VERDIGRIS is a basic copper acetate of varying composi tion. Dissolved in pine balsam, it formed one of the permanent greens of the Middle Ages. Owing to its behaviour as an oil colour (turning from dark green to black) and as a water colour (fading), it is replaced as a pigment by the more permanent chromium and cobalt greens and is now used mainly in anti fouling compositions and wood preservatives. It is an irritant
poison; the best antidote is white of egg and milk. See PAINTS, CHEMISTRY OF.