Editing Fire (section)

=== Flame ===
{{Main|Flame}}

{{See also|Flame test}}
[[File:Candle-light-animated.gif|thumb|upright|left|A [[candle]]'s [[flame]]]]
A [[diffusion flame]] is a mixture of reacting gases and solids emitting visible, [[infrared]], and sometimes [[ultraviolet]] light, the [[frequency spectrum]] of which depends on the [[chemical composition]] of the burning material and intermediate reaction products. During the burning of [[hydrocarbon]]s, for example wood, or the incomplete [[combustion]] of gas, [[incandescent]] solid particles called [[soot]] produce the familiar red-orange glow of "fire".<ref>{{cite book | title=Principles of Combustion | first1=Allan T. | last1=Kirkpatrick | first2=Kenneth K. | last2=Kuo | year=2024 | page=369 | isbn=9781394187072 | publisher=Wiley | url=https://www.google.com/books/edition/Principles_of_Combustion/uokoEQAAQBAJ?gbpv=1&pg=PA369 }}</ref><ref>{{cite book | title=Fundamentals of Combustion | first=D. P. | last=Mishra | year=2007 | pages=172–174 | isbn=9788120333482 | publisher=PHI Learning | url=https://www.google.com/books/edition/FUNDAMENTALS_OF_COMBUSTION/PwDVwvFBqA0C?gbpv=1&pg=PA172 }}</ref> This light has a [[continuous spectrum]]. Complete combustion of gas has a dim blue color<ref>{{cite web | title=Why does natural gas burn blue? | date=October 31, 2023 | website=Met | url=https://group.met.com/en/media/energy-insight/why-does-natural-gas-burn-blue | access-date=2025-03-03 }}</ref> due to the emission of single-wavelength radiation from various electron transitions in the excited molecules formed in the flame.

Usually oxygen is involved, but [[hydrogen]] burning in [[chlorine]] also produces a flame, producing [[hydrogen chloride]] (HCl).<ref>{{cite journal | title=The Atomic Weight of Chlorine: An Attempt to Determine the Equivalent of Chlorine by Direct Burning with Hydrogen | last1=Dixon | first1=Harold B. | last2=Edgar | first2=E. C. | journal=Philosophical Transactions of the Royal Society of London. Series A, Containing Papers of a Mathematical or Physical Character | volume=205 | pages=169–200 | year=1906 | doi=10.1098/rsta.1906.0005 | bibcode=1906RSPTA.205..169D }}</ref> Other possible combinations producing flames, amongst many, are [[fluorine]] with [[hydrogen]],<ref>{{cite journal | title=The Premixed Hydrogen-Fluorine Flame and its Burning Velocity | last1=Grosse | first1=A. V. | last2=Kirshenbaum | first2=A. D. | journal=Journal of the American Chemical Society | volume=77 | issue=19 | pages=5012–5013 | date=October 1955 | doi=10.1021/ja01624a018 | bibcode=1955JAChS..77.5012G }}</ref> and [[hydrazine]] with [[dinitrogen tetroxide]].<ref>{{cite conference | last1=Melof | first1=Brian M. | last2=Grubelich | first2=Mark C. | date=November 15, 2000 | title=Investigation of Hypergolic Fuels with Hydrogen Peroxide | url=https://www.osti.gov/biblio/767866 | language=English | conference=3rd International Hydrogen Peroxide Propulsion Conference | osti=767866 }}</ref> Hydrogen and hydrazine/[[UDMH]] flames are similarly pale blue, while burning [[boron]] and its compounds, evaluated in mid-20th century as a [[Zip fuel|high energy fuel]] for [[Jet engine|jet]] and [[rocket engine]]s, emits intense green flame, leading to its informal nickname of "Green Dragon".<ref>{{cite web | title=Diborane: The Story of an Undergraduate vs a Nobel Laureate | first1=Ollie | last1=Whitley | first2=Stephen | last2=Belding | series=Molecule of the Month | date=October 2020 | publisher=University of Bristol School of Chemistry | url=https://www.chm.bris.ac.uk/motm/diborane/diboraneh.htm | access-date=2025-03-03 }}</ref>

[[File:Northwest Crown Fire Experiment.png|thumb|A [[controlled burn]] in the [[Northwest Territories]], showing variations in the flame color due to temperature. The hottest parts near the ground appear yellowish-white, while the cooler upper parts appear red.]]
The glow of a flame is complex. [[Black-body radiation]] is emitted from soot, gas, and fuel particles, though the soot particles are too small to behave like perfect blackbodies. There is also [[photon]] emission by de-excited [[atom]]s and [[molecule]]s in the gases. Much of the radiation is emitted in the visible and infrared bands. The color depends on temperature for the black-body radiation, and on chemical makeup for the [[emission spectra]].<ref>{{cite web | title=Examples of blackbody radiators | date=November 12, 1998 | publisher=NASA – Atmospheric Chemistry and Dynamics Laboratory | url=https://acd-ext.gsfc.nasa.gov/anonftp/acd/daac_ozone/Lecture4/Text/Lecture_4/blkbdyexamples.html#candle | access-date=2025-03-05 }}</ref>

[[File:Space Fire.jpg|thumb|Fire is affected by gravity. Left: Flame on Earth; Right: Flame on the [[International Space Station|ISS]]]]
The common distribution of a flame under normal gravity conditions depends on [[convection]], as soot tends to rise to the top of a general flame, as in a [[candle]] in normal gravity conditions, making it yellow. In [[Weightlessness|microgravity or zero gravity]],<ref>{{cite web | url=https://science.nasa.gov/headlines/y2000/ast12may_1.htm | title=Spiral flames in microgravity] | archive-url=https://web.archive.org/web/20100319113411/http://science.nasa.gov/headlines/y2000/ast12may_1.htm | archive-date=2010-03-19 | publisher=[[National Aeronautics and Space Administration]] | year=2000 }}</ref> such as an environment in [[outer space]], convection no longer occurs, and the flame becomes spherical, with a tendency to become more blue and more efficient (although it may go out if not moved steadily, as the CO<sub>2</sub> from combustion does not disperse as readily in microgravity, and tends to smother the flame). There are several possible explanations for this difference, of which the most likely is that the temperature is sufficiently evenly distributed that soot is not formed and complete combustion occurs.<ref>{{cite web | url=http://microgravity.grc.nasa.gov/combustion/cfm/usml-1_results.htm | title=CFM-1 experiment results |  archive-url=https://web.archive.org/web/20070912095009/http://microgravity.grc.nasa.gov/combustion/cfm/usml-1_results.htm |archive-date=2007-09-12 | publisher=National Aeronautics and Space Administration | date=April 2005 }}</ref>

Experiments by [[National Aeronautics and Space Administration|NASA]] reveal that [[diffusion flame]]s in microgravity allow more soot to be completely oxidized after they are produced than diffusion flames on Earth, because of a series of mechanisms that behave differently in micro gravity when compared to normal gravity conditions.<ref>{{cite web | url=http://microgravity.grc.nasa.gov/combustion/lsp/lsp1_results.htm | title=LSP-1 experiment results | archive-url=https://web.archive.org/web/20070312020123/http://microgravity.grc.nasa.gov/combustion/lsp/lsp1_results.htm | archive-date=2007-03-12 | publisher=National Aeronautics and Space Administration | date=April 2005 }}</ref> These discoveries have potential applications in [[applied science]] and [[Private industry|industry]], especially concerning [[fuel efficiency]].

==== Typical adiabatic temperatures ====
{{Main|Adiabatic flame temperature}}

The adiabatic flame temperature of a given fuel and oxidizer pair is that at which the gases achieve stable combustion.
* [[Oxygen|Oxy]]–[[dicyanoacetylene]] {{convert|4990|C|F|sigfig=2}}<ref name=ScienceNotes>{{cite web | title=Adiabatic Flame Temperature Chart | website=Science Notes | date=January 6, 2021 | first=Anne | last=Helmenstine | url=https://sciencenotes.org/adiabatic-flame-temperature-chart/ | access-date=2025-03-05 }}</ref>
* [[Oxygen|Oxy]]–[[acetylene]] {{convert|3997|C|F|sigfig=2}}<ref name=Engineering_Toolbox>{{cite web | title=Adiabatic Flame Temperatures | website=Engineering Toolbox | year=2003 | url=https://www.engineeringtoolbox.com/adiabatic-flame-temperature-d_996.html | access-date=2025-03-01 }}</ref>
* [[Oxyhydrogen]] {{convert|3473|C|F|sigfig=2}}<ref name=Engineering_Toolbox/>
* [[Air]]–[[acetylene]] {{convert|2500|C|F|sigfig=2}}<ref name=Engineering_Toolbox/>
* [[Blowtorch]] (air–[[MAPP gas]]) {{convert|2020|°C|°F|abbr=on|sigfig=2}}<ref name=ScienceNotes/>
* [[Bunsen burner]] (air–[[natural gas]]) {{convert|1300|to|1600|C|F|sigfig=2}}<ref>{{Cite web|url=http://www.derose.net/steve/resources/engtables/flametemp.html|title=Flame temperatures|website=www.derose.net|access-date=2007-07-09|archive-date=2014-04-17|archive-url=https://web.archive.org/web/20140417022946/http://www.derose.net/steve/resources/engtables/flametemp.html|url-status=live}}</ref>
* [[Candle]] (air–[[paraffin wax|paraffin]]) {{convert|1000|°C|°F|abbr=on|sigfig=2}}<ref name=ScienceNotes/>