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. Five grams of luminol will produce about 625ml 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.)
Experiment to Demonstrate Chemiluminescence...
- SOLUTION A: 1g luminol, 8g potassium hydroxide, and 125ml water.
- SOLUTION B: 3% Hydrogen peroxide (common store-bought concentration) PLUS just a pinch (~0.1g) of Potassium ferricyanide to act as a catalyst.
- PROCEDURE: In a clear test tube or small 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.
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