Self-Igniting High Temperature Reaction

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Introduction: Self-Igniting High Temperature Reaction

About: My goal in life is to be a chemistry professor, because a) I've had lots of awesome influential teachers b)Bill Nye kicks ass c)I like things that burn, pop, explode, fizzle, and bubble.

This is a pretty basic but nonetheless awesome demo. Glycerine (Glycerol, 1,2,3-propantriol) is mixed with potassium permanganate (KMnO4), and within about 30 seconds, the pile starts to smoke, then burns with a very hot lavender colored flame.

Jargon:
-This is a hot-burning reduction/oxidation reaction. It doesn't spark as a thermite reaction would, but still, don't do something dumb like put it on a wood table.
-KMnO4 likes to stain stuff. If it comes into contact with moisture it will form a purple solution that will render anything purple permanently (your skin will turn brown but that comes off in a few days)
-Non-science types don't understand chemistry. People fear things they don't understand. In other words, many ignorant people think chemistry is evil/terrorism/just plain bad, so don't do this around people if you know they are going to flip.
-I am not liable in the event of fire, explosion, injury, disability, death, act of God/Goddess, rabid squirrel attacks, subpoena, lawsuits, or any other dumb situation you might manage to get yourself in. Use your brain and use basic common sense

Warning: Science content!
If you want to figure out how to get a stoichiometric reaction (basically molecule for molecule reaction, most efficient burn) you can start with this equation:

14 KMnO4 + 4 C3H5(OH)3 --> 7 K2CO3 + 7 Mn2O3 + 5 CO2 + 16 H2O + HEAT

That calculates out to be 6 g KMnO4 for 1 g glycerin. Honestly, there isn't any point to weighting it out, it works just as well mixing approximate amounts.

Step 1: Prepare Your Materials

You will definitely need:
-Potassium permanganate - this is sold at small hardware stores like Ace as filter cleaner - $5
-Glycerine - sold at RiteAid - $3

-Additionally, you can use antifreeze or windshield washer fluid if it contains the ingredient ethylene glycol. Ethylene glycol is C2H4(OH)2 whereas glycerin is C3H5(OH)3. It's the multiple alcohol group that makes it work. Also, make sure it is of the highest concentration possible. Water typically does not help with fire-making processes.

Stuff that's a good idea to have
-Burn plate - I used a granite tile I got as a sample from a countertop store
-Goggles - this isn't a super dangerous reaction, use your own discretion
-Sand - if for some reason you have to put it out - water will make a HUGE mess because it forms KMnO4 solution which stains anything and everything purple

Step 2: Prepare the KMnO4

Find a nice suitable place to be burning things. This should be away from flammable things, tall grass, small children etc.

Make a small pile of KMnO4. The size isn't critical, obviously the more permanganate you use the more glycerin you will need.

Furrow out a "bird's nest" in the middle of the pile. If you've ever made bread before (rustic method), it's the same concept.

Step 3: Add Glycerin

Pour the glycerin into the furrow. The ratio between KMnO4 and glycerin is very forgiving, but you should have about 1.5:1 KMnO4:glycerin, volumetrically.

Depending on the ambient temperature, the reaction might not self initiate at this point. Give it some time. If it doesn't start smoking after 45 seconds, either mix it with a stick, or drop some HCl onto it. The reaction is slow to start up, you will see smoke before the fire with enough time for you to react and get your hands away.

The chemistry here is called a hypergolic reaction. Compounds that are reactive enough to begin a reaction just by being in contact with each other are said to be hypergolic. Other examples include hydrazine and nitrous oxide, and sodium and water. The rate of reaction depends on the fuel used, the temperature, and water content. Water obviously retards the reaction.

Warning: Science Content!
Ethylene glycol: It has the smallest molecular weight, and thus the most active; concentrated or pure it will react very fast

Glycerin: Slightly less reactive than ethylene glycol, the reaction could be hypergolic on a hot day and not on a cold one.

Propylene glycol: The least reactive due to high molecular weight and lower reactivity (less function groups). Anything but pure might not react at all.

Alcohols: These won't work at all, they aren't reactive enough to start the reaction by itself.

Anecdote time! I had a Dixie cup full of the stuff in my hand (this was at the time when I had to set it off with HCl because it was colder) but that day was very hot. I saw it starting to smoke in my hand and I threw it, only to have it burst into flames mid-air.

Step 4: Fire!

After a short time, the reaction will start to smoke. This is your cue to step back a little. It will burst into flames and depending on how close to stoichiometric you got, it will burn something like a road flare or rocket engine.

Uses: Aside from a really neat chemistry demo, the reaction burns hot enough to initiate other reactions with exorbitant activation energies, namely, thermite. I don't have any thermite to play with, so I haven't tested it myself, but I've seen it work. The KMnO4/glycerin doesn't spark and cause excessive destruction around it, but if you use it to initiate a thermite reaction, the thermite WILL do what it's good at: melting and setting fire to everything around it, so take this into account when picking a location.




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    82 Comments

    user

    best way to light thermite is to use 3 sparklers at the same time.

    3 replies

    its the most efficient/easy/cheap/ foolproof way. its fairly difficult to light Mg ribbon in mildly windy conditions, whereas sparklers will burn even in mild rain. and sparklers can be inserted directly into a pile of thermite, without being extinguished. if you want a better way than either mg ribbon or thermite, use very thin-walled Mg tubing, filled with potassium nitrate. at the tip of the device, pack slow burning gunpowder for easy ignition.

    Where the HECK do you get Mg Tubing?

    my reaction exactly!

    You could make this like a grenade, so when you pull the pin it mixes the two chemicals and eventually explodes.

    Hey, that's a great idea!

    It really won't explode, just catch on fire. I suppose you could make it into some kind of fire paste like napalm if you could slow down the ignition time...

    We did this in chemistry class, it works great!

    @ pyromaniac3-2-1 - unfortunately as oxidizers go, KMnO4 is no where near as reactive as nitrates, chlorates, or perchlorates. I've tried making firecrackers using fine charcoal and permanganate but it did bubkus. And I found this out through my awesome 10th grade chem teacher. Imagine the Roaming Gnome or Santa Claus in a lab coat. At the end of the year he'd shoot spudguns out the window. @Andrew - Wikipedia says that early flashpowder formulations used permanganate, but I have no clue what other ingredients were used with. I would think that permanganate reacts too slow, but maybe if you had aluminum and KMnO4 in a 1:3 ratio, with a dash of KClO3 for sensitivity, I think that would work. You would need very fine aluminum and you would probably have to run the permanganate through a ball mill first.

    2 replies

    You had Mr. Albee for Chemistry too?

    sulpher and fine mesh dark german aluminum powder is what your missing.

    hey great 'ible
     do you know if this could ignite thermite?

    It can burn through wood and plastic pretty easily, although not very much of it. It doesn't quite have the penetrating power of Thermite.

    DeusXMachina- where did you get the KMnO4, I found some at tractor supply $24 for 5 lbs, and at ace $12 for 1.5lbs. where did you find it so cheap?

    3 replies

    Ace. I dunno why you got charged so much or why I got charged so little.

    Yours was probably on sale.

    that's what.... *cackling*