Nitric acid trends

These trends are general ones, observed with other oxoadds of the nonmetals. Recall, for example, that nitric acid, HNO3 (oxid. no. N = +5), is a strong acid, completely ionized in water. In contrast, nitrous add, HN02 (oxid. no. N = +3), is a weak acid (Ka = 6.0 X 10-4). The electronegativity effect shows up with the strengths of the oxoadds of sulfur and selenium ... 

J(PQ) and J(PN)). Trends in J(P170) have been used to study the protonation of phosphoryl tribromide, phosphoryl trifluoride and dif1uorophosphoric acid. Nitric acid had a greater protonation power than Hammett acidity functions indicated.77 This coupling has been the subject of a semiempirical sum over states theoretical study.7 ... 

These trends have been quantified for some reactions. Nitration studies showed carbazole to react 222,000 times faster than benzene, with nitric acid-acetic anhydride having partial rate factors of 32,100 (C-1), 1,100 (C-2), 77,600 (C-3), and too small to measure (C-4). Carbazole reacts about 20 times more slowly than diphenylamine. The partial rate factor for nitration at C-3 can be compared with a value of 50,100 found for the perchloric add protodesilylation of 3-trimethylsilylcarbazole. ... 

To what extent do electrostatic potential maps constructed for neutral acids and bases reflect acid and base strengths If they do, one should be able to replace having to look at a reaction energy by the simpler and more intuitive task of looking at a property of a molecule. It is clear that electrostatic potential maps uncover gross trends, for example, the acidic hydrogen in a strong acid, such as nitric acid, is more positive than that in a weak acid, such as acetic acid, which in turn is more positive than that in a very weak acid, such as ethanol. 

The use of nitroglycerine tablets has been known for several decades to dilate the blood vessels promptly thereby decreasing the blood pressure and thus giving instant relief from angina. However, the present trend is to use other esters of nitric acid such as erythritol tetranitrate, mannitol hexanitrate, PETN and other similar derivatives instead of NG for this purpose. These nitric acid esters being crystalline, are not assimilated readily and therefore, act more slowly but produce a longer lasting effect. 

There has been a trend toward the production of ammonium phosphates in powder form, Concentrated phosphoric acid is neutralized under pressure, and the heat of neutralization is used to remove the water in a spray tower. The powdered product then is collected at the bottom of the tower. Ammonium nitrate/ammonium phosphate combination products can be obtained either by neutralizing mixed nitric acid and phosphoric acid, or by the addition of ammonium phosphate to an ammonium nitrate melt. 

The Australian domestic nitric acid market was found to suffer from cyclical variations, with seasonal highs and lows each year. This fluctuation is attributed to the major acid consumers (fertilizer and explosives manufacturers) being susceptible to seasonal variations in demand, and to the level of world commodity prices. However, the overall trend has been for 3% annual growth. Current Australian production is 200 000 tonnes each year (100% acid basis). Exports from and imports into Australia are virtually non-existent. A protective barrier in the form of high shipping costs, has in the past effectively closed the domestic market. 

Worldwide annual production of nitric acid is at present approximately 34 million tonnes. The USA, UK, Poland and France are the largest producers. The trend in the last decade has been for growth by the larger producers, very much at the expense of the smaller ones. The global scene is a much more stable market. This can be attributed historically to consumption being more broadly based with a sizable consumption in chemical production processes. 

In order to establish the feasibility of the project, a study of the history of the nitric acid market over the last decade is presented, both in a domestic and global perspective. The size and nature of the market is studied, including the determination of general trends in industry and potential growth areas. 

Australia currently produces approximately 200 000 tonnes of nitric acid (100% basis) per year (Ref. MD5). It is a cyclical market that responds directly to the performance of the agricultural and mining sectors. This occurs because Australian nitric acid is used almost exclusively for the production of ammonium nitrate (a nitrogen-based fertilizer and a mining explosive). The nitric acid industry has grown from a production capacity of 32 000 tonnes in 1967 (Ref. MD1 ). During the last decade, large deviations in production levels have occurred (Refe. MD3, MD4, and MD5). The overall trend has been for a 3% increase each year. 

Figure B.l Australian production trend for nitric acid (1976-86). Table B.l Australian annual production data for nitric acid (1976-86).

FIGURE B.l Australian production trend for nitric acid. 

A discounted cash flow analysis is performed on those capital cost and production cost figures reported in Ref. PT1 (plant capacity of 280 tonne of 60% nitric acid). Although the plant cost data relates to a US plant, the figures still indicate the trend. 

In addition to ice formation, salts also precipitate as these solutions are lofted to higher altitudes. A consequence of the formation of these solid phases (ice and salts) and the low-temperature eutectics of strong acids (Fig. 3.5) is that the atmospheric solutions become more and more acidic with altitude (Fig. 5.8). For example, the final elevation (temperature) examined is 11.54 km (—50 °C). At this point, the calculated concentrations of the Hubbard Brook solution are H+ = 7.55m with acid anions (Cl-, NO3, SO4-, HSOJ) = 7.91m. Similarly, for the Mt. Sonnblick solution, H+ = 6.50 m and acid anions = 6.90 m. These acidic trends are in line with stratospheric chemistries, which are predominantly sulfuric/nitric acid aerosols (Carslaw et al. 1997). For example, the total acid concentration at 20.7km in the stratosphere is 10.17m (calculated from fig. 7 in Carslaw et al. 1997), which is in line with our lower atmospheric concentrations. 

Some of the principal variations between these processes are different operating temperatures, different operating pressures and different concentrations of the nitric acid product. Other differences include catalysts and spent catalyst recovery systems. In the 1990 s, new air emission control requirements necessitated the modification of some plants and prompted the re-evaluation of processes for new plants. This resulted in a trend toward plants... 

The mechanism of the substitution of sulphonic groups in phenol by nitro groups was extensively studied by Lesniak and T. Urbartski [130 and to this purpose the chromato-polarographic method introduced by Kemula and associates 11311 was used. The trend of the nitration of o and p-phenolsulphonic acids with nitric acid can be depicted by diagram (16a) ... 

No change in composition of the uranate product was found in the equimolar sodium-potassium nitrate following dissolution of the original uranate with nitric acid vapor and subsequent thermal decomposition of that soluble species. Analyses of the uranate produced over 300°C to 450°C indicated that only the diuranate species is formed. There was, however, a trend toward a decreasing potassium content as the reaction temperature increased. 

Evidence to support this "counterion modified" model comes from the investigation of hydrated Ln(NC>3)Cl2 prepared in the usual way in water (LnCl3, AgN03). The lanthanide(III) chlorides themselves show little or no catalytic activity for nitrations. A possible rationale for this is obtained by noting that HC1 is a poor activator of nitric acid in nitration chemistry since it is not sufficiently acidic to protonate nitric acid. However, the IR spectra of the Ln(NC>3)Cl2 salts are essentially identical to those of Ln(N03)(0Tf)2 indicating that the chloride ions are outer sphere in these complexes. Additionally the nitrate bands show the same trend as demonstrated for the triflate series (e.g., for La(N03)Cl2 the characteristic nitrate stretch is observed at 1459 cm1 and for Yb(NC>3)Cl2 the band appears at 1497 cm-1)- This indicates that the lanthanide chlorides are capable of activating nitric acid (via metal-nitrate interactions) but critically, the counterion (i.e. chloride) is incapable of fulfilling its role (in whatever capacity that may be) and hence no nitration occurs. 

The data in the present work, allowing for extraction of nitric acid into the organic phase, were used in equation 1 to calculate values of the apparent rate constant k. These are shown in Figure 6 and demonstrate a marked trend. It can only be concluded from this that either (a) equation 1 is not the true rate equation, (b) the distribution coefficient for toluene changes appreciably with conversion, or (c) the measured rate includes a contribution from mass transfer. 

Hanson, Marsland and Wilson ( ) measured the acid phase concentration of nitric acid in the reactor, and without this information no meaningfiil quantitative correlation and interpretation of their resiilts is possible. Lastly, Hanson, Marsland and Giles (1), in the most recent study, obtained very similar resiilts and trends to those of McKinley and White ( l). 

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