Nitrous acid particle

Adsorption of nitric and sulfuric acids on ice particles provides the sol of the nitrating mixture. An important catalyst of aromatic nitration, nitrous acid, is typical for polluted atmospheres. Combustion sources contribute to air pollution via soot and NO emissions. The observed formation of HNO2 results from the reduction of nitrogen oxides in the presence of water by C—O and C—H groups in soot (Ammann et al. 1998). As seen, gas-phase nitration is important ecologically. 

Nitrous acid/nitrite can also be oxidized in the aqueous solutions found in the atmosphere in the form of fogs, clouds, and particles. Nitrite is well known to be slowly oxidized in the dark to nitrate by dissolved oxygen in the liquid phase. However, it has been reported that the rate of this oxidation increases remarkably during freezing of the solution containing the nitrite (Takenaka et al., 1992, 1996). Figure 7.11, for example, shows the rate of nitrate formation in a nitrite solution at 25°C and in one with the cooling bath at — 21°C (Takenaka et al., 1992). This unusual phenomenon has also been observed with respect to the... 

Chang, S. G., R. Toossi, and T. Novakov, The Importance of Soot Particles and Nitrous Acid in Oxidizing S02 in Atmospheric Aqueous Droplets, Atmos. Environ., 15, 1287-1292(1981). 

In developing the reactivity scale, Nielsen first investigated the transformation rates of 25 PAHs and four derivatives of anthracene in water-methanol-dioxane solutions, taken as a model of wet particles, and containing small amounts of dinitrogen tetroxide and nitric and nitrous acids. The measured half-lives and relative rates are shown in Table 10.29. The range of reactivities in solution for PAHs of different structures is remarkable, from 100,000 (arbitrarily set) for an-thanthrene (XXXII) to <0.2 for the least reactive compounds ... 

Chang S.G., Toosi R. and Novakov T., The importance of soot particles and nitrous acid in oxidizing SO in atmospheric aqueous droplets. Atmos. Environ. , 15, 1287-1292 (1981). 

Jefferson DA (2000) The surface activity of ultrafine particles. Phil Trans Roy Soc Lond A 358 2683-2692 Jose-Yacamai M (1998) The role of nanosized particles. A frontier in modem materials science, from nanoelectronics to environmental problems. Metall Mater Trans A 29 713-725 Kalberer M, Ammann M, Arens F, Gaggeler HW, Baltensperger U (1999) Heterogeneous formation of nitrous acid (HONO) on soot aerosol particles. J Geophys Res 104 13825-13832 Kamm S, Mohler O, Naumann KH, Saathoff H, Schurath U (1999) The heterogeneous reaction of ozone with soot aerosol. Atmos Environ 33 4651-4661... 

These data in Fig. 12.2 and 12.3 leave no doubt that chemical nitrification of nitrites to nitrates occurs readily in 1% potassium phosphate solutions that are more acid than about pH 4.0. In soils it has been shown (Stevenson and Swaby, 1964 Fuhr and Bremner, 1964a Stevenson et al., 1970) that a portion of any nitrous acid formed can react with soil organic matter, especially at the lower pH values, but a considerable portion of it decomposes to liberate NO. Quantitative data on the extent of these reactions under a wide variety of soil conditions have not yet been reported. Mortland and Wolcott (1965) and Mortland (1965) have shown that NO can penetrate the interlamellar surfaces of montmorillonite and in the presence of air it is oxidized at a rate dependent upon its diffusion to the edge of the particle. All of the nitric oxide was oxidized in 24 h or less. These data leave no doubt that nitrite undergoes nitrification in soils very much as in phosphate buffer solutions, except possibly to a lesser extent since a portion of it is fixed... 

This I consider to be the true state of nitrous air. Let us now suppose another particle of dephlogisticated air c to unite to P, it will combine only with the force of 4, whereby a b c and P will gravitate toward one another. Such is the state of the red nitrous vapour, or the red nitrous acid. 

Let us again suppose a fourth particle of dephlogisticated air d to combine with P, it will unite only with the force of 3f. This I think is the state of the pale or straw-coloured nitrous acid. 

The 5-ifitrosothiols are generally formed by reaction of nitrous acid with the parent thiol and are reported to require copper-mediated decomposition, reaction with ascorbate, or cleavage by light to release NO. NO donors are incorporated into materials either by blending discrete NO donors within polymeric films or covalently attached to polymer backbones and/or to the inorganic polymeric filler particles that are often employed to enhance the strength of biomedical polymers (e.g., fumed silica or titanium dioxide). ... 

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