Concentrations of cations and anions

Cp C2, Ap and A2 are the concentrations of cations and anions on sides one and two. In practice, it was found that Tris was an impermeant cation and HEPES an impermeant anion, and so salts of these compounds were used to simplify the experimental conditions. For cations the selectivity sequence was... 

For the above-described model, the average concentration of cations and anions in the intermolecular spaces can be calculated using equations derived in [51] ... 

The pH at which the concentration of the zwitterion is a maximum is equal to the isoelectric point pi, strictly that pH at which the concentrations of cationic and anionic forms of the amino acid are equal. With a simple amino acid, this is the mean of the two pAT values ... 

It should be noted here that this system is not completely homogeneous but involves some element of a heterogenous system, since high concentrations of cations and anions are directly reacted with each other at an extremely high supersaturation so that nucleation constantly occurs throughout the whole process. If the dissolu-... 

In the case of a metal/solution interface, the charge on the metal is one of the signals that can be picked up. This electrode charge is mirrored on the solution side by an equal and opposite net charge constituted of separate contributions of the positive and negative charges, i.e., the relative concentrations of cations and anions in the interphase. However, are these ions on the metal or near the metal ... 

This model is based on the Gouy-Chapman theory (diffuse double-layer theory). The theory states that in the area of the boundary layer between solid and aqueous phase, independently of the surface charge, increased concentrations of cations and anions within a diffuse layer exists because of electrostatic forces. In contrast to the constant-capacitance model, the electrical potential does not change up to a certain distance from the phase boundaries and is not immediately declining in a linear manner (Fig. 14 a). Diffusion counteracts these forces, leading to dilution with increasing distance from the boundary. This relation can be described physically by the Poisson-Boltzmann equation. 

Concentration of dilute electrolytes An ion-exchange column is effective for collecting ionic substances from large volumes of dilute solutions. By elution employing a small volume of solution, a considerable concentration effect can be achieved. As examples may be cited the concentration of cations and anions in natural waters, beryUium from bones, copper from milk, and silver in atmospheric precipitation. Ion-exchange beads have been proposed as chemical microstandards since they can retain small measurable quantities (10 g) of ions such as sodium, potassium, calcium, and uranium. It is highly desirable that the beads be uniform in size and homogeneous in the trace constituent. 

The difference between the total concentrations of cations and anions, (Ecations — Eanions), in the bottom row, and the sum of the constituents of the last column equals the value of the alkalinity, 2.42 meqkg. See the discussion in Chapter 4. 

Table 4.2. 1 Concentrations of cation and anion species that do not significantly exchange protons in the pH range of seawater (35%o) ...

Concentration of Cations and Anions in Plasma Water and Interstitial Fluids-... 

The Galvani potential difference may not be found experimentally because single ion quantities are not subject to experimental determination. However, because of the requirement of electroneutrality, the concentration of cations and anions in each phase is equal. Furthermore, in the limit of dilute solutions, the activities of these ions are equal in each phase. Thus, by equating (8.9.5) and (8.9.6), one obtains for dilute electrolyte concentrations... 

Both ions move in the same direction from the solution of higher concentration to that of lower concentration. If the concentration Cj is higher than Ci then the ions on the left-hand side move across the liquid junction from the left to the right. The movement is governed by the law of electroneutrality which requires that the local concentrations of cation and anion be the same throughout the system. This condition is met by requiring that the local flux of the two ions be equal, that is. 

Nevertheless, the behaviour of oxide-containing melts as a kind of background for acid-base reactions can be described in a manner similar to the solvosystem concept. However, for this purpose the solvosystem concept should be generalized in some ways. As mentioned above, the main object in the basis of Franklin s solvosystem concept is a molecular solvent prone to auto-ionization, and this process results in the formation of small concentrations of cations and anions of the solvent. Water, glycol, different spirits and some other room-temperature liquids are to be mentioned as typical examples of such solvents. 

If the contributions of carbenium ions are discarded due to their low concentrations, the protolysis equilibria link the concentration of cations and anions CHQl =C/ +C, where... 

FIGURE 7.6 Cell model for the theoretical calculations of the DNA hybridization-induced ion-concentration redistribution as well as the average concentration of cations and anions in the intermolecu-lar spaces. Both the ssDNA and dsDNA have been modeled as negatively charged cylinders with a radius = 0.5 nm and = 1 nm, respectively, which form a hexagonal lattice with a cell radius of R the DNA molecules are arranged normal to surface of the FED with a center-to-center average separation distance of = 2R n r) is the ion concentration as a function of the coordinate r from the DNA axis and tiq is the bulk-ion concentration. 

In this equation mineral calcite is underlined as it is not part of the solution composition and does not participate in its electrostatic balance. Molal concentrations of cations and anions due to electric neutraHty of the solution are tied up by the equation... 

Figure 2.21 Concentration of cations and anions in diffusion layer of individual particle (a) and in capillary (b) where the surface charge obstructs migration of anions in the solution.

Besides, at pH > 11 is possible the formation of CaOH+. Due to this, in very alkaline medium the value drops below 1, and solubility of calcite again increases. Therefore, the equation derived above is applicable only at pH <11. The pH value, in its turn, depends on the balance of charges of the dissolved electrolytes. As the solutions are electrically neutral, molar concentrations of cations and anions are always tied up between themselves by the electric neutrality equation ... 

Fig. 12 Concentration of cations and anions at a dissolving pit surface as a function of the potential drop AUq within the electrolyte and the related product (c,pr [26].

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