Chrome yellow

Chrome Yellow is a natural yellow pigment made of lead(II) chromate (PbCrO4). It was first extracted from the mineral crocoite by the French chemist Louis Vauquelin in 1809. Because the pigment tends to oxidize and darken on exposure to air over time, and it contains lead, a toxic, heavy metal, it has been largely replaced by another pigment, Cadmium Yellow.

It is commonly produced by mixing solutions of lead nitrate and potassium chromate and filtering off the lead chromate precipitate.