Flame Analysis

Bunsen examined the spectra; the colors of light emitted when a substance was subjected to intense flame. When air is admitted at the base of a Bunsen burner it mixes with hydrocarbon gas to produce a very hot flame at approximately 3,272°F (1,800°C). This temperature is sufficient to cause the emission of light from certain elements. Often termed "spectral fingerprints," the color of the flame and its spectral distribution of component colors is unique for each element.

To examine the spectra of elements, Bunsen used a simple apparatus that consisted of a prism, slits, and a magnifying glass or photosensitive film. Bunsen determined that the spectral patterns of elements that emitted light when subjected to flame analysis differed because each pattern represented limited portions of the total possible spectrum.

Flame analysis or atomic emission spectroscopy is based on the physical and chemical principle that atoms—after being heated by flame—return to their normal energy state by giving off the excess energy in the form of photons of light. The mathematically related frequencies and wavelengths of the photons emitted are characteristic for each element and this is the physical basis of the uniqueness of spectral fingerprints.