Interstitial ions concentration

Holdren, G.C., Armstrong, D.E., 1986. Interstitial ion concentrations as an indicator of phosphorus release and mineral formation in lake sediments. In Sly, P.G. (Ed.). Sediments and Water Interactions. Springer, New York. pp. 1.3.3-147. 

The concentration of the solution within the glass bulb is fixed, and hence on the inner side of the bulb an equilibrium condition leading to a constant potential is established. On the outside of the bulb, the potential developed will be dependent upon the hydrogen ion concentration of the solution in which the bulb is immersed. Within the layer of dry glass which exists between the inner and outer hydrated layers, the conductivity is due to the interstitial migration of sodium ions within the silicate lattice. For a detailed account of the theory of the glass electrode a textbook of electrochemistry should be consulted. 

Pai Vemeker and Kannan [1273] observe that data for the decomposition of BaN6 single crystals fit the Avrami—Erofe ev equation [eqn. (6), n = 3] for 0.05 < a < 0.90. Arrhenius plots (393—463 K) showed a discontinuous rise in E value from 96 to 154 kJ mole-1 at a temperature that varied with type and concentration of dopant present Na+ and CO2-impurities increased the transition temperature and sensitized the rate, whereas Al3+ caused the opposite effects. It is concluded, on the basis of these and other observations, that the rate-determining step in BaN6 decomposition is diffusion of Ba2+ interstitial ions rather than a process involving electron transfer. 

Fig. 3 -13. (a) A ion levels at the surface and in the interior of ionic compound AB, and (b) concentration profile of lattice defects in a surface space charge layer since the energy scales of occupied and vacant ion levels are opposite to each other, ion vacancies accumulate and interstitial ions deplete in the space charge layer giving excess A ions on the surface. 

A simple yet valuable starting point for treating ionic conductivity, tr, is as the product of the concentration, C(, of mobile species (interstitial ions or vacancies), their charge, q and their mobility, u, ... 

Intrinsic Frenkel disorder, in which some of the oxygens are displaced into normally unoccupied sites, is responsible for the oxide ion conduction in, for example, Zr2Gd207, Fig. 2.11. The interstitial oxygen concentration is rather low, however, and is responsible for the low value of the preexponential factor and for the rather low (by -Bi203 standards ) conductivity. 

As mentioned earlier, in zinc oxide there exists a certain concentration of interstitial zinc in excess of stoichiometry as a result of equilibrium (1) and a corresponding concentration of free conduction electrons according to equilibrium (2). If now a cation of higher valency than 2, such as Ga + is dissolved in the zinc oxide lattice and takes the place of a Zn + ion in regular lattice position, electrical neutrality can be maintained if a Zni+ interstitial ion disappears while a free electron remains in the lattice. Thus solution of a trivalent oxide in zinc oxide decreases the concentration of interstitial excess zinc but increases the concentration of free electrons. This was verified by Wagner (27) for solutions of Ga2O3 in ZnO and by... 

The relationship between the intrinsic diffusivity, D, of charged interstitial ions in an ionic solid and the ionic electrical conductivity, p, due to the motion of these ions in the absence of a significant concentration gradient is given by Eq. 3.50 that is,... 

There are two types of lattice defects that occur in all real crystals and at very high concentration in irradiated crystals. These are known as point defects and line defects. Point defects occur as the result of displacements of atoms from their normal lattice sites. The displaced atoms usually occupy sites that are not in the lattice framework they are then known as interstitials. The empty lattice site left behind by the interstitial is called a vacancy. Avacancy produced by displacement of an anion or cation, along with its interstitial ion, is called a Frenkel pair, or simply a... 

Furosemide (frusemide) produces a rapid decrease in the plasma and blood volumes and a concomitant increase in the total protein concentration. This effect is maximal about 30 min after its i.v. administration but is attenuated, in part, over the next few hours by fluid shifts into the vascular compartment from the intestinal tract and intracellular and interstitial fluid spaces (Hinchcliff Mitten 1993). The changes in the plasma and blood volumes are accompanied by decreases in the plasma concentrations of potassium, chloride, calcium and hydrogen ions (a mild metabolic alkalosis is produced). In contrast, the sodium ion concentration remains essentially unchanged (Hinchcliff Mitten 1993). These electrolyte changes can be exacerbated and a mild decrease in the sodium ion concentration may also be observed if horses are allowed to replace water losses by drinking. 

The parameters in these equations are as follows x> a> P, and n are the oxidation state of the cation in the barrier layer the polarizability of the film/solution interface (i.e., the dependence of the potential drop across the film/solution interface on the applied voltage) the dependence of the potential drop across the film/solution interface on the pH and the kinetic order of the film dissolution reaction with respect to hydrogen ion concentration, respectively. Note that, in deriving Eqs (12) and (13), the oxidation state of the cation in the barrier layer (x) is set equal to the oxidation state of the same cation in the solution/outer layer. The standard rate constants, k , and a, correspond to the reaction shown in Fig. 4, e is the electric field strength, Y = F/RT, and K = sy. The three terms on the right side of Eq. (12) arise from the transmission of cation interstitials, the transmission of cation vacancies, and the transmission of oxygen vacancies (or dissolution of the film), respectively. Values for these parameters are readily obtained by optimizing the PDM on... 

Extracellularly, calcium ions circulate in the blood plasma and interstitial fluid (Sect. 3.3.1). In blood plasma, calcium ions are chelated to albumin and citrate. Albumin (mol. wt. 66,700 kDa) is present at 50-60 mg/mL in plasma, corresponding to 0.9 m mol/L. Although plasma albumin has many different sites that can chelate calcium ions in vitro, only one site binds to calcium ions at physiological albumin concentrations and pH. Thus, albumin binds 0.9 mmol/L of free plasma Ca2+. In addition, citrate (Fig. 10.7), a tricarboxylic acid that the liver secretes into plasma, chelates a free calcium ion to two of its three carboxyl groups, replacing two Na+ ions. Citrate has a molar concentration of 0.08 mM in venous blood and therefore binds to an equivalent concentration of free calcium. Because the total calcium ion concentration of venous blood is 1.14 mmol/L (range 0.2), and the free calcium ion concentration is 0.1 mM, it appears that 0.15 mM of the plasma calcium ion concentration is bound to other plasma components. 

Bean et al. [18] considered that mobile interstitial ions are created within the film when the metal ions move out of their normal sites, leaving vacancies. The creation of mobile ions is a field-dependent process, so a fixed concentration of interstitial ions exists at characteristic field strength. This kind of transport occurs frequently in amorphous oxides. 

The variable c/ introduced in Eq. (7.29) and now appearing in Eq. (7.34) represents the total concentration of the diffusing ions in the crystal. For example, in calcia-stabilized zirconia which is an oxygen ion conductor, qon is the total number of oxygen ions in the crystal and not the total number of defects (see Worked Example 7.4). On the other hand, in a solid in which the diffusion or conductivity occurs by an interstitial mechanism, cjon represents the total number of interstitial ions in the crystal, which is identical to the number of defects. 

Oncotic pressure (or colloid osmotic pressure) is the osmotic pressure that results from the difference between the protein (mainly albumin) concentrations of plasma and the interstitial fluid. Water is lost from the body via feces, urine, salivation, insensible respiration, and through the skin, with sensible perspiration of sweat occurring in a few species. Although the movement of proteins between spaces is restricted, water and small ions can move across permeable membranes between the spaces. The volume of ECF is highly dependent on its sodium concentration and, under physiological conditions, the sodium ion concentrations of plasma and interstitial fluids are similar. 

Owing to the very high activation energy needed to move electrons or positive holes from one ion to another, semiconductors when in the stoichiometric condition have the low conductivity of insulators. The conductivity can, however, be increased by the addition of an excess of either the cationic or anionic constituent, which introduces lattice defects either as interstitial ions or as lattice vacancies. The introduction of foreign altervalent ions also increases or decreases the concentration of the lattice defects. Thus the introduction of 2-mol.% LiaO, in the presence of air, into NiO increases the conductivity about 10,000-fold 21). 

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