Copper stability constant

The extinction coefficient at 20 C and normal pressures is shown which corresponds to the pink colored solutions of bivalent hexaquo cobalt complexes. At 300 C and the relatively modest pressure of 350 bar, the adsorption is considerably increased and shifted to greater wavelengths. The solutions are blue, tetrahedral four-ligand cobalt complexes prevail. This tendency is even more pronounced at 500 C. In equilibrium, such compressed supercritical solutions contain the bivalent metal ions mainly as complexes with the lower coordination number of four. Analogous behavior has been found for nickel and copper. Stability constants have been determined, which may be useful in the discussion of corrosion products in supercritical steam and of the composition of hydrothermal fluids. 

Table 8-4. Stability constant data for copper(ii) and nickel(ii) ammine complexes.

Mapsi et al. [16] reported the use of a potentiometric method for the determination of the stability constants of miconazole complexes with iron(II), iron(III), cobalt(II), nickel(II), copper(II), and zinc(II) ions. The interaction of miconazole with the ions was determined potentiometrically in methanol-water (90 10) at an ionic force of 0.16 and at 20 °C. The coordination number of iron, cobalt, and nickel was 6 copper and zinc show a coordination number of 4. The values of the respected log jSn of these complexes were calculated by an improved Scatchard (1949) method and they are in agreement with the Irving-Williams (1953) series of Fe2+ < Co2+ < Ni2 < Cu2+ < Zn2+. 

Copper may exist in particulate, colloidal, and dissolved forms in seawater. In the absence of organic ligands, or particulate and colloidal species, carbonate and hydroxide complexes account for more than 98% of the inorganic copper in seawater [285,286]. The Cu2+ concentration can be calculated if pH, ionic strength, and the necessary stability constants are known [215,265-267]. In most natural systems, the presence of organic materials and sorptive surfaces... 

Ruzic [278 ] considered the theoretical aspects of the direct titration of copper in seawaters and the information this technique provides regarding copper speciation. The method is based on a graph of the ratio between the free and bound metal concentration versus the free metal concentration. The application of this method, which is based on a 1 1 complex formation model, is discussed with respect to trace metal speciation in natural waters. Procedures for interpretation of experimental results are proposed for those cases in which two types of complexes with different conditional stability constants are formed, or om which the metal is adsorbed on colloidal particles. The advantages of the method in comparison with earlier methods are presented theoretically and illustrated with some experiments on copper (II) in seawater. The limitations of the method are also discussed. 

Playle, R.C., D.G. Dixon, and K. Bumison. 1993b. Copper and cadmium binding to fish gills estimates of metal-gill stability constants and modelling of metal accumulation. Canad. Jour. Fish Aquat. Sci. 50 2678-2687. 

Figure 4. Copper complexation by a pond fulvic acid at pH 8 as a function of the logarithm of [Cu2+]. On the x-axis, complex stability constants and kinetic formation rate constants are given by assuming that the Eigen-Wilkens mechanism is valid at all [M]b/[L]t. The shaded zone represents the range of concentrations that are most often found in natural waters. The + represent experimental data for the complexation of Cu by a soil-derived fulvic acid at various metakligand ratios. An average line, based on equations (26) and (30) is employed to fit the experimental data. Data are from Shuman et al. [2,184]...

Metal-complex stability is also related to the basic strength of the ligand entity. For a series of 1 2 complexes of the bidentate naphthylazophenol ligand (5.64) with copper(II) ion, the acidic dissociation constants (pKa) are linearly related to the stability constants (log K1 2), the more acidic groups forming the less stable complexes. Thus where X = N02 in structure 5.64 then pKa = 8.1 and log K1 2 = 17.2, and where X = OCH3 then pKa = 8.5... 

In a similar investigation of the tautomeric tridentate ligand 2 -hydroxyphenylazo-2-naphthol (5.65 in Scheme 5.17), the first and second acidic dissociation constants (pKa) related to the two hydroxy groups in the parent structure (X = H) were found to be 11.0 and 13.75 respectively. On introduction of an electron-withdrawing substituent (X) the first dissociation constant decreased from 11.0 to 10.55 (X = Cl) or 7.67 (X = N02). The stability constants (log K1 1) of the derived 1 1 complexes were dependent on the metal ion introduced [46], being particularly high for nickel(n) at 19.6 and copper(II) at 23.3. 

The presence of residual unbound transition-metal ions on a dyed substrate is a potential health hazard. Various eco standards quote maximum permissible residual metal levels. These values are a measure of the amount of free metal ions extracted by a perspiration solution [53]. Histidine (5.67) is an essential amino acid that is naturally present as a component of perspiration. It is recognised to play a part in the desorption of metal-complex dyes in perspiration fastness problems and in the fading of such chromogens by the combined effects of perspiration and sunlight. The absorption of histidine by cellophane film from aqueous solution was measured as a function of time of immersion at various pH values. On addition of histidine to an aqueous solution of a copper-complex azo reactive dye, copper-histidine coordination bonds were formed and the stability constants of the species present were determined [54]. Variations of absorption spectra with pH that accompanied coordination of histidine with copper-complex azo dyes in solution were attributable to replacement of the dihydroxyazo dye molecule by the histidine ligand [55]. 

Ion-selective electrodes have been used to determine the stability constants for the complexation of copper II ions with soil fulvic acids [4], Two classes of binding sites were found with conditional stability constants of about 1 xf 06 and 8xl03. 

Van den Berg, C. M. G., and J. R. Kramer (1979), "Conditional Stability Constants for Copper Ions with Ligands in Natural Waters", in E. Jenne, Ed., On Chemical Modeling Speciation, Sorption, Solubility and Kinetics in Aqueous Systems, ACS Symp. Series. 

Tfie electroless deposition of copper is usually done in solutions containing EDTA as a complexing agent. Tfie stability constant for the CuEDTA complex is... 

Trihydroxyglutaric acid forms a 1 1 complex with chromium(iii) which has a stability constant of 0.9 x 10. In the presence of copper(n) a mixed complex is formed and dark bluish-green crystals of Na3[CuCrCioH70i4],5H20 have been isolated. The substituted benzoic acid complexes (60) have been prepared by heating a mixture of CrCL,6H20 and RCgH4C02H in Pr OH. The... 

The stability constants of yttrium tartrates have been determined and a mixed copper-yttrium tartaric (T) acid species, Y2CuT3H q unknown), was detected. ... 

TABLE 8.2. Stability Constants (log fS and piTa Values)" of Neomycin B in 1 1 Complex Formation with Copper Ion... 

Much more pronounced is the macrocyclic or [l]-cryptate effect found in 10 as compared with 2 the stability constant for K+ complexation increases by about 104 (in methanol) on ring formation. A similar increase has been observed between copper-(II) complexes of acyclic and macro-cyclic tetra-aza ligands (139). 

Correlation of Potentials to Copper(ll) Complex Stability Constants... 

Tab.4 Correlation of Cu(ll/I) redox potentials and stability constants of copper complexes in aqueous solution at 25 °C, jx = 0.1...

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