<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>Dear Richard and All combustors, gasifiers and Pyrolysers:</div><div><br></div><div>Good question, "Why is the match flame blue near the base, but turns yellow in the outer region?"</div><div><br></div><div><><><></div><div><br></div><div>As the wood in the match heats, the cellulose in the wood breaks down to form CO and H2. (The lignin in the wood turns to charcoal.) </div><div><br></div><div>I could write a long equation using cellulose (C6H10O5)n, but the chemistry is easier if I approximate it for Carbo-Hydrates, "CH2O", an approximate formula for all sugars, starch and cellulose. </div><div><br></div><div> CH2O ===> CO + H2 </div><div><br></div><div>Solids emit black body radiation mostly proportional to their surface temperature. But burning gases emit arbitrary colors due to the flame reactions. So the flame close to the match shows these blue flame colors. </div><div><br></div><div><><><></div><div>So why does the flame give off black body radiation at a greater distance from the burning match? </div><div><br></div><div>Carbon monoxide is a queer duck. It is THE MOST STABLE molecule at high temperatures. However, at low temperatures (below ~700C as the flame gas cools) it disproportionates to carbon and CO2. </div><div><br></div><div> 2CO ===> C(soot) + CO2</div><div><br></div><div>This is known as the Reverse Boudouard reaction. However, it takes a while for the soot to form. </div><div><br></div><div>The same thing is true if you look very closely at a candle flame.</div><div><><><></div><div><br></div><div>I started to answer your question this morning, but did not have a good answer. When I returned to the question in the afternoon my subconscious must have accessed "Reverse Boudouard". Funny how the mind works. </div><div><br></div><div>Your flame chemist, </div><div><br></div><div>Tom Reed </div><div><br>Thomas B Reed<span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.294118); -webkit-composition-fill-color: rgba(175, 192, 227, 0.231373);"> </span><div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469);">280 Hardwick Rd</span></div><div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469);">Barre, MA 01005</span></div><div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469);">508 353 7841</span></div></div><div><br>On Oct 19, 2013, at 2:52 PM, Richard Stanley <<a href="mailto:rstanley@legacyfound.org">rstanley@legacyfound.org</a>> wrote:<br><br></div><blockquote type="cite"><div>Hi Tom, <div>Thanks much for that but what about the bluish color at base of the flame, both immediately above and beneath stick ?</div><div><br></div><div>Richard Stanley</div><div><br></div><div>===========<br><div><div>On Oct 19, 2013, at 7:02 AM, Thomas Reed wrote:</div><br class="Apple-interchange-newline"><div dir="auto"><div style="-webkit-text-size-adjust: auto;">Dear Stephen, Dean and All</div><div style="-webkit-text-size-adjust: auto;"><br></div><div style="-webkit-text-size-adjust: auto;">I recently warned that "temperature" is only really defined when solids and gases are in thermal equilibrium. </div><div style="-webkit-text-size-adjust: auto;"><br></div><div style="-webkit-text-size-adjust: auto;">During flaming pyrolysis of wood they are not in equilibrium. The gases could be over 1000C while the surface of the solid, cooled by the reaction, is below 500C. However, the subjective color is a good indication of approximate temperature as indicated in the following table from Wikipedia. </div><div style="-webkit-text-size-adjust: auto;"><br></div><div><h3 style="background-image: none; margin: 0px 0px 0.3em; overflow: hidden; padding-top: 0.5em; padding-bottom: 0.17em; border-bottom-style: none;"><font size="3"><span style="-webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);"><span class="mw-headline" id="Subjective_color_to_the_eye_of_a_black_body_thermal_radiator">"Subjective color to the eye of a black body thermal radiator</span><span class="mw-editsection" style="-webkit-user-select: none; font-weight: normal; margin-left: 1em; vertical-align: baseline; display: inline-block; padding-right: 0.25em; unicode-bidi: -webkit-isolate;"><span class="mw-editsection-bracket">[</span><a href="http://en.wikipedia.org/w/index.php?title=Thermal_radiation&action=edit§ion=5" title="Edit section: Subjective color to the eye of a black body thermal radiator" style="text-decoration: none; background-image: none;">edit</a><span class="mw-editsection-bracket">]</span></span></span></font></h3><span style="-webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);"><br class="Apple-interchange-newline"></span><table class="wikitable" style="margin: 1em 0px; border: 1px solid rgb(170, 170, 170); border-collapse: collapse;"><tbody><tr style="font-family: sans-serif; line-height: 19px;"><th style="border: 1px solid rgb(170, 170, 170); padding: 0.2em; background-color: rgb(242, 242, 242); text-align: center;"><font face="UICTFontTextStyleBody"><span style="line-height: normal; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);">°C (°F)</span></font></th><th style="border: 1px solid rgb(170, 170, 170); padding: 0.2em; background-color: rgb(242, 242, 242); text-align: center;"><font face="UICTFontTextStyleBody"><span style="line-height: normal; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);">Subjective color<sup id="cite_ref-5" class="reference" style="unicode-bidi: -webkit-isolate; font-weight: normal;"><a href="http://en.wikipedia.org/wiki/Thermal_radiation#cite_note-5" style="text-decoration: none; background-image: none;">[5]</a></sup></span></font></th></tr><tr style="font-family: sans-serif; line-height: 19px;"><td style="border: 1px solid rgb(170, 170, 170); padding: 0.2em;"><font face="UICTFontTextStyleBody"><span style="line-height: normal; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);">480 °C (896 °F)</span></font></td><td style="border: 1px solid rgb(170, 170, 170); padding: 0.2em;"><font face="UICTFontTextStyleBody"><span style="line-height: normal; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);">faint red glow</span></font></td></tr><tr style="font-family: sans-serif; line-height: 19px;"><td style="border: 1px solid rgb(170, 170, 170); padding: 0.2em;"><font face="UICTFontTextStyleBody"><span style="line-height: normal; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);">580 °C (1,076 °F)</span></font></td><td style="border: 1px solid rgb(170, 170, 170); padding: 0.2em;"><font face="UICTFontTextStyleBody"><span style="line-height: normal; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);">dark red</span></font></td></tr><tr style="font-family: sans-serif; line-height: 19px;"><td style="border: 1px solid rgb(170, 170, 170); padding: 0.2em;"><font face="UICTFontTextStyleBody"><span style="line-height: normal; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);">730 °C (1,350 °F)</span></font></td><td style="border: 1px solid rgb(170, 170, 170); padding: 0.2em;"><font face="UICTFontTextStyleBody"><span style="line-height: normal; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);">bright red, slightly orange</span></font></td></tr><tr style="font-family: sans-serif; line-height: 19px;"><td style="border: 1px solid rgb(170, 170, 170); padding: 0.2em;"><font face="UICTFontTextStyleBody"><span style="line-height: normal; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);">930 °C (1,710 °F)</span></font></td><td style="border: 1px solid rgb(170, 170, 170); padding: 0.2em;"><font face="UICTFontTextStyleBody"><span style="line-height: normal; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);">bright orange</span></font></td></tr><tr style="font-family: sans-serif; line-height: 19px;"><td style="border: 1px solid rgb(170, 170, 170); padding: 0.2em;"><font face="UICTFontTextStyleBody"><span style="line-height: normal; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);">1,100 °C (2,010 °F)</span></font></td><td style="border: 1px solid rgb(170, 170, 170); padding: 0.2em;"><font face="UICTFontTextStyleBody"><span style="line-height: normal; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);">pale yellowish orange</span></font></td></tr><tr style="font-family: sans-serif; line-height: 19px;"><td style="border: 1px solid rgb(170, 170, 170); padding: 0.2em;"><font face="UICTFontTextStyleBody"><span style="line-height: normal; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);">1,300 °C (2,370 °F)</span></font></td><td style="border: 1px solid rgb(170, 170, 170); padding: 0.2em;"><font face="UICTFontTextStyleBody"><span style="line-height: normal; -webkit-text-size-adjust: auto; background-color: rgba(255, 255, 255, 0);">yellowish white</span></font></td></tr><tr style="font-family: sans-serif; line-height: 19px;"></tr></tbody></table>During flaming pyrolysis, the flames appear to me to be a bright orange, (due to incandescence of small particles) and so are 930 or higher. At the same time, the pyrolysing material appears black, and so could be less than 480C. Here's a picture of a burning match to ponder...</div><div><br></div><div><image.jpeg><br><span style="-webkit-text-size-adjust: auto;">Thomas B Reed</span><span class="Apple-style-span" style="-webkit-text-size-adjust: auto; -webkit-tap-highlight-color: rgba(26, 26, 26, 0.294118); -webkit-composition-fill-color: rgba(175, 192, 227, 0.231373);"> </span><div style="-webkit-text-size-adjust: auto;"><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469);">280 Hardwick Rd</span></div><div style="-webkit-text-size-adjust: auto;"><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469);">Barre, Ma 01005</span></div><div style="-webkit-text-size-adjust: auto;"><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469);">508-353-7841</span></div></div><div style="-webkit-text-size-adjust: auto;"><br></div></div></div></div></div></blockquote></body></html>