Remember Remember...

Remember, remember the Fifth of November,
The Gunpowder Treason and Plot,
I know of no reason
Why Gunpowder Treason
Should ever be forgot.
Guy Fawkes, Guy Fawkes, t'was his intent
To blow up King and Parli'ment.
Three-score barrels of powder below
To prove old England's overthrow;
By God's providence he was catch'd
With a dark lantern and burning match.
Holloa boys, holloa boys, let the bells ring.
Holloa boys, holloa boys, God save the King!

Happy Guy Fawkes Day! I thought that today would be a great day to discuss gunpowder. From a very early age I knew that gunpowder was made from three things: Carbon, Sulfur, and Saltpetre. I knew what carbon and sulfur were but all I knew about saltpetre was that it came from bat guano. This did not stop me from sharing my vast knowledge of gun powder with my other geek friends "If only we had some carbon, sulfur, and saltpetre we this wall wouldn't pose any problems..."

I continued to dream about making my own gunpowder through my undergraduate time but I never made any even though I had access to all the chemicals. Many of my professors were happy to give me different chemicals for my own projects but I made a decision that I would never use any of the chemicals from school to make explosives. That way if something went wrong the school couldn't be held accountable in any way. During this time however I learned a lot about how gunpowder works. Carbon is the primary fuel in the reaction, sulfur is also a fuel but it also reduces the ignition temperature and speeds us the reaction, saltpetre is also known as potassium nitrate KNO₃ and provides the reaction with the oxygen it needs. A very simplified chemical reaction for the combustion of gunpowder is:

KNO₃ + 3 S + 8 C → 2 K₂CO₃ + 3 K₂SO₄ + 6 CO₂ + 5 N₂

We start with 8 moles of solids and end up with 5 moles of solids and 11 moles of gasses. While the solids take up very little room (a few cubic centimeters at most in a firework) the each mole of gas takes up 22.4 L of volume at stp. It is the rapid evolution of all of these gasses that causes an explosion.

My desire to make gunpowder went from dream to reality when I was at our local pharmacy picking up a prescription. While waiting I was perusing the shelves of vitamins and supplements (I always do this when I have the time because it's good to know what chemicals are available if I need them) I found a bottle labeled "Flowers of Sulfur" and then right next to it from the same company "Saltpetre." It had to be a sign. I bought both bottles and the pharmacist didn't even bat an eye. When I brought both of them home and explained it to my wife she was very understanding and asked me not to blow up our house or our son.

So with these ground rules I got down to business. I had two of the three and all I was missing was the carbon. I called all of the local pharmacies and apothecaries but none of them had any activated charcoal. So I set out to make my own. I knew that the best form of charcoal to use was from softwood charcoal but all I had was newspaper so I burned it and collected the ashes. I weighed out the ashes and used them as my limiting reagent. I weighed out the appropriate amounts of KNO₃ and S to make gunpowder (75% KNO₃, 15% C, 10% S). I put it all into the mortar my mother-in-law gave me and set about grinding it until it was a fine grey powder. I had done it, I had made my own gunpowder. To test it I put a little trail on the ground and I lit it. It burned wonderfully.

So while King James I and Parliament have nothing to fear from me there are some pumpkins around who might.

Edit 11/06: I made this video of burning Guy Fawkes in effigy last night using some of my gunpowder. I also made the wick which isn't very good.