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Anne Marie Helmenstine, Ph.D.

Thermite Reaction to Light Solstice Bonfire

By December 15, 2013

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The winter solstice marks the first day of winter. This year it occurs at 17:11 (17:11 am) Coordinated Universal Time (UTC) on December 21, 2013. Are you looking for a way to celebrate using chemistry? Here's a festive holiday video for those of you with pyro tendencies: Lighting a Solstice Bonfire with Thermite. The thermite reaction has nondestructive practical applications, such as welding and ore purification, plus it's an interesting way to light a traditional solstice fire. The reaction basically involves burning metal, much as you might burn wood, except a higher temperature is required. Thermite consists of aluminum powder together with a metal oxide, usually iron oxide. These are mixed with a binder to keep them from separating. Thermite is stable until it is heated to its ignition temperature. This temperature is very high, so you can't just put a match to thermite and initiate the reaction. A propane torch can be used, though it's dangerous. More commonly, magnesium strips are used as fuses. Sparklers burn hot enough to ignite thermite. So does the reaction between potassium permanganate and ethylene glycol or glycerine. Very finely powdered iron(III) oxide and aluminum can be ignited by a lighter or book of matches, though tongs must be used to avoid getting a flash burn.

Although black or blue iron oxide (Fe3O4) is most often used as an oxidizing agent, red iron(III) oxide (Fe2O3), manganese oxide (MnO2), chromium oxide (Cr2O3), or copper(II) oxide may be used. Aluminum is almost always the metal that is oxidized.

Fe2O3 + 2Al → 2Fe + Al2O3 + heat and light

Here's a photo of the thermite reaction:

Thermite Reaction (CaesiumFluoride, Wikipedia)

Comments

December 29, 2008 at 4:38 pm
(1) Bill says:

I have used commercial thermite welding mix to weld railroad track end-to-end. It takes a bit of practice to get things just right so that the product weld is x-ray quality with no voids or inclusions, but oh boy! is it fun!

I assume that the thermite welding mix contains a special steel in powder or chip form, but I wonder about chemical changes (de-carbonization for example) in that steel that would have to be taken into account such that the final product, the steel making up the weld, would be the same as the rail steel.

May 16, 2009 at 2:18 pm
(2) Vladimir says:

The mixrures of Al + MnO2 and Al + CuO react with explosion.

December 19, 2011 at 6:21 am
(3) Alan Crooks says:

Liberal use of old-fashioned nomenclature here, Anne- Marie:

“So does the reaction between potassium permanganate and ethylene glycol or glycerine”.

= Potassium manganate (VII)
Ethane 1,2, diol
Propane 1,2,3 triol

January 4, 2012 at 3:40 pm
(4) Ian Donaldson says:

Since the terrorist attacks on the London Underground several years ago, it’s almost impossible to buy aluminum powder here in the UK!

Magnesium dust can be made by filing down metal pencil sharpeners, best are those “Made in Germany”

Magnesium blocks can still be bought at camping shops – shavings made with a hacksaw blade will act as tinder for damp wood.

December 2, 2012 at 12:02 pm
(5) Alan Crooks says:

Are you sure that metl pencil sharpeners are made of magnesium Ian? Souinds potentially dangerous. I always assumed they were made from aluminium!

December 3, 2012 at 7:40 am
(6) Andy Ewen says:

Starting a fire with a thermite reaction. I love your ‘spark’, Anne.

Btw, just as a matter of interest. When using thermite as a method of welding, what’s the risk of dissimilar metal corrosion occurring due to the presence of the aluminium within the weld matrix?

June 20, 2013 at 4:32 am
(7) Precious says:

It seem’s i will try it in the rail roads in abia Nigeria

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