Peroxides in atmosphere

Lazrus, A. L., G. L. Kok, S. N. Gitlin, and J. A. Lind, Automated Fluorometric Method for Hydrogen Peroxide in Atmospheric Precipitation, Anal. Chem., 57, 9f7-922 (f985). 

Aqueous-phase photochemical peroxide production occurred in >90% of all samples at all sites, with no peroxide production in dark controls [108]. This photoproduction was hypothesized to result from the absorption of Hght by chromophores in the samples, followed by the formation of peroxyl radical intermediates, the dominant precursor of peroxides in atmospheric waters [108]. Under simulated suidight, the average rate of total peroxide photoproduction... 

Concentrations of hydrogen peroxide in atmospheric water samples such as rainwater are usually considerably higher than those determined in surface water samples. For example, Zika et al. (1982) found rainwater collected in southern Florida and the Bahamas to contain levels ranging from 1-7 x 10" M. Levels of up to 3 X 10 M were detected in southern California and Tokyo rainwater (Kok, 1980 Yoshizumi et al., 1984), although the usual hourly mean concentration was about an... 

Scott, G., 1965, Peroxides. In Atmospheric Oxidation and Antioxidants (G. Scott, ed.), Elsevier, Chapter 2 Scott, G., 1965, Antioxidants radical chain mechanisms. In Atmospheric Oxidation and Antioxidants (G. Scott, ed.), Elsevier, Chapter 4 Scott, G., 1965, Oxidation of Olefinic Oils, Fats and Polymers. In Atmospheric Oxidation and Antioxidants (G. Scott, ed.), Elsevier, Chapter 8. 

Tantalum is severely attacked at ambient temperatures and up to about 100°C in aqueous atmospheric environments in the presence of fluorine and hydrofluoric acids. Flourine, hydrofluoric acid and fluoride salt solutions represent typical aggressive environments in which tantalum corrodes at ambient temperatures. Under exposure to these environments the protective TajOj oxide film is attacked and the metal is transformed from a passive to an active state. The corrosion mechanism of tantalum in these environments is mainly based on dissolution reactions to give fluoro complexes. The composition depends markedly on the conditions. The existence of oxidizing agents such as sulphur trioxide or peroxides in aqueous fluoride environments enhance the corrosion rate of tantalum owing to rapid formation of oxofluoro complexes. 

The same goes for peroxides and superoxides. Thus, tin powdered which was in contact with sodium peroxide in a carbon dioxide atmosphere in the presence of water traces glowed before combusting. With potassium superoxide there is an immediate incandescence of the mixture. 

However, the reaction rate is not uniform. The maximum reaction rate must be known to calculate the area needed for heat exchange. This can and should be determined in a laboratory. For the suspension polymerization of polystyrene at 80°C using 0.5% benzoyl peroxide in an inert atmosphere, the reaction takes 4.5 hr to reach completion and the maximum conversion rate is 20% in 0.5 hr.24 Although... 

Pentane and ethane (end products of n-6 and n-3 polyunsaturated fatty acid peroxidation, respectively) in expired air are useful markers of in vivo lipid peroxidation. Nevertheless, when gas chromatography is used to measure hydrocarbons, some technical difficulties may be experienced because chromatographic resolution of pentane from isoprene and isopentane is extremely difficult to achieve. Another possible problem could be the presence of these gases as contaminants in atmosphere. Furthermore, the production of hydrocarbon gases depends on the presence of metal ions to decompose lipid peroxides. If such ions are only available in limited amounts, this index may be inaccurate. 

Zuo, Y., and J. Hoigne (1992), "Formation of Hydrogen Peroxide and Depletion of Oxalic Acid in Atmospheric Water by Photolysis", Env. Sci. Technol., submitted. 

The scission reaction was carried out with a fixed addition of 1.50g of the dry resin, 10 mg of ferrous sulfate heptahydrate and 50 ml of 3% w/v hydrogen peroxide in a round Pyrex flask. The evolved carbon dioxide was vented to the atmosphere through serial traps containing sulfuric acid followed by a soda lime sorption tube. The magnetically stirred reaction flask was submerged in an oil bath heated with an immersed electrical coil and a magnetic stirrer positioned below the bath. The temperature was maintained at 50 +/- 1 C. After varied times 1.0 ml samples of liquid were withdrawn. There were fewer than six withdrawals in a given reaction sequence. 

The present section is an overview of the varied involvement of peroxides in natural phenomena, ranging from atmospheric chemistry to important physiological systems in all living organisms, and the functions fulfilled by these compounds in industry. All this requires adequate analytical methods to identify, determine and characterize peroxides. This section should not be considered as a comprehensive review on natural and industrially relevant peroxides, but rather as a structured set of examples related to analytical methods described in the sequel. 

Penkett, S. A., B. J. Bandy, C. E. Reeves, D. McKenna, and P. Hignett, Measurements of Peroxides in the Atmosphere and Their Relevance to the Understanding of Global Tropospheric Chemistry, Faraday Discuss., 100, 155-174(1995). 

Penkett, S. A., B. M. R. Jones, K. A. Brice, and A. E. J. Eggleton, The Importance of Atmospheric Ozone and Hydrogen Peroxide in Oxidizing Sulphur Dioxide in Cloud and Rain Water, Atmos. Environ., 13, 123-137 (1979). 

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