Flame Test Colors and Procedure (Chemistry)   Recently updated !


Flame Test Colors
The flame test is a technique in analytical chemistry that helps identify elements (usually metal ions) in a sample.

The flame test is an analytical chemistry technique that helps identify elements in samples based on their characteristic emission spectra. Mostly the flame test detects metal ions, but some nonmetals color flames as well.

How the Flame Test Works

The basic premise is that heat from a flame gives atoms enough energy that their electrons become excited. Dropping to a more stable energy state involves the release of photons. These photons have a frequency (light color) that is a characteristic of the element.

However, not all elements release light in the visible portion of the spectrum. Some elements don’t change a flame’s color at all. For example, gold, silver, platinum, and palladium do not yield a flame test result. However, some of these metals produce sparks in a flame and other deposit pure metal onto a surface.

Advantages and Disadvantages of the Flame Test

The flame test offers both advantages and disadvantages as an analytical technique.

Advantages

  • Extremely quick and easy
  • Only requires a tiny sample
  • Good at eliminating possible elements in a sample
  • Visually appealing, so it’s great at raising student interest in science

Disadvantages

  • Does not definitively identify a sample
  • Results are subjective
  • Results are highly susceptible to contamination, particularly from sodium
  • Several elements yield approximately the same color results
  • Some samples yield brighter colors than others
  • Results vary somewhat depending on the exact chemical composition of the sample and the fuel
  • Qualitative rather than quantitative technique
  • Does not work with extremely dilute samples

The bead test is a related technique. Better techniques include flame photometry, flame emission spectroscopy, and flame absorption spectroscopy. However, these methods are quite a bit more expensive.

How to Do the Flame Test

There are several ways of performing the flame test.

  1. Dissolve the sample in water or another solvent, soak a wooden splint in the liquid, and let it dry.
  2. Dip a Nichrome wire into a solid or liquid sample.
  3. Make a paste of a solid sample with hydrochloric acid (HCl) and dip a splint or wire into the paste.
  4. Dip a cotton swab into the sample. (This method is prone to sodium contamination.)
  5. Dissolve the sample in a small amount of methanol. Dip a bit of melamine sponge (e.g., Magic Eraser) into the sample.

Options for the flame include a candle flame, Bunsen burner flame, or gas flame.

Basically, you dip a wire or splint into a solid sample or its solution and expose the sample to a colorless flame. Viewing the results through a cobalt blue glass filters out excess yellow and makes identification a bit easier. Once you have a color, compare it to a table of flame test colors.

Use common household chemicals to make flames in any color of the rainbow.

Make Colored Fire

The flame test is the basis for firework colors, colored fire spray bottles, and colored campfires.

Table of Flame Test Colors

This is a table of flame test colors, ordering the elements alphabetically by symbol.

SymbolNameColor
AlAluminumSilvery-white
AsArsenicBlue
BBoronBright green
BaBariumLight apple green
BeBerylliumWhite
BiBismuthAzure blue
CCarbonOrange
CaCalciumBrick red
CdCadmiumBrick red
CeCeriumYellow
CoCobaltSilvery white
CrChromiumSilvery white
CsCesiumBlue violet
Cu(I)Copper(I)Blue-green
Cu(II)Copper(II)Green (non-halide) to blue-green (halide)
GeGermaniumPale blue
Fe(II)Iron(II)Gold
Fe(III)Iron(III)Orange brown
HHydrogenPale blue
HfHafniumWhite
HgMercuryRed
InIndiumIndigo blue
KPotassiumLilac
LiLithiumCarmine red
MgMagnesiumColorless to white
Mn(II)Manganese(II)Yellowish green
MoMolybdenumYellowish green
NaSodiumBright yellow
NbNiobiumGreen or blue
NiNickelColorless to silvery white
PPhosphorusPale blue-green
PbLeadBlue-white
RaRadiumCrimson red
RbRubidiumViolet red
SbAntimonyPale green
ScScandiumOrange
SeSeleniumAzure blue
SnTinBlue-white
SrStrontiumCrimson or scarlet red
TaTantalumBlue
TeTelluriumPale green
TiTitaniumSilver-white
TlThalliumTrue green
VVanadiumYellowish green
WTungstenGreen
YYttriumRed: carmine, scarlet, or crimson
ZnZincColorless to blue-green
ZrZirconiumDull red

References

  • Barrow, R. F.; Caldin, E. F. (1949). “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
  • Landis, Arthur M.; Davies, Malonne I.; Landis, Linda; Thomas, Nicholas C. (2009). “‘Magic Eraser’ Flame Tests”. Journal of Chemical Education. 86 (5): 577. doi:10.1021/ed086p577
  • Patnaik, Pradyot (2002). Handbook of Inorganic Chemicals. McGraw-Hill. ISBN 0-07-049439-8.
  • Sanger, Michael J.; Phelps, Amy J.; Banks, Catherine (2004). “Simple Flame Test Techniques Using Cotton Swabs”. Journal of Chemical Education. 81 (7): 969. doi:10.1021/ed081p969