Paris green

Paris green (copper(II) acetate triarsenite or copper(II) acetoarsenite) is an arsenic-based organic pigment. As a green pigment it is also known as Schweinfurt green, emerald or Vienna green. It is a highly toxic emerald-green crystalline powder that has been used as a rodenticide and insecticide, and also as a pigment. It was manufactured in 1814 to be a pigment to make a vibrant green paint, and was used by many notable painters in the 19th century. 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. Due to the presence of arsenic, the pigment is extremely toxic and in paintings, the color can degrade quickly. Paris green may be prepared by combining copper(II) acetate and arsenic trioxide. The structure was confirmed by X-ray crystallography. In 1814, Paris green was invented by paint manufacturers, Wilhelm Sattler and Friedrich Russ, in Schweinfurt, Germany for the Wilhelm Dye and White Lead Company. They were attempting to produce a more stable pigment than Scheele's green, seeking to make a green that was less susceptible to darkening around sulfides. In 1822, the recipe for emerald green was published by Justus von Liebig and André Braconnot. In 1867, the pigment was named Paris green and was officially recognized as the first chemical insecticide in the world. Because of its arsenic content, the pigment was dangerous and toxic to manufacture, often resulting in factory poisonings. At the time, emerald green was praised as a more durable and vibrant substitute for Scheele’s green, even though it would later prove to degrade quickly and react with other manufactured paints. In paintings, the pigment produces a rich, dark green with an undertone of blue. In comparison, Scheele's green is more yellow, and therefore, more lime-green. Paris green became popular in the 19th century because of its brilliant color. It was also called Emerald green because of its resemblance to the gemstone's deep color. Paris green was widely used by 19th-century artists.