Nitrogen dioxide, to nitric acid

If this reaction takes place in air, the evolved nitrogen monoxide is oxidised to the dioxide and this dissolves again as in equation (9.1) hence virtually complete conversion of nitrogen dioxide to nitric acid can occur (see nitric acid, below). With alkalis, a mixture of nitrite and nitrate is formed ... 

Sunlight initiates the transformation of nitrogen dioxide to nitric acid, IINO, which, along with sulfriric acid, is a prime component of acid rain. In aerosols, sunlight splits nitrogen dioxide into nitrogen monoxide and atomic oxygen ... 

More recently, chemiluminescence detectors based on redox reactions have made possible the detection of many classes of compounds not detected by flame ionization. In the redox chemiluminescence detector (RCD), the effluent from the column is mixed with nitrogen dioxide and passed across a catalyst containing elemental gold at 200-400°C. Responsive compounds reduce the nitrogen dioxide to nitric oxide. The nitric oxide is reacted with ozone to give the chemiluminescent emission. The RCD yields a response from compounds capable of undergoing dehydrogenation or oxidation and produces sensitive emissions from alcohols, aldehydes, ketones, acids, amines, olifins, aromatic compounds, sulfides, and thiols. 

The most important industrial use of nitric oxide is in the preparation of other nitrogen-containing compounds, especially nitrogen dioxide (N02), nitric acid (HN03), and nitrosyl chloride (N0C1). It also finds some application in the bleaching of rayon (a synthetic, or artificially created, fabric) and as a polymerization inhibitor with certain compounds such as propylene and methyl ether. Such compounds have a tendency to react with each other to form large, complex molecules known as polymers. 

The redox chemiluminescence detector (RCD) is also based on the nitric oxide-ozone reaction. However, unlike the two detectors previously described, the analytes do not contain any oxidizable nitrogen. In this case a nitrogen-containing reagent such as nitrogen dioxide or nitric acid is reduced to nitric oxide by the analyte at a heated gold surface (reaction [IV]) ... 

A competitive route now in commercial operation involves the oxidation of isobutene by a mixture of nitric acid and nitrogen dioxide to hydroxyisobutyric acid, which is dehydrated to methacrylic acid ... 

Peroxonitrous acid can decompose by two pathways isomerization to nitric acid, and dissociation into the hydroxyl radical and nitrogen dioxide. 

A portion of nitrogen dioxide in the atmosphere is converted to nitric acid (HNO3) and ammonium salts. Nitrate aerosol (acid aerosol) is removed from the atmosphere... 

The nitrogen dioxide product is converted to nitric acid for recycle in the process. The process has been described in detail by Spealman (Ref 11)... 

The steady-state ratio of nitrogen dioxide concentration to nitric acid can be readily found to be... 

Chemical/Physical. In a smog chamber, methanol reacted with nitrogen dioxide to give methyl nitrite and nitric acid (Takagi et al., 1986). The formation of these products was facilitated when this experiment was accompanied by UV light (Akimoto and Takagi, 1986). 

Tuazon et al. (1984a) investigated the atmospheric reactions of TV-nitrosodimethylamine and dimethylnitramine in an environmental chamber utilizing in situ long-path Fourier transform infared spectroscopy. They irradiated an ozone-rich atmosphere containing A-nitrosodimethyl-amine. Photolysis products identified include dimethylnitramine, nitromethane, formaldehyde, carbon monoxide, nitrogen dioxide, nitrogen pentoxide, and nitric acid. The rate constants for the reaction of fV-nitrosodimethylamine with OH radicals and ozone relative to methyl ether were 3.0 X 10 and <1 x 10 ° cmVmolecule-sec, respectively. The estimated atmospheric half-life of A-nitrosodimethylamine in the troposphere is approximately 5 min. 

Chemical/Physical. In an environmental chamber, nitrogen trioxide (10,000 ppb) reacted quickly with phenol (concentration 200 ppb to 1.4 ppm) to form phenoxy radicals and nitric acid (Carter et al., 1981). The phenoxy radicals may react with oxygen and nitrogen dioxide to form quinones and nitrohydroxy derivatives, respectively (Nielsen et al, 1983). 

Nitrogen dioxide can be identified by color, odor, and physical properties. It is dissolved in warm water and converted to nitric acid. The latter may be measured by acid-base titration or from analysis of nitrate ion by nitrate ion-specific electrode or by ion chromatography. Alternatively, nitrogen dioxide may be passed over heated charcoal to produce nitrogen and carbon dioxide that may be analysed by GC-TCD or GC/MS (See Nitrogen, Analysis). The characteristic masses for N2 and CO2 formed for their identification are 28 and 44, respectively. 

Finally, nitrogen dioxide is oxidized to nitric acid in a number of ways. For example, it may react with a hydroxyl radical, producing the acid ... 

The interaction of a mixture of nitric oxide and nitrogen dioxide with sulphuric acid has already been referred to (p. 153) nitric oxide alone is only slightly absorbed by the pure acid and not appreciably by the somewhat diluted acid such as is used in the nitrometer.5... 

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