Consider the following reaction, and keep in mind Le Chatelier's Principle.
Nitrocellulose Polymer. The dashed lines indicate repeating units to "infinity". Image courtesy of Wikipedia
(C6H8(NO2)2O5)n + flame ----> CO2 + H2O + CO + N2
What we see here is that a solid, the nitrocellulose is ignited and is self consumed. This quick tutorial video about the reaction shows a nice ignition flash- but notice there's no smoke nor ash! Why is this so?
All of the products of the reaction are gaseous, which means there is no solid residue to leave behind. The smoke and ash in normal fires are caused by bits of solid carbon from the paper clumping together from incomplete combustion- but the energy coming out of the nitrocellulose combustion is so great (and self-sustained) that all of the carbon gets converted into its gaseous oxides. The gasses leave the reaction area by a physical process called diffusion, which makes the equilibrium of the reaction shift to the right. Remember- removing products shifts the equilibrium in that direction!
Periodic Videos gives a great basic introduction to the cellulose molecule in the beginning and a historical perspective on the uses of nitrocellulose since it was discovered. The videos on that site are great. Note, however, that their cotton was not fully nitrated. It left behind some embers after a rather impressive flame.
A note on the nitric acid. Commercial production of this strong acid is carried out via the "Ostwald Process", which uses ammonia as a feedstock- ammonia usually obtained from the "Haber Process" that I mentioned in my last post!
https://www.youtube.com/watch?v=QQ5q9G1lHUc
http://chemistry.about.com/od/makechemicalsyourself/a/make-nitrocellulose-flash-paper.htm
http://www.periodicvideos.com/videos/mv_guncotton.htm
+Joseph Meany
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