Statues coated with white lead on long exposure to atmosphere turn black and the original colour can be restored on treatment with $H_{ 2 }$$O_{ 2 }$. Why?
On long exposure to atmosphere, white lead is converted into black PbS due to the action of H _{ 2 }S present in the atmosphere. As a result, statues turn black.
On treatment of these blackened statues with $H_{ 2 }$$O_{ 2 }$, the black PbS gets oxidised to white PbSO_{4} and the colour is restored.
