What is luminol?

Answer 1

Luminol is a relatively simple chemical containing only carbon, nitrogen, oxygen and hydrogen and is a white to slightly yellow crystalline solid powder, soluble in water and most polar organic solvents.

Luminol is used by forensic investigators to detect trace amounts of blood left at crime scenes. Although it can detect small traces of blood, forensic investigators use this only as a last resort because it also reacts with soils, detergents, bleaches, carpets, metal objects, tools, plastic panels, wood, and some vegetable compounds.

To exhibit its luminescence, the luminol must first be activated with an oxidant. Usually, a solution of hydrogen peroxide (H2O2) and a hydroxide salt in water is used as the activator. In the presence of a catalyst such as an iron compound, the hydrogen peroxide is decomposed to form oxygen and water:

2 H2O2 → O2 + 2 H2O

In a laboratory setting, the catalyst used is often potassium ferricyanide. In the forensic detection of blood, the catalyst is the iron present in hemoglobin. Enzymes in a variety of biological systems may also catalyze the decomposition of hydrogen peroxide.