What is "flame reaction"

Flame \Flame\ (fl[=a]m), n. [OE. flame, flaume, flaumbe, OF. flame, flambe, F. flamme, fr. L. flamma, fr. flamma, fr. flagrare to burn. See Flagrant, and cf. Flamneau, Flamingo.]

1. A stream of burning vapor or gas, emitting light and heat; darting or streaming fire; a blaze; a fire.

2. Burning zeal or passion; elevated and noble enthusiasm; glowing imagination; passionate excitement or anger. ``In a flame of zeal severe.''
   --Milton.

   Where flames refin'd in breasts seraphic glow.
   --Pope.

   Smit with the love of sister arts we came, And met congenial, mingling flame with flame.
   --Pope.

3. Ardor of affection; the passion of love.
   --Coleridge.

4. A person beloved; a sweetheart.
   --Thackeray.

   Syn: Blaze; brightness; ardor. See Blaze.

   Flame bridge, a bridge wall. See Bridge, n.,

5. Flame color, brilliant orange or yellow.
   --B. Jonson.

   Flame engine, an early name for the gas engine.

   Flame manometer, an instrument, invented by Koenig, to obtain graphic representation of the action of the human vocal organs. See Manometer.

   Flame reaction (Chem.), a method of testing for the presence of certain elements by the characteristic color imparted to a flame; as, sodium colors a flame yellow, potassium violet, lithium crimson, boracic acid green, etc. Cf. Spectrum analysis, under Spectrum.

   Flame tree (Bot.), a tree with showy scarlet flowers, as the Rhododendron arboreum in India, and the Brachychiton acerifolium of Australia.