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Flame test

Flame test

Overview
A flame test is a procedure used in chemistry
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....

 to detect the presence of certain metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

 ions, based on each element's
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...

 characteristic emission spectrum
Emission spectrum
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted by the element's atoms or the compound's molecules when they are returned to a lower energy state....

. The color of flame
Flame
A flame is the visible , gaseous part of a fire. It is caused by a highly exothermic reaction taking place in a thin zone...

s 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.
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Encyclopedia
A flame test is a procedure used in chemistry
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....

 to detect the presence of certain metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

 ions, based on each element's
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...

 characteristic emission spectrum
Emission spectrum
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted by the element's atoms or the compound's molecules when they are returned to a lower energy state....

. The color of flame
Flame
A flame is the visible , gaseous part of a fire. It is caused by a highly exothermic reaction taking place in a thin zone...

s 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. 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
Cotton swab
Cotton swabs or cotton buds or ear buds consist of a small wad of cotton wrapped around one or both ends of a short rod, usually made of either wood, rolled paper, or plastic...

 or melamine foam (eraser) as a support have also been suggested.
Sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 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
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 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
Subjectivity
Subjectivity refers to the subject and his or her perspective, feelings, beliefs, and desires. In philosophy, the term is usually contrasted with objectivity.-Qualia:...

 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
Photoelectric flame photometer
A photoelectric flame photometer is a device used in inorganic chemical analysis to determine the concentration of certain metal ions, among them sodium, potassium, lithium, and calcium....

 or flame emission spectroscopy. Flame Atomic absorption spectroscopy
Atomic absorption spectroscopy
Atomic absorption spectroscopy is a spectroanalytical procedure for the qualitative and quantitative determination of chemical elements employing the absorption of optical radiation by free atoms in the gaseous state. In analytical chemistry the technique is used for determining the concentration...

 Instruments, made by e.g. PerkinElmer or Shimadzu, can be operated in emission mode according to the instrument manuals.

Common metals


Some common metals and corresponding colors are:
Symbol Name Color
As Arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...

Blue
Blue
Blue is a colour, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 440–490 nm. It is considered one of the additive primary colours. On the HSV Colour Wheel, the complement of blue is yellow; that is, a colour corresponding to an equal...

B Boron
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...

Bright green
Green
Green is a color, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 520–570 nanometres. In the subtractive color system, it is not a primary color, but is created out of a mixture of yellow and blue, or yellow and cyan; it is considered...

Ba Barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...

Pale/Apple green
Ca Calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

Brick red
Cs Caesium
Caesium
Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...

Blue-Violet
Violet (color)
As the name of a color, violet is synonymous with a bluish purple, when the word "purple" is used in the common English language sense of any color between blue and red, not including either blue or red...

Cu(I) Copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

(I)
Blue
Cu(II) Copper(II) (non-halide
Halide
A halide is a binary compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative than the halogen, to make a fluoride, chloride, bromide, iodide, or astatide compound. Many salts are halides...

)
Green
Cu(II) Copper(II) (halide) Blue-green
Blue-green
Blue-green is a color that is a representation of the color that is between blue and green on a typical traditional old-fashioned RYB color wheel.Blue-green is belongs to the cyan family of colors....

Fe Iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

Gold
Gold (color)
Gold, also called golden, is one of a variety of orange-yellow color blends used to give the impression of the color of the element gold....

In Indium
Indium
Indium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two...

Blue
K Potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

Violet
Li Lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...

Red
Mn (II) Manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...

 (II)
Yellowish green
Mg Magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

No color
Mo Molybdenum
Molybdenum
Molybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...

Yellowish green
Na Sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

Intense yellow
Yellow
Yellow is the color evoked by light that stimulates both the L and M cone cells of the retina about equally, with no significant stimulation of the S cone cells. Light with a wavelength of 570–590 nm is yellow, as is light with a suitable mixture of red and green...

P Phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

Pale bluish green
Turquoise
Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium, with the chemical formula CuAl648·4. It is rare and valuable in finer grades and has been prized as a gem and ornamental stone for thousands of years owing to its unique hue...

Pb Lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

Blue/White
Rb Rubidium
Rubidium
Rubidium is a chemical element with the symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group. Its atomic mass is 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other elements in group 1, such as very rapid...

Red-violet
Red-violet
Red-violet is a rich color of high medium saturation about 3/4 of the way between red and magenta, closer to magenta than to red. It is classified in color theory as one of the purple colors—a non-spectral color between red and violet. Both its saturation and brightness falling short of...

Sb Antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...

Pale green
Se Selenium
Selenium
Selenium is a chemical element with atomic number 34, chemical symbol Se, and an atomic mass of 78.96. It is a nonmetal, whose properties are intermediate between those of adjacent chalcogen elements sulfur and tellurium...

Azure blue
Sr Strontium
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...

Red
Red
Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...

Te Tellurium Pale green
Tl Thallium
Thallium
Thallium is a chemical element with the symbol Tl and atomic number 81. This soft gray poor metal resembles tin but discolors when exposed to air. The two chemists William Crookes and Claude-Auguste Lamy discovered thallium independently in 1861 by the newly developed method of flame spectroscopy...

Pure green
Zn Zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

Bluish green

Uses in industry of Flame tests


There are some uses of the flame test in industry;
1. It is particularly useful for the identification of polymers, because many of them give off unique burn patterns.
2. It is also used in salt analysis

See also

  • Colored fire
    Colored fire
    Colored fire is a common pyrotechnic effect used in stage productions, fireworks and by fire performers the world over. Generally, the color of a flame may be red, orange, yellow, or white, and is dominated by blackbody radiation from soot and steam...

  • Emission spectrum
    Emission spectrum
    The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted by the element's atoms or the compound's molecules when they are returned to a lower energy state....

  • Photoelectric flame photometer
    Photoelectric flame photometer
    A photoelectric flame photometer is a device used in inorganic chemical analysis to determine the concentration of certain metal ions, among them sodium, potassium, lithium, and calcium....

  • Qualitative inorganic analysis
    Qualitative inorganic analysis
    Classical qualitative inorganic analysis is a method of analytical chemistry which seeks to find elemental composition of inorganic compounds. It is mainly focused on detecting ions in an aqueous solution, so that materials in other forms may need to be brought into this state before using standard...

  • Burning splint test
    Burning splint test
    The burning splint test is a test for hydrogen. It usually involves setting a thin piece of wood alight, and inserting it into a test tube containing the analyte. A pop sound usually suggests the presence of hydrogen gas, which has a very wide range of flammability....

  • Glowing splint test
    Glowing splint test
    The glowing splint test is a test for oxygen. It involves a thin piece of wood being lit, with the flame blown out, leaving an ember at the tip...


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