Gun Cotton
(Nitrocellulose)

Presentation: Ringstand, iron ring, wire screen, extended reach flame source.
Preparation: Glass dish capable of holding the amount of cotton to be converted in a single layer, glass stir rod, wide wooden applicator stick, 1 pair rubber gloves with no holes, 1 pair disposable gloves, 6 plastic tubs (the preparation can be done with fewer tubs, but it is easier with 6).

Concentrated nitric acid and sulfuric acid, cotton batting (cellulose), baking soda

1. Cut the cotton into the sample size you wish to use. A 3x4 inch piece makes for a very impressive demonstration. This works out to be about 6 grams of cotton batting.
2. Place the cotton pieces into the glass dish and place the dish in a fume hood.
3. Don appropriate protective gear and pour the nitrating solution over the cotton. Pour enough solution so that the cotton pieces are thoroughly soaked. You do not need to completely cover the cotton pieces.
4. Use the wooden applicator to press the cotton down into the nitrating solution and work air bubbles out of the cotton. The applicator will blacken from contact with the nitrating solution, but it will last for the procedure. Rince the acid off between uses.
5. After 15-30 minutes, carefully use the applicator and the stir rod to flip the cotton over so that the top will be covered with the nitrating solution. The cotton pieces will be quite stiff and this will make the flipping easier.
6. More nitrating solution may be added if any parts of the cotton look like they are not thoroughly soaked.
7. Leave the cotton to soak for 7-8 hours.
8. Fill 6 plastic tubs 2/3 full of tap water.
9. Add half a box (~250 g) of baking soda (sodium bicarbonate, NaHCO₃) to one of the tubs.
10. Put on both pairs of gloves and all other safety equipment.
11. Take a piece of cotton out of the nitrating solution. Press the cotton between your hands to remove some of the nitrating solution.
12. Place the piece of cotton into the first rinsing bath.
13. Repeat steps 11 and 12 for all of the pieces.
14. Pick up a piece of cotton from the first bath and press it between your gloved hands. Do not wring or ball up the pieces of cotton. Place the piece into the second bath. Repeats for all pieces.
15. Press the pieces and place them in the sodium bicarbonate bath. Carbon dioxide will be produced from the residual acid in the cotton and the pieces will float to the top of the bath. Press them to release the carbon dioxide. Repeat until no more carbon dioxide is produced.
16. Press and transfer the pieces to baths 4, 5 and 6 successively.
17. Remove the pieces from the last rinse bath and press out the excess liquid.
18. You may remove the gloves now. Press the pieces between several layers of paper towels to remove more water.
19. Allow the pieces to air dry overnight or longer if necessary.
20. Tear off a small piece about the size of 1/4 of a cotton ball and test its reactivity. A small fireball should flash and leave almost no residue. If the gun cotton burns slowly or leaves a significant residue, the nitration was not effective.
21. Store the gun cotton pieces in an mesh bag until ready for use.

1. Attach the iron ring to the ringstand, place the wire screen on the ring.
2. Place the gun cotton on the wire screen so that a small portion hangs over the edge of the screen.
3. This is most impressive if the room lights are dimmed.
4. Use a flame source that allows you to be several feet from the gun cotton.
5. Bring the flame under the gun cotton that is hanging over the edge of the screen. A fireball with a diameter roughly 10 times the dimesion of the original piece of gun cotton will be produced.

1. ???B. Z. Shakhashiri, Chemical Demonstrations, A Handbook for Teachers of Chemistry, Wisconsin, 1989, Vol.3, p.186-187