Which is hotter: an orange flame or blue flame?

Question

Provide documentation, please. Thanks!

Answer 1

It is misleading to make the general statement that "blue is *hotter* than yellow or orange"

The different colors in a flame are a result of *different physical and chemical processes* within the flame, not strictly because of differences in temperature. (most web materials get this wrong....)

If you read the fine print in a good physics book, you will find that a blue color corresponds to a temperature of about 20,000 degrees and upwards. This is far hotter than any known flame, and the only places you are likely to find these kind of temperatures is in electric arcs, lightning bolts, and very hot stars. Most flames are on the order of 1,500 - 4,000 degrees, the hottest being an oxygen+acetylene welding flame, which is around 5,000 degrees, about that of a lightbulb. Not hot enough by far to produce a blue color....

So where does the blue color come from?

The blue color is caused by "chemiluminescence," this is light which is produced *directly* from the chemical reactions of combustion, not indirectly as a result of heat (e.g. a red hot stove, or light bulb filament...)

So where does the yellow color come from? Why are some flames white-yellow, and some flames completely blue?

If some region of a flame does not have enough oxygen to burn completely, it will begin to form tiny soot particles. These soot particles are far more dense than the surrounding gas, so they glow a nice bright yellow color. As they reach the top of the flame, in-rushing air brings enough oxygen to burn up the soot particles completely.

A reddish or orange flame usually means it contains excess soot or impurities; such flames will usually produce a lot of smoke. in particular, a yellowish orange comes from excess sodium.

A flame that has enough oxygen, or a correct ratio of fuel to air, won't produce any soot at all, thus eliminating the bright yellow color. Incidentally, such flames usually burn more efficiently than those that are oxygen starved, hence the misleading assumption that "blue is hotter" Flames that don't contain carbon, such as those of burning hydrogen, ammonia, or sulfur, are usually bluish or colorless.....

Probably way more than you wanted to know about fire....
~W.O.M.B.A.T.

Answer 2

A blue flame is hotter.

Answer 3

Flame temperature, if not affected by the chemical composition of substances in the fuel or added on the side, follows the visible color sequence of the electromagnetic spectrum. Red is the coolest, then orange, then yellow, then blue, and finally blue-white. Green is seldom seen in pure flame colors. You can get more details from Wikipedia - search "flame color".

Answer 4

The pale blue flame is hotter. Look in any Chemistry text book for the temperature ranges.

Answer 5

the blue flame is hotter

Answer 6

Blue. There's no "documentation" to provide. Certain colors are just hotter than others.

Answer 7

blue is hotter
because we can see blue flames only when there is complete combustion of air(hydrogen in air)/or any other combustable substance.
thats why blue starts are very hot.......

Answer 8

I have always been taught that the light blue closest to the orange in the flame is the hottest part of the fire. I have no documentation except for in my head when my 8th grade science teacher taught it to us! Thanks Mr. Williams!

Answer 9

Blue.

Answer 10

blue.

in a bunsen burner, you open the hole at the side to admit more oxygen and make the flame hotter