Flame Emission Spectroscopy

Quantitative identification of metals using spectroscope and flame

Qualitative Analysis Advanced (University) 60 min ~$15.00

Objective

Use a spectroscope to observe and measure the emission line wavelengths of different metal ions in a flame.

Background

While simple flame tests show color, a spectroscope reveals the discrete emission lines responsible for those colors. Each element has a unique set of emission lines (an atomic fingerprint). This experiment bridges qualitative flame testing with the quantitative science of atomic emission spectroscopy, demonstrating Bohr's model of the atom and the origin of spectral lines.

Safety Warnings

  • Methanol is highly flammable and toxic — handle with extreme care
  • Do not look directly at the flame without the spectroscope
  • Keep all flammable materials away from the burner
  • Ensure good ventilation

Required PPE

goggles gloves lab_coat

Materials

  • Metal salt solutions (0.5M) (5 mL each)
    Na, Li, K, Cu, Sr, Ca, Ba chlorides
  • Hydrochloric acid (1M) (20 mL)
    Wire cleaning
  • Methanol (50 mL)
    For solution flame method
  • Distilled water (50 mL)

Equipment

Handheld spectroscope or diffraction grating Bunsen burner Nichrome wire loops (7) Watch glasses (7) Spray bottle (for mist method)

Procedure

1

Set up the spectroscope by viewing a fluorescent light to calibrate and identify the mercury emission lines as reference.

5 min
2

Clean a nichrome wire with HCl. Dip in sodium chloride solution and hold in the flame. View through the spectroscope and record the bright yellow emission at 589 nm.

7 min
3

Repeat with lithium chloride. Record the bright red emission line near 671 nm.

7 min
4

Repeat with potassium chloride. View through cobalt glass to filter sodium contamination. Record the violet emission near 766 nm.

7 min
5

Test copper, strontium, calcium, and barium chlorides in sequence. For each, record all visible emission lines and their approximate wavelengths.

20 min Clean wire between samples
6

Compile an emission spectrum chart showing each element's characteristic lines. Compare with published spectral data.

14 min

Expected Results

Each metal shows distinct spectral lines: Na at 589 nm (yellow doublet), Li at 671 nm (red), K at 766 nm (violet, visible through cobalt glass), Cu at 510–515 nm (green) and 325 nm, Sr at 461 nm (blue) and 606 nm (orange-red).

Cleanup

Clean all nichrome wires with HCl. Dispose of metal salt solutions in inorganic waste. Rinse watch glasses.

Details

Category
Qualitative Analysis
Difficulty
Advanced (University)
Duration
60 min
Est. Cost
$15.00
Steps
6
Materials
4

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Frequently Asked Questions

What is the objective of Flame Emission Spectroscopy?
Use a spectroscope to observe and measure the emission line wavelengths of different metal ions in a flame.
How difficult is Flame Emission Spectroscopy?
This experiment is rated as Advanced (University). It takes approximately 60 minutes to complete.
What safety precautions are needed for Flame Emission Spectroscopy?
Key safety precautions include: Methanol is highly flammable and toxic — handle with extreme care; Do not look directly at the flame without the spectroscope; Keep all flammable materials away from the burner.
What materials are needed for Flame Emission Spectroscopy?
The main materials required are: Metal salt solutions (0.5M), Hydrochloric acid (1M), Methanol, Distilled water.
What results should I expect from Flame Emission Spectroscopy?
Each metal shows distinct spectral lines: Na at 589 nm (yellow doublet), Li at 671 nm (red), K at 766 nm (violet, visible through cobalt glass), Cu at 510–515 nm (green) and 325 nm, Sr at 461 nm (blue) and 606 nm (orange-red).