Paris green

Paris green, which has the chemical name copper(II) acetoarsenite, is a chemical compound. Its chemical formula is Cu(C2H3O2)2 · 3 Cu(AsO2)2. It has copper, acetate, and arsenite ions in it. The copper is in its +2 oxidation state.
Properties.
Paris green is a blue-green solid. It is extremely toxic. It has a very bright blue-green color. It darkens in air.
Preparation.
It is made by reacting copper(II) acetate with arsenic trioxide and water.
Uses.
Paris green was first used to kill rats in sewers in Paris. This is where it got its name from. It was used as an insecticide. It was dropped from airplanes to stop malaria in Italy. It was used as a bright green pigment. It was painted on ships to prevent barnacles from growing. In many places, Paris green is banned because it is so toxic. It is only used in a very few places.
Safety.
Paris green is extremely toxic. It used to be common and so was a common poison.