Diphenyl oxalate is a solid whose oxidation products are responsible for the chemiluminescence in a glowstick. This chemical is the double ester of phenol with oxalic acid. Upon reaction with hydrogen peroxide, 1,2-dioxetanedione is formed, along with release of the two phenols. The dioxetanedione then reacts with a dye molecule, decomposing to form carbon dioxide and leaving the dye in an excited state. As the dye relaxes back to its unexcited state, it releases a photon of visible light.