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Science Forum Index » Chemistry Forum » Bunsen burners: Why different flame colors?...
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| Joris Dolderer... |
 Posted: Thu Jun 12, 2008 1:12 pm |
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Guest
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Hello,
if you turn an bunsen burner to a non-lighting flame, you'll see two
flame cones [1].
a) Where does the color and light intensity change come from?
b) Why are the borders so sharp?
[1] http://www.hpwt.de/Chemie/Brenner2.jpg
Joris |
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| Posted: Thu Jun 12, 2008 1:35 pm |
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| Androcles... |
| Posted: Thu Jun 12, 2008 3:35 pm |
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"Joris Dolderer" <stdio at (no spam) 123mail.cl> wrote in message
news:48516729$0$27447$9b4e6d93 at (no spam) newsspool4.arcor-online.net...
| Hello,
|
| if you turn an bunsen burner to a non-lighting flame, you'll see two
| flame cones [1].
|
| a) Where does the color and light intensity change come from?
| b) Why are the borders so sharp?
|
| [1] http://www.hpwt.de/Chemie/Brenner2.jpg
|
| Joris
The flame is where the two gases are reacting chemically, in this case
oxygen and a butane/propane mixture producing H2O and CO2. This
reaction is light emitting (energy releasing) and the colour comes from
the emission spectrum involved.
http://library.thinkquest.org/19662/images/eng/pages/model-bohr-3.jpg
The inner cone is just the region where the reaction is taking place, shaped
by the moving gas. The outer envelope is hot burnt gas which is now cooling.
If you look more carefully at the photograph you provided you'll see it is
not a cone at all, it has no apex, but a moving column that bends upwards.
--
Androcles
Why did Einstein say
the speed of light from A to B is c-v,
the speed of light from B to A is c+v,
the "time" each way is the same?
1/2[tau(A)+tau(A')]= tau(B)
where
A = (0,0,0,t)
A' =(0,0,0,t+x'/(c-v) +x'/(c+v))
B = (x',0,0,t+x'/(c-v))
x' = x-vt
Ref: http://www.fourmilab.ch/etexts/einstein/specrel/www/figures/img22.gif
"Easy: he did NOT say that." - cretin harald.vanlintelButNotThis at (no spam) epfl.ch
According to moron van lintel, Einstein did not write the equation he wrote. |
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| Farooq W... |
| Posted: Fri Jun 13, 2008 7:33 pm |
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Guest
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On Jun 12, 11:12 pm, Joris Dolderer <st... at (no spam) 123mail.cl> wrote:
Quote: Hello,
if you turn an bunsen burner to a non-lighting flame, you'll see two
flame cones [1].
The inner cone is called the primary combustion zone and the envelope,
light blue in color, is called secondary combustion zone.
Quote:
a) Where does the color and light intensity change come from?
Since flame is a exotheric chemical reaction, involving a hydrocarbon
and oxygen, a number of excited molecules are formed. These excited
molecules are responsible for the colors we see in the flame like C2,
CN etc.. The blue color of the inner cone is typical of hydrocarbon
flames. Under a spectroscope, this blue cone appears as extremely
beautiful spectrum. These bands are called Swan bands and are
attributed to the diatomic C2 molecule and perhaps CN.
Quote: b) Why are the borders so sharp?
I think this must be too complex a problem. No idea. This might be
related to the burning velocity of the gases.
M. Farooq.
Quote:
[1]http://www.hpwt.de/Chemie/Brenner2.jpg
Joris |
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| Marvin... |
| Posted: Sat Jun 14, 2008 11:02 am |
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Androcles wrote:
Quote: "Marvin" <physchem at (no spam) verizon.net> wrote in message
news:Ogx4k.2072$ul.231 at (no spam) trndny08...
| Joris Dolderer wrote:
| > Hello,
|
| > if you turn an bunsen burner to a non-lighting flame, you'll see two
| > flame cones [1].
|
| > a) Where does the color and light intensity change come from?
| > b) Why are the borders so sharp?
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| > [1] http://www.hpwt.de/Chemie/Brenner2.jpg
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| > Joris
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| Nobody else mentioned that the flame in your picture isn't
| on a Bunsen burner.
Oh, but it is. The device Bunsen invented, a chimney in which the gases
mix as the flow from one gas draws in the air, is exactly what is shown.
Changing the design doesn't change the principle. Nor would it change
the patent if Bunsen still had one that was current.
A Bunsen burner has openings at the bottom to admit air,
with a rotating sleeve to allow for control of the amount of
air admitted. (http://en.wikipedia.org/wiki/Bunsen_burner)
I saw no such mechanism in the photo of the burner from
Dolderer. It looks like a home soldering burner, which
usually burns propane. |
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| Androcles... |
| Posted: Sat Jun 14, 2008 3:46 pm |
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"Marvin" <physchem at (no spam) verizon.net> wrote in message
news:6YR4k.6061$1x.104 at (no spam) trndny06...
| Androcles wrote:
| > "Marvin" <physchem at (no spam) verizon.net> wrote in message
| > news:Ogx4k.2072$ul.231 at (no spam) trndny08...
| > | Joris Dolderer wrote:
| > | > Hello,
| > | >
| > | > if you turn an bunsen burner to a non-lighting flame, you'll see two
| > | > flame cones [1].
| > | >
| > | > a) Where does the color and light intensity change come from?
| > | > b) Why are the borders so sharp?
| > | >
| > | > [1] http://www.hpwt.de/Chemie/Brenner2.jpg
| > | >
| > | > Joris
| > |
| > | Nobody else mentioned that the flame in your picture isn't
| > | on a Bunsen burner.
| >
| > Oh, but it is. The device Bunsen invented, a chimney in which the gases
| > mix as the flow from one gas draws in the air, is exactly what is shown.
| > Changing the design doesn't change the principle. Nor would it change
| > the patent if Bunsen still had one that was current.
|
| A Bunsen burner has openings at the bottom to admit air,
| with a rotating sleeve to allow for control of the amount of
| air admitted. (http://en.wikipedia.org/wiki/Bunsen_burner)
| I saw no such mechanism in the photo of the burner from
| Dolderer. It looks like a home soldering burner, which
| usually burns propane.
The rotating sleeve is rendered redundant by the accurate manufacture
of the opening to admit air (which the device has). As to your second
point, nobody solders homes these days although Bunsen may have
plumbed (leaded) some pipes. The Bunsen burner depicted is for
removing old lead paint and has nothing to do with soldering; after
removing the paint the residue should be hoovered up. A vacuum is
necessarily clean and therefore all vacuum cleaners are misnamed.
http://www.thefreedictionary.com/hoovering
--
Androcles
Why did Einstein say
the speed of light from A to B is c-v,
the speed of light from B to A is c+v,
the "time" each way is the same?
1/2[tau(A)+tau(A')]= tau(B)
where
A = (0,0,0,t)
A' =(0,0,0,t+x'/(c-v) +x'/(c+v))
B = (x',0,0,t+x'/(c-v))
x' = x-vt
Ref: http://www.fourmilab.ch/etexts/einstein/specrel/www/figures/img22.gif
"Easy: he did NOT say that." - cretin harald.vanlintelButNotThis at (no spam) epfl.ch
According to moron van lintel, Einstein did not write the equation he wrote. |
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