Some highs and lows (and in-betweens) of solubility measurements of solid electrolytes

Abstract

Recent solubility measurements of a variety of solid electrolytes in water and aqueous solutions in the author's laboratories are reviewed. The experimental challenge of performing such measurements with high accuracy is demonstrated using the solubility of solid sodium chloride in water at near-ambient temperatures as a paradigm. The special difficulties of measuring low solubilities are demonstrated using Pb(ll) sulfate in various aqueous solutions and Pb(Il) oxide in sodium hydroxide solutions, and the usefulness of such measurements for obtaining reliable information on homogeneous reactions in solution is briefly discussed. It is also shown, using the alkali metal trit1ate salts as examples, that determination of the solubilities of even highly soluble salts can be problematic. Lastly, data for the solubilities of a series of sodium carboxylate salts of industrial relevance are discussed and are used to illustrate why the theoretical prediction of solid electrolyte solubilities remains such a challenge.

Densities and Apparent Molar Volumes of Aqueous Solutions of Sodium and Potassium Triflates up to High Concentrations at Temperatures 293.15–343.15 K

“…On the other hand, the concentration range examined has been rather limited, with molalities m ≲ 0.3 mol·kg –1 , except for the study by Xiao and Tremaine ( m ≲ 1.7 mol·kg –1 ; although almost all their measurements were at m ≲ 1.0 mol·kg –1 ) . However, even the highest of these concentrations represents only a small fraction (<20%) of the solubility of this highly soluble salt . The accurate characterization of the apparent molar volumes, V ϕ , of NaTf­(aq) and KTf­(aq) over such wide concentration ranges provides an opportunity to compare the performance of the two most widely employed semiempirical V ϕ fitting equations, along with a potentially interesting alternative based on an extended Debye–Hückel (e-DH) model.…”

“…11 However, even the highest of these concentrations represents only a small fraction (<20%) of the solubility of this highly soluble salt. 1 The accurate characterization of the apparent molar volumes, V ϕ , of NaTf(aq) and KTf(aq) over such wide concentration ranges provides an opportunity to compare the performance of the two most widely employed semiempirical V ϕ fitting equations, along with a potentially interesting alternative based on an extended Debye−Huckel (e-DH) model. Particular attention has also been paid to measurements at low concentrations to elucidate reliable standard partial molar volumes, V o , for both salts at infinite dilution.…”

“…Salts of trifluoromethanesulfonic (“triflic”) acid, HTf, attract a lot of attention because of their generally high solubilities in a wide variety of solvents (usually including water) and their relatively low tendency to associate, even in solvents with modest dielectric constants. , In addition, triflate salts are thermally stable and chemically unreactive, showing little acid–base or redox activity. , These characteristics make such salts particularly attractive for batteries and other electrochemical applications and for replacing less-stable substances such as perchlorates and fluoroborates in various contexts . Although triflate salts are expensive to purchase commercially, they are easily prepared, typically by the reaction of HTf with the relevant metal carbonate or oxide; HTf itself is readily available in good purity and is easily distilled.…”

Editorial: Guidelines for the Measurement of Solid–Liquid Solubility Data at Atmospheric Pressure

“…Various methods used in the older literature have been discussed by Zimmerman . While modern trace analytical techniques have enabled the measurement of very low solubilities, the uncertainties involved are much larger (also because of the presence, often in vast excess, of other solution components such as background electrolytes) than those in the case of higher solubilities, where the most reliable and accurate methods of quantitative analysis, gravimetry and volumetry, can be applied. , For moderately to highly soluble solutes, it would therefore be counterproductive to dilute saturated solutions by many orders of magnitude then use a routine trace-analytical method such as atomic absorption or inductively coupled plasma spectrometry. Characterization of the solid phase. After the solubility experiment has been finished and the phases have been separated, the mother liquor permeating the “wet residue” needs to be removed by washing the solid with a suitable solvent, filtering and drying (usually applicable to sparingly soluble solids).…”

Aqueous electrolyte solution modelling: Some limitations of the Pitzer equations

“…A selection of literature Pitzer models for these electrolyte solutions is shown in Table 1 (Table A1 of Appendix A gives similar details for other multidimensional chemical systems). Rogers and Pitzer (1982) 273-573 0.1-100 5.5 Pitzer et al (1984) 273-573 0.1-100 6 Archer (1992) a 250-600 0.1-100 6 Archer and Carter (2000) a 250-600 0.1-100 6 MgCl 2 (aq) Phutela et al (1987) 273 Most of the present work was performed using the JESS (Joint Expert Speciation System) software package Murray, 1991, 2001;May et al, 2010May et al, , 2011Rowland and May, 2010, 2012, 2013, 2014. The JESS physicochemical property database (FIZ) currently contains more than 400,000 data entries, mostly for electrolytes (ca.…”