Ionic components of charge

The r.h.s. s only contain measurable variables. The ionic components of charge and or are obtainable except for a constant, by Integration of the Esln-Markov coefficient with respect to a°, see 13.4.16). Here, no single ionic excesses are counted but sums of electroneutral combinations, including the negative adsorption of electrolyte,, see 13.4.8). Therefore, dy is also... 

Generally, Esln-Markov coefficients are useful tools to study ionic components of charge and, hence, specific adsorption. They are also required In obtaining the Gibbs energy of a double layer In the case of specific adsorption, see 13.3.9). 

In the Gouy-Chapman model the countercharge consists of an excess of counterions and a deficit of co-ions. For a positive surface the corresponding ionic components of charge = zFT and a = -zFF are both negative and defined by equations like (3.4.8a and 8b for silver iodide, or (1.5.6.3c and 3d( for oxides. Let us consider the latter systems and let. as usual,. ... 

Donnan effect, i.e. the expulsion of electrolyte by charged particles. As which is positive, cannot be measured without simultaneously measuring (also positive), cannot be measured by titration, but changes of <7 are coupled to those in T° via the Esln-Markov coefficient, see (3.4.14-16). so that after all they can be assessed except for a constant. The negative adsorption of neutral electrolyte can be measured as an Increase in the bulk concentration caused by the addition of the particles. Negative adsorption studies are therefore useful to compute the ionic components of charge for a diffuse double layer. 

Figure 3.8. Ionic components of charge for a flat diffuse double layer the absolute values of and are the areas indicated. Symmetrical electrolytes. The (positive) dimensionless potential is also indicated z = 1. These curves are scaled proportionally to the electrolyte concentration.

A.L. Loeb, J.Th.G. Overbeek and P.H. WIersema. The Electrical Double Layer around a Spherical Colloid Particle, M.I.T. Press (1961). (Covers symmetrical and asymmetrical electrolytes, ionic components of charge and Gibbs energies.)... 

V j(Xj)) all required double layer properties can be found. For instance, the surface charge density of each species, l.e. the Ionic components of charge, are Immediately found by integrating with respect to, considering the appropriate boundaiy conditions. 

The availability of r° (or pAg) curves at several electrolyte concentrations enables the establishment of the Esin-Markov coefficient 3.4.14) and the ensuing determination of the ionic components of charge, integrating 3.4.16] l Figures 3.45 and 3.46 give results of the former and the latter, respectively. 

Figure 3.46 gives the ionic components of charge. The situation around the p.z.c. is not well established and there is the additional problem of finding a reference point for the integration of [3.4.16]. However, it is seen that close to the... 

Figure 3.46. Ionic components of charge in the double layer on silver iodide. Temperature 25 C.

Figure 3.54. Ionic components of charge in the double layer on mercury. Electrolyte, 0.3 M NaCl. Temperature 25°C. Potentials with respect to a 1.0 M NaCl-calomel electrode. Symbols have the same meaning as in secs. 3.5b and 3.6c. (Redrawn from D.C. Grahame. loc. clt. 467.)...

Figure 3.62. ionic components of charge for the double layer on haematite. Electrolyte. 10 > M KCi. Drawn curves homodis-perse sol dashed curves purified heterodisperse sol. (Redrawn from N.H.G. Fenners. L.K. Koopal and J. Lyklema. Colloids Surf. 21 (1986) 457.)... 

The GC theory also allows us to calculate the ionic components of charge of a diffuse layer, i.e. the charge densities due to the surface excess amounts of the cations and anions that compensate the surface charge [7, 8] ... 

In summary, having identified the surface ions and indifferent ions, it is possible to obtain information about the surface charge and the ionic components of charge. This information can be used to verify double layer models [1]. 

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