Occurrence, extraction and uses

Phosphorus-based flame retardants include tris(l,3-dichloroisopropyl) phosphate, used in polyurethane foams and polyester resins. Once again, there is debate concerning toxic side-effects of such products although these flame retardants may save lives, they produce noxious fumes during a fire. 

Many inorganic compounds are used as flame retardants for example 

Tin-based flame retardants appear to have a great potential future they are non-toxic, apparently producing none of the hazardous side-effects of the widely used phosphorus-based materials. 

Martin (1998) Chemistry in Britain, vol. 34, June issue, p. 20 - In the line of fire . 

Letcher, ed. (2003) Environment International, vol. 29, issue 6, pp. 663-885 - A themed issue of the journal entitled The state-of-the-science and trends of bromi-nated flame retardants in the environment . 

The industrial separation of N2 is discussed in 8ection 15.4. Mining of phosphate rock takes place on a vast scale (in 2008, 161 Mt was mined worldwide), with the majority destined for the production of fertilizers (see Box 15.10) and animal feed supplements. Elemental phosphorus is extracted from phosphate rock (which approximates in composition to Ca3(P04)2) by heating with sand and coke in an electric furnace (eq. 15.3) phosphorus vapour distils out and is condensed under water to yield white phosphoras. 

In contrast to the toxic effects of arsenic, some prokaryotic (anaerobic) bacteria depend upon arsenic. Mono Lake, California, is a closed, saline basin (i.e. no water outlet) that is fed by freshwater streams and underwater springs including volcanic sources. In 2008, researchers discovered that cyanobacteria and photosynthetic, prokaryotic bacteria in Mono Lake use arsenic(III) compotmds as their only photosynthetic electron donor. The process converts As(III) to As(V). The discovery may he relevant to an understanding of the arsenic cycle on ancient Earth in which oxygen played no role. 

Bleiwas (2000) US Geological Survey, http //minerals. usgs.gOv/minerals/mflow/d00-0195/ - Arsenic and old waste . 

Wang and CM. Wai (2005) J. Chem. Educ.,yo. 81, p. 207 Arsenic in drinking water - a global environmental problem . 

The principal source of As is FeAsS, and the element is extracted by heating (eq. 15.4) and condensing the As sublimate. An additional method is air-oxidation of arsenic sulfide ores to give AS2O3 which is then reduced by C. AS2O3 is also recovered on a large scale from flue dusts in Cu and Pb smelters. 

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Occurrence, extraction and uses Physical properties The metals Halides... 

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