Demonstrating the Presence of Cyanide in Bitter Seeds while Helping Students Visualize Metal-Cyanide Reduction and Formation in a Copper Complex Reaction

An activity for hydrogen cyanide detection in bitter seeds is presented. The procedure is based on the absorption of hydrogen cyanide (HCN) from a mixture of chopped seeds into a ninhydrin or tetramminecopper(II) complex solution followed by their reaction. A qualitative experiment is proposed in order to demonstrate the presence of HCN in bitter seeds and to visualize metal-cyanide reduction and formation of an interesting mixed valence copper amino-cyanide complex: Cu-3(NH3)(4)(CN)(4).