Verdigris

ver'di-gres, literally green of copper. It is a coloring substance obtained by exposing plates of copper to air in the presence of acetic acid. It is much used in dyeing wool, in printing calico, in gilding, and in various other arts. Verdigris is a dangerous poison. The best common antidote is white of eggs and milk. The acid of many fruits, if boiled in a copper kettle, combines with copper to form verdigris in sufficient amounts to render the fruit poisonous. Food taking on the slightest tinge of green from cooking in copper should be thrown away. The vinegar of sour pickles corrodes copper and produces verdigris.