Flame test

The flame test carried out on a copper halide. Note the characteristic bluish-green color of the flame due to the copper.

Different flame types of Bunsen Burner depending on air flow through the valve:
1. air valve closed
2. air valve nearly fully closed
3. air valve semi-opened
4. air valve maximally opened.

Gas flame

A flame test is an analytic procedure used in chemistry to detect the presence of certain elements, primarily metal ions, based on each element's characteristic emission spectrum. The color of flames in general also depends on temperature; see flame color.

The test involves introducing a sample of the element or compound to a hot, non-luminous flame, and observing the color that results. Samples are usually held on a platinum wire cleaned repeatedly with hydrochloric acid to remove traces of previous analytes. 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. 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 or melamine foam (eraser) as a support have 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 fast and easy to perform, and does not require any equipment not usually found in a chemistry laboratory. However, the range of detected elements is small, and 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 drown out weaker signals.

Although the flame test only gives qualitative information, not quantitative data about the actual 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.

Common elements

Some common elements and their corresponding colors are:

Symbol	Name	Color	Image
As	Arsenic	Blue
B	Boron	Bright green
Ba	Barium	Pale/Apple green
Ca	Calcium	Brick red
Cs	Caesium	Blue-Violet
Cu(I)	Copper(I)	Bluish-green
Cu(II)	Copper(II) (non-halide)	Green
Cu(II)	Copper(II) (halide)	Blue-green
Fe	Iron	Gold
In	Indium	Blue
K	Potassium	Lilac
Li	Lithium	Red
Mn (II)	Manganese (II)	Yellowish green
Mo	Molybdenum	Yellowish green
Na	Sodium	Intense yellow
P	Phosphorus	Pale bluish green
Pb	Lead	Blue/White
Ra	Radium	Crimson red
Rb	Rubidium	Red-violet
Sb	Antimony	Pale green
Se	Selenium	Azure blue
Sr	Strontium	Crimson
Te	Tellurium	Pale green
Tl	Thallium	Pure green
Zn	Zinc	Colorless (sometimes reported as bluish-green)

See also

• Colored fire
• Emission spectrum
• Photoelectric flame photometer
• Qualitative inorganic analysis
• Burning splint test
• Glowing splint test

External links

• Flame Test - Coloring Fire - Pictures of Several Flame Tests, Includes Instructions
• WebMineral.com - Flame Coloration by Element

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