Scheele's Green

Scheele's Green, also called Schloss Green, is chemically a cupric hydrogen arsenite (also called copper arsenite or acidic copper arsenite), CuHAsO
3. It is chemically related to Paris Green. Scheele's Green was invented in 1775 by Carl Wilhelm Scheele.[2][3] By the end of the 19th century, it had virtually replaced the older green pigments based on copper carbonate. It is a yellowish-green pigment commonly used during the early to mid-19th century in paints as well as being directly incorporated into a variety of products as a colorant.[4] It began to fall out of favor after the 1860s because of its toxicity and the instability of its color in the presence of sulfides and various chemical pollutants.[5] The acutely toxic nature of Scheele's green as well as other arsenic-containing green pigments such as Paris Green may have contributed to the sharp decline in the popularity of the color green in late Victorian society.[5] By the dawn of the 20th century, Scheele's green had completely fallen out of use as a pigment but was still in use as an insecticide into the 1930s.[6][7] At least two modern reproductions of Scheele's green hue with modern non-toxic pigments have been made, with similar but non-identical color coordinates: one with hex#3c7a18 (RGB 60, 122, 24) and another with hex#478800 (RGB 71, 136, 0).[8][9] The latter is the more typically reported color coordinate for Scheele's green.[10]

Not to be confused with copper arsenate.
Scheele's Green
Names
IUPAC name
copper hydrogen arsenite
Other names
Copper arsenite
Copper arsenate
Swedish Green
Cupric Green
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.030.573
  • InChI=1S/AsHO3.Cu/c2-1(3)4;/h2H;/q-2;+2 checkY
    Key: BPQWCZKMOKHAJF-UHFFFAOYSA-N checkY
  • InChI=1/AsHO3.Cu/c2-1(3)4;/h2H;/q-2;+2
    Key: BPQWCZKMOKHAJF-UHFFFAOYAR
  • [Cu+2].[O-][As]([O-])O
Properties
AsCuHO3
Molar mass 187.474
Hazards
NIOSH (US health exposure limits):
PEL (Permissible)
 [1910.1018] TWA 0.010 mg/m3[1]
REL (Recommended)
 Ca C 0.002 mg/m3 [15-minute][1]
IDLH (Immediate danger)
 Ca [5 mg/m3 (as As)][1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

Preparation
Scheele's Green
 
About these coordinates     Color coordinates
Hex triplet#478800
sRGBB (r, g, b)(71, 136, 0)
HSV (h, s, v)(89°, 100%, 53%)
CIELChuv (L, C, h)(51, 68, 118°)
Source[10]
B: Normalized to [0–255] (byte)

The pigment was originally prepared by making a solution of sodium carbonate at a temperature of around 90 °C (194 °F), then slowly adding arsenious oxide, while constantly stirring until everything had dissolved. This produced a sodium arsenite solution. Added to a copper sulfate solution, it produced a green precipitate of effectively insoluble copper arsenite. After filtration the product was dried at about 43 °C (109 °F). To enhance the color, the salt was subsequently heated to 60–70 °C (140–158 °F). The intensity of the color depends on the copper : arsenic ratio, which in turn was affected by the ratio of the starting materials, as well as the temperature.

It has been found that Scheele's green was composed of a variety of different compounds, including copper metaarsenite (CuO·As
2O
3), copper arsenite salt (CuHAsO
3 and Cu(AsO
3)
2·3H
2O)), neutral copper orthoarsenite (3CuO·As
2O
3·2H
2O), copper arsenate (CuAsO
2 and Cu(AsO
2)
2), and copper diarsenite (2CuO·As
2O
3·2H
2O).[11]

Uses

Scheele's Green was used as a color for paper, e.g. for wallpapers and paper hangings, and in paints, wax candles, and even on some children's toys.[12] It was also used to dye cotton and linen.[13] Scheele's Green is more brilliant and durable than the then-used copper carbonate pigments. However, because of its copper content it tends to fade and blacken when exposed to sulfides, whether in the form of atmospheric hydrogen sulfide or in pigment mixtures based on or containing sulfur. Emerald green, also known as Paris Green, was developed later in an attempt to improve Scheele's Green. It had the same tendency to blacken, but was more durable.

By the end of the 19th century, both greens were made obsolete by cobalt green, also known as zinc green, which is far less toxic.

Despite evidence of its high toxicity, Scheele's Green was also used as a food dye for sweets such as green blancmange,[14] a favorite of traders in 19th-century Greenock; this led to a long-standing Scottish prejudice against green sweets.[15]

Scheele's Green was used as an insecticide in the 1930s, together with Paris Green.[7][16][17]

Toxicity

In the 19th century, the toxicity of arsenic compounds was not readily known. Nineteenth-century journals contained reports of children wasting away in bright green rooms, of ladies in green dresses swooning, and of newspaper printers being overcome by arsenic vapors. There is one example of acute poisoning of children attending a Christmas party where dyed candles were burned.[18]

Although some European nations started banning arsenic-containing pigments in the 1830s and 1840s, Scheele's green did not completely fall out of favor until the 1860s.[19] Publicity associated the 1861 death of 19-year-old Matilda Scheueur as a result of her job dusting artificial foliage with the pigment increased public awareness of the toxicity of Scheele's green. An article "Pretty Poison-Wreaths" described her repeated illness from arsenic poisoning leading to her death, and detailed autopsy findings of eyes and fingernails turned green from the pigment.[5] By the 1890s the last brand of wallpaper using it ceased production.[6]

Illness associated with arsenic containing wallpaper
Woman doing embroidery in the light coming in through the window of a room with bright green wallpaper. A guitar lays on the couch in the background.
Woman Embroidering by Georg Friedrich Kersting (1812)

Two main theories on the cause of wallpaper poisoning events have been proposed: dust particles caused by pigment and paper flaking, and toxic gas production. Tiny particles of the pigment can flake off and become airborne, and then are absorbed by the lungs. Alternatively, toxic gas can be released from compounds containing arsenic following certain chemical processes, such as heating, or metabolism by an organism. When the wallpaper becomes damp and moldy, the pigment may be metabolised, causing the release of poisonous arsine gas (AsH
3). Fungi genera such as Scopulariopsis or Paecilomyces release arsine gas, when they are growing on a substance containing arsenic.[20][21] The Italian physician Bartolomeo Gosio published in 1893 his results on "Gosio gas", that was subsequently shown to contain trimethylarsine.[22] Under wet conditions, the mold Scopulariopsis brevicaulis produced significant amounts of methyl arsines via methylation[23] of arsenic-containing inorganic pigments, especially Paris green and Scheele's Green.

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 reduced to trivalent arsenic and trivalent arsenic tends to proceed via oxidative methylation in which the trivalent arsenic is made into mono, di and trimethylated products by methyltransferases and an S-adenosyl-methionine methyl donating cofactor.[24][25] However, newer studies indicate that trimethylarsine has a low toxicity, and could therefore not account for the death and the severe health problems observed in the 19th century.[26][27]

Arsenic is not only toxic, but it also has carcinogenic effects.[25]

Role in Napoleon's death

During his exile on St. Helena, Napoleon resided in a house in which the rooms were painted bright green, his favorite color. The cause of his death is generally believed to have been stomach cancer, and arsenic exposure has been linked to an increased risk of gastric carcinoma. Analysis of samples of his hair revealed significant amounts of arsenic.[13] As St. Helena has a rather damp climate, it is likely that fungus grew on the walls. It has also been suggested that the presence of such abnormally high levels of arsenic might be due to attempts at preserving his body.[28] However, more recent research has proven this theory to be false, and Napoleon did indeed die of stomach cancer.[29][30]

See also

References
  1. NIOSH Pocket Guide to Chemical Hazards. "#0038". National Institute for Occupational Safety and Health (NIOSH).
  2. Scheele, Carl Wilhelm (1778). "Tilrednings-saettet af en ny groen Faerg" [Method of preparation of a new green color]. Kungliga Vetenskaps Akademiens Handlingar (in Swedish). 39: 327–328.
  3. "StudioMara – History of Pigments". www.lilinks.com.
  4. Ruiz, Ada (2018-08-01). "Poisonous Pigments: Scheele's Green". Los Angeles Art College | Fine Art | Concept Art | Degrees | Community Classes. Retrieved 2022-09-27.
  5. "Scheele's Green - The Shunning of Green in the Victorian Era". DIEDFAMOUS. Retrieved 2022-09-27.
  6. "Explore Meural's Permanent Art Collection | Digital Artwork". my.meural. Retrieved 2022-09-27.
  7. "Early Insecticides Used Against Insects in the 1930s". www.livinghistoryfarm.org.
  8. "Samson Scheeles Green Precisely Matched For Paint and Spray Paint". MyPerfectColor.com. Retrieved 2022-09-27.
  9. Petherick, Andrew (2021-12-11). "Scheele's green as a home interior colour". Artichoke. Retrieved 2022-09-27.
  10. "Scheele's Green color hex code is #478800". www.color-name.com. Retrieved 2022-09-27.
  11. Nicholas Eastaugh; Valentine Walsh; Tracey Chaplin; Ruth Sidall. Pigment Compodium: A Dictionary of Historical Pigments. p. 122.
  12. Pye Henry Chavasse (1998). Advice to a Mother on the Management of her Children. Toronto: Willing & Williamson. ISBN 0-659-99653-7.
  13. St. Clair, Kassia (2016). The Secret Lives of Colour. London: John Murray. pp. 224–226. ISBN 978-1-4736-3081-9. OCLC 936144129.
  14. Timbrell, John (2005). "Butter Yellow and Scheele's Green". The Poison Paradox: Chemicals as Friends and Foes. Oxford University Press. ISBN 978-0-19-280495-2.
  15. "Media Release". www.abdn.ac.uk. University of Aberdeen Web Team.
  16. "Dangers in the Manufacture of Paris Green and Scheele's Green". Monthly Review of the U.S. Bureau of Labor Statistics. 5 (2): 78–83. 4 February 2018. JSTOR 41829377.
  17. "Scheele's green". Cameo – cameo.mfa.org.
  18. "Acute Poisoning". Archived from the original on 2013-01-15.
  19. Moonlight, Under The (2018-03-17). "A Dark History of Arsenic Greens". Under The Moonlight. Retrieved 2022-09-27.
  20. "Fungal Glossary". www.dehs.umn.edu. University of Minnesota, Department of Environmental Health & Safety.
  21. "Mold Types and Mold Species".
  22. Frederick Challenger (1955). "Biological methylation". Q. Rev. Chem. Soc. 9 (3): 255–286. doi:10.1039/QR9550900255.
  23. Ronald Bentley & Thomas G. Chasteen (2002). "Microbial Methylation of Metalloids: Arsenic, Antimony, and Bismuth". Microbiology and Molecular Biology Reviews. 66 (2): 250–271. doi:10.1128/MMBR.66.2.250-271.2002. PMC 120786. PMID 12040126.
  24. PL Goering; HV Aposhian; MJ Mass; M Cebrian; BD Beck; MP Waalkes (1999). "The enigma of arsenic carcinogenesis: role of metabolism". Toxicological Sciences. 49 (1): 5–14. doi:10.1093/toxsci/49.1.5. PMID 10367337.
  25. "Was Napoleon Murdered?". 20 October 2012. Archived from the original on 20 October 2012.
  26. William R. Cullen; Ronald Bentley (2005). "The toxicity of trimethylarsine: an urban myth". J. Environ. Monit. 7 (1): 11–15. doi:10.1039/b413752n. PMID 15693178.
  27. Frederick Challenger; Constance Higginbottom; Louis Ellis (1933). "The formation of organo-metalloidal compounds by microorganisms. Part I. Trimethylarsine and dimethylethylarsine". J. Chem. Soc.: 95–101. doi:10.1039/JR9330000095.
  28. Jones, David (14 October 1982). "The Singular Case of Napoleon's Wallpaper". New Scientist. Reed Business Information: 101.
  29. "Debunking myths in history: The true death cause of Napoleon". Hyped For History. 2023-09-12. Retrieved 2023-09-16.
  30. HINDMARSH, J. T.; CORSO, P. F. (1998-07-01). "The Death of Napoleon Bonaparte: A Critical Review of the Cause". Journal of the History of Medicine and Allied Sciences. 53 (3): 201–218. doi:10.1093/jhmas/53.3.201. ISSN 0022-5045.
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