Nitric acid acts upon copper

The vigorous reaction between copper metal and nitric oxide famously propelled chemist Ira Remsen into an esteemed career in research and education that spanned the turn of the 20th century. In a memoir, Remsen recalled his frustration with the lack of color and detail in the chemistry textbook he learned from, which said vague things like “nitric oxide acts upon copper.” Oscar Poll, an undergraduate chemistry student at the University of Oxford, decided to follow Remsen’s example and see the reaction for himself. He and his father stripped electrical wire to get copper; Poll poured nitric acid over the wire in a beaker and photographed the results.

“In the concentrated nitric acid environment, the ligand field of the nitrate Cu(II) complex gives the pastel green/shamrock colour. After addition of water, the Jahn-Teller distorted [Cu(H₂O)₆]²⁺ complex is formed with its distinctive sky-blue colour,” Poll explains. Remsen went on from this experiment to found the chemistry department at the Johns Hopkins University. For Poll, who says he is “interested in indole alkaloid total synthesis and the pharmacology of serotonergic psychedelics,” the journey is just beginning.