in Water.

The behavior of ionic liquids as electrolytes is strongly influenced by the transport properties of their ionic constituents. These transport properties relate to the rate of ion movement and to the manner in which the ions move (as individual ions, ion-pairs, or ion aggregates). Conductivity, for example, depends on the number and mobility of charge carriers. If an ionic liquid is dominated by highly mobile but neutral ion-pairs it will have a small number of available charge carriers and thus a low conductivity. The two quantities often used to evaluate the transport properties of electrolytes are the ion-diffusion coefficients and the ion-transport numbers. The diffusion coefficient is a measure of the rate of movement of an ion in a solution, and the transport number is a measure of the fraction of charge carried by that ion in the presence of an electric field. 

In the case of ionic solid substances, an important quantity is the free lattice energy AGS, i.e., the energy liberated when one type of crystalline substance is formed from its ionic constituents in the gas phase. This definition implies that this magnitude for a simple 1 1 solid electrolyte is a sum of the real potentials of cation and anion ... 

Donnan-Type Equilibria in Polyelectrolyte Gels.—In a somewhat more rigorous fashion we consider the reduction of the chemical potential of the solvent in the swollen gel to be separable into three terms which severally represent the changes due to the mixing of polymer and solvent, to the mixing with the mobile ionic constituents, and to the elastic deformation of the network. Symbolically... 

According to Eq. (26), which directly ensues from Eq. (22), the distribution potential is the arithmetic mean of the Galvani potentials of cations and anions. These potentials are the ionic constituents of the distribution potential, and in fact, according to Eq. (5) they can be considered as electrical representations of the ionic transfer energies AG or limiting distribution coefficients of the ions, Bj [3]. Here, the reader is referred to the following equations ... 

Standard ionic potentials Ajy can be calculated from the ionic distribution coefficients or transfer energies see Eq. (30). In order to perform such calculations, an appropriate nonthermodynamic assumption that allows division of the E> mx) or electrolyte function into ionic constituents has to be made. At the present time, the assumption about the equality of the transfer energies of tetraphenylarsonium cations (TPhAs ) and tetra-phenylborate anions (TPhB ) is considered as most appropriate [2,36]. It can be presented in the following form ... 

An insight into the equilibria present in solutions of several complexes of the type (R3P)2HgX2 (X = C104, CF3COO) is provided by electrospray mass spectrometry (ES MS) (cf. Section 6.9.2.1.8). 39 In all cases the principal ions [(R3P)2HgX]+ are observed, even if these ions and other ionic constituents of the equilibria are known to be labile on the NMR timescale. In the presence of excess R3P the principal ions [(R3P)3HgX]+ appear. Also fragments of collisionally activated decomposition (CAD, can be influenced and controlled to some extent) are detected, e.g., [(R3P)HgX]+. 

The subscripts i and x label the ionic constituents of the ion pair and aixm refers to the activity of the ion pair in the membrane phase. At a constant counter-ion activity, axw, and for the ideal case that yiw and yix = 1, equation (25) can be converted to the commonly defined distribution ratio Dixmw ... 

A survey of leach rate measurements has been made by Mendel ( 3). As examples of relatively simple procedures, three methods are described below. All such methods require either analyses of bulk liquids for ionic constituents (at low concentrations) after leaching or a drastic increase in the surface area prior to leaching to get higher concentrations that are easier to measure. 

However the question of whether the salt should be considered as a molecular or ionic constituent is raised. The laws of solution theory suggest the latter. Hence, unless the salt is either fully associated or fully dissociated over the entire liquid composition range, the varying degree of salt dissociation over this range is important. In other words, since both species of ion and salt molecules contribute to the total effect caused by a partially dissociated salt, the total number of salt particles (ions and molecules) present should be considered. This would suggest that an even more correct expression of liquid composition for use in calculating liquid phase activity coefficients would be... 

The following tabulation gives concentrations not only of K+ and Na+ but also of the other principal ionic constituents in human blood plasma and within cells of skeletal muscle. 1 Units are mmol/kg H20. 

The use of ion-exchange resins tall into live categories I. Transformation of ionic constituents 2. Removal of ionic impurities 2, Concentration of ionic substances 4. fractionation ol tome substances and 5 A variety of other applications. 

Table 12.1 lists elements in seawater that have concentrations greater than 0.1/tmol kg-1. The first seven elements in Table 12.1 (Cl, Na, Mg, S, Ca, K and C) have concentrations greater than or equal to 0.002 mol kg 1 and are generally treated as the major ionic constituents of seawater. The ion pairing constants of these relatively weakly interacting elements have been studied as a function of temperature, pressure and ionic strength. An equilibrium speciation...

J. Fordtran, T. Locklear, Ionic Constituents and Osmolality of Gastric and Small-intestinal Fluids After Eating, Harper and Row Publishers Inc., New York, New Series ll(7) (1966). 

Because the conductance of an ionic solution depends on the number of ionic charges, it is convenient to define it in terms of the conductance per unit concentration of ionic constituent... 

Combined with densities, molecular weights, and transference numbers (fractions of the current carried by the various ionic constituents), the conductivity yields the relative velocities of the ionic constituents under the influence of an electric field. The mobilities (velocity per unit electric field, cm2 s-1 V-1) depend on the size and charge of the ion, the ionic concentration, temperature, and solvent medium. In dilute aqueous solutions of dissociated electrolytes, ionic mobilities decrease slightly as the concentration increases. The equivalent conductance extrapolated to zero electrolyte concentration may be expressed as the sum of independent equivalent conductances of the constituent ions... 

The absolute values of the Madelung energies Em for naphthalene TCNE and hexamethylbenzene p-chloranil are smaller than the cost of ionizing the lattice Iu Aa, so they are predicted by Eq. (12.2.8) to be complexes of almost neutral constituents, in agreement with experiment Em for TMPD TCNQ and TMPD chloranil are larger than fD — Aa, so they are predicted by Eq. (12.2.7) to be complexes of almost fully ionic constituents, in agreement with experiment these results are for mixed-stack crystals, where the D and A species are stacked atop each other, with large intermo-lecular overlap [13]. 

Mineral solubility and precipitation were discussed in Chapter 2 as techniques for predicting the release of ionic constituents to water or soil solutions or the removal of ionic constituents from water or soil solutions. In this chapter, a second source/sink for ionic constituents (e.g., contaminants or nutrients) is presented and the mechanisms controlling this sink are referred to as adsorption or sorption. Both terms denote the removal of solution chemical species from water by mineral surfaces (e.g., organics, metal oxides, and clays) and the distinction between the two terms is based on the mechanism(s) responsible for this removal. In adsorption, a chemical species may be adsorbed by a surface either electrostatically or chemically (electron sharing), whereas in sorption, a chemical species may accumulate on a minerars surface either through adsorption, hydrophobic interactions, and/or precipitation. 

If we also allow for interactions between ions and electrons, the situation becomes qualitatively different (see Fig. 56) even on the level of electronic and ionic constituents. In such cases we introduce variable valence states by permitting O and 0° as valence states, i.e.,... 

Determine the equilibrium constant for the dissociation of Hg2Ci2 into ionic constituents. Determine both the mean molal activity coefficient and molality of the ions in equilibrium with the undissolved salt at 25°C. 

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