Luminol is an organic compound which, when oxidized, emits light — a phenomenon known as chemiluminescence. This is similar to the reactions that fireflies uses to emit light, and to those used in "glow-sticks" and some roadside emergency lights.
In this reaction, a small amount of luminol (3-aminophthalhydrazide or 5-amino-2,3-dihydro- 1,4-phthalazinedione) is dissolved in a basic aqueous solution, which also contains a small amount of copper(II) sulfate. To this solution is added a solution of a mild oxidizing agent