Brown cloud

Pipette 25 mL of the standard 0.1 M silver nitrate into a 250 mL conical flask, add 5mL of 6M nitric acid and 1 mL of the iron(III) indicator solution. Run in the potassium or ammonium thiocyanate solution from a burette. At first a white precipitate is produced, rendering the liquid of a milky appearance, and as each drop of thiocyanate falls in, it produces a reddish-brown cloud, which quickly disappears on shaking. As the end point approaches, the precipitate becomes flocculent and settles easily finally one drop of the thiocyanate solution produces a faint brown colour, which no longer disappears upon shaking. This is the end point. The indicator blank amounts to 0.01 mL ofO.lM silver nitrate. It is essential to shake vigorously during the titration in order to obtain correct results. ... 

An alcoholic solution of iodine is decolorised by arsine, some arsenious acid being formed in solution, and after passing the gas for some time a black precipitate appears.4 Admixture of arsine with hydrogen chloride results in the formation of a brown cloud of arsenic 5 aqueous hydrochloric acid and arsine yield arsenic trichloride.6 Arsine reacts quantitatively with iodine monochloride in aqueous solution with liberation of iodine, thus ... 

Liu, D.H, and B,G. Liptbak Air Pollution, Lewis Publishers, Boca Raton, FL, 1999. Lyons, C.E. Environmental Problem Solving The 1987-88 Denver Brown Cloud Study, Chem. Eng. Progress. 6171 (May 1990). 

Jupiter and Uranus are outer planets composed mainly of gases. Jupiter s atmosphere contains reddish-brown clouds of ammonia. Uranus has an atmosphere made up mainly of hydrogen and helium with clouds of water vapor. This combination looks greenish to an outside observer. In addition, Mars has an atmosphere that is 95% carbon dioxide, and Venus has a permanent cloud cover of sulfur dioxide that appears pale yellow to an observer. Mercury has no permanent atmosphere. Saturn has 1 km thick dust and ice rings that orbit the planet. The eight planets in our solar system are diverse, each having different chemical compositions within and surrounding the planets. Out Earth is by far the friendliest planet for human existence. 

Fig. 10.13 Ar/H2 plasma (3 parts Ar to 1 part H2) burning over Cu(CF3S03)2 dissolved in [EMIM][TfO] with a brown cloud and black deposits. The distance amounts to only 4.5 cm, thus the plasma consists mostly of dark space (Faraday space).

Ramanathan, V. and P.J. Crutzen New directions Atmospheric brown "Clouds", Atmospheric Environment, 37 (2003)4033-4035. 

Distribution of the aerosol optical and microphysical properties in the Atmospheric Brown Clouds... 

The optical and microphysical properties of aerosol allowed the identification of the days during which the aerosol concentration in separate layers exceeded the background 10. .. 10 times. Two such layers were identified the Atmospheric Brown Cloud (ABC) in the upper troposphere (5.5-9.1 km) and ABC in the lower troposphere (1.7-4.3 km). The highest aerosol concentrations in the separate layers of the troposphere were observed most frequently in warm periods (May - September), and much less often in cold seasons. 

Here is another example of two elements reacting to form a compound whose properties are different from either element. Heated steel (iron) wool reacts with chlorine gas to form iron(III) chloride, the brown cloud you see in the flask. 

Groblicki, R J., Wolff, G. T., and Countess, R. J. (1981) Visibility-reducing species in the Denver brown cloud —I. Relationships between extinction and chemical composition, Atmos. Environ. 15, 2473-2484. 

Colorless oil with an unpleasant odor. M.p. —21°C, b.p. (19.5 mm.) 64°C, (760 mm.) 164.7°C. Decomposes at 150°C, explosively at 180 °C. May be stored without decomposition in a sealed tube filled with Ng. Fumes explosively in air, at first forming white and then (rapidly) brown clouds accompanied by violent detonation. Decomposed by HgO with a characteristic crackling sound continuing for hours on end. d (21.7°C) 1.653. 

Characters and Tests.—Colourless liquid. Sp. gr. 1 42 boiling-point 250 F. Exposed to air, it emits acrid and corrosive fumes. Copper dropped into a mixture of equal parts of the add and water causes the evolution of a colourless gas (nitric oxide), which, as it mixes with the oxygen of the air, forms ruddy fumes (nitric trioxide and nitric peroxide). A crystal of ferrous sulphate dropped into the add, diluted with an equal bulk of water, becomes surrounded by a brown cloud if the mixture be cold. The add should leave no residue on evaporation. Diluted with six times its volume of distilled water, it should give no precipitate with barium nitrate or silver nitrate, showing the absence of sulphuric and hydrochloric acids. 

New research has found that the sooty brown clouds, caused primarily by the burning of coal and other organic materials in India, China and other parts of south Asia, might be responsible for some of the atmospheric warming that had been attributed to greenhouse gases (Ramanathan and Crutzen 2003, Ramanathan et al. 2007). 

Region A corresponds to the behaviour of the dry acetonitrile solution. In these conditions, polypyrrole films are powdered and are low adherents. From elemental analysis it is observed that these films contain an important excess of hydrogen [46,54,133,134]. Moreover, electrosynthesis is accompanied by the simultaneous formation of a brown cloud of oligomers around the electrode [130]. As water is added, in region B, this cloud disappears and the electrical and mechanical properties of polypyrrole are strongly improved [128,130,135]. 

Reaction 3 takes into account two possible acid-catalyzed ways of producing electroactive (3 a) and nonelectroactive (3b) polymers. Reaction 3a facilitates the electrochemical process of polymerization. Reaction 3b promotes the generation of non-conducting oligomers. This non-electroactive polymer can deposit on the electrode or diffuse into the solution, producing a brown cloud. Low participation of the acid-catalyzed process 3b would increase the electroactivity of the final polymers and subsequently their conductivity and obtention rate. This seems to be the effect of water addition to a pyrrole/acetonitrile solution, due to the higher basic nature of water compared to pyrrole. 

Asian Brown Cloud Climate and Health Effects... 

Gustafson, Otjan, Martin Krusa, Zdenek Zencak, Rebecca J. Sheesley, Lennart Granat, Erik Engstidm, RS.P. Rao, Caroline Leek, and Henning Rodhe, Brown Clouds over South Asia Biomass or Fossil Fuel Combustion Science 323,495—498 (2009). 

Jacobs, Andrew, Haunting Asia, a Brown Cloud Blots Out Sun, New York Times Health Science http //www. nytimes.com/2008/1 l/13/health/13iht-cloud.4.17808200.html, 2008. 

In what sense is the brown cloud a counteracting measure against global warming Does that mean that measures should not be taken to counteract the brown cloud ... 

Ramanathan, V, Ramana, M. V., Roberts, G. (2007). Warming trends in Asia amplified by brown cloud solar absorption. Nature, 448, 575-578. 

As a drop of thiocyanate solution is added to Ag ion solution containing Fe ion, a reddish-brown cloud is first formed which quickly disappears on shaking because of its reaction with Ag ion ... 

Member of the steering committee of the Atmospheric Brown Clouds programme, in collaboration with the United Nations Environmental Program (UNEP), La JoUa/Nairobi (2001-). 

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