Nitric acid concentration, activity coefficient

Figure 2. Activity coefficients of HNOs and NOs as a function of the molar nitric acid concentration...

As the medium is still further diluted, until nitronium ion is not detectable, the second-order rate coefficient decreases by a factor of about 10 for each decrease of 10% in the concentration of the sulphuric acid (figs. 2.1, 2.3, 2.4). The active electrophile under these conditions is not molecular nitric acid because the variation in the rate is not similar to the correspondii chaise in the concentration of this species, determined by ultraviolet spectroscopy or measurements of the vapour pressure. " ... 

Considering first pure nitric acid as the solvent, if the concentrations of nitronium ion in the absence and presence of a stoichiometric concentration x of dinitrogen tetroxide are yo and y respectively, these will also represent the concentrations of water in the two solutions, and the concentrations of nitrate ion will be y and x- y respectively. The equilibrium law, assuming that the variation of activity coefficients is negligible, then requires that ... 

If, for example, a mixture of ethanol and water is distilled, the concentration of the alcohol steadily increases until it reaches 96 per cent by mass, when the composition of the vapour equals that of the liquid, and no further enrichment occurs. This mixture is called an azeotrope, and it cannot be separated by straightforward distillation. Such a condition is shown in the y — x curves of Fig. 11.4 where it is seen that the equilibrium curve crosses the diagonal, indicating the existence of an azeotrope. A large number of azeotropic mixtures have been found, some of which are of great industrial importance, such as water-nitric acid, water-hydrochloric acid, and water-alcohols. The problem of non-ideality is discussed in Section 11.2.4 where the determination of the equilibrium data is considered. When the activity coefficient is greater than unity, giving a positive deviation from Raoult s law, the molecules of the components in the system repel each... 

In the U.S.S.R., the D.V.S. is often named the coefficient of dehydration and a slightly different way of calculating the nitric composition of sulphuric acid mixtures is in use there. This is

nitrating activity suggested by Kholevo. According to Gorst [2], it is the concentration of sulphuric acid in the mixture when the nitric acid is converted into the equivalent quantity of water. 

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 ... 

The authors prepared Al2(Se03)3(s), Ga2(Se03)3(s), In2(Se03)3(s), and Tl2(Se03)3(s). The solubilities of the salts were measured in nitric, perchloric, or sulphuric acid at 298 K. No primary experimental data are furnished and the review assumes that the pH values, 1.7 to 2.0, reported refer to the saturated solutions. The solubility products were calculated from the analytical concentration of dissolved metal ion with corrections for the protonation of the selenite ion and the activity coefficients. No recalculation with the values of these quantities accepted by the review is possible. 

Stelson and Seinfeld (1981) have shown that solution concentrations of 8-26 M can be expected in wetted atmospheric aerosol. At such concentrations the solutions are strongly nonideal, and appropriate thermodynamic activity coefficients are necessary for thermodynamic calculations. Tang (1980), Stelson and Seinfeld (1982a-c), and Stelson et al. (1984) have developed activity coefficient expressions for aqueous systems of nitrate, sulfate, ammonium, nitric acid, and sulfuric acid at concentrations exceeding 1M. 

The rate-increasing portion of the nitration rate profile can readily be explained by the increasing concentration of nitronium ion up to about 90% sulfuric acid, at which point the nitric acid is essentially completely converted to nitronium ion. It is not clear exactly why the nitration rate declines thereafter however, it has been suggested that the effects of the medium on the aromatic activity coefficients are responsible. (13)... 

Feed and removal volumetric flow Concentration of hexamine in feed Molar mass of hexamine Concentration of nitric acid in feed Molar mass of nitric acid Pre-exponential factor Apparent energy of activation Order of the reaction Thermal capacity of hexamine Feed temperature of hexamine Thermal capacity of nitric acid Feed temperature of nitric acid Overall coefficient of heat transfer Area for heat transfer (jacket + coU) Enthalpy of reaction Reaction temperature... 

Wilhelmy found the equation satisfied with nitric acid. He used hydrochloric, nitric, sulphuric, oxalic and phosphoric acids, the last being less active he found acetic acid inactive (it acts only very slowly). The influence of temperature was assumed to follow the same exponential law as concentration, the increase in volume also having an influence. The temperature-free velocity coefficient was thus found to be ... 

The ionic strength depends not only on the concentration of Ag" and Cl ions but also on all the other ions. Thus, for example, the addition of nitric acid HNO3, which adds H" " and NOJ ions to the system, will change the activity coefficient. But the equilibrium constant, which is a function of Tonly (8.3.19), remains constant if T is constant. As a result, the value of m (or solubility in molal) will change with the ionic strength I. If the concentration of nitric acid (which dissociates completely) is mnNOs. the ionic strength will be... 

Vesely, Beranova, and Mal have Investigated the extraction of uranium and fission pi Oducts by several methylalkyl ketones methylhexyl, methylamyl, methlbutyl, and methylproi l in addition to methyl Isobutyl and methyl-cyclohexanone. The partition coefficients of both uranium and fission product activity -fere measured as a function of acid concentration In the range of -0.4 to 3M nitric acid. 

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