Nitric Henry coefficient

The thermodynamic equilibrium is calculated with the Henry coefficients corrected for the electrolyte influence. As nitric acid is a strong electrolyte, the solubilities of nitrogen oxides in water [81] must be recalculated according to [20] to account for the non-ideal electrolyte behavior. 

Nitric acid is a strong electrolyte. Therefore, the solubilities of nitrogen oxides in water given in Ref. 191 and based on Henry s law are utilized and further corrected by using the method of van Krevelen and Hofhjzer (77) for electrolyte solutions. The chemical equilibrium is calculated in terms of liquid-phase activities. The local composition model of Engels (192), based on the UNIQUAC model, is used for the calculation of vapor pressures and activity coefficients of water and nitric acid. Multicomponent diffusion coefficients in the liquid phase are corrected for the nonideality, as suggested in Ref. 57. 

Using the literature data for the concentrations of the non-hydrated acid in the HN03-H20 system, its states in the HN03-H2S04-H20 system, and its partial vapour pressures, the applicability of Henry s law has been demonstrated to non-hydrated nitric acid in these systems.128 On the basis of a study129 of the systems HN03-H20-M(N03)n (MB+ = Na+, Cu2+, Be2+, U02+, La3+, Fe3+, or Al3+), the salting-out activity of the nitrates is characterized by the separation coefficient I described by ... 

Oxides of Nitrogen Nitric oxide (NO) and nitrogen dioxide (N02) are also characterized by small solubility in water (Henry s law coefficients 0.002 and 0.01 Matm-1 at 298 K). A negligible fraction of these species is dissolved in cloudwater, and their aqueous-phase concentrations are estimated to be on the order of 1 nM or even smaller. 

Let us estimate the above timescales for a 10 pm radius droplet at 298 K. For O3, a gas with low water solubility, the calculated timescale using (11.62) is 5 x 10" s. For SO2 at pH 5, and an accommodation coefficient of 0.1, the timescale using (11.61) is approximately 0.05 s. Since the timescale depends linearly on the effective Henry s law constant, it will be even smaller for lower pH values, while it will increase to approximately 1 s at pH 6. For H2O2 with an accommodation coefficient on water over 0.2, the timescale is less than 0.1 s. For relatively soluble species like NH3 the characteristic time is roughly 1 s for a = 1 and 18 s for a = 0.1. For extremely soluble species like nitric acid the timescale... 

The main release of gaseous radionuclides occurs when UNF is breached and dissolved in boiling nitric acid. The following radionuclides iodine-129 (1-129), and krypton-85 (Kr-85) are likely to appear in the off-gas of an air sparge of the dissolver in a conventional PUREX fuel-reprocessing flowsheet. Iodine in the fuel element is believed to occur mainly as iodide (I") however, when contacted with nitric acid, the iodide rapidly oxidizes to elemental I2. Much of the elemental iodine is volatilized to the off-gas, but a portion remains dissolved in solution this ratio (gas phase/liquid phase) is the distribution coefficient or sometimes expressed as a Henry s Law constant. Further oxidation of the liquid phase iodine results in the formation of fhe nonvolatile iodate ion, IO3". However, the formation of the iodate ion occurs slowly and reduction back to elemental iodine is promoted by nitrous acid, which is present in the dissolver system (McKay, Miquel, and White, 1982). 

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