Test de Flamme au Potassium

Identification du potassium par sa flamme lilas/violette

Flame Tests Beginner (Middle School) 20 min ~$6,00

Objectif

Observer la couleur lilas/violette de la flamme produite par les ions potassium, et apprendre à utiliser le verre bleu cobalt pour la distinguer de la contamination par le sodium.

Contexte

Potassium produces a pale lilac or violet flame when heated. The emission occurs at 766.5 nm and 769.9 nm (near-infrared/deep red doublet). Because the flame is quite faint and easily overwhelmed by sodium's intense yellow, cobalt blue glass is used as a filter to block sodium emission and reveal potassium's true color.

Avertissements de sécurité

  • Wear safety goggles at all times
  • Keep hair tied back near open flames
  • Handle HCl with care

EPI requis

goggles lab_coat

Matériaux

  • Potassium chloride (KCl) (1 g)
  • Hydrochloric acid (HCl) (10 mL)
    1M concentration
  • Cobalt blue glass (1 piece)
    For filtering sodium light

Équipement

Bunsen burner Nichrome wire loop Watch glass Forceps

Procédure

1

Clean the nichrome wire thoroughly by dipping in HCl and heating.

2 min
2

Place potassium chloride on the watch glass and collect a sample on the clean wire.

1 min
3

Hold the sample in the Bunsen burner flame. Observe with the naked eye first.

2 min
4

Now observe the flame through cobalt blue glass to filter out any sodium contamination.

2 min
5

Record the difference in appearance with and without the cobalt blue glass filter.

2 min

Résultats attendus

Without the filter, you may see a faint lilac color possibly masked by yellow from sodium impurities. Through the cobalt blue glass, a clear violet/lilac flame should be visible as the glass absorbs the yellow sodium emission.

Nettoyage

Clean the wire loop with HCl. Return cobalt blue glass to storage.

Détails

Catégorie
Flame Tests
Difficulté
Beginner (Middle School)
Durée
20 min
Coût estimé
$6,00
Étapes
5
Matériaux
3

Plus d'expériences

Laboratoire de Comparaison des Tests de Flamme 45 min Test de Flamme au Baryum 20 min Test de Flamme au Calcium 15 min Test de Flamme au Cuivre 15 min Test de Flamme au Lithium 15 min Test de Flamme au Sodium 15 min Test de Flamme au Strontium 15 min

Frequently Asked Questions

What is the objective of Test de Flamme au Potassium?
Observer la couleur lilas/violette de la flamme produite par les ions potassium, et apprendre à utiliser le verre bleu cobalt pour la distinguer de la contamination par le sodium.
How difficult is Test de Flamme au Potassium?
This experiment is rated as Beginner (Middle School). It takes approximately 20 minutes to complete.
What safety precautions are needed for Test de Flamme au Potassium?
Key safety precautions include: Wear safety goggles at all times; Keep hair tied back near open flames; Handle HCl with care.
What materials are needed for Test de Flamme au Potassium?
The main materials required are: Potassium chloride (KCl), Hydrochloric acid (HCl), Cobalt blue glass.
What results should I expect from Test de Flamme au Potassium?
Without the filter, you may see a faint lilac color possibly masked by yellow from sodium impurities. Through the cobalt blue glass, a clear violet/lilac flame should be visible as the glass absorbs the yellow sodium emission.