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

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 degrees C) and boiling point (128 degrees C) of a saturated solution. The temperature of the transition between the hemihydrate and anhydrous NaNO2 solid phases occurs at ca. -5 degrees C. There is excellent agreement between most studies above 0 degrees C, with the average solubility at 25 degrees 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 degrees C. The intrinsic volume of dissolved NaNO2 determined in this study (36.5 cm(3).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 similar to 0.87 mol of water per mole of dissolved ion at 128 degrees C, the extremely high solubility of NaNO2 in water resembles a hydrated molten salt. A thermodynamic-based solubility model was developed.

Automated summary

This study reviews the solubility of sodium nitrite (NaNO2) in water, providing data on solubility, electrical conductivity, viscosity, and density at different temperatures. The results show that concentrated NaNO2 solutions behave more like molten salt. A thermodynamic-based solubility model was developed to further understand the solubility of NaNO2 in water.