Make Thermite out of Sand





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Uploaded on Feb 12, 2011

See my blog for a writeup of this experiment (from one of my first experiments!): http://thehomescientist.blogspot.com/...

Here, I show you how to make a thermite composition out of sand! Just get some sand (the whiter the better), aluminum, and sulfur and make sure everything is a very fine powder. You'll have to grind the sand in a mortar and pestile (interesting side note: I found that's a pretty good way to clean your mortar and pestile!). Then simply ignite it using your favorite thermite ignition method.

The ideal ratio for this type of thermite is 1.67:1 SiO2:Al, but here I use a 9:10:12 mix of SiO2:Al:S (by weight). The ideal composition of just sand and aluminum is very difficult to ignite, so the sulfur is needed for a side reaction with the extra aluminum that provides the heat to drive the real reaction.
Side reaction: 2Al + 3S == Al2S3
Thermite reaction: 4Al + 3SiO2 == 2Al2O3 + 3Si
As you can see, this makes pure silicon! It's pretty amazing to me that you can get a metal from sand (well, technically a metalloid).

As seen in my other videos on thermite, my preferred ignition method is to use potassium permanganate with a piece of magnesium ribbon stuck down through it and into the thermite. Adding some glycerin causes the permanganate to ignite, which lights the magnesium, which then burns hot enough to ignite the thermite. Seems complicated, but it's never failed to light whatever type of thermite I've used it on.


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