View source for It07:Copper arsenate

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! {{chembox header}} | General
|- 
| [http://en.wikipedia.org/wiki/IUPAC Systematic name]
| Arsenic acid (H3AsO4) copper(2+) salt (2:3)
|-
| Other names
| Copper arsenate, Copper orthoarsenate, Tricopper arsenate, Tricopper orthoarsenate
|-
| [http://en.wikipedia.org/wiki/Chemical_formula Molecular formula]
| As<sub>2</sub>Cu<sub>3</sub>O<sub>8</sub> 
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| [http://en.wikipedia.org/wiki/Molar_mass Molar mass]
| 468.476 g/mol
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| Appearance
| Pale green solid
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| [http://en.wikipedia.org/wiki/CAS_registry_number CAS number]
| 7778-41-8
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! {{chembox header}} | Properties
|-
| [http://en.wikipedia.org/wiki/Density Density] & [http://en.wikipedia.org/wiki/Phase_%28matter%29 phase]
| 5.07 - 5.25 g/ml <!-- ? g/cm³, solid / ? g/ml, liquid / ? g/l, gas -->
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| [http://en.wikipedia.org/wiki/Solubility Solubility]
| Highly soluble in HCl <!--  at least put miscible with, not soluble in -->
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! {{chembox header}} | Structure
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| [http://en.wikipedia.org/wiki/Coordination_geometry Coordination<br />geometry] <!-- for a metal complex or an ionic crystal, otherwise omit -->
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| [http://en.wikipedia.org/wiki/Crystal_structure Crystal structure] <!-- omit if not a solid -->
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| [[Dipole#Molecular_dipoles|Dipole moment]]
| {{{DM}}} [[Debye|D]]
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! {{chembox header}} | Hazards <!--  Summary only- MSDS entry provides more complete information -->
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| [[Material safety data sheet|MSDS]]
| [[{{PAGENAME}} (data page)#Material Safety Data Sheet|External MSDS]] <!-- please replace with proper link-->
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| Main [[Worker safety and health|hazard]]s highly toxic, carcinogenic
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| [[NFPA 704]]
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! {{chembox header}} | Related compounds
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| Other [[Ion|anion]]s <!-- please omit if not applicable -->
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| Related compounds 
<!-- A miscellaneous heading - use for covalent inorganics;  e.g. for PCl<sub>3</sub> you would list PCl<sub>5</sub>, POCl<sub>3</sub>, PF<sub>3</sub>, PBr<sub>3</sub>, NCl<sub>3</sub> and AsCl<sub>3</sub>. 
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| {{{Relative_Compounds}}}
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| {{chembox header}} | <small>Except where noted otherwise, data are given for<br /> materials in their [[standard state|standard state (at 25&nbsp;°C, 100&nbsp;kPa)]]<br />[[wikipedia:Chemical infobox|Infobox disclaimer and references]]</small>
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{{Chem-Data_Structure}}


==Scheele's Green==
[[Image:Scheelepic.jpg]]
''Taken from http://de.wikipedia.org/wiki/Carl_Wilhelm_Scheele''

Developed in 1775, by the Swedish-German chemist [http://en.wikipedia.org/wiki/Carl_Wilhelm_Scheele Carl Wilhelm Scheele], Scheele's green (also known as Schloss green- Schloss meaning castle/mansion in German) is a vibrant yellowish green colour, composed of a mixture of various copper arsenite compounds. It is the predecessor to the more vibrant Paris Green (also known as Schweinfurt Green, or Emerald Green) and was used as an insecticide, as well as a pigment, until the hazards connected to its use were acknowledged. Before the discovery of this pigment, the known green pigments were based on copper carbonate and had the tendency to fade, which made this choice of colour unsustainable. The popularity of Scheele's green was based on its bright colour, as well as the fact that it was a lot more durable than previous pigments, which meant that the colour green could be used in its full splendour, without having to worry too much about its progressive degradation. 

[[Image:Scheelesgreenwallpaper.JPG]] ''Taken from http://www.grand-illusions.com/napoleon/images/walpaper.JPG<sup>[5]</sup>''

'''3-D image of CuAsHO<sub>3</sub>'''


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===Preparation <sup>[1]</sup>===
The pigment was originally prepared by making a solution of sodium carbonate at a temperature of around 90°C, then slowly adding in arsenious oxide, while constantly stirring until everything had dissolved. This sodium arsenite solution was then added to a copper sulphate solution. The sodium would displace the copper, which resulted in the formation of the desired product in the form of a green precipitate. This copper arsenite was then filtered off and warmed to around 43°C to dry the crystals. To enhance the colour, the salt was subsequently heated to 60-70°C. The intensity of the colour depends on the copper : arsenic ratio, which in turn was affected by ratio of the starting materials, as well as the temperature. 

Another method used to produce Scheele's green was by directly adding dilute copper sulphate solution to an alkali solution of arsenic. This would then precipitate- the precipitate also being Scheele's green.

It has been found that Scheele's green was composed of a variety of different compounds, including copper metaarsenite (CuO.As<sub>2</sub>O<sub>3</sub>), copper arsenite salt (CuAsHO<sub>3</sub> and Cu<sub>3</sub>(AsO<sub>3</sub>)<sub>2</sub>.3H<sub>2</sub>O)), neutral copper orthoarsenite (3CuO.As<sub>2</sub>O<sub>3</sub>.2H<sub>2</sub>O), copper arsenate (CuAsO<sub>2</sub> and Cu(AsO<sub>2</sub>)<sub>2</sub>), copper diarsenite (2CuO.As<sub>2</sub>O<sub>3</sub>.2H<sub>2</sub>O).
===Uses===
The beautiful green colour of this compound meant that it was largely used in pigments- be these for paints, dyes for cloths, or otherwise.  It was even used to colour foodstuffs, such as sweets and alcoholic beverages, to colour candles and to paint toys. Later, once its toxicity was vaguely understood, Scheele’s green was used as an insecticide. Today it is no longer used in any form.

===Toxicity===
Today it is intuitive to most that an complex containing arsenic is most likely to be toxic, however in the 19th century this was not really known. 19th century journals reported of children wasting away in bright green rooms, of ladies in green dresses swooning and newspaper printers being overcome by arsenic vapours. There is even one report of a Christmas party that resulted in mass arsenic poisoning, due to the use of green candles. <sup>[2]</sup> 
  
Arsenic poisoning was usually caused by the inhalation of arsine gas (AsH<sub>3</sub>), which can be released from compounds containing arsenic following certain chemical processes, such as heating, or its metabolism by an orgnanism. Fungi such as Scopulariopsis, or the Paecilomyces species release arsine gas, when they are growing on a substance containing arsenic.<sup>[http://www.dehs.umn.edu/iaq_fib_fg_gloss.htm [3]]</sup> <sup>[http://www.alerchek.com/MoldTypesMoldSpecies.htm [4]]</sup> In these compounds, the Arsenic is either pentavalent, or trivalent (arsenic is in group 15), depending on the compound. In humans, arsenic of these valences is readily absorbed by the gastrointestinal tract, which accounts for its high toxicity. Pentavalent arsenic tends to be oxidised to trivalent arsenic and trivalent arsenic tends to proceed via oxidative methylation in which the trivalent arsenic is made into a mono, di and trimethylated products by the S adenosyl methionine (an enzyme) and its cofactor glutatione.<sup>[6]</sup><sup>[7]</sup>. Arsenic is not only toxic, but it also has carcinogenic effects <sup>[7]</sup>.

===Scheele's Green and Napoleon===

During Napoleon's exile in St. Helena, he resided in a very luxurious bright green room. His cause of death is generally believed to be stomach cancer, however, analysis of his hair samples revealed significant amounts of arsenic. As St. Helena has a rather damp climate, it is more than possible that fungus grew on the wall. So as to remove the toxic arsenic, the fungus would release it in the form of arsine gas, which when inhaled causes arsenic poisoning.<sup>[7]</sup>

===References===
<sup>[1]</sup> [http://books.google.com/books?id=TKFiYsc_xOAC&pg=PA122&lpg=PA122&dq=scheele's+green&source=web&ots=3IvbK3Qjd4&sig=WqswVShzEkivMk2BtQgSu5JlQcE#PPA122,M1 Pigment Compodium: A Dictionary of Historical Pigments, by Nicholas Eastaugh, Valentine Walsh, Tracey Chaplin, Ruth Sidall page 122]

<sup>[2]</sup>[http://www.harvestfields.ca/HerbBooks/01/01/047.htm Acute poisoning]

<sup>[3]</sup> [http://www.dehs.umn.edu/iaq_fib_fg_gloss.htm Fungus Glossary]

<sup>[4]</sup> [http://www.alerchek.com/MoldTypesMoldSpecies.htm Fungus Glossary]

<sup> [5]</sup> http://www.grand-illusions.com/napoleon/images/walpaper.JPG

<sup> [6]</sup> [http://toxsci.oxfordjournals.org/cgi/content/abstract/49/1/5 The enigma of arsenic carcinogenesis: role of metabolism]

<sup>[7]</sup> [http://www.btinternet.com/~ian.borthwick/LADAS/prog/01_napoleon.html Napoleon and his wallpaper]