verdigris

n. [ F. vert-de-gris, apparently from verd, vert, green + de of + gris gray, but really a corruption of LL. viride aeris (equivalent to L. aerugo), from L. viridis green + aes, aeris, brass. See Verdant, and 2d Ore. ] 1. (Chem.) A green poisonous substance used as a pigment and drug, obtained by the action of acetic acid on copper, and consisting essentially of a complex mixture of several basic copper acetates. [ 1913 Webster ]

2. The green rust formed on copper. [ Colloq. ] [ 1913 Webster ]

☞ This rust is a carbonate of copper, and should not be confounded with true verdigris. U. S. Disp. [ 1913 Webster ]

Blue verdigris (Chem.), a verdigris having a blue color, used as a pigment, etc. --
Distilled verdigris (Old Chem.), an acid copper acetate; -- so called because the acetic acid used in making it was obtained from distilled vinegar. --
Verdigris green, clear bluish green, the color of verdigris. [ 1913 Webster ]