Nitric acid: modeling osmotic coefficients and acid–base dissociation using the BIMSA theory

Abstract

This work is aimed at a description of the thermodynamic properties of highly concentrated aqueous solutions of nitric acid salts at 25 °C within the binding mean spherical approximation (BIMSA) theory. The predictive capability of this model was examined. First, Raman spectroscopy was used to study the proportion of associated nitric acid as a function of concentration. The corresponding apparent association constant values were compared with literature values. Besides, the BIMSA model, taking into account complex formation, was used to represent literature experimental osmotic coefficient variation with concentration. This theoretical description led to an assessment of the degree of association. The so calculated amount of associated nitric acid coincides accurately with our Raman experimental results up to a high concentration of acid.

Redox Potential Evolution of Nitric Species and Plutonium in HNO3-HNO2 System

“…with an equilibrium constant equal to aHNO aNO aH = K 3 3 − + = 15 at 25° [4] These results are in good agreement with Sicsic and Ruas's degrees of dissociation of nitric acid (4,10). From the Davis's data, the effect of the initial concentration of nitric acid on activities of protons (black triangles), nitrate ions (black squares), undissociated nitric acid (black circles) and water (black diamond) at 25°C is presented in Figure 3 Many studies show that the nitric acid reduction is very complex (2)(3)(4)(11)(12)(13)(14)(15).…”

Insights into the Mechanism of Extraction of Uranium (VI) from Nitric Acid Solution into an Ionic Liquid by using Tri‐n‐butyl phosphate

“…This meanst hat some nitrate entities are co-extracted with the uranyl complex, not as NO 3 À ions (which are visible by EXAFS if they are in the uranyl first coordination sphere), but as HNO 3 molecular entities to be extracted as adducts. Nitric acid is not fully dissociated above a2m concentration, [46] and can form adducts with TBP. [47,48] Moreover,i nt his complex, the HNO 3 entity would lie in the uranyl second coordination sphere, at too large ad istance from uranium to be detected by EXAFS.…”

Raman spectroscopic determination of the degree of dissociation of nitric acid in binary and ternary mixtures with HF and H2SiF6

“…However, it is not advantageous to compensate the time‐dependent signal drift of a typical Raman spectrometer by adding an internal standard to concentrated HF/HNO 3 /H 2 SiF 6 acid mixtures. A repeating measurement of an external standard (e.g., CCl 4 ) is, in principle, possible, however, less applicable for continuous measurements, such as online etch bath monitoring and should, therefore, be avoided.…”

“…Consequently, the method of Levanov and Hlushak was extended to determine the degree of dissociation of nitric acid in HF/HNO 3 /H 2 SiF 6 acid mixtures of unknown nitric acid concentration and the influence of HF and H 2 SiF 6 on the degree of nitric acid dissociation. The total nitric acid content in such acid mixtures can be determined, for example, by ion chromatographic determination of the nitrate content in highly diluted aliquots.…”