INDEX stability constants

Other important properties for photovoltaic materials are their refractive index, stability, brittleness, toxicity, crystal lattice constant, thermal expansion coefficient, temperatures required for processing into cells, energy investment for cell production, ability to be doped both types, level of technological knowledge and industrial maturity, cost, and abundance. Issues particular to passivation and the trapping of weakly absorbed light include the availability of compatible and affordable passivation and surface texturing methods. ... 

Note The more common rock-forming minerals are italicized (cf. Deer et ai. 1992). Single pATjp values are presumably for well-crystallized, least soluble forms. Where p/T p ranges are given, they reflect the solubility range between relatively amorphous and well-crystallized forms, values have been computed assuming specific solution speciation models (e.g., specific complexes and complex stability constants), which must also be used when these constants are employed in mineral saturation index calculations. 

The stability constant is probably the most important quantitative parameter for the characterization of a metal-ligand complex in that it provides a numerical index of the affinity of the metal cation for the ligand and allows the development of quantitative models able to predict the speciation of metal ions in the system studied. Several different theoretical and experimental approaches have been attempted for the determination of stability constants of metal—HS complexes and modeling metal-HS complexation reactions. Data analysis and interpretation is, however, still controversial, due to the intrinsically complex and ill-defined nature of HSs. The multiligand, polyelectrolitic nature of HS macromolecules results in the inability to describe quantitatively the types, concentrations, and strengths of the several nonidentical binding sites in HSs and in the impossibihty to ascertain and measure the stoichiometry of metal-HS complexation (MacCarthy and Perdue, 1991). 

The lUPAC has not explicitly defined the symbols and terminology for equilibrium constants of reactions in aqueous solution. The NBA has therefore adopted the conventions that have been used in the work Stability Constants of Metal ion Complexes by Sillen and Martell [64SIL/MAR], [71S1L/MAR]. An outline is given in the paragraphs below. Note that, for some simple reactions, there may be different correct ways to index an equilibrium constant. It may sometimes be preferable to indicate the number of the reaction to which the data refer, especially in cases where several ligands are discussed that might be confused. For example, for the equilibrium ... 

Raos, N. (2002) Suitability of the topological index for estimation of the stability constants of coordination compounds. Croat. Chem. Acta, 75, 117-120. 

In practice, answers to questions about the extent to which given minerals influence the chemistry of specified ground waters require expert judgment. In addition to the simple test of mineral presence or absence used in the prototype saturation index module, a realistic evaluation would include such criteria as reaction rates, stability relative to other minerals of the same or closely similar composition, uncertainty in mineral stability constants due to compositional variation, temperature and its effect on... 

Thus, any complex compound has several stepwise stability constants and only one overall. Stepwise stability constants characterize the complex formation on the account of joining only one ligand. For this reason index a in them defines both the sequential number of elementary reactions and the number of ligands in its product. Overall stability constants characterize the formation of any complex compoxmd directly from dissociated ions, and index a in them defines their number. In order to distinguish overall constants from the stepwise ones they are often denoted by the symbol Overall and stepwise constants are associated between themselves by equations... 

Table 11.2 Stability constants (logarithmic) of some complexing agents (in water at 20°C) (saturated constants reported as log P). The ratio is given as a pre-index thus manganese forms a 2 1 complex with bipyridyl (log = 6), reported as 6 whereas it forms only a 1 1 complex with EDTA (log = 13), reported as 13... 

More quantitative data can be obtained either from reference books or from computerized databanks. Let us deal first with the books. A selection of ionization constants is given in Albert and Serjeant (1984). Exhaustive compilations of ionization constants are listed on p. 383. Recently determined values may be located through Chemical Abstracts through the entry Ionization in Liquids in the General Subject Index, or under the name of the particular substance in the Chemical Substance Index. For the prediction of ionization constants from the chemical structure, see Perrin, Dempsey and Serjeant (1981). The standard compilations of the stability constants of chelated metals are given at the end of Section 11.3 (p. 459). 

The lUPAC Stability Constants Database (SC-Database) provides an electronic source of stablity constants the database is kept up to date through regular upgrades (http //www.acadsoft.co.uk/index.htm]). 

Solubilities of sulfides in pure water are very low, but they increase significantly in saline and H2S-bearing aqueous solutions. This is due to the stable existence of complexes such as chloro- and thio-complexes. The solubilities of sulfides strongly depend on stability constants of these complexes. Sulfides precipitate when saturation index (S.I.) (S.I. is defined as S.l. = log(I.A.P/Ksp, where I.A.P is activity product and K p is solubility product.) exceeds zero during the flow of ore fluids accompanied by the changes in physico-chemical variables (e.g., decrease of temperature). As an example, precipitation of PbS is considered below. Ionic activity product for PbS (I.A.P) is expressed as... 

Table 243 Decrease in the successive stability constants with the index n examples of octahedral complexes...

For ligands forming complexes with 1 1 stoichiometry, the redox potential depends upon the ratio of the stability constants of the Mt L and Mt L complexes and respectively the lower case index 1 , indicating... 

Large range of service temperatures Constant viscosity (viscosity index) Pour point, thermal stability... 

The Michaelis constant (fCM) is an index of the stability of an enzyme-substrate complex. Does a high Michaelis constant indicate a stable or an unstable enzyme-substrate complex Explain your reasoning. 

As thermodynamic stability indexes for the hydrocarbon ions, pA R+ and pA a values [(4) and (5)] have been widely applied for the carbocation and carbanion, respectively, in solution. Here K + stands for the equilibrium constant for the reaction (6) of a carbocation and a water molecule stands for the equilibrium constant for the reaction (7) of a hydrocarbon with a water molecule to give the conjugate carbanion. The equilibrium constants are given by (8) and (9) for dilute aqueous solutions. Obviously, the reference system for the pKn+ scale is the corresponding alcohol, and... 

As a measure of their thermodynamic stability, the pAfR+ values for the carbocation salts were determined spectrophotometrically in a buffer solution prepared in aqueous solution of acetonitrile. The KR+ scale is defined by the equilibrium constant for the reaction of a carbocation with water molecule (/CR+ = [R0H][H30+]/[R+]). Therefore, the larger p/CR+ index indicates higher stability for the carbocation. However, the neutralization of these cations was not completely reversible. This is attributable to instability of the neutralized products. The instability of the neutralized products should arise from production of unstable polyolefinic substructure by attack of the base at the aromatic core. 

Effective Hamaker constant, 234 Emulsifying activity index, 186,188/ Emulsions, concentrated oil-in-water, effea of interdroplet forces on centrifugal stability, 229-245 Enhancers of taste. See Taste enhancers Enzymatic modification of soy proteins, 181-190... 

The investigation of viscosities, electrical conductivities, refractive indexes and densities of binary liquid systems of sulphuric acid with nitromethane, nitrobenzene and 0-, m and p-nitrotoluene was made in order to obtain a clearer picture of the behaviour of these binary mixtures, regarding the stability of the addition compounds formed between the components. The application of these methods of physicochemical analysis to a number of binary systems with sulphuric acid [1, 2, 3] has enabled us to get some idea of the way in which the formation and stability of addition compounds affects the liquid phase properties of these systems. The binary systems of sulphuric acid with mononitrocompounds are particularly suitable for comparison with each other, because of the close similarity of the liquid media in these systems, due to comparable values of dielectric constants and liquid phase properties of the mononitrocompounds. The stability of the addition compounds in these systems in the crystalline phase [4] has... 

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