Solution speciation in the aqueous Na(I)–EDTA and K(I)–EDTA systems

Abstract

. Speciation in the aqueous sodium(1) -ethylenediaminetetraacetic acid and potassium(1) -ethylenediaminetetraacetic acid equilibrium systems was investigated by automated gravimetric potentiometric titration. It was found that in both cases, particularly below neutral pH values, speciation includes a previously uncharacterized diprotonated complex. All formation and acid dissociation constants were measured for the full systems. The validity of previous literature equilibrium constants, which are based on incomplete equilibrium models, is discussed.MIN CHEN et R. STEPHEN REID. Can. J. Chem. 71, 763 (1993).Faisant appel 2 des titrages gravimetriques potentiomCtriques automatisCs, on a Ctudie la speciation des systemes aqueux a 1'Cquilibre des sels de sodium (ou de potassium) avec l'acide CthylknediaminetCtraacCtique. On a trouvC que, dans les deux cas, particulierement 2 des pH inferieurs i ceux de la neutralitk, la speciation inclut un complexe diprotone qui n'avait pas Ct6 caractCrisC anterieurement. On a mesure, pour tous les systemes, toutes les constantes de formation et de dissociation. On discute de la validit6 des constantes d'equilibre rapportees antkrieurement dans la 1ittCrature et basCes sur des modeles d'Cquilibre incomplets.[Traduit par la rCdaction]

Reaction Mechanisms of Ethylenediaminetetraacetic Acid and Diethanolamine in the Precursor Solution for Producing (K, Na)NbO3 Thin Films with Outstanding Piezoelectric Properties

“…This is because alkali metal cations do not have an extra orbital for accepting the lone pair electrons from either the oxygen or nitrogen in the functional groups of the chelating agents. This point has already been understood and claimed in the literature. − However, the oxidation states of potassium and sodium in this work are enhanced when EDTA and DEA are added into the KNN precursor solution whereby the binding energies for potassium and sodium in the KNN-E-D film are found shifted to a lower value as compared to KNN-W film, as shown in Figure a, b. Furthermore, the volatilization of potassium and sodium oxides is also effectively reduced in KNN-E-D as compared to KNN-W from the TG–MS analysis of our previous work .…”

Novel CDTA-based, Bifunctional Chelators for Stable and Inert MnII Complexation: Synthesis and Physicochemical Characterization

“…This may be attributed to the lower ligand basicity as the stability In the presence of 1.0 M Na I ions, the ligand forms a weak sodium complex in alkaline solution which leads to a reduced basicity (a similar decrease was reported for the protonation constants of several polyaminocarboxylate ligands such as EDTA, CDTA and DOTA). [45][46][47] Focusing solely on the data for the Mn II complexes, one observes that the thermodynamic stability decreases in the order 1,4-DO2A > CDTA > 4-HET-CDTA > EDTA, which is in perfect agreement with the Σ log Ki H values discussed in the previous section. Interestingly, the pMn value for [Mn(1,4-DO2A)] is significantly lower than those calculated for the Mn II complexes of EDTA, 4-HET-CDTA and CDTA.…”

“…This may be attributed to the lower ligand basicity as the stability constant of [Cu­(4-HET-CDTA)] 2– had to be determined in 1.0 M instead of 0.15 M NaCl (log K 1 H = 8.78(2), log K 2 H = 5.68(3), log K 3 H = 3.59(3), log K 4 H = 2.59(3), and log K 5 H 1.24(3) making Σ log K i H = 21.88 in 1.0 M NaCl and 25 °C). In the presence of 1.0 M Na I ions, the ligand forms a weak sodium complex in alkaline solution which leads to a reduced basicity (a similar decrease was reported for the protonation constants of several polyaminocarboxylate ligands such as EDTA, CDTA, and DOTA). − …”

Cadmium Complexation with Bisulfide

“…Accuracy of the value of Ksp obtained by the indirect solubility method that we used is strongly dependent on the accuracy of the stability constants for the complex of the strong ligand with H + , with the metal studied (Cd) and with the cations involved to adjust the ionic strength (e.g., Na) since these constants are all influential in the calculation of [Cd 2+ ]. The 4th acidity constant of EDTA (or the 5th acidity constant of DTPA) and the stability constants of EDTA (or DTPA) with monovalent cations such as Na + are not wellestablished because of experimental difficulties involved in their determination (20). In the present study, we adopted the set of constants for EDTA given in NIST (14; see Table A in Supporting Information) for the calculation of Ksp; using other consistent sets of EDTA constants would have given slightly different Ksp values.…”