Formation constant determination

Speciation of Pb(II) in Glatt river. The concentrations given for CO2, Pb(II), Cu(II) and [Ca2+] as well as for the pollutants EDTA and NTA are representative of concentrations encountered in this river, The speciation is calculated from the surface complex formation constants determined with the particles of the river and the stability constants of the hydroxo-, carbonate-, NTA- and EDTA-complexes.The presence of [Ca2+] and [Cu2+] is considered. 

Enthalpies of activation are comparable but entropies differ. The maximum number of ligands is two, and the formation constants determined (equation 10) were /Jj = 1013 and / 2 = 10. 136... 

Unlike V(II), both the V(III) and V(IV) oxidation states are stable in water. However, neither the V(III) nor the V(IV) oxidation states are easily maintained in the presence of oxygen if the pH is neutral or above, although, under acidic conditions, both these states are rather easily maintained. Somewhat surprisingly, the V(IV) species is more readily oxidized by 02 than is the V(III) species. In aqueous acidic solution, the vanadium(III) ion exists as a hexaqua octahedral complex that can deprotonate to form the 2+ and 1+ species, dependent on pH. Additionally, di, tri and tetra polymeric forms are known. Structures have been proposed and their formation constants determined [10], The occurrence of the various polymeric forms in the presence of sulfate has also been described and is particularly relevant to concentration of vanadium by bioaccumulators [10],... 

HBPHA, a chelating agent and the donors TBP and TOPO were found58 to associate forming 1 1 adducts and the adduct formation constants, determined in several diluents,... 

The calculation results are shown in table II. We also report formation constants determined from spectrophotometry for Ho and Nd, and by solvent extraction for Er. Without going into detail for these two methods, it may be noted that the results show fair agreement. That fact points out the inner sphere character of orthophenanthrolinium lanthanous complexes. The main absorption band of Am (III] is modified by the presence of orthophenanthroline. We used these spectral variations to calculate the formation constants of Am (III], as described in the previous paragraph. As for azide complexes, we observed that Am monoorthophe-nanthroline is more stable than the equivalent lanthanide complex, and for the bis orthophenanthroline species, the difference... 

Table 3.15 Results Summary for Formation Constant Determination ...

Studies of complexes of iodine with imidazoles have demonstrated that the 1 1 charge transfer complexes are of the n-a type with donation of the electron pair from N-3. Formation constants determined for the complexes with 1-methylimidazole, methimazole, and clotrimazole indicate strong donor-receptor interaction, implying an expected effect on thyroid metabolism of these imidazoles <83BSB923, 86H(24)1955>. 

Nici Nicij were assumed to be nearly constant with increasing MCI concentration, and were included in the reported formation constants (see discussion on [89BJE]). The method used by the author is more appropriate to the study of weak complex formation than the constant ionic medium principle if very high and varying concentrations of a complex-forming anion is used, (see discussion on [89BJE]). Nevertheless, the formation constants determined in this way are not compatible with the log P° values extracted from the SIT analysis... 

The formation constants determined so far for representative neutral ionophores and the primary ions are listed in Table 7.2. Also, Table 7.4 lists the formation constants for both primary and interfering ions and reveals the very high complexation selectivity of the ionophores. 

TABLE 12.7 Comparison of Cadogan-Pnmell (C/P) and Martire-RiedI (M/R) Methods of Complex Formation Constant Determination... 

The protonation constants of ligand 24 and 25 were determined by Arena and coll. [34], who reevaluated the literature pKa values of compound 24 [35] because they were not in agreement with solid state evidences [33]. Only two titrable protons were found in the pH region 2.5-11.0 and the proton formation constants determined (Log K = 3.34 and 11.5) rule out the existence of a "super acidic proton" (pKa < 1) for compound 24 [35]. However, this proton is much more acidic (5.3 log units) than the monomeric... 

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