Schweinfurt green

Structural formula
General
Surname	Schweinfurt green
other names	Copper (II) arsenite acetate Viennese green Parisian green Mitis green Urania green Parrot green Kaiser green New green Original green Moss green Cover paper green Patent green CI 77410 (Pigment Green 21)
Molecular formula	C 4 H 6 As 6 Cu 4 O 16
Brief description	green, crystalline powder
External identifiers / databases
CAS number 12002-03-8 12310-22-4 EC number 601-658-7 ECHA InfoCard 100.125.242 PubChem 22833492 ChemSpider 17215797 Wikidata Q339657
properties
Molar mass	1013.80 g mol −1
Physical state	firmly
Melting point	decomposes when heated
solubility	heavy in water
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary danger H and P phrases H: 331-301-410 P: ?
MAK	no MAK, as carcinogenic
Toxicological data	22 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Schweinfurt green (also Paris green , patent green or mitis green ) or copper (II) arsenite acetate is a double salt that contains copper , arsenic and the acetic acid anion . The chemical formula is given as Cu (CH ₃ COO) ₂  · 3 Cu (AsO ₂ ) ₂ .

Schweinfurt green was used as paint in the 19th century. It was valued for its color intensity and lightfastness , but its toxicity was known early on. It was used as one of the first pesticides in the second half of the 19th century to around the middle of the 20th century .

history

A can of Schweinfurt green pigment

In 1805 the Austrian technician Ignaz von Mitis discovered a precipitation product that was named after him Mitisgrün. This pigment was first produced around 1805 in Kirchberg am Wechsel , which is why it was also called Kirchberger Grün. The first industrial production of Mitisgrün took place in Schweinfurt in Lower Franconia by the industrialist Wilhelm Sattler , the product was named after this place of manufacture. In 1814 production was relocated to Schonungen in the Schweinfurt district. The pigment was marketed under a variety of names, around 80 are known.

The evidence of the toxic effects of wallpapers printed with Schweinfurt green was first published by the Merseburg doctor Carl von Basedow in 1844. He showed that a certain fungus ( Penicillium brevicaule ) from glue-bound Schweinfurt green releases organic arsenic compounds which lead to poisoning via the air we breathe. For a long time there was speculation about the cause of Napoleon Bonaparte's death , which could be justified in arsenic poisoning from the wallpaper paint. However, this was questioned in 2008 by an Italian research group who, through hair analyzes, came to the conclusion that similarly high levels of the toxic semi-metal were present in the body in all phases of life considered and therefore there was no (at least intentional) poisoning.

In 1882, Schweinfurt green was banned as a color in Germany; since 1887, processing in aqueous binders and pastels has been banned . After that it was used as an insecticide and as a paint for ships .

Manufacturing

Schweinfurt green in the narrower sense is produced by pouring together boiling solutions of crystallized copper acetate (verdigris) and arsenic acid ( arsenic (III) oxide ). This initially creates a dirty green, flaky precipitate, which turns into microscopic, shiny, green crystals by standing for two to three days , which are then squeezed out and dried. In order to obtain a dye with higher hiding power , the mixed liquids are allowed to continue to boil for a short time . The dye then separates out quickly as a fine powder. It is better suited for oil and lacquer paints, but does not have the "fire" of the larger crystals.

${\displaystyle {\ce {4 CuO + 3 As2O3 + 2 CH3COOH -> 3 Cu(AsO2)2 * Cu(CH3COO)2 + H2O}}}$

Schweinfurt green was often mixed with gypsum, barite , lead (II) sulfate or chrome yellow .

The name "Schweinfurt Green" was also used as a collective name for all green colors that contained copper and arsenic as essential components. They came under a variety of names such as Kaiser green, Parisian, Viennese, Kasseler, Neuwied, Mitis, Berggrün and Scheelesches green in the trade and differed in their tints and the livelier or matt color.

proof

To quickly determine whether a green color is Schweinfurtergrün, Merck's Warenlexikon from 1884 recommends dissolving it in ammonia . If the color contains copper, the resulting solution turns bluish in color. This solution is dripped onto paper. If a light blue to blue-greenish residue remains after the ammonia has evaporated , then there is only a copper color without arsenic. If there is arsenic, the residue is a dirty yellow-green color.

If you pour some Schweinfurt green with hydrochloric acid , it dissolves with a yellow color. If this solution is kept in a sealed bottle together with a bare copper sheet, after a while the sheet will be covered with a black crust of arsenic and arsenic copper.

Use as a plant protection product

In the USA in 1868 a JP Wilson patented the mixture of one part Paris Green with two parts mineral oil for use against Colorado beetles . Schweinfurt green was also used in other insecticide formulations, for example mixed with wood ash. It was the first chemical insecticide to be used on a large scale. By the mid-1890s, 2,000 tons were sold annually in the United States. Around this time people tried to use Schweinfurt green against the gypsy moth, for which it was unsuitable. When looking for a suitable insecticide, lead arsenate turned out to be more effective. Because it left less burn damage on the leaves and stayed there longer, lead arsenate became the most widely used insecticide in the USA.

In Germany in 1905 experiments with Schweinfurt green and other arsenic compounds for use in viticulture and fruit growing began. Only after arsenic was included in the first list of pesticides by the Biological Reichsanstalt in 1920 did Schweinfurt green begin to be used as a pesticide. In 1936 in Germany the Kupferarsenitacetat preparations were Urania Green , Elafrosin , Franconiagrün , Saxoniagrün , Silesiagrün and St. Urban Green approved for use in the wine. It was mainly used against hayworms and sourworms , the grape moth larvae . To apply the active ingredient, 150–200 g of copper arsenite acetate were dissolved in 100 liters of copper lime broth .

While the arsenic residues in the wine were low, the pomace wine produced by the winemakers as a house drink for their own use contained between 2 and 8.9 mg arsenic / liter. If drunk for a long time it could lead to chronic arsenic poisoning. Between 1925 and 1934 this affected around 100 winegrowers on the Kaiserstuhl and between 1938 and 1942 around 1,000 winegrowers on the Moselle . In Germany, the use of arsenic-containing substances in viticulture was banned by a law of November 1942.

In Switzerland, Schweinfurter Grün was offered as Vert de Schweinfurt 1914 for use in viticulture. However, it was not of great importance there because an alternative was available with lead arsenate.

literature

• H. Andreas: Schweinfurt green - the brilliant poison . In: Chemistry in our time , 30 1996, pp. 23-31, doi: 10.1002 / ciuz.19960300105 .
• LM Mokler: The industrial Germany. Complete paint factory for room, wallpaper and art painters; and mainly for the operation of larger and smaller factories; by practical testing and the principles of the most famous factories in Germany ... . Claß, Heilbronn 1838, p. 31 ff. Digital version of the SLUB Dresden via EOD .
• F. Schweizer, B. Mühletaler: Some green and blue copper pigments , color and lacquer, 74 1968, p. 1159-73
• Lucinda Hawksley: Dangerously beautiful. Poisonous wallpapers in the 19th century , Gerstenberg Verlag, Hildesheim 2018, ISBN 978-3-8369-2138-1

Web links

• Emerald Green at ColourLex

Individual evidence

1. ↑ ^{a b c d e} Entry on copper (II) arsenite acetate in the GESTIS substance database of the IFA , accessed on February 16, 2017(JavaScript required) .
2. ↑ Not explicitly listed in Regulation (EC) No. 1272/2008 (CLP) , but with the specified labeling it falls under the group entry arsenic compounds, with the exception of those named in this appendix in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA) on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
3. ↑ Entry on Schweinfurt Green in the ChemIDplus database of the United States National Library of Medicine (NLM)
4. ↑ Entry on Schweinfurt Green. In: Römpp Online . Georg Thieme Verlag, accessed on January 3, 2015.
5. ↑ John Emsley: Murderous Elements, Prominent Deaths. ISBN 3-527-31500-4
6. ^ No poison attack on Napoleon
7. ↑ ^{a b c} Schweinfurt Green . In: Merck's Warenlexikon . 3rd ed. 1884 ff., P. 511 f.
8. ↑ Georg Brauer: Schweinfurt green . In: Handbook of Preparative Inorganic Chemistry . Ferdinand Enke Verlag, Stuttgart 1954, p. 762 .
9. ↑ Schweinfurt Green . In: Meyers Konversations-Lexikon 1885-1892, Volume 14, Page 745
10. ^ Thomas R. Dunlap: DDT: Scientists, Citizens and Public Policy . Princeton University Press, 1981, ISBN 0-691-04680-8 , p. 19
11. ↑ ^{a b} Lukas Straumann: Useful pests . Chronos, Zurich 2005, ISBN 3-0340-0695-0 .
12. ^ Paul Claus: Arsenic for pest control in viticulture 1904–1942 . In: Writings on Wine History , No. 58, Wiesbaden 1981, ISSN  0302-0967