Aureolin is a pigment sparingly used in oil and watercolor painting. Its color index name is PY40. It was first made in 1831 by Nikolaus Wolfgang Fischer in Breslau characterizing it as "Doppelsalze" or double-salts and its chemical composition is potassium cobaltinitrite. He characterized it again and wrote more extensively about it in 1842, naming it "Salpetrichtsaures Kobaltoxydkali". In 1851–1852, Edouard Saint-Evre synthesized cobalt yellow independently. He is credited with the introduction of cobalt yellow as an artists pigment. The investigation by Gates gives the exact modern procedures for the preparation of aureolin and also the methods for its identification in paintings.
