Certain metals, when exposed to a flame, will emit light in the visible region of the electromagnetic spectrum. These metals cause the flame to turn a bright colour. In many cases, the colours exhibit sufficient vividness to allow the identification of the metal.
At the most basic level, a flame test requires a burner or torch, a piece of wire and a solution that contains a dissolved metal. The use of a simple handheld spectroscope offers a more definitive test by allowing the experimenter to actually measure the wavelengths of the light emitted by the metal atoms.
How It Is Used
In general, the experimenter bends a loop into one end of the wire, dips the loop into the metal-containing solution, holds it in the flame and observes the colour of the flame. If using a spectroscope, the experimenter simply holds the eyepiece of the scope up to one eye with his other hand while holding the wire in the flame.
In the absence of a spectroscope, a flame test can usually only narrow the range of possible metals in the test solution. A red-coloured flame, for example, could indicate lithium, strontium or yttrium. Even with a spectroscope, a flame test provides no information about the actual amount of metal in the test solution.