Chimioluminescence avec le Luminol

Production de lumière bleue par une réaction chimique sans chaleur

Classroom Demonstrations Intermediate (High School) 30 min ~$15,00

Objectif

Démontrer la chimioluminescence en oxydant le luminol avec du peroxyde d'hydrogène en présence d'un catalyseur, produisant une lumière bleue visible.

Contexte

Luminol (3-aminophthalhydrazide) produces an eerie blue glow when oxidized by hydrogen peroxide in basic solution with a transition metal catalyst. The oxidation produces 3-aminophthalate in an excited electronic state, which releases energy as a photon of blue light (425 nm) as it returns to the ground state. This is the same reaction used by forensic scientists to detect trace amounts of blood at crime scenes, where the iron in hemoglobin acts as the catalyst.

Avertissements de sécurité

  • NaOH is corrosive — handle with care
  • Potassium ferricyanide is harmful if ingested
  • Perform in a dark room for best effect
  • Do not mix stock solutions until ready to demonstrate

EPI requis

goggles gloves lab_coat

Matériaux

  • Luminol (0.5 g)
    3-aminophthalhydrazide
  • Sodium hydroxide (NaOH) (5 g)
    To make solution basic
  • Hydrogen peroxide (3%) (50 mL)
    Household concentration
  • Potassium ferricyanide (K₃[Fe(CN)₆]) (0.5 g)
    Catalyst
  • Distilled water (500 mL)

Équipement

Beakers (500 mL, 2) Spiral glass tubing or clear tubing Dark room or blackout curtains Magnetic stirrer (optional)

Procédure

1

Prepare Solution A: Dissolve 0.5 g luminol and 5 g NaOH in 250 mL distilled water.

5 min NaOH is corrosive
2

Prepare Solution B: Dissolve 0.5 g K₃[Fe(CN)₆] in 250 mL of 3% H₂O₂.

5 min
3

Darken the room completely. Allow eyes to adjust for 1–2 minutes.

2 min
4

Pour both solutions simultaneously into a large beaker or through spiral glass tubing. A bright blue glow appears immediately.

3 min
5

Observe the glow lasting for several minutes. Stirring or agitation renews the glow by mixing fresh reactants.

10 min
6

Discuss the mechanism: luminol oxidation → excited 3-aminophthalate → photon emission (425 nm). Compare with bioluminescence and fluorescence.

5 min

Résultats attendus

A vivid blue glow appears when the solutions are mixed. The light intensity peaks immediately and fades over several minutes. The glow is bright enough to read by in a completely dark room.

Nettoyage

The spent solution is relatively non-toxic. Pour down the drain with copious water. Rinse all glassware.

Détails

Catégorie
Classroom Demonstrations
Difficulté
Intermediate (High School)
Durée
30 min
Coût estimé
$15,00
Étapes
6
Matériaux
5

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Frequently Asked Questions

What is the objective of Chimioluminescence avec le Luminol?
Démontrer la chimioluminescence en oxydant le luminol avec du peroxyde d'hydrogène en présence d'un catalyseur, produisant une lumière bleue visible.
How difficult is Chimioluminescence avec le Luminol?
This experiment is rated as Intermediate (High School). It takes approximately 30 minutes to complete.
What safety precautions are needed for Chimioluminescence avec le Luminol?
Key safety precautions include: NaOH is corrosive — handle with care; Potassium ferricyanide is harmful if ingested; Perform in a dark room for best effect.
What materials are needed for Chimioluminescence avec le Luminol?
The main materials required are: Luminol, Sodium hydroxide (NaOH), Hydrogen peroxide (3%), Potassium ferricyanide (K₃[Fe(CN)₆]), Distilled water.
What results should I expect from Chimioluminescence avec le Luminol?
A vivid blue glow appears when the solutions are mixed. The light intensity peaks immediately and fades over several minutes. The glow is bright enough to read by in a completely dark room.