This two color chemiluminescent reaction is a show-stopping science demonstration or chemistry project. The reaction initially glows red and then glows blue. It’s perfect for a high school or college chemistry class or a general demonstration that raises interest in luminescence. The reaction illustrates oxidation reactions and chemiluminescence.
Color Change Chemiluminescence Materials
You need the following chemicals, as well as glassware and proper lab safety gear.
- 40 ml distilled water
- 0.8 g sodium hydroxide (NaOH)
- 0.005 g luminol (3-aminophthalhydrazide, C8H7N3O2)
- 25.0 g potassium carbonate (K2CO3)
- 1.0 g pyrogallol (pyrogallic acid or 1,2,3-trihydroxybenzene, C6H6O3)
- 10 ml 40% formaldehyde (CH2O)
- 30 ml 30% hydrogen peroxide (H2O2)
Most of these chemicals are readily available and familiar. The exceptions are luminol and pyrogallol. Find these chemicals from any chemical supply company (Fisher, Sigma-Aldrich, Thermo Scientific. Luminol is also sold via eBay and Amazon, while pyrogallol finds use in furniture restoration and (less commonly) as a hair dye ingredient and photography chemical.
Perform the Two Color Chemiluminescent Reaction
Once you have the chemicals, the procedure is simply. Basically, it involves combining all of the materials except the hydrogen peroxide solution. The peroxide initiates the chemiluminescent reaction.
- Pour 40 milliliters of distilled water into a 250-ml beaker.
- Dissolve 0.8 grams of sodium hydroxide in the water.
- Add 0.005 grams of luminol, 25.0 grams of potassium carbonate, and 1.0 grams of pyrogallol.
- Stir these chemicals until everything dissolves.
- Add 10 milliliters of 40% formaldehyde.
- Pour this solution into a 1-liter beaker. Either place the beaker inside a large one or else place it into a shallow pan.
- Dim the lights and start the reaction by adding 30 milliliters of 30% hydrogen peroxide. You do not need to stir the solution following this addition.
Initially, the liquid glows dull red. After several seconds, the color transitions to bright blue for a few seconds. The reaction foams, which is why you place the beaker in a second container. It is exothermic, so it gets hot.
If you enjoyed this project, why not perform another exciting color change chemical reaction?
How It Works
The chemiluminescent reaction is an example of two oxidation reactions. Many people are familiar with the blue glow from the oxidation of luminol. However, few have seen red glow that precedes it, which comes from singlet molecular oxygen (1O2). Singlet oxygen arises from the oxidation of pyrogallol and formaldehyde by alkaline hydrogen peroxide. The reaction glows more faintly in the presence of either pyrogallol (or gallic acid) or formaldehyde, but it’s brighter with both chemicals. The red chemiluminescent reaction froths and releases heat, triggering the oxidation of luminol.
The mechanism of the reaction is complex, but it appears that it involves free radicals. The luminol starts glowing after the oxygen chemiluminescence ends. So, the two colors are distinct from one another.
Safety and Disposal
- Wear gloves and eye protection. Do not touch, inhale, or ingest the sodium hydroxide, formaldehyde, luminol, pyrogallol, or hydrogen peroxide. Pyrogallol and formaldehyde are known toxins. Hydrogen peroxide is a strong oxidizer. Sodium hydroxide is a corrosive strong base.
- Ideally, perform the reaction within a fume hood.
- All of the chemicals are water soluble. Safely wash them down the drain following the reaction.
- Cayman Chemical (2018). “Pyrogallol“. Safety Data Sheet. Fiege, Helmut; Heinz-Werner, Voges; et al. (2014). Ullmann’s Encyclopedia of Industrial Chemistry (7th ed.). Weinheim, Germany: Wiley-VCH. doi:10.1002/14356007.a19_313 ISBN 9783527334773.
- Khan, Parvez; Idrees, Danish; MOxley, Michael A.; et al. (May 2014). “Luminol-Based Chemiluminescent Signals: Clinical and Non-clinical Application and Future Uses”. Applied Biochemical Biotechnology. 173 (2): 333–355. doi:10.1007/s12010-014-0850-1
- Shakhashiri, Bassam Z. (1983). Chemical Demonstrations: A Handbook for Teachers of Chemistry (Volume 1). University of Wisconsin Press. ISBN: 978-0299088903.
- Slawinska, Danuta (1978). “Chemiluminescence and the Formation of Singlet Oxygen in the Oxidation of Certain Polyphenols and Quinones”. Photochem. Photobiol. 28(4-5): 453-458. doi:10.1111/j.1751-1097.1978.tb06947.x