Calorimetric investigation of complex formation in the aqueous Fe (III)–citrate system

1993 ◽  
Vol 71 (7) ◽  
pp. 937-941 ◽  
Author(s):  
Qiyuan Chen ◽  
Xin Zhang ◽  
Ching-Hsien Wu ◽  
Loren G. Hepler
Keyword(s):  
Complex Formation ◽  
Aqueous Solutions ◽  
Ferric Chloride ◽  
Thermal Effects ◽  
Sodium Citrate ◽  
Equilibrium Constants ◽  
Calorimetric Investigation ◽  
Calorimetric Measurements ◽  
Solute Water

We have made calorimetric measurements of thermal effects associated with adding NaOH(aq) or HCl(aq) to aqueous solutions (pH = 1.623) of ferric chloride + sodium citrate. Combination of these measured heats with concentrations of various species calculated from stoichiometric compositions and previously known K and ΔH values leads to ΔH values for four aqueous Fe(III)–citrate complexes. Further combination of ΔG0 values from equilibrium constants with our ΔH values leads to ΔS0 values, which are discussed in relation to conventional ideas about relationships between entropy and solute–water interactions.

scholarly journals Spectrophotometric investigations of the reaction between gold(III) and potassium iodide

2000 ◽  
Vol 65 (5-6) ◽  
pp. 345-352 ◽  
Author(s):  
Vesna Vasic ◽  
Suzana Premovic ◽  
Mira Cakar ◽  
Bojan Radak ◽  
Gordana Milovanovic
Keyword(s):  
Complex Formation ◽  
Aqueous Solutions ◽  
Absorption Spectra ◽  
Potassium Iodide ◽  
Equilibrium Constants ◽  
Hydrogen Ion

The equilibria of the complex formation between AuCl4-n(OH)n - and I- was studied spectrophotometrically in aqueous solutions containing KI:Au(III)?2 in the acidity range from 1 M HCl to pH 7 at 25?C. From the hydrogen ion and Cl-ion dependence of the absorption spectra, it was found that AuCl2I2 - and Au(OH)2I2 - complexes were formed. The equilibrium constants of complex formation were determined.

The reactions of oligoalcohols with arsenic, arsenous, boric and germanic acids

1980 ◽  
Vol 45 (10) ◽  
pp. 2645-2655 ◽  
Author(s):  
Antonín Mikan ◽  
Miloš Bartušek
Keyword(s):  
Aqueous Solutions ◽  
Equilibrium Constants ◽  
Dilute Aqueous Solutions

The reactions of sorbitol, mannitol, adonitol, dulcitol, glucose and glycerol with H3AsO4, H3AsO3, H3BO3 and GeO2 acids in dilute aqueous solutions were studied by potentiometric neutralization titrations. The formation of the following chelates was demonstrated: As(V)L3-, As(III)L(OH)2-, HAs(III)L(OH)2, BL2-, GeL2(OH)- and GeL32- and the equilibrium constants for their formation were found. Conditions for formation of these chelates of organic oligohydroxy compounds are discussed.

Ionic dissociation in complexes of iodine with triphenylarsine and triphenylstibine

1991 ◽  
Vol 69 (4) ◽  
pp. 606-610 ◽  
Author(s):  
Ying Ru Zhang ◽  
Ira Solomon ◽  
Seymour Aronson
Keyword(s):  
Complex Formation ◽  
Chemical Nature ◽  
Equilibrium Constants ◽  
Electrochemical Technique ◽  
High Iodine ◽  
Ionic Complex ◽  
Ionization Mechanisms ◽  
Iodine Complex ◽  
Ionic Dissociation ◽  
Iodine Complexes

An electrochemical technique has been employed to study the ionization of the iodine complexes of (C6H5)3As, (C6H5)3Sb, and pyridine. Several different ionization mechanisms are proposed depending on the chemical nature and concentration of the reactants. A new ionic complex, (C6H5)3MI22+ is postulated for the interaction of iodine with (C6H5)3As and (C6H5)3Sb at high iodine concentrations. Equilibrium constants have been calculated from the emf data for the various ionization steps. Key words: triphenylarsine, triphenylstibine, iodine, complex formation, ionization.

scholarly journals Synthesis of Mn(II)-containing paratungstate B from aqueous solutions acidified by acetic acid

2021 ◽  
pp. 39-48
Keyword(s):  
Thermal Analysis ◽  
Acetic Acid ◽  
Aqueous Solutions ◽  
Equilibrium Constants ◽  
Background Electrolyte ◽  
Equilibrium Processes ◽  
Transformation Processes ◽  
Paratungstate B ◽  
Solution Acidity ◽  
Tungstate Anion

The method of pH-potentiometric titration and mathematical simulation were used to study the equilibrium processes in aqueous solutions of the WO42––CH3COOH–H2O system in the acidity range Z=(CH3COOH)/(Na2WO4)=0.8–1.7 at СW=0.01 mol L–1 and T=2980.1 K, a constant ionic strength being maintained by sodium nitrate as a background electrolyte ((NaNO3)=0.10 mol L–1). We developed the models of polyoxotungstate anions formation and the equilibrium transformation processes, which adequately describe experimental pH vs. Z dependences. It was found that acetic acid using to create the solution acidity that is necessary for the formation of isopoly tungstate anion contributes only to the formation of protonated paratungstate B anions Нх[W12O40(ОН)2](10–х)– (where x=0–4). We calculated the logarithms of the concentration equilibrium constants of the polyanion formation and plotted the distribution diagrams. Double sodium-manganese(II) paratungstate B Na8(H2O)28Mn(H2O)2[H2W12O42]4H2O was synthesized at Z=1.00 to confirm the results of the mathematical modeling. The chemical composition of the prepared salt was established by chemical elemental analysis, thermal analysis, FTIR spectroscopy, and single crystal X-ray analysis. The stepwise process of salt dehydration was studied by means of differential thermal analysis.

The complexation of glucose and other monosaccharides with cyclodextrins

1997 ◽  
Vol 75 (1) ◽  
pp. 52-55 ◽  
Author(s):  
Frank Hacket ◽  
Jose-Miguel Coteron ◽  
Hans-Jörg Schneider ◽  
Vladimir P. Kazachenko
Keyword(s):  
Molecular Modelling ◽  
Equilibrium Constants ◽  
Association Constants ◽  
Cyclodextrin Complexes ◽  
Cyclodextrin Complex ◽  
Intermolecular Hydrogen Bonds ◽  
Calorimetric Measurements ◽  
Computer Aided ◽  
Molecular Modelling Studies ◽  
Modelling Studies

Equilibrium constants of complexes between β-cyclodextrin and glucose, galactose, or mannose have been determined by fluorometric competition titrations in water to be as low as K = 1 – 0.5 M−1, in sharp contrast to recently published values for glucose around K = 400 M–1. The pentoses ribose, xylose, and arabinose show association constants between 6.3 and 1.5 M−1, in agreement with published values. Preliminary computer-aided molecular modelling studies suggest that the small values observed for the hexoses are not due to steric hindrance of an intracavity inclusion but to a smaller number of intermolecular hydrogen bonds and to some strain as a result of cyclodextrin deformation. Calorimetric measurements of the glucose–β-cyclodextrin complex show, again in contradiction with the literature, an endothermic reaction, or a free enthalpy value close to zero. Key words: cyclodextrin complexes, sugar complexation, glucose complexation, calorimetry, computer-aided molecular modelling.

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