Ion Trios: Cause of Ion Specific Interactions in Aqueous Solutions and Path to a Better pH Definition.

Many important thermodynamic calculations for aqueous systems are profoundly limited because ion specific interactions have not been understood. Here an alternative modeling paradigm with compelling advantages is presented based on fundamental insights regarding ion-ion interactions at higher electrolyte concentrations. We also show how an intense ongoing controversy regarding single ion activity coefficients (SIACs) can be resolved and how SIACs can be quantified in full thermodynamic compliance using an overlooked convention.

Predicting the risk of kidney stone formation in the nephron by 'reverse engineering'.

Although most kidney stones are found in the calyx, they are usually initiated upstream in the nephron by precipitation there of certain incipient mineral phases. The risk of kidney stone formation can thus be indicated by changes in the degree of saturation of these minerals in the nephron fluid. To this end, relevant concentration profiles in the fluid along the nephron have been calculated by starting with specified urine compositions and imposing constraints from the corresponding, much less variable, blood compositions.

Formation constants of copper(I) complexes with cysteine, penicillamine and glutathione: implications for copper speciation in the human eye.

Protonation constants for the biologically-important thioamino acids cysteine (CSH), penicillamine (PSH) and glutathione (GSH), and the formation constants of their complexes with Cu(I), have been measured at 25 °C and an ionic strength of 1.00 mol dm(-3) (Na)Cl using glass electrode potentiometry. The first successful characterisation of binary Cu(I)-CSH and Cu(I)-GSH species over the whole pH range was achieved in this study by the addition of a second thioamino acid, which prevented the precipitation that normally occurs.

JESS, a joint expert speciation system--V: approaching thermodynamic property prediction for multicomponent concentrated aqueous electrolyte solutions.

Considerable difficulties persist in modelling the thermodynamics of multicomponent aqueous electrolyte solutions, especially at high concentrations. The widely adopted Pitzer formalism suffers from severe disadvantages, particularly with the combinatorial increase in mixing parameters required in multicomponent systems. As an alternative, the simple mixing rules of Young, of Harned and of Zdanovskii have been employed to predict the properties of mixtures using only the properties of the binary constituents with few or no additional parameters.

JESS, a Joint Expert Speciation System--IV: a large database of aqueous solution physicochemical properties with an automatic means of achieving thermodynamic consistency.

The JESS software package, which is a widely-used tool for modelling chemical speciation in complex aqueous environments, has been extended to allow comprehensive predictions of physicochemical properties for strong electrolytes in aqueous solution. Another large database, this time of physicochemical property data, has been added to the JESS suite, along with the computational methods which automatically turn these diverse literature data into a thermodynamically-consistent calculation for water activities, densities, heat capacities, etc. Given the recent emphasis on the role of water activity in predicting electrolyte mixing behaviour, we expect that this capability will lead to major changes in the way aquatic chemistry is modelled in future.

Spectroscopic characterisation of weak interactions in acidic titanyl sulfate-iron(II) sulfate solutions.

The titanyl equilibria in strongly acidic solutions related to the hydrometallurgical production of titania have been investigated in the presence of inorganic ions (ClO(4)(-), NO(3)(-), Cl(-), SO(4)(2-), Fe(2+) and Fe(3+)) using spectroscopic (UV-Vis and EPR) methods. UV-Vis experiments showed no interaction or ion pairing effect in the acidic titanyl nitrate and titanyl perchlorate samples indicating that they would be suitable background electrolytes for further thermodynamic measurements. The stoichiometry of the titanyl chloride complex was determined as TiOCl(2)(0) and its stability constant was calculated (log beta(2) = 1.

Characterization of chemical speciation of titanyl sulfate solutions for production of titanium dioxide precipitates.

Ion association in concentrated aqueous solutions of titanyl sulfate in sulfuric acid has been investigated at 25 degrees C by Raman spectroscopy under conditions like those used in the preparation of titania nanoparticles. Systematic variation of titanyl (M), sulfate (L), and hydrogen ion concentrations and a detailed quantitative analysis of the spectra reveal that two weak titanyl sulfato complexes (ML and ML(2)) are formed, with ML predominating. This assignment conflicts with the recent results of Baillon et al.

(27)Al NMR and Raman spectroscopic studies of alkaline aluminate solutions with extremely high caustic content - Does the octahedral species Al(OH)(6)(3-) exist in solution?

(27)Al NMR and Raman spectra of alkaline aluminate solutions with 0.005M View Article and Find Full Text PDF

Reflections on the calculation and publication of potentiometrically-determined formation constants.

Calculation and reporting procedures are described, which aim to improve the quality and comparability of published formation constant values obtained by glass-electrode potentiometry. Ways in which the processing of data by computer optimization programs can be standardized are the main concern, particularly in respect of improving the usefulness of equilibrium data through incorporation into large publically available databases. These recommendations may be particularly valuable to researchers beginning in this field as well as to those who determine formation constants only occasionally.

Chemical speciation in concentrated alkaline aluminate solutions in sodium, potassium and caesium media. Interpretation of the unusual variations of the observed hydroxide activity.

A detailed electrochemical investigation using H2/Pt electrode potentiometry as well as Raman and NMR spectroscopy was carried out to develop a comprehensive chemical explanation for the unusual patterns of hydroxide concentrations observed in strongly alkaline, highly concentrated aluminate solutions (Bayer-liquors). For this, aluminate solutions with various alkaline metal background cations were investigated. The effect of the temperature on the observed patterns was also studied, and for comparison with solutions of similar concentrations, the chemical speciation of borate solutions was also studied.

Quantitative determination of an aluminate dimer in concentrated alkaline aluminate solutions by Raman spectroscopy.

Raman spectra of concentrated alkaline aluminate solutions in various M'OH media (M'(+) = Na(+), K(+), Cs(+) and (CH(3))(4)N(+)) have been investigated systematically as a function of concentration and water activity, a(w). All spectra at [Al(III)](T) < or = 1 M and at 0.1 < or = [M'OH](T)/M < or = 5 (where the square brackets denote concentrations and the subscript T totals) exhibit one significant Raman mode in the low frequency region, at ca.

Critical appraisal of available thermodynamic data for the complexation of antimony(III) and antimony(V) by low molecular mass organic ligands.

Antimony is an element of increasing environmental significance but one whose chemical speciation has received little attention and, until recently, one which had not been modelled in any comprehensive way. This paper reports thermodynamic data for computer speciation models of antimony in aqueous, multicomponent solutions of environmental and biological interest involving low molecular mass organic ligands. The available data have been critically evaluated and entered into a thermodynamic database.

Hydration and ion pairing in aqueous sodium oxalate solutions.

Dielectric spectra have been measured for aqueous sodium oxalate solutions up to the saturation concentration (0.04 < or = c[mmol L-1] < or = 0.25) at 25 degrees C over the approximate frequency range 0.