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THIS erratum is to correct the title of Appendix A. The title contains the chemical formula of a chlorine isotope, which is written as 36CL. This is incorrect and should be changed to 36Cl. It should appear as: APPENDIX A: POTENTIAL SOURCES, ANALYSES, AND ENVIRONMENTAL IMPACT OF 36Cl REPORTED IN THE LITERATURE The original article has been corrected.

No thermodynamic data for the solution of Cl in ferrous alloys were found in the literature. This is in accord with recent Accelerator Mass Spectroscopy (AMS) analyses which showed that Cl contents in stainless steel (SS) are in the order of a few ppb. However, based on older chemical analyses of Cl in the order of 100 ppm, SS that has been irradiated with thermal neutrons in nuclear reactors is considered a major source of the long-lived 36Cl isotope in nuclear waste. In this study, the potential Cl contamination of SS originating from production and refinement processes is investigated. Unlike ferrous alloys, blast-furnace and steelmaking slags can dissolve significant amounts of Cl. The equilibrium distribution of Cl species between slags and gas phase was calculated for various steelmaking processes using the FactSage 7.2 software and databases. The results showed that despite the high volatility of metal chlorides at high temperatures, significant fractions of Cl can be retained in the slag phase even at 1600 °C. Chloride may also be incorporated in non-metallic inclusions originating from secondary refining. Based on these results and on several further assumptions, various scenarios for explaining, and also avoiding, Cl contamination of steel are discussed.

The solubility of solid calcium oxalate monohydrate (CaC2O4·H2O, COM) has been measured in aqueous solutions of four 1:1 electrolytes (NaCl, KCl, CsCl, and Me4NCl) at temperatures T = 298.15, 323.15, and 343.15 K. Solubilities at industrially relevant electrolyte concentrations of up to 5.0 mol·kg–1 were determined by atomic absorption spectrophotometry of the dissolved calcium ions. The solubility of COM in 1.0 mol·kg–1 electrolyte solutions was 2–4 times higher than in pure water but varied little at higher ionic strengths for all of the systems studied. Most of the observed solubilities were well correlated at all temperatures and electrolyte concentrations using a simple Specific Ion-interaction Theory (SIT) model with only one adjustable, temperature-independent, interaction parameter. For Me4NCl solutions, an additional empirical ionic strength dependence of the SIT parameter significantly improved the fit.

We became aware of the above paper by Kang et al., published online in the Journal of Chemical and Engineering Data.(1)

The composition and structures of the two protonated species formed from uncharged molybdic acid, MoO2(OH)2(OH2)20, in strongly acidic solutions have been investigated using a combination of density functional theory calculations, first-principles molecular dynamics simulations, and Raman spectroscopy. The calculations show that both protonated species maintain the original octahedral structure of molybdic acid. Computed pKa values indicated that the ═O moieties are the proton acceptor sites and, therefore, that MoO(OH)3(OH2)2+ and Mo(OH)4(OH2)22+ are the probable protonated forms of Mo(VI) in strong acid solutions, rather than the previously accepted MoO2(OH)2–x(OH2)2+xx+ (x = 1, 2) species. This finding is shown to be broadly consistent with the observed Raman spectra. Structural details of MoO(OH)3(OH2)2+ and Mo(OH)4(OH2)22+ are reported.

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. A model for supersaturation within ten sections of both long and short nephrons has accordingly been developed based on this ‘reverse engineering’ of the necessary substance concentrations coupled with chemical speciation distributions calculated by our Joint Expert Speciation System (JESS). This allows the likelihood of precipitation to be assessed based on Ostwald’s ‘Rule of Stages’. Differences between normal and stone-former profiles have been used to identify sections in the nephron where conditions seem most likely to induce heterogeneous nucleation.

Solubility data have frequently been reported without sufficient attention to experimental detail, including a proper description of apparatus and measurements, the evaluation of uncertainties, and the validation of the experimental protocol. This editorial focuses on solubility measurements of solids in liquids at atmospheric pressure. It provides guidelines that are intended to help researchers to select and validate appropriate experimental techniques, and consequently improve the accuracy of their measured data. It should also assist reviewers in assessing the reliability of solubility data considered for publication in this Journal.

Professor Heinz Gamsjäger was an Associate Editor of Monatshefte für Chemie/Chemical Monthly since 1998...

The solubility of solid sodium oxalate (Na2Ox) has been measured in a variety of concentrated aqueous electrolyte solutions at T = 298.15, 323.15, and 343.15 K by titration of dissolved oxalate with permanganate. The electrolyte solutions studied (not necessarily at all temperatures) were NaCl, NaClO4, NaOH, LiCl, KCl, Me4NCl, and KOH at concentrations ranging from approximately 0.5 mol·kg–1 to at least 5 mol·kg–1. Where comparisons were possible, the present results were in excellent agreement with literature data. The solubility of Na2Ox(s) decreased markedly with increasing concentrations of Na+(aq), due to the common ion effect. This decrease was almost independent of the electrolyte anion. A number of ternary mixtures of these electrolytes were also investigated at constant ionic strength. Consistent with the binary mixtures, the solubility of Na2Ox(s) showed almost no dependence on solution composition at constant Na+(aq) concentrations. Solubilities in non-Na+ media, with the exception of Me4NCl, showed small but regular increases with increasing concentration of added electrolyte, probably reflecting activity coefficient variations. The solubility data in certain Na+-containing media could be correlated accurately at all temperatures and concentrations using a relatively simple Pitzer model with interaction parameters for Na2Ox(aq) assumed to be identical to those available in the literature for Na2SO4(aq).

New Raman spectra of Na2S dissolved in hyper-concentrated NaOH(aq) and CsOH(aq) cast serious doubt on the widely-assumed existence of S2−(aq). To avoid conceptual and practical problems with sulfide equilibria in numerous applications, S2−(aq) should be expunged from the chemical literature. Thermodynamic databases involving sulfide minerals also need careful revision.

Solubility constants reported in the literature for ammonium hydrogenurate (NH4HU), an occasional constituent of urinary calculi in humans, show a large scatter, probably due to the tendency of hydrogenurates to form supersaturated solutions that persist over long periods of time. In this study, the solubility of NH4HU(s) was measured as a function of p[H] = − lg{[H+]/mol dm−3} (4.5–8) and temperature (25 and 37 °C) at constant ionic strength, Ic = 0.300 mol dm−3 NH4Cl, which is similar to the ionic strength of urine. Highly reproducible values for the solubility product (Ks0) of NH4HU(s) were obtained. The first dissociation constant (K1) of uric acid determined in this work agrees well with values obtained in our previous studies of uric acid solubilities in electrolyte solutions relevant to urolithiasis. This study confirms our earlier findings that in the ionic strength range of urine, the solubilities of uric acid and hydrogen urates as a function of p[H] can be described consistently by unique values of their solubility constants (Ks, Ks0) and the first dissociation constant of uric acid (K1). In addition, no appreciable complexation between uric acid or hydrogenurates and other urine constituents has been found.

The formation of kidney stones is a significant human health problem. Calcium minerals are involved in a majority of these stones. Despite much research, the processes involved in stone formation remain poorly understood and, hence, reliable procedures for preventing their formation have yet to be developed. However, recent advances point to some key steps in mineral formation and transformation involving calcium phosphates, which can help to illuminate these issues. A computer model has been developed to express the current status of literature data succinctly and to illustrate that computer modeling is a powerful tool for calculating mineral solubilities and for providing insight into the processes involved. Determining the nature of the initial solid phase of calcium phosphate formed is evidently important.

An internally consistent thermodynamic network for arsenic minerals and aqueous species is being developed based on a high quality starting point: arsenolite and arsenolite solubility. Current research is refining the properties of scorodite solubility as a function of temperature along with improved aqueous species stability constants and activity coefficients for ions and ion pairs based on potentiometric measurements of redox, pH, and conductivity for 5-90 °C. The second and third hydrolysis constants for arsenic acid have been calculated as a function of temperature and thermodynamic properties have been derived.

The complexation of copper(I) by cyanide ions (CN−) in aqueous solution has been studied by glass electrode potentiometry at 25 °C and ionic strengths (I) of 1, 3 and 5 M in NaCl media. Overall formation constants, βn, for the equilibria: Cu+(aq) + nCN−(aq) ⇌ Cu(CN)n(n − 1)−(aq) with n = 2, 3 and 4, were quantified, along with the ionization constant (Kw) of water and the acid dissociation constant (Ka) of HCN(aq). The solubility constants *Ksn for the equilibria: CuCN(s) + (n − 1)HCN0(aq) ⇌ Cu(CN)n(n − 1)−(aq) + (n − 1)H+(aq) were also determined from a re-analysis of published solubility data for CuCN(s) in acidic cyanide solutions at I = 1 M(NaCl) and 25 °C. Because of the instability of uncomplexed Cu+(aq) and parameter correlations in the data, neither β1 nor the solubility product Ks0 (CuCN(s) ⇌ Cu+(aq) + CN−(aq)) could be reliably determined from the present data although estimates are presented.

The extraction of rare earth oxides from fluorapatite rich phosphate concentrates often involves a weak acid leach of fluorapatite and a sulphuric acid bake of the leach residue followed by water leach and precipitation to obtain an intermediate product. The main aim of this study was to determine and rationalize the solubility of rare earth metal ions in synthetic solutions representing various process liquors at the temperatures 40, 60 and 80 °C. The liquors contained different acid and metal ion concentrations with respect to sulphuric acid, phosphoric acid and sulphate salts of sodium, magnesium, aluminium, potassium, calcium and iron(III). A solid of mixed rare earth carbonates was used as the source of rare earth metal ions. The solubility tests and characterisation of solids using XRD were conducted at Murdoch University laboratories as part of the process development for the Arafura Resources Nolans rare earth project. The composition of initial carbonate solids and the solids and solutions formed after saturation were analysed for rare earth and other elements at TSW Analytical Laboratories in Perth using ICP-MS and ICP-OES. The precipitated solid in sodium-rich acidic sulphate solutions is the double salt NaRE(SO4)2 based on the solid assays. However, in acidic solutions free of sodium or of low concentrations of sodium the precipitated solid appears to be RE2(SO4)3.

Summary This title takes an interdisciplinary approach to the central role of solubility in pathological biomineralisation, ranging from traditional thermodynamics and kinetics to unusual concepts such as the PILP process. The scientific background and expertise of the contributors, ranges accordingly from solubility modelling and database development, renal stone and bone implant research, Mössbauer spectroscopy and structural chemistry to biochemistry and crystallisation. The chapters all have a quantitative, physico-chemical component rather than giving purely phenomenological descriptions. The contributors deal with aspects and concepts that have not previously been common in the study of pathological biomineralisation processes.

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. Appropriate combinations of binary and ternary (mixed ligand) titration data were used to optimise the speciation models and formation constants for the binary species. The results obtained differ significantly from literature data with respect to the detection and quantification of protonated and polynuclear complexes. The present results are thought to be more reliable because of the exceptionally wide pH and concentration ranges employed, the excellent reproducibility of the data, the close agreement between the calculated and observed formation functions, and the low standard deviations and absence of numerical correlation in the constants. The present formation constants were incorporated into a large Cu speciation model which was used to predict, for the first time, metal-ligand equilibria in the biofluids of the human eye. This simulation provided an explanation for the precipitation of metallic copper in lens and cornea, which is known to occur as a consequence of Wilson's disease.

Despite intense efforts, general thermodynamic modelling of aqueous electrolyte solutions still presents a difficult challenge, with no obvious method of choice. Even though the Pitzer equations seemingly provide a well-established theoretical framework applicable to many chemical systems over a wide range of temperatures and pressures, they are not as widely adopted as their early promise might have suggested. This is strikingly illustrated by the simultaneous appearance in the literature of numerous, different (and potentially incompatible) Pitzer models alongside a proliferation of alternative theoretical approaches with inferior capabilities.To better understand this problem, the ability of the Pitzer equations to represent the physicochemical properties of aqueous solutions has been systematically investigated for exemplar electrolyte systems. Pitzer ion-interaction parameters have been calculated for selected systems by least-squares regression analysis of published solution data for activity coefficients, osmotic coefficients, relative enthalpies, heat capacities, volumes and densities to high temperatures and pressures. Although satisfactory fits can be achieved when the ranges of conditions are carefully chosen and when sufficient data are available to constrain the regression, the fits obtained tend otherwise to be unsatisfactory. The Pitzer equations do not cope well with gaps and other deficiencies in the regressed data. Profound difficulties, poorly recognized hitherto, can also arise because of variation in the sensitivity of the Pitzer functions to values for different physicochemical properties when these are combined. Given the dimensionality of numerous related thermodynamic properties, all changing as functions of composition, temperature and pressure, these problems are difficult to detect, let alone address, especially in multicomponent systems. The growing practice of improving fits simply by adding basis functions (thereby increasing the numbe

Quantitative geochemical calculations are not possible without thermodynamic databases and considerable advances in the quantity and quality of these databases have been made since the early days of Lewis and Randall (1923), Latimer (1952), and Rossini et al. (1952). Oelkers et al. (2009) wrote, “The creation of thermodynamic databases may be one of the greatest advances in the field of geochemistry of the last century.” Thermodynamic data have been used for basic research needs and for a countless variety of applications in hazardous waste management and policy making (Zhu and Anderson 2002; Nordstrom and Archer 2003; Bethke 2008; Oelkers and Schott 2009). The challenge today is to evaluate thermodynamic data for internal consistency, to reach a better consensus of the most reliable properties, to determine the degree of certainty needed for geochemical modeling, and to agree on priorities for further measurements and evaluations. Recent attention has been directed to arsenic (As) thermodynamic data, partly because of the worldwide recognition of arsenic poisoning in more than 70 countries (Nordstrom 2002; Ravenscroft et al. 2009) and the need to interpret As mobility more quantitatively in groundwater and surface-water systems. Unfortunately, not as many useful thermodynamic measurements have been made on reactions involving As compared to other major solutes and trace elements. Grenthe et al. (1992), when reviewing As data for the Organization for Economic Cooperation and Development/Nuclear Energy Agency (OECD/NEA) thermodynamic database on U, stated “Although needed, a complete reanalysis of the chemical thermodynamic data for arsenic species is not within the scope of the current review.” Although a complete reanalysis is not feasible at this time, this chapter reviews As thermodynamic data with a focus on internal consistency and the quality of the original measurements, updates with new data, points out some areas of discrepancies, makes recommendations for

The solubility of tenorite, CuO(s), has been measured at 25 °C and 60 °C as a function of total hydroxide concentration, [OH−]T, at constant ionic strength (I = 5 or 6 mol kg− 1) in Li(OH,ClO4)(aq) and Na(OH,ClO4)(aq) media. Additional measurements were also made in highly concentrated (≥ 6 mol kg− 1) NaOH(aq) and KOH(aq). The solubility (S) of CuO(s), measured as the total concentration of dissolved Cu(II) by atomic absorption spectroscopy, decreased at approximately constant [OH−]T in the order LiOH ≫ NaOH > KOH and increased with temperature and [OH−]T in all media. Plots of log S against log [OH−]T were linear with a slope of ~ 2.0, indicating, consistent with UV–Vis spectra, that the only significant Cu(II) species in solution was Cu(OH)42 −(aq) under all conditions studied. Detailed analysis indicates that previous studies overestimated S because of the presence of fine particles of CuO(s). Using equilibrium constants and SIT parameter values derived from the present experimental data, the solubility of CuO(s) could be described with good precision up to the highest hydroxide concentrations investigated in all media.

Because of their potential occupational safety and health implications, the formation of volatile substances is of interest to many hydrometallurgical plants, including alumina refineries using the Bayer process. Rigorous thermodynamic models for various groups of volatile compounds have been incorporated into the database of the Murdoch Bayer liquor model to simulate their distribution among different process streams. Under conditions prevailing in a high-temperature digestion stage of the Bayer process, only hydrogen, low hydrocarbons, and mercury are predicted to be present in the gas phase in significant amounts. The other volatiles primarily remain dissolved in the liquor and are therefore transported to the flash vessels. Flash train simulations confirm that hydrophobic substances accumulate in the vapor phase where they can be destroyed by thermal oxidation. However, large fractions of hydrophilic substances are predicted to dissolve in the aqueous phases. They may therefore be released into the environment when digestion condensate is used for washing and dilution purposes. Mercury constitutes a special case because liquid Hg may precipitate in the first heat exchanger when the condensate/vapor ratio is high.

The extraction of rare earth metals from fluoroapatite rich phosphate concentrates often involves a weak acid leach of fluoroapatite and a sulphuric acid bake of leach residue followed by water leach and precipitation to obtain an intermediate product. The main aim of this study was to determine and rationalize the solubility of rare earth metal ions in synthetic solutions representing various process liquors at three temperatures 40, 60 and 80oC containing different acid and metal ion concentrations with respect to sulphuric acid, phosphoric acid and sulphate salts of sodium, magnesium, aluminium, potassium, calcium and iron(III). Solid mixture of rare earth metal carbonates was used as the source of rare earth metal ions. The solubility tests and characterization of solids using XRD were conducted at Murdoch University laboratories. The composition of initial carbonate solids and the solids and solutions formed after saturation were analysed for rare earth and other elements at TSW Analytical Laboratories in Perth using ICP-MS and ICP-OES. The precipitated solid in sodium rich acidic sulphate solutions is the double salt NaRE(SO4)2 based on the solid assays. However, in acidic solutions free of sodium or of low concentrations of sodium the precipitated solid appears to be RE2(SO4)3.

A critical evaluation of selected arsenic minerals and aqueous species and a separate review of aqueous arsenic speciation were completed recently as part of a new volume on arsenic geochemistry, mineralogy, toxicity, and microbiology (Reviews in Mineralogy and Geochemistry #79). We developed a thermodynamic network based on the most reliable and fundamental data in the arsenic system, using the most direct pathways to build the network, and checking for internal consistency at each step. Arsenolite, As2O3-cubic, is the cornerstone or anchor of the network from which thermodynamic properties of the aqueous species of arsenate and arsenite and their hydrolysis products are derived. Thermodynamic data on aqueous arsenate ions are essential for the evaluation of metal arsenate minerals and their solubilities. Very few measurements of metal arsenate and metal arsenite complexes are reported from the literature but by using a consistent chemical model and the same equation of state, several metal arsenate and metal arsenite complexes have been estimated by Marini and Accornero (2007, Environ. Geol. 52, 1343). The solubilities and solubility-product constants of several metal arsenates have been reported but many are of variable quality and in need of better measurements and further evaluation. Scorodite solubility is well characterized, consistent with recent calorimetric data at ambient temperatures. The solubility of some calcium arsenates is well characterized and there is some agreement between investigations but inconsistencies still exist and some phases are poorly characterized or not measured at all. Application of estimated metal-arsenate and metal-arsenite stability constants to waters with a wide range of composition and temperature shows that arsenite speciation is affected very little (98-99% as free forms of hydrolyzed arsenite) but that arsenate speciation can be affected substantially (24-71% of the arsenate species in the free forms). Calcium and magnesi

The IUPAC Subcommittee on Solubility and Equilibrium Data has been selecting, editing and reviewing projects and manuscripts for publication as part of the IUPAC-NIST Solubility Data Series (SDS). This series provides comprehensive reviews of data from the primary literature for solubilities of gases, liquids and solids in liquids or solids. Data are compiled in a uniform format, critically evaluated and, where high-quality data from independent sources agree sufficiently, recommended values are proposed [1]. SDS Volume 102 was published recently [2]. A current IUPAC project is dealing with solubilities of subs tances related to urolithiasis [3]. Kidney stones consist of a range of inorganic and organic substances that are sparingly soluble in urine, thereby producing ionic and uncharged aqueous species which can undergo a wide variety of protonation and complexation reactions. Using these data as an example, this work explores the features of the JESS solubility database [4] that assist with the presentation, manipulation and critical evaluation of solubility data. In particular, the unique combination of databases available in JESS for speciation equilibria [5], physicochemical properties of solutions [6] and solubilities provides improved evaluation facilities, including the assessment of thermodynamic consistency among solubility, calorimetric and speciation data as described in a recent SDS volume [7]. Systems of different chemical complexity will highlight the benefits of applying the JESS software package to the production of future SDS volumes.

At the present state-of-the-art, the modelling of equilibria occurring in concentrated reactive electrolyte mixtures remains problematic: the theoretical deficiencies related to calculating the activity of species in multicomponent solutions seem unlikely to be overcome soon. However, thermodynamic data for reactive systems, e.g. solubility values, are widespread in the chemical literature and need to be better utilised. A key challenge for storing this information is expressing the complete chemistry of a large number of potentially complicated solutions – such as phosphate and borate buffers – in a compact, and ultimately machine-processable, form. The approach taken to date (e.g. [1]) records only the analytical concentrations of well-defined components. We are seeking to build the data repository which will be required in future to parameterise theoretical solution chemistry frameworks estimated to involve at least five million experimental data values. A major issue is that existing databases do not store information relating to the chemical behaviour of the solution components that is needed for processing experimental data. We find that defining all solution species and the set of allowed reactions is necessary and sufficient for describing the chemistry of the solution. A database system implementing this design is in development building upon our existing chemical reaction [2] and physicochemical property [3] databases. Accordingly, the new database can store a vast range of properties including solubility, pH, density, mean activity coefficients and equilibrium constants. Methods to harmonise these data, which is a preliminary step prior to extracting reliable thermodynamic parameters for modelling, are described.

The importance of solid-solution-aqueous-solution (SSAS) equilibria requires the incorporation of solid solutions into thermodynamic models for industrially and environmentally relevant applications. Insights from appropriate measurements and recent database developments have made such extensions feasible. Examples illustrating various types of stable and metastable equilibria involving solid solutions will be given.

The alkaline earth carbonates are an important class of minerals. This volume compiles and critically evaluates solubility data of the alkaline earth carbonates in water and in simple aqueous electrolyte solutions. Part 1, the present paper, outlines the procedure adopted in this volume in detail, and presents the beryllium and magnesium carbonates. For the minerals magnesite (MgCO 3), nesquehonite (MgCO 3.3H 2O), and lansfordite (MgCO 3.5H 2O), a critical evaluation is presented based on curve fits to empirical and=or thermodynamic models. Useful side products of the compilation and evaluation of the data outlined in the introduction are new relationships for the Henry constant of CO 2 with Sechenov parameters, and for various equilibria in the aqueous phase including the dissociation constants of CO 2(aq) and the stability constant of the ion pair MCO 3 0(M=alkaline earth metal). Thermodynamic data of the alkaline earth carbonates consistent with two thermodynamic model variants are proposed. The model variant that describes the Mg 2+-HCO 3 - ion interaction with Pitzer parameters was more consistent with the solubility data an d with other thermodynamic data than the model variant that described the interaction with a stability constant.

Reliable solubility data for oxides and hydroxides of heavy metals in alkaline solutions are relevant to a number of industrial and geochemical processes, including the production of high-purity alumina in the Bayer process, the formation of ores from geothermal solutions at high pH, hydrometallurgical leaching processes for the extraction of metal values from ores and plant residues, and the storage and processing of certain types of radioactive waste. Recent results obtained for various systems will be reported, including experimental and modelling aspects. A new facility for the storage, handling and processing of solubility data will be outlined.

This presentation in honour of Professor Heinz Gamsjäger on his 80th birthday will highlight his seminal contributions to our understanding of solubility phenomena in aqueous media. These include the development of apparatus for accurate solubility measurements, particularly of solid solutions, and theoretical methods to extract thermodynamic quantities from these experimental data. Recent applications to systems of industrial, geochemical and medical interest will be discussed.

Boehmite, rather than gibbsite, precipitation has been proposed in the literature as a potential energy-saving modification of the Bayer process for the production of alumina. Previous experimental studies have reported that true equilibrium solubilities were not attained during boehmite precipitation. Instead, a pseudo-equilibrium or an apparent 'steady-state' aluminate concentration of about twice the boehmite solubility was reached. In this work, the dissolution and precipitation reactions in synthetic and plant liquors using seeds of (i) pure boehmite and (ii) various boehmite/gibbsite ratios were investigated at 95 °C. Only boehmite precipitation was observed on pure boehmite seed at relatively low supersaturation (alumina (A)/total caustic (TC) 0.56). The aluminate concentrations measured as a function of time decreased continuously and did not exhibit an apparent 'steady state'. Stable equilibrium, as established by boehmite solubility measurements, was approached very slowly but not attained even after ten weeks. At higher supersaturation (A/TC 0.67), after an initial desupersaturation, 'steady-state' aluminate concentrations of about twice the boehmite solubility were observed. There is convincing evidence that these 'steady states' correspond to metastable solubility equilibria with gibbsite, which is precipitated initially and gradually transforms into the stable phase, boehmite. Gibbsite also nucleated in the case of pure boehmite seeds. 'Steady states' were attained in one up to several days and remained constant for one to ten days. The length of these periods correlated with the gibbsite content of the seeds. After sufficient recrystallisation of gibbsite to boehmite, the aluminate concentrations decreased significantly and eventually approached boehmite solubility, thereby following a much slower precipitation kinetics typical for boehmite. Due to short observation times, previous workers did not detect the end of the 'steady-state' periods and there

This paper, devoted to cadmium(II) carbonate, is the first in a series dedicated to the solubility of compounds relevant to mobility of metals in the environment. Here, we present compilations and critical evaluation of the experimental solubility data for cadmium(II) carbonate, otavite, in aqueous ternary and higher-order systems. The solubility of cadmium(II) carbonate depends on temperature, carbon dioxide partial pressure, pH, the presence of complexing ions, and ionic strength of the solution. Papers referring to solubility of cadmium(II) carbonate have been published since 1901; the thorough search of the literature in this field covered the period from 1901 through 2009. The compilation of the available experimental data is introduced with a critical evaluation. The evaluation of the experimental data considers the possible correlation between the data obtained under similar experimental conditions of temperature, carbon dioxide partial pressure, electrolyte, and ionic strength. Those experiments where the solid phase was well identified and the interactions between the electrolyte and the dissolved cadmium(II) ion were considered practically negligible were used to determine the thermodynamic properties of the solid cadmium(II) carbonate. Recommended values for the thermodynamic quantities are lg*K(ps0)(degrees) = 6.11 +/- 0.10, Delta(f)G degrees(CdCO(3), cr, 298.15 K) = -(674.3 +/- 0.6) kJ mol(-1), Delta(f)H degrees(CdCO(3), cr, 298.15 K) = -(752.2 +/- 0.8) kJ mol(-1), S degrees(CdCO(3), cr, 298.15 K) = (103.9 +/- 0.2) J K(-1) mol(-1).

The thermodynamic properties of the binary aqueous solutions of 183 electrolytes at 25 degrees C and 1 bar have been fitted using a standard form of the Pitzer equations. Where possible, all thermodynamic properties have been treated simultaneously, in contrast to previous compilations of Pitzer parameters. Prior to fitting, a critical assessment of the available information for each system was made using the JESS database and software. Employing linear regression with singular value decomposition and using an appropriate objective function criterion, more than two-thirds of the systems could be satisfactorily fitted to the upper concentration limit of the available data. Only six electrolytes proved to be completely intractable using the present Pitzer model. All of these systems (which included HF, H(2)SO(4), and H(3)PO(4)) are known to exhibit significant changes in chemical speciation at low concentrations (even though ion association per se does not preclude a satisfactory fit). The present Pitzer ion-interaction parameters provide a coherent, up-to-date set of empirical coefficients that can be combined in a self-consistent manner to produce multicomponent electrolyte solution models having a minimum of computational uncertainty in bulk solution properties such as density, heat capacity, and water activity.

The solubility data for well-defined binary, ternary, and multicomponent systems of solid-liquid type are reviewed. One component, which is 2-, 3-, and 4-hydroxybenzoic acids, 4-hydroxybenzoate alkyl esters (parabens), or hydroxybenzoic acid salts, is in the solid state at room temperature and another component is liquid water, meaning that all of the systems are aqueous solutions. The ternary or multicomponent systems include organic substances of various classes (hydrocarbons of several structural types, halogenated hydrocarbons, alcohols, acids, ethers, esters, amides, and surfactants) or inorganic substances. Systems reported in the primary literature from 1898 through 2000 are compiled. For seven systems, sufficient binary data for hydroxybenzoic acids or parabens in water are available to allow critical evaluation. Almost all data are expressed as mass and mole fractions as well as the originally reported units, while some data are expressed as molar concentration.

ThermoML is an XML-based approach for storage and exchange of experimental, predicted, and critically evaluated thermophysical and thermochemical property data. Extensions to the ThermoML schema for the representation of speciation, complex equilibria, and properties of biomaterials are described. The texts of 14 data files illustrating the new extensions are provided as Supplementary Information together with the complete text of the updated ThermoML schema.

The solid-liquid solubility data for well defined nonaqueous binary and ternary systems are reviewed. One component includes hydroxybenzoic acid, hydroxybenzoate, and hydroxybenzoic acid salt, and another component includes a variety of organic compounds (hydrocarbons, alcohols, halogenated hydrocarbons, carboxylic acids, esters, et al.) and carbon dioxide. The ternary systems include mixtures of organic substances of various classes and carbon dioxide. The total number of compilation sheets is 270 for six types of system. Almost all data are expressed as mass percent and mole fraction as well as the originally reported units, while some data are expressed as molar concentration. Critical evaluation was carried out for the binary nonaqueous systems of 2-, 3-, and 4-hydroxybenzoic acids and hydroxybenzoates (methylparaben, ethylparaben, propylparaben, and butylparaben) in alcohols, 1-heptane, and benzene.

ThermoML is an XML-based approach for storage and exchange of measured and critically evaluated thermophysical and thermochemical property data. Extensions to the ThermoML schema for the representation of speciation and complex equilibria are described. The text of ThermoML (xml) is provided to illustrate application of the new extensions. These are provided as Supporting Information together with the complete updated ThermoML schema.

Impurities in hydrometallurgical process liquors frequently impact on product quality and yield, change physicochemical properties of the liquor, and form hard scale on heat exchangers and condensers. Organic compounds are of particular concern especially in the Bayer process, where impurities build up in the recycled liquor if not controlled. Depending on the redox state of the liquor, such compounds can undergo a variety of complex chemical reactions, including the formation of volatiles that can potentially cause environmental, health, and safety concerns. To aid in the development of appropriate control strategies, robust thermodynamic models for multicomponent aqueous systems containing large numbers of electrolytes and nonelectrolytes are required. Applications of thermodynamic models are discussed that range from the partitioning of volatile compounds in flash trains to the prediction of mixing properties of organic impurities with major Bayer liquor components.

A modified commercial (Setaram C80) calorimeter has been used to measure the isobaric volumetric heat capacities of concentrated alkaline sodium aluminate solutions at ionic strengths from 1 to 6 mol kg-1, with up to 40 mol.% substitution of hydroxide by aluminate, at temperatures from 50 to 300 °C and a pressure of 10 MPa. Apparent molar heat capacities for the mixtures, Cpφ{symbol}, derived from these data were found to depend linearly on the aluminate substitution level, i.e., they followed Young's rule. These quantities were used to estimate the apparent molar heat capacities of pure, hypothetical sodium aluminate solutions, Cpφ{symbol} ('NaAl(OH)4'(aq)). Slopes of the Young's rule plots were invariant with ionic strength at a given temperature but depended linearly on temperature. The heat capacities of ternary aqueous sodium hydroxide/aluminate mixtures could therefore be modelled using only two parameters in addition to those needed for the correlation of Cpφ{symbol} (NaOH(aq)) reported previously from these laboratories. An assessment of the standard thermodynamic quantities for boehmite, gibbsite and the aluminate ion yielded a set of recommended values that, together with the present heat capacity data, accurately predicts the solubility of gibbsite and boehmite at temperatures up to 300 °C.

Densities of highly alkaline sodium aluminate Solutions have been measured by vibrating-tube densimetry over the temperature range 323 <= T/K <= 573 at a pressure of 10 MPa. Ionic strengths, 1, of these mixed solutions were 1 <= l/mol.kg(-1) <= 6, and the degree of Substitution of hydroxide by aluminate, alpha, ranged from 0.1 <= alpha <= 0.4, where alpha = m(A)/m and m(A) and m (= l) ire the aluminate and total molalities, respectively. Apparent molar volumes, V-phi, derived from the density data for the (NaOH + NaAl(OH)(4))(aq) Solutions, were found to follow Young's rule; that is, they depended linearly on the level Of Substitution of aluminate for hydroxide at all temperatures. The slopes of the Young's rule plots were independent of ionic strength at a given temperature but depended linearly on temperature. It is therefore possible to model V-phi (and hence the densities) of ternary (NaOH + NaAl(OH)(4))(aq) mixtures using only two parameters in addition to those needed for the correlation of the binary NaOH(aq) Solutions. This also means that the standard state (infinite dilution) partial molar volumes, V-2 degrees, of pure, hypothetical NaAl(OH)(4)(aq) call readily be obtained from V-2 degrees for NaOH(aq) by linear extrapolation using the two Young's rule parameters.