Why are flames coloured?

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Why are flames coloured?
« on: 10/06/2009 16:30:02 »
sarab asked the Naked Scientists:
Please out-line the colours of a flame and the function of each category of flame naming the type of gas involved. i.e. the details of the output of a flame.

What do you think?


Offline Chemistry4me

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Why are flames coloured?
« Reply #1 on: 11/06/2009 06:01:28 »
Flame color depends on several factors, the most important typically being blackbody radiation and spectral band emission, with both spectral line emission and spectral line absorption playing smaller roles. In the most common type of flame, hydrocarbon flames, the most important factor determining color is oxygen supply and the extent of fuel-oxygen "pre-mixture", which determines the rate of combustion and thus the temperature and reaction paths, thereby producing different color hues.


Spectrum of blue flame


Offline canchem

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Why are flames coloured?
« Reply #2 on: 19/06/2009 19:23:57 »
It is based on each element's characteristic emission spectrum. The color of flames in general also depends on temperature.

newbielink:http://en.wikipedia.org/wiki/Flame_test [nonactive]

Symbol   Name   Color
As   Arsenic   Blue
B   Boron   Bright green
Ba   Barium   Pale/Apple green
Ca   Calcium   Brick red
Cs   Caesium   Blue
Cu(I)   Copper(I)   Blue
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
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   Bluish green


Offline Shadec

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Why are flames coloured?
« Reply #3 on: 21/06/2009 22:47:55 »
colour of regular wood flames is a yellow orange from the overpowering sodium ions in it, (various chemicals with Na+ in them that the tree uses for something or other).
but in addition to canchem's excellent list there, i would add only that most heavy metals are a lovely sky blue.
Ive always wondered what silver (Ag) the transuranic elements look like... do any of you know?