Flame test

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The flame test carried out on a copper halide. The characteristic bluish-green color of the flame is due to the copper.
A flame test showing the presence of lithium.
Flame test of a few metal ions

A flame test is an analytical procedure used in chemistry to detect the presence of certain elements, primarily metal ions, based on each element's characteristic flame emission spectrum (which may be affected by the presence of chloride ion). The color of flames in general also depends on temperature and oxygen fed; see flame color.


The test involves introducing a sample of the element or compound to a hot, non-luminous flame, and observing the color of the flame that results. The idea of the test is that sample atoms evaporate and since they are hot, they emit light when being in flame. The solvent of the solution evaporates first, leaving finely divided solid particles which move to the hottest region of the flame where gaseous atoms and ions are produced through the dissociation of molecules. Here electrons are excited by the heat, and the spontaneously emit photon to decay to lower energy states.

Bulk sample emits light too, but its light is not good for analysis. Bulk samples emit light with hydrochloric acid to remove traces of previous analytes.[1] The compound is usually made into a paste with concentrated hydrochloric acid, as metal halides, being volatile, give better results. Different flames should be tried to avoid wrong data due to "contaminated" flames, or occasionally to verify the accuracy of the color. In high-school chemistry courses, wooden splints are sometimes used, mostly because solutions can be dried onto them, and they are inexpensive. Nichrome wire is also sometimes used.[1] When using a splint, one must be careful to wave the splint through the flame rather than holding it in the flame for extended periods, to avoid setting the splint itself on fire. The use of cotton swab[2] or melamine foam (used in "eraser" cleaning sponges)[3] as a support has also been suggested.

Sodium is a common component or contaminant in many compounds and its spectrum tends to dominate over others. The test flame is often viewed through cobalt blue glass to filter out the yellow of sodium and allow for easier viewing of other metal ions.


The flame test is relatively quick and simple to perform and can be carried out with the basic equipment found in most chemistry laboratories. However, the range of elements positively detectable under these conditions is small, as the test relies on the subjective experience of the experimenter rather than any objective measurements. The test has difficulty detecting small concentrations of some elements, while too strong a result may be produced for certain others, which tends to cause fainter colors to not appear.

Although the flame test only gives qualitative information, not quantitative data about the proportion of elements in the sample, quantitative data can be obtained by the related techniques of flame photometry or flame emission spectroscopy. Flame atomic absorption spectroscopy Instruments, made by e.g. PerkinElmer or Shimadzu, can be operated in emission mode according to the instrument manuals.[4]

Common elements[edit]

Coloured flames of methanol solutions of different compounds, burning on cotton wool. From left to right: lithium chloride, strontium chloride, calcium chloride, sodium chloride, barium chloride, trimethyl borate, copper chloride, cesium chloride and potassium chloride.

Some common elements and their corresponding colors are:

Symbol Name Color Image
Al Aluminium Silver-white, in very high temperatures such as an electric arc, light blue
As Arsenic Blue FlammenfärbungAs.jpg
B Boron Bright green FlammenfärbungB.png
Ba Barium Pale/Apple Green[5] Flame resulting from Barium Chloride combustion in a Bunsen burner
Be Beryllium White
Bi Bismuth Azure
C Carbon Bright orange Bunsen burner flame types.png
Ca Calcium Brick red, light green as seen through blue glass. FlammenfärbungCa.png
Cd Cadmium Brick red
Ce Cerium Yellow
Co Cobalt Silver-white CobaltFlameTestOxyHydrogen.png
Cr Chromium Silver-white ChromiumFlameTestOxyHydrogen.png
Cs Caesium Blue-violet CaesiumFlameTestOxyHydrogen.png
Cu(I) Copper(I) Bluish-green[5]
Cu(II) Copper(II) (non-halide) Green Flame test on copper sulfate
Cu(II) Copper(II) (halide) Blue-green
Ge Germanium Pale blue
Fe(II) Iron(II) Gold, when very hot such as an electric arc, bright blue, or green turning to orange-brown
Fe(III) Iron(III) Orange-brown An iron (III) flame, generated using the thermite reaction
H Hydrogen Pale blue
Hf Hafnium White
Hg Mercury Red
In Indium Indigo/Blue
K Potassium Lilac; invisible through cobalt blue glass (purple) FlammenfärbungK.png
Li Lithium Carmine red; invisible through green glass FlammenfärbungLi.png
Mg Magnesium Colorless due to Magnesium Oxide layer, but burning Mg metal gives an intense white
Mn(II) Manganese(II) Yellowish green ManganeseFlameTestOxyHydrogen.png
Mo Molybdenum Yellowish green
Na Sodium Intense yellow;[5] invisible through cobalt blue glass. See also Sodium-vapor lamp Flametest--Na.swn.jpg
Nb Niobium Green or blue
Ni Nickel Silver-white (sometimes reported as colorless) NickelFlameTestOxyHydrogen.png
P Phosphorus Pale bluish green
Pb Lead Blue/white FlammenfärbungPb.png
Ra Radium Crimson
Rb Rubidium Red-violet Die Flammenfärbung des Rubidium.jpg
Sb Antimony Pale green FlammenfärbungSb.png
Sc Scandium Orange
Se Selenium Azure
Sn Tin Blue-white
Sr Strontium Crimson to Scarlet,[5] yellowish through green glass and violet through blue cobalt glass FlammenfärbungSr.png
Ta Tantalum Blue
Te Tellurium Pale green
Ti Titanium Silver-white
Tl Thallium Pure green
V Vanadium Yellowish Green
W Tungsten Green
Y Yttrium Carmine, Crimson, or Scarlet
Zn Zinc Colorless (sometimes reported as bluish-green) Zinc burning.JPG
Zr Zirconium Mild red

Gold, silver, platinum, palladium, and a number of other elements do not produce a characteristic flame color, although some may produce sparks (as do metallic titanium and iron); salts of beryllium and gold reportedly deposit pure metal on cooling.

See also[edit]


  1. ^ a b Clark, Jim (August 2018). "Flame Tests". chemguide.co.uk. Archived from the original on November 27, 2020. Retrieved January 10, 2021.
  2. ^ Sanger, Michael J.; Phelps, Amy J.; Banks, Catherine (2004). "Simple Flame Test Techniques Using Cotton Swabs". Journal of Chemical Education. 81 (7): 969. Bibcode:2004JChEd..81..969S. doi:10.1021/ed081p969.
  3. ^ Landis, Arthur M.; Davies, Malonne I.; Landis, Linda; Thomas, Nicholas C. (2009). "'Magic Eraser' Flame Tests". Journal of Chemical Education. 86 (5): 577. Bibcode:2009JChEd..86..577L. doi:10.1021/ed086p577.
  4. ^ "Atomic Absorption (AA)". Perkin Elmer. Retrieved 2 May 2013.
  5. ^ a b c d Barrow, R F; Caldin, E F (1949-01-01). "Some Spectroscopic Observations on Pyrotechnic Flames". Proceedings of the Physical Society. Section B. 62 (1): 32–39. doi:10.1088/0370-1301/62/1/305. ISSN 0370-1301.

External links[edit]

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