A Pitzer-based characterization of aqueous magnesium chloride, calcium chloride and potassium iodide solution densities to high temperature and pressure

Abstract

Rowland, D. and May, P.M. (2013)AThis is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Abstract A comprehensive characterization of densities / apparent molar volumes for the aqueous solutions of magnesium chloride, calcium chloride and potassium iodide to high temperatures and pressures has been performed based on the Pitzer equations. The unusual availability of overlapping high quality independent sets of experimentally measured data for these systems allows the relevant thermodynamic quantities to be calculated with a high degree of confidence over wide ranges of conditions (< 8 mol/kg; 273-573 K; 0.1-100 MPa). A realistic assessment of experimental uncertainty indicates that an adequate description of volumetric behaviour is achieved by the standard Pitzer model without extensions. The experimental accuracy implied by differences between independent observers, however, is more than one order of magnitude worse than typically-claimed estimates of experimental precision.

Aqueous electrolyte solution modelling: Some limitations of the Pitzer equations

“…Only then can they be better addressed. Until that time, the Pitzer equations (used with appropriate caution) will remain a useful tool in the characterization and harmonization of aqueous physicochemical properties Rowland and May, 2013). Table A1 lists some Pitzer equation models covering wide ranges of temperature.…”

“…300 binary and >200 ternary systems). This database provides sufficient coverage to explore the modelling of physicochemical properties in systematic ways not previously practicable Rowland and May, 2013). Most importantly, for meaningful analysis of modelling functions, it is necessary to have systems, such as NaCl(aq), MgCl 2 (aq) and CaCl 2 (aq), that have been measured sufficiently often by independent investigators to permit a realistic assessment of experimental errors (Rowland and May, 2013).…”

“…ion-interaction parameters have been employed to reduce the deviations to less than ±0.005 in . Such extensions are rarely justified (NaCl(aq) is a possible exception) given the differences between independent measurements but, worse, they conjure up a picture of agreement between observed data and model calculations that depends upon the data selected and which is subjective and non-trivial to verify independently (Rowland and May, 2013).…”

Comparison of the Pitzer and Hückel Equation Frameworks for Activity Coefficients, Osmotic Coefficients, and Apparent Molar Relative Enthalpies, Heat Capacities, and Volumes of Binary Aqueous Strong Electrolyte Solutions at 25 °C

“…Unless and until these lanthanide chloride osmotic coefficients are independently measured, the presence of some kind of systematic error should not be discounted. 8 Whatever the truth of the preceding matter may be, no grounds exist to think that the superior precision of the Pitzer equations is achieved by anything more than its greater inherent numerical flexibility. There are many cases in which a more linear behavior in the activity/osmotic coefficient is wellfitted by the Pitzer function so, in Figure 3 and Supporting Information Figures S7−S12, the model is for the most part following the data, not imposing the undulating curvature.…”

Parámetros de Interacción Iónica de las Soluciones Acuosas Concentradas del Líquido Iónico Trifluorometanosulfonato de 1-Etil-3-Metil-Imidazolio a Varias Temperaturas

“…Sin embargo, estos modelos por su empirismo implícito en su desarrollo, requieren la evaluación de los parámetros de interacción a partir de datos experimentales (Rowland et al, 2013;Song, 2010), afortunadamente Pitzer y Simomson desarrollaron un modelo alternativo basado en fracción molar (Pitzer et al, 1986). Luego, Clegg y Pitzer (1992) extendieron el modelo introduciendo términos dependientes de la concentración en la expresión de Debye-Hückel y un parámetro adicional de corto alcance para la interacción entre el solvente y un anión y un catión en soluciones altamente concentradas, estos se han usado con éxito en la correlación del volumen molar aparente de algunos líquidos iónicos con diversos solventes (Yang et al, 2005;Tong et al, 2009).…”