Luminol is a versatile chemical that demonstrates chemiluminescence when mixed with the proper oxidizing agent. It is supplied as a whitish-yellow crystalline powder that is soluble in high pH (potassium hydroxide added) water solutions. One gram of luminol will produce about 125ml of solution.
Luminol is used by forensic investigators for blood trace detection because when properly mixed it will react with iron found in hemoglobin. It is also used by biologists in cellular assays to test for the presence of copper, iron, and cyanides.
To produce a blue glowing reaction, luminol powder is mixed with a liquid containing hydrogen peroxide, a hydroxide such as potassium hydroxide, and a catalyst such as potassium ferricyanide. The mixture’s blue glow is evidence of the presence of the catalyst which accelerates the chemiluminescence reaction. (Iron in hemoglobin for the forensic scientist or iron in the potassium ferricyanide in our laboratory mixture.)
- Potassium hydroxide
- 3% hydrogen peroxide (common store-bought concentration)
- Potassium ferricyanide
- Three small beakers.
- Solution A: In one of your beakers, add 1g luminol, 8g potassium hydroxide to 125ml of distilled water. Stir thoroughly with a glass stir rod or stainless steel mixing spoon to completely dissolve the chemicals.
- Solution B: In another beaker, add at least 10ml hydrogen peroxide PLUS just a pinch (~0.1g) of Potassium ferricyanide to act as a catalyst.
- In third beaker measure 10ml of Solution A then add 10ml of Solution B to activate the blue glow.
Rather than iron, you can also catalyze the luminol reaction by adding copper and its compounds (such as copper sulfate), horseradish, or bleach.