Boric acid imparts a pale green color to a flame.
A very pale green color is imparted to the flame by boron in boric acid. A few tinges of yellow-orange sodium color appear as a consequence of traces of sodium impurity in the boric acid solution. The intensity of the boron flame color can be increased by burning boron-containing samples in alcohol, but for consistency with the other tests, this was not done here.
Aqueous solutions of various compounds are sprayed into a Meeker burner flame from an atomizer. The flame colors are demonstrated close up. Except for boric acid, all compounds are chlorides. Aluminum chloride or magnesium chloride can be used to demonstrate that chlorine imparts no color to the flame.
These movies are 3 to 5 seconds in length. There is no sound or voice over.
Metal salts introduced into a flame give off light characteristic of the metal. Metal ions combine with electrons in the flame and the metal atoms are raised to excited states because of the high flame temperature. Upon returning to the ground state, they give off light (a line spectrum) characteristic of that metal.
Several metal salts give off a characteristic color visible to the human eye as is demonstrated by the alkali metals and a few other elements, but a fair number of metal salts give off light that may be observed, but is not sufficiently different in color to be differentiated from other metal salts. Some metal salts give off light outside of the visible region of the electromagnetic spectrum.
In these video sequences selected compounds, mostly metal salts, show the flame color in a Meeker burner flame. A homemade atomizer was used to form a fine spray of the solution, which was sprayed directly into the burner flame.
It should be noted that sodium is present as an impurity in many if not most metal salts. Because sodium imparts an especially intense color to a flame, flashes of the sodium may be observed in nearly all solutions tested.
- Design and Demonstration
- Frederick Mattes Hastings College, Hastings, NE 68902
- Video
- Jerrold J. Jacobsen University of Wisconsin - Madison, Madison, WI 53706
- Text
- Frederick Mattes Hastings College, Hastings, NE 68902