Sciencemadness Discussion Board

Methanols invisible flame

Trashcanman - 20-7-2024 at 13:31

Why does methanol burn with a clear flame?
I looked for the answer but there are different explanations.

Some say methanol burns with a clear flame because it has a a relatively low carbon content(less than 40%) and it needs less oxygen to be fully oxidized than other fuels.
The reasoning behind that is that without unreacted carbon aka soot there aren't enough solid particles to be heated which then would glow yellow/orange.

But if that explanation is correct then why does something that is burned in pure oxygen(like a candle) still produce a visible flame?

fx-991ex - 20-7-2024 at 13:40

I have no clue but i take a guess.

Maybe because the alcohol flame burn cold its not ionizing gas and not emitting light?
That along a more complete combustion leaving no carbon/soot to be heated and emitting light.

If you take a propane torch the flame is blue, theres no red/orange from leftover carbon being heated, the blue light probably come from the intense heat/ionizing gas?

I know am probably completely wrong.

Trashcanman - 20-7-2024 at 14:03

Quote: Originally posted by fx-991ex  
I have no clue but i take a guess.

Maybe because the alcohol flame burn cold its not ionizing gas and not emitting light?
That along a more complete combustion leaving no carbon/soot to be heated and emitting light.

If you take a propane torch the flame is blue, theres no red/orange from leftover carbon being heated, the blue light probably come from the intense heat/ionizing gas?

I know am probably completely wrong.


The propane torch ensures proper mixing to enable almost complete combustion => almost no soot.
If propane isn't properly mixed with air then it will produce a yellow flame.
Methanol can simply be poured onto a surface and ignited and will burn with a clear flame.
Methanol and Propane reach a similar temperature during combustion.