Ultra-violet nitric acid

The O-nitro group (the nitroxy group) gives an absorption band of about 270 va.fi, in the ultra-violet region, i.e. a band similar to that of the C-nitro group. A relatively small amount of work has been done on the ultra-violet absorption spectra of nitric acid esters but it has been established that in esters containing no other chromophoric groups absorption is extremely low (e = 10-20) even lower than in case of aliphatic nitro compounds. 

Hantzsch opposed the theory of N205 existing in the nitrating mixture HN03 + + H2S04 Due to the importance of the Hantzsch theory in the development of our views on the nature of the nitration process, we shall discuss it in detail. In a number of works Hantzsch [21-23] developed a theory based on Schafer s experiments [24] on the absorption spectrum in ultra-violet light. Schafer s chief observation was, that the spectrum of anhydrous nitric acid in a non-aqueous solvent (hexane, sulphuric acid, etc.) is analogous with the spectra of nitric acid esters,... 

To obtain further Mguments for the confirmation of his theory in 1925 Hantzsch [21] examined the ultra-violet absorption spectra of nitric acid. On dilution with water a band appeMs which may be ascribed to the N03 ion. The band is not present in solutions of nitric acid in sulphuric acid, since, as the author says, the ions H2N03+ and H3N032+ must appear in such circumstances. 

The similarity between the ultra-violet absorption spectrum of nitric acid Mid that of ethyl nitrate in sulphuric acid confirms this conception. 

Ultra-violet absorption spectrum. The first investigations into the ultra-violet absorption spectra of nitric acid, containing certain quantities of water, were carried out by Hartley [55]. He observed that the band at about 302 mp characteristic for the nitrate ion disappears gradually with increase in concentration of nitric acid. 

Fig. 6. Ultra-violet absorption spectra of nitric acid (Halban and Eisenbrand [18]).

Further experiments on ultra-violet absorption spectra of nitric acid in organic solvents have been carried out by a number of authors (Dalmon and Beilin [56], Kortiim [57], Eventually R. N. Jones, Thom et al. [58] expressed the view that nitrogen pentoxide is present in nitric acid of 95-96% and higher concentrations. 

Fig. 7. Ultra-violet absorption spectra of solutions of N205 in anhydrous nitric acid. (R. N. Jones, Thom, Lyne and E. G. Taylor [58]).

The absorption spectrum of morphine has been determined by Hartley [594], Mayer (in sulphuric-nitric acid) [595], and Kitasato [596], and the ultra-violet absorption spectrum (shown in comparison with that of codeine in Chap. IV) by other workers [597-602],... 

Acidic precipitation is a growing environmental problem. Acid rain, snow or fog is formed when oxides of sulfur and nitrogen from fossil fuel combustion are oxidized in the atmosphere by ultra-violet light and ozone to give sulfuric and nitric acids. These acids then mix with atmospheric water to form acidic precipitation. Since the normal pH of atmospheric water is 5.6-5.7, precipitation having a pH below 5.6 is termed acid rain (J, ). 

According to the Co/o r/ ultramarine violet (. v.) with gaseous hydrochloric acid at 200 C for four hours or at a higher temperature with gaseous nitric acid. The Colour Index further comments that ultra-marine red is the acid of which ultramarine violet is the salt... 

The basic product of the ignition is Ultramarine Green. This is converted into Ultramarine Blue by further heat treatment in the presence of sulfur, or into Ultra-marine Violet by heating with 5% ammonium chloride for four days at 200-250°C. Ultramarine Violet is converted into Ultramarine Red by treating it with gaseous hydrochloric acid at 70-200°C for four hours or by reaction with gaseous nitric acid at higher temperatures. 

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