Search results for "aqueous solution"
showing 10 items of 1610 documents
The interaction of amino acids with the major constituents of natural waters at different ionic strengths
2000
Abstract The interaction of amino acids with the major constituents of natural waters has been studied potentiometrically by determining protonation constants at different ionic strengths (e.g., I ≤5.6 mol (kg H 2 O) −1 (NaCl)) and in artificial seawater (containing Na + , K + , Ca 2+ , Mg 2+ , Cl − and SO 4 2− ) at different salinities. For glycine determinations in mixed NaCl–MgCl 2 , electrolyte solutions were also performed. The data included in this work, together with some already published, make it possible to calculate parameters for dependence on ionic strength using different models, i.e. an extended Debye–Huckel type equation and Pitzer equations. The results can be interpreted b…
Application of the Generalized Molar-Ratio Method to the Determination of the Stoichiometry and Apparent Binding Constant of Nanoparticle-Organic Cap…
2015
A generalization of the molar-ratio method is applied to the determination of the stoichiometry and apparent binding constant of metal nanoparticle-organic capping complexes (MmLx) using voltammetric data for the oxygen reduction reaction (ORR) in air-saturated aqueous phosphate buffer solutions. The method is applied to the formation of binary nanohybrids consisting of gold nanoparticles (AuNPs) capped with a rigid spacer, cucurbit[7]uril (CB), termed AuNP@CB, as well as to the formation of their ternary complexes (MmLxBz) with methylene blue (MB), termed AuNP@CB@MB. The obtained stoichiometries correspond to binding of four Au surface atoms for each CB unit.
Thermodynamic study of the interaction of long open-chain polyazaalkanes with cobalt(II) and nickel(II) ions
1993
Complexation equilibria between the open-chain terminally methylated polyamines 1,14-bis(methylamino)-3,6,9,12- tetraazatetradecane (L1), 1,17-bis(methylamino)-3,6,9,12,15-pentaazaheptadecane (L2), 1,20-bis(methylamino)- 3,6,9,12,15,18-hexaazaicosane (L3) and 1,23-bis(methylamino)-3,6,9,12,15,18,21-heptaazatricosane (L4) with Co2+ and Ni2+ have been studied by means of potentiometric and spectrophotometric methods in 0.15 mol dm−3 NaClO4 aqueous solution at 298.15 K The stability constants for the complexes formed have been determined from e.m.f, data. All these ligands form mononuclear ML2+ complexes of similar stability with Co2+ and Ni2+. Binuclear Co2L44+, Ni2L34+ and Ni2L44+ are also f…
Estimation of free energies of anion transfer from solid-state electrochemistry of alkynyl-based Au(I) dinuclear and Au(I)–Cu(I) cluster complexes co…
2011
A method is presented to determine the free energy for anion transfer between two solvents. This is based on solid-state electrochemistry of alkynyl-based dinuclear Au(I) complexes (AuC2R)2PPh2C6H4PPh2 (L1: R=Fc; L2: R=C6H4Fc) and heterometallic Au(I)–Cu(I) [{Au3Cu2 (C2R)6}Au3(PPh2C6H4PPh2)3](PF6)2 (L3: R=Fc; L4: R=C6H4Fc) complexes. These compounds exhibit a reversible ferrocenyl-centred solid-state oxidation processes involving anion insertion in contact with aqueous, MeOH and MeCN electrolytes. Voltammetric data can be used for a direct measurement of the free energy of ion transfer using midpeak potentials in solutions of suitable salts in the solvents separately or in mixtures of the s…
Mass Action Model Applied to the Thermodynamic Properties of Transfer of Nonionic Copolymers from Water to the Aqueous Surfactant Solutions
2003
A thermodynamic model which enables the properties of aqueous copolymer/surfactant mixtures to be fit quantitatively was proposed. Namely, a relationship between the properties of transfer of the unassociated copolymer from water to the aqueous surfactant solutions (DeltaY(t)) and the surfactant concentration was derived. The model was based on the idea that AY, can be expressed in terms of the following contributions: (1) interaction between monomers of copolymer and surfactant, (2) displacement of the monomer-micelle equilibrium induced by the copolymer, (3) formation of the surfactant-copolymer aggregation complex, and (4) formation of the mixed micelles. Such a model was applied to most…
Stabilities and coordination modes of histidine in copper(II) mixed-ligand complexes with ethylenediamine, diethylenetriamine or N,N,N′,N″,N″-pentame…
2008
Abstract Solution equilibrium studies on the Cu(II)–polyamine–methionine ternary systems (polyamine: ethylenediamine (en), diethylenetriamine (dien), N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (Me5dien)) have been performed by pH-potentiometry, UV–Vis spectrophotometry and EPR methods. The obtained results suggest the formation of the mixed-ligand complexes with [Cu(A)(Met)]+ stoichiometry in all studied systems. Our spectroscopic results indicate the tetragonal geometry for [Cu(en)(Met)]+, the geometry slightly deviated from square pyramidal for [Cu(dien)(Met)]+ and strongly deviated from square pyramidal towards trigonal bipyramidal for the [Cu(Me5dien)(Met)]+ species. The coordination …
Hydrolysis of dioxouranium(VI): a calorimetric study in NaClaq and NaClO4aq, at 25°C
2004
Abstract We report the results of a calorimetric study on the hydrolysis of UO 2 2+ in different ionic media (NaClO 4 aq , NaCl aq ) at 25 °C. Experiments in NaCl were performed at different ionic strength, at I ≤1 mol l −1 . The species considered in both ionic media were UO 2 (OH) + , (UO 2 ) 2 (OH) 2 2+ and (UO 2 ) 3 (OH) 5 + , and in addition (UO 2 ) 3 (OH) 4 2+ and (UO 2 ) 3 (OH) 7 − in NaCl aq . The dependence on ionic strength of enthalpy changes in NaCl aq was expressed by the simple linear equation Δ H pq =Δ H ° pq + aI 1/2 ( a , empirical parameter). Comparison with literature findings is given and some recommended values are reported.
Polyacrylate Protonation in Various Aqueous Ionic Media at Different Temperatures and Ionic Strengths
2000
The protonation constants of the polyacrylate anion (molecular mass 2000 Da) in Et4NI, Me4NCl, LiCl, LiNO3, NaCl, NaNO3, and KCl aqueous solution, were determined in a wide range of ionic strengths. A three-parameter approximation was used to express protonation constants as a function of the dissociation degree α, and their dependence on ionic strength was considered using a simple polynomial expansion. Differences in log KH between different data in different media were interpreted in terms of weak complex formation between polyacrylate and alkali metal cations. Measurements were also performed at different temperatures (15 ≤ T/°C ≤ 55) in order to calculate enthalpy and entropy changes f…
Kinetic and Mechanistic Aspects of a Poly(o-Toluidine)-Modified Gold Electrode. 2. Alternating Current Electrogravimetry Study in H2SO4 Solutions
2012
International audience; Electrodeposited poly(o-toluidine) (POT) on gold electrodes was investigated in 0.5 M H2SO4 aqueous solutions using alternating current electrogravimetry (simultaneous electrochemical impedance and mass transfer functions). The kinetic aspects of the three different redox transitions proposed for this polymer (leucoemeraldine-polaron transition, polaron-bipolaron transition, and bipolaron-pernigraniline transition) and the species involved, cation (hydrated proton), anion (bisulfate ion), and free solvent (water), are studied by means of the mass impedance technique. An ionic transfer model is proposed with coherent results where anion transfer is the fastest process…
Complex formation of copper( ), nickel( ) and zinc( ) with ethylophosphonoacetohydroxamic acid: solution speciation, synthesis and structural charac…
2019
We present herein the thermodynamic and X-ray characterisation of a novel ethyl phosphonohydroxamic acid-based Cu( ) metallacrown, predominating in solution in a broad pH range.