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

• Published in: Journal of chemical and engineering data Vol. 66; no. 8; pp. 2931 - 2941
• Main Authors: Reynolds, Jacob G, Britton, Michael D, Belsher, Jeremy D
• Format: Journal Article
• Language: English
• Published: American Chemical Society 12-08-2021
• ISSN: 0021-9568; 1520-5134
• DOI: 10.1021/acs.jced.1c00175

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.