Paris green

Paris green (copper(II) acetate triarsenite or copper(II) acetoarsenite) is an inorganic compound. It is a highly toxic emerald-green crystalline powder that has been used as a rodenticide and insecticide, and also as a pigment, despite its toxicity. It is also used as a blue colorant for fireworks. The color of Paris green is said to range from a pale blue green when very finely ground, to a deeper green when coarsely ground.Paris green pigmentMixing 'Paris green' and road dust preparatory to dusting streams and breeding places of mosquitoes during World War IIUse as insecticide, poster issued by US Public Health Service Paris green (copper(II) acetate triarsenite or copper(II) acetoarsenite) is an inorganic compound. It is a highly toxic emerald-green crystalline powder that has been used as a rodenticide and insecticide, and also as a pigment, despite its toxicity. It is also used as a blue colorant for fireworks. The color of Paris green is said to range from a pale blue green when very finely ground, to a deeper green when coarsely ground. Paris green may be prepared by combining copper(II) acetate and arsenic trioxide. At the turn of the 20th century, Paris green, blended with lead arsenate, was used in America and elsewhere as an insecticide on produce such as apples. The toxic mixture is said 'to have burned the trees and the grass around the trees'. Paris green was heavily sprayed by airplane in Italy, Sardinia, and Corsica during 1944 and in Italy in 1945 to control malaria. It was once used to kill rats in Parisian sewers, which is how it acquired its common name. It was also used heavily in the Americas to control the tobacco budworm, Heliothis virescens. Paris green, also called emerald green, was a popular pigment used in artists' paints by (among others) the English painter W. Turner, Impressionists such as Monet and Renoir, and Post-Impressionists such as Gauguin, Cézanne, and Van Gogh. Similar natural compounds are the minerals chalcophyllite Cu18Al2(AsO4)3(SO4)3(OH)27·36H2O, conichalcite CaCu(AsO4)(OH), cornubite Cu5(AsO4)2(OH)4·H2O, cornwallite Cu5(AsO4)2(OH)4·H2O, and liroconite Cu2Al(AsO4)(OH)4·4H2O. These vivid minerals range from greenish blue to slightly yellowish green. Scheele's green is a chemically simpler, less brilliant, and less permanent, synthetic copper-arsenic pigment used for a rather short time before Paris green was first prepared, which was approximately 1814. It was popular as a wallpaper pigment and would degrade, with moisture and molds, to arsine gas. Paris green may have also been used in wallpaper to some extent and may have also degraded similarly. Both pigments were once used in printing ink formulations. The ancient Romans used one of them, possibly conichalcite, as a green pigment. The Paris green paint used by the Impressionists is said to have been composed of relatively coarse particles. Later, the chemical was produced with increasingly small grinds and without carefully removing impurities; its permanence suffered. It is likely that it was ground more finely for use in watercolors and inks, too.