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1.
Farrokh Gharib Ali Shamel Sahar Mohajeri 《Russian Journal of Inorganic Chemistry》2010,55(10):1651-1656
The dependence on ionic strength of protonation of nitrilotriacetic acid and its complexation with W(VI) is reported in sodium
perchlorate, sodium nitrate and sodium chloride solutions as background salts. The measurements have been performed at 25°C
and various ionic strengths in the range 0.1–1.0 mol dm−3, using a combination of potentiometric and spectrophotometric techniques. The overall analysis of the present and the previous
data dealing with the determination of stability constants at different ionic strengths allowed us to obtain a general equation,
by which a formation constant determined at a fixed ionic strength can be calculated, with a good approximation, at another
ionic strength, if 0.1 ≤ ionic strength ≤ 1.0 mol dm−3 sodium perchlorate, sodium nitrate or sodium chloride. 相似文献
2.
B. Mohammadi J. Mohammadi 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(10):1627-1631
By using spectrophotometric and potentiometric techniques, the formation constants of the species formed in the systems H++W(VI) + ethylenediaminediacetic acid and H+ + ethylenediaminediacetic acid were determined in aqueous solutions of propanol at 25°C and a constant ionic strength of
0.1 mol dm−3 sodium perchlorate. The composition of the complex was determined by the continuous variation method. It was shown that tungsten(VI)
formed a mononuclear 1: 1 complex with ethylenediaminediacetic acid of the type WO3L3− at −log[H+] = 5.8. The formation constants in various media were analyzed in terms of the Kamlet-Taft parameters. Solvents were parameterized
by dipolarity/polarizability scales π*, hydrogen-bond donor (HBD) strength α, and hydrogen-bond acceptor strength β. Linear
dependences (LSERs) on these solvent parameters were used to correlate and predict a wide variety of solvent effects and provide
an analysis of them. Linear relationships were observed when log KS values were plotted versus π*. Finally, the results are discussed in terms of the effect of solvents on complex formation.
The article is published in the original. 相似文献
3.
《Physics and Chemistry of Liquids》2012,50(3):257-268
The formation constants of species formed in the systems H+?+?W(VI)?+?nitrilotriacetic acid (NTA) and H+?+?NTA have been determined in aqueous solution for pH?=?4–9 at 25°C and different ionic strengths ranging from 0.1 to 1.0?mol?dm?3 NaClO4, using potentiometric and spectrophotometric techniques. It was shown that tungsten(VI) forms a mononuclear 1?:?1 complex with NTA of the type WO3L3? at pH?=?7.5. The composition of the complex was determined by the continuous variations method. The complexation of molybdenum(VI) with glutamic acid was investigated in aqueous solution ranging in pH from 4 to 9, using polarimetric, potentiometric and spectrophotometric techniques. The composition of the complex was determined by the continuous variations method. It was shown that molybdenum(VI) forms a mononuclear 1?:?1 complex with glutamic acid of the type MoO3L2? at pH?=?6.0. The dissociation constants of glutamic acid and the stability constants of the complex were determined at 25°C and at ionic strengths ranging from 0.1 to 1.0?mol?dm?3 sodium perchlorate. In both complex formation reactions the dependence of the dissociation and stability constants on ionic strength is described by a Debye-Huckel type equation. Finally, a comparison has been made between the patterns of ionic strength dependence for the two complexes and the results have been compared with data previously reported. 相似文献
4.
Kavosh Majlesi Mohammadreza Gholamhosseinzadeh Saghar Rezaienejad 《Journal of solution chemistry》2010,39(5):665-679
The main aim of this research is to study the complexation of molybdenum(VI) with methyliminodiacetic acid in NaClO4 aqueous solutions at pH = 6.00 and ionic strengths (0.1<I/mol⋅dm−3<1.0) at 25 °C by using potentiometric and UV spectrophotometric measurements in order to obtain thermodynamic stability constants
at I=0 mol⋅dm−3. A comparison with previous literature data was made for the stability constants, though few data were available. The stability
constants data have been analyzed and interpreted by using extended Debye-Hückel theory, specific ion interaction theory and
parabolic model. Finally it might be concluded that parabolic model applies better for this complexation reaction. 相似文献
5.
Kavosh Majlesi Karim Zare Saghar Rezaienejad Fatemeh Nemati 《Russian Journal of Inorganic Chemistry》2009,54(5):803-807
Equilibrium of the reaction of tungsten(VI) with ethylenediaminediacetic acid (EDDA) has been investigated in aqueous solution
of pH 7.5 and 25°C. All measurements have been carried out at different ionic strengths ranging from (0.1 to 1.0) mol dm−3 (NaClO4). According to our results the metal to ligand ratio is 1: 1. Stability constants and stoichiometry of the complex have been
determined from a combination of potentiometric and UV spectroscopic measurements. In this semi-empirical model, two parameters
have been introduced in a Debye-Huckel type equation based on the Gauss—Newton nonlinear least-squares method and minimizing
the sum of the squares of the errors. Comparison of the ionic strength effect on these complex formation reactions has been
made using a Debye-Huckel type equation and Bronsted—Guggenheim—Scatchard specific ion interaction theory (SIT).
Published in Russian in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 5, pp. 864–868.
The article is published in the original 相似文献
6.
Clemente Bretti Concetta De Stefano Claudia Foti Ottavia Giuffrè Silvio Sammartano 《Journal of solution chemistry》2009,38(10):1225-1245
Protonation constants of one thiocarboxylate (thioacetate) and four sulfur-containing carboxylates (2-methylthioacetate, thiolactate,
thiomalate, 3-mercaptopropionate) were determined by potentiometric measurements in a wide ionic strength range [0≤I≤5 mol⋅L−1 in NaCl and 0 ≤I≤3 mol⋅L−1 in (CH3)4NCl] at t=25 °C. For two of these ligands (2-methylthioacetate and thiolactate), the protonation enthalpies were also determined by
calorimetric measurements in NaCl ionic medium [0 ≤I≤5 mol⋅L−1] at t=25 °C. Individual UV spectra of the protonated and unprotonated 3-mercaptopropionate species, together with values of the
protonation constants, were obtained by spectrophotometric titrations. Results were analyzed in terms of their dependence
on the ionic medium by using different thermodynamic models [Debye-Hückel type, SIT (Specific ion Interaction Theory) and
Pitzer’s equations]. Differences among protonation constants obtained in different media were also interpreted in terms of
weak complex formation. 相似文献
7.
The stability of molybdenum(VI) complex formed by iminodiacetic acid(IDA) has been studied at 25°C, pH = 6.0, and different
ionic strengths ranging from (0.3 to 1.0) mol dm−3 of sodium perchlorate. A combination of potentiometric and spectrophotometric techniques have been used based on the continuous
variations method. According to our investigations, the metal-to-ligand ratio is 1: 1. The Solver, Microsoft Excel 2000 powerful
optimization package, has been used to perform non-linear least-squares curve fitting. In order to obtain better consistency
between the experimental and calculated results, two empirical parameters have been introduced in a Debye-Huckel-type equation.
This equation enables us to calculate the values of stability constants in the desired range of ionic strength.
This article was submitted by the authors in English 相似文献
8.
The stability constants of complexes of dioxovanadium (V) ion and L-asparrtic acid were determined potentiometrically at various
ionic strengths of I = 0.1, 0.3, 0.5, and 0.7 mol. dm−3 at 25°C. A sodium chloride solution was used to maintain the ionic strength. The parameters based on these formation constants
were calculated and the dependence of protonation and the stability constants on ionic strength are described by a Debye-Huckel
type equation. 相似文献
9.
Ahmed A. El-Sherif 《Journal of solution chemistry》2012,41(3):392-409
The interaction of trimethyltin(IV) (TMT) with imino-bis(methylphosphonic acid) (IDP), abbreviated as H4L, was investigated at 25 °C and at ionic strength 0.1 mol⋅dm−3 (NaNO3) using a potentiometric technique. The formation constants of the complexes formed in solution were calculated using the
nonlinear least-squares program MINIQUAD-75. The stoichiometry and stability constants are reported for the complexes formed.
The results show the formation of 110, 111, 112 and 11-1 complexes for the TMT–IDP system. The concentration distribution
of the various complex species was evaluated. The effect of dioxane as a solvent, on both the protonation constants and the
formation constants of trimethyltin(IV) complexes with IDP, is discussed. The thermodynamic parameters ΔH
∘ and ΔS
∘ calculated from the temperature dependence of the equilibrium constants were evaluated. The effect of ionic strength on the
protonation constants of IDP is also discussed. 相似文献
10.
Clemente Bretti Concetta De Stefano Claudia Foti Silvio Sammartano 《Journal of solution chemistry》2006,35(9):1227-1244
The protonation constants of phthalate were determined in aqueous NaCl (0.1 ≤ I ≤ 5,mol⋅L−1) and in aqueous Me4NCl (0.1 mol⋅L−1 ≤ I ≤ 3,mol⋅L−1) at t = 25,∘C. Experimental data were employed in conjunction with literature data from studies in different ionic media (Et4NI: 0 ≤ I ≤ 1,mol⋅L−1; NaClO4: 0.05 mol⋅L−1 ≤ I ≤ 2,mol⋅L−1)to study the dependence on ionic strength using different models, such as the SIT and Pitzer equations, and an Extended Debye-Hückel type equation. Experimental calorimetric data in NaCl and protonation constants at different temperatures in Et4NI (5 ≤ t ≤ 45∘C) and in NaClO4 (15 ≤ t ≤ 35 ∘C) were also used to study their dependence on temperature. Recommended equilibrium data are reported together with a short discussion of a prospective protocol for drawing these data. 相似文献
11.
A new ternary ion-association complex of tungsten(VI), 4-nitrocatechol (NC), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide (Thiazolyl Blue, MTT) was obtained and studied using an extraction-spectrophotometric method. The optimum pH, reagent
concentrations, and extraction time were determined. The composition of the complex was found to be W(VI): NC: MTT = 1: 2:
2. The extraction process was investigated quantitatively and the key constants were calculated. The molar absorptivity of
the chloroform extract at λmax = 415 nm was 2.8 × 104 dm3 mol−1 cm−1, and the Beer’s law was obeyed up to 8.8 μg cm−3 tungsten(IV). The limit of detection and limit of quantification were calculated to be 0.27 μg cm−3 and 0.92 μg cm−3, respectively. The effect of foreign ions and reagents was studied and a competitive method for determination of tungsten
in products from ferrous metallurgy was developed. The residual standard deviation and the relative error were 0.53 % and
0.2 %, respectively. 相似文献
12.
Complexation constants of the Al3+/F− system were determined at different ionic strengths in a NaClO4 (1.0, 2.0 and 3.0 mol⋅dm−3) ionic medium by means of a potentiometry using two electrode systems: an ion fluoride selective electrode as well as a glass
electrode. All the experimentation was performed at 25 °C. The main species in the complexation equilibria were determined
as AlF2+, AlF2+, AlF30, AlF4−, AlF52− and AlF63−. The differences found in the complexation constants for the ionic strength considered were explained by the different behavior
of the interaction parameters for the AlF
n
3−n
species. These parameters were calculated using the Modified Bromley’s Methodology (MBM). The corresponding thermodynamic
quantities were also determined. From all the results obtained, it can be concluded that pH, fluoride concentration and ionic
strength influenced the distribution of the fluoride-aluminium complexes. 相似文献
13.
Reactions of carbonate radical (Co3
−) generated by photolysis or by radiolysis of a carbonate solution, with Cu(II) complexes of aminopolycarboxylic acids viz.,
Cu(II)ethylenediamine tetraacetate [CuIIEDTA]2− and Cu(II)-iminodiacetate [CuIIIDA] were studied at pH 10. 5 and ionic strength 0.2 mol·dm−3. Time-resolved spectroscopy and kinetics for the transients were studied using flash photolysis and stable products arising
from the ligand degradation of the complex were ascertained by steady-state radiolysis experiments. From the kinetic data
it is observed that CO3
−, radical reacts initially with CuII-complex to form a transient intermediate having maximum absorption at 335 nm and 430 nm. From the subsequent reactions of
this intermediate it was assigned to be CuIII. species. This Cu(III) species undergoes intermolecular electron transfer with the CuII-complex to give a radical intermediate which again slowly reacts with CuII-complex to give a long lived species containing Cu−C bond. This long lived species, however, slowly decomposed to give glyoxalic
reaction between CuIII-complex and a suitable donor, the one electron reduction potential for [CuIIIEDTA]1−/[CuIIEDTA]2− and [CuIIIIDA]+1/CuIIIDA was determined. 相似文献
14.
J. M. Berg D. K. Veirs R. B. Vaughn M. A. Cisneros C. A. Smith 《Journal of Radioanalytical and Nuclear Chemistry》1998,235(1-2):25-29
Titrations of Pu(IV) with HNO3 in a series of aqueous HClO4 solutions ranging in ionic strength from 2 to 19 molal were followed using visible and near-infrared absorption spectrophotometry.
The Pu 5f-5f spectra in the visible and near IR range change with complex formation. At each ionic strength, a series of spectra
were obtained by varying nitrate concentration. Each series was deconvoluted into spectra of Pu4+ (aq), Pu(NO3)3− and Pu(NO3)2
2+ complexes, and simultaneously their formation constants were determined. When corrected for the incomplete dissociation of
nitric acid, the ionic strength dependence of each formation constant can be described by two parameters, β0 and Δε using the formulae of specific ion interaction theory. 相似文献
15.
V. A. Volkovich B. D. Vasin D. A. Danilov D. E. Aleksandrov 《Russian Journal of Electrochemistry》2010,46(6):640-645
The behavior of molybdenum(III), tungsten(IV), and uranium(VI) ions in NaCl-2CsCl-eutectic-mixture-based melt at 550°C is
studied by spectroelectrochemical method. Anodic oxidation of MoCl63− and WCl62− yields melt-soluble chloride compounds MoCl62− and WCl6− respectively. It is shown that the electrochemical recharging in the Mo(III)/Mo(IV) system is reversible; the formal standard
potential E*Mo(IV)/Mo(III)and the Gibbs energy $
\Delta G_{MoCl_4 (melt)}^*
$
\Delta G_{MoCl_4 (melt)}^*
are evaluated. The cathodic reduction of U(VI) yields U(V) ions. The cathodic reduction of W(IV) ion does not yield melt-soluble
tungsten compounds of lower oxidation state. 相似文献
16.
The stability constants of complexes of a thallium(I) ion with cytosine and thymine were determined in aqueous solution at
25°C and 0.1 mol dm−3 ionic media, using a combination of potentiometric and spectrophotometric techniques. Sodium perchlorate was used to maintain
the ionic strength. The composition of the formed complexes was determined and it was shown that thallium(I) forms two mononuclear
1:1 species with cytosine of the type TIHL+ and TIL, and a mononuclear 1:1 complex species with thymine in the form TIHL, in the pH range of study (1–11), where L represents
the fully dissociated ligand. The cumulative stability constants, β
xyz, of the complexes, [(thallium)x(H)y(ligand)z], were calculated by a nonlinear fitting method and their distributions were presented as a function of-log[H+].
This text was submitted by the authors in English. 相似文献
17.
Interactions in the WO
2
2−
-H+-H2O system was studied by pH-potentiometric titration at 25 ± 0.1°C for c
w
0
= 8 × 10−3 to 2 × 10−2 mol/l. An accurate mathematical model for polycondensation of tungsten(VI) anions in aqueous solution was proposed. The concentration constants of formation were calculated and the diagrams of distribution of isopolyanions of tungsten(VI) were plotted for pH from 1 to 8 with nitrate ions as a supporting electrolyte at different ionic strengths of the solution (I = 0.10 to 0.50). The dependences of the concentration equilibrium constants in solutions on the ionic strength were approximated by Pitzer’s method. The thermodynamic constants of formation and standard Gibbs energies of formation of isopolytungstates from WO
4
2−
were calculated. The most probable scheme of interconversions of isopolyanions in solution at different pH values was proposed.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 8, 2005, pp. 583–589.Original Russian Text Copyright © 2005 by Rozantsev, Sazonova. 相似文献
18.
19.
B. B. Tewari 《Russian Journal of Inorganic Chemistry》2011,56(1):133-138
Quantitative indication of the process of forming a complex comes from the evaluation of the stability constants or formation
constant, which characterize the equilibria corresponding to the successive addition of ligands. Paper electrophoretic technique
is described for the study of beryllium(II) and cobalt(II) biologically significant binary complexes with sarcosine. The stability
constants of ML and ML2 complex species of Be(II)/Co(II)—sarcosine have been found to be (6.17 ± 0.09, 4.06 ± 0.04) and (4.27 ± 0.07, 2.98 ± 0.11)
(log-arithm stability constant values), respectively at ionic strength 0.1 Mol L−1 and a temperature of 35°C. 相似文献
20.
Equilibrium constants for formation of a cobalt(II) complex with the bidentate ligand dopamine have been studied with spectrophotometric
methods in water + ethanol cosolvent systems at 15, 25, and 35 (±0.1) °C and an ionic strength of 0.2 mol⋅dm−3. The ionic strength was maintained using sodium chloride and a phosphate buffer. The stability constants of the complex and
the resulting Gibbs energy changes are obtained. The results are discussed in terms of the effect of solvent on protonation
and complexation. 相似文献