Introduction
Salt slurries in petri dishes with methanol are ignited and characteristic colors for various metals are observed.
Colors of emission spectra are due to loosely-bound valence electrons being excited in a flame and dropping back down while emitting light.
Warning!
Once the flame has started, DO NOT add more methanol to the salts. If the methanol bottle is in close proximity with the flame the whole bottle can catch on fire posing a fire hazard to the demonstrator.
To Conduct Demonstration
- Add a few mL of distilled water to each metal salt in its petri dish and mix to form a slurry.
- Pour methanol into each dish to a depth of ½”.
- Carefully ignite the methanol with a match. After 15-60 sec., colors should appear. DO NOT attempt to add more methanol if it doesn't work, this is a very serious fire hazard!
Demo Time: ~15 minutes
Salts
| Cupric Chloride |
| Lithium Chloride |
| Stronium Chloride |
| Cupric Sulfate |
| Boric Acid |
| Borax (Sodium Borate) |
| Calcium Chloride |
| Potassium Chloride |
| Sodium Chloride |
| Sodium Carbonate |
Safety
Salts may spatter and eye protection should be worm. Place dishes on heat-proof surface. Dishes remain hot after the flame goes out and should be handled with care. The methanol bottle should be kept well away from any flames, and more should NOT be added in the event the flames go out. See this article on accidents that have occurred with this demo: https://cenblog.org/the-safety-zone/2014/09/denver-student-hit-in-chest-with-jet-of-flaming-methanol/
Acknowledgment
John Ohlsson, Summer 1988
Ken Brooks, Summer 1989