A Review of Sodium Nitrite Solubility in Water and Physical Properties of the Saturated Solutions

Abstract

The solubility of sodium nitrite (NaNO2) in water is important to many industries, including those of heat pumps, oil extraction, and the management of alkaline nuclear waste. This study reviews solubility data for NaNO2 in water between the freezing point (−19 °C) and boiling point (128 °C) of a saturated solution. The temperature of the transition between the hemihydrate and anhydrous NaNO2 solid phases occurs at ca. −5 °C. There is excellent agreement between most studies above 0 °C, with the average solubility at 25 °C reported being 12.4 mol·kg–1 water. The electrical conductivity, viscosity, and density of saturated solutions were also reviewed, with mean values from several studies reported at 25 °C. The intrinsic volume of dissolved NaNO2 determined in this study (36.5 cm3·mol–1) is only 6% different from the value determined by extrapolating the density of molten salt to ambient temperatures. The flow in concentrated NaNO2 solutions behaves more like a molten salt than a soft colloidal behavior that more hydrated electrolytes resemble. Indeed, given that there is only ∼0.87 mol of water per mole of dissolved ion at 128 °C, the extremely high solubility of NaNO2 in water resembles a hydrated molten salt. A thermodynamic-based solubility model was developed.

A Review of Sodium Oxalate Solubility in Water

“…The data are compiled and statistically assessed. This study compliments existing reviews of the dissociation constants of oxalic acid as well as reviews of the solubility of other salts relevant to Hanford waste. − This study also compliments a recent study on the solubility trends of salts in multicomponent solutions simulating nuclear waste …”

A method to apply Zavitsas' aqueous electrolyte model to multicomponent solutions and its equivalence to Zdanovskii's rule

“…F I G U R E 1 Water activity of sodium nitrite solution as a function of concentration at 50 C. Data from Reynolds et al 24 Zavitsas has successfully fit his model to water activity data for aqueous NaNO 2 solution up to saturation at 25 C. 5 The present author has fit Zavitsas' model up to 17.74 molal NaNO 2 concentration at 100 C, and found an excellent fit. 16 The model may not fit osmotic coefficients for some electrolyte solutions at concentrations less than 0.1 molal, but the model appears to be a good choice for modelers who are interested in solutions with higher concentrations. For some highly soluble electrolytes,…”

“…An example is aqueous NaNO 2 solution, where Reynolds et al found the best fit to Equation (1) was 0.772 for H d and 2.02 for i e . 16 NaNO 2 cannot break into more than two ions, so i e was forced to be 2.00 and the model was refit to the same data. The new fit was insignificantly worse than the original, but the H d parameter changed from 0.772 to 0.819, a 6% change.…”

Tracking nitrite's deviation from Stokes–Einstein predictions with pulsed field gradient 15N NMR spectroscopy

“…[1][2][3][4] Studying the structure, stability, and dynamics of these oxyanion solutions is of benefit to ongoing activities to transport the waste out of the tanks for safe processing and long-term storage. 5 Determining the intermolecular interactions of oxyanions with other constituents within concentrated alkaline electrolytes has proved challenging due to the disparate sensitivities of experimental techniques to those interactions. 6 These ambiguities challenge the inclusion or omission of terms defining ion-pair formation in solubility models, such as those used to predict the stability of oxyanion-bearing electrolyte solutions.…”