Introduction:

Nitrocellulose, cellulose nitrate, or gun-cotton, comes from the nitration of ordinary cellulose, the most prevalent form of which is cotton.  Cellulose is glucose molecules, linked together, which means that it is a polymer.  When cellulose is immersed in concentrated sulfuric acid, the hydroxyl groups are protonated, and leave as molecules of water.  These molecules of water are soaked up by the sulfuric acid, which strives to dilute itself.  Once the hydroxyl groups are removed, the nitrate group from concentrated nitric acid attacks the substituent-less carbons.  The result is a cellulose, with each hydroxyl group replaced with a nitro group.  Nitrocellulose is ignited by heat, and is four times as explosive as gunpowder, yet much more stable.  One of the advantages of working with nitrocellulose as opposed to gunpowder is that it is not sensitive to static electricity, which causes unexpected explosions when working with gunpowder.

Nitrocellulose is also used as a laquer finish, although not frequently, because of its explosive properties.  The difference between explosive nitrocellulose and laquer cellulose is its degree of nitration.  The more hydroxyl groups that are replaced by nitro groups, that is, the more nitrated the cellulose is, the more explosive the final result.

Preparation:

1. I cannot overemphasize the importance of gloves and eye protection throughout this experiment. Concentrated nitric acid will cause burns that are recognized by a yellow discoloration of the skin, which will later peel. Concentrated sulfuric acid, also known as battery acid, causes severe chemical burns, and has a tendency to boil and splatter, because it ionizes rapidly in water.  If either acid or the mixture comes into contact with skin, rinse the skin well with copious amounts of water.  Cellulose is harmless as is sodium bicarbonate (NaHCO₃).
2. In a fume hood, prepare a 60:40 solution of concentrated nitric acid (HNO₃) to concentrated sulfuric acid (H₂SO₄).  This can be done in the following order: Pour sixty parts of concentrated nitric acid in a large beaker, and then, slowly, pour forty parts concentrated sulfuric acid down the inside of the beaker, to avoid splattering.  This is the equivalent to pouring acid into water because sulfuric acid is stronger than nitric acid.  This is an extremely dangerous acid mixture.  Do not allow it to come in contact with skin.  Note- if the concentration of sulfuric acid is too high, it will dissolve the cellulose.  If the concentration of nitric acid is too high, it will evolve NO₂ gas.
3. Add cellulose, in the form of cotton balls, to the beaker until no more can fit under the surface of the acid mix.  If it needs to be stirred slightly, do so with a large glass test tube or a large glass stirring rod. Remember, too much cotton or too little cotton can cause the evolution of NO₂, a toxic gas.  If brown fumes begin to form, drop the fume hood.
4. Allow the mixture of acid and cellulose to react for 5-6 hours.
5. After the reaction is allowed to proceed, pour off as much acid from the beaker as possible.  Dispose of in an aqueous acidic hazard waste container.  Do not simply pour down the drain. Squeeze the cotton balls with the glass test tube to remove excess acid.
6. The acid-soaked cotton balls will need to be neutralized and rinsed.  Add a saturated solution of sodium bicarbonate and water to the acid-soaked cellulose, and stir.  Do this gradually, as the sodium bicarbonate solution will evolve CO₂ gas.  When the beaker fills up, empty it into the aqueous acidic hazardous waste container as it is carbonic acid (H₂CO₃).
7. Continue to add sodium bicarbonate solution until no more CO₂ gas is evolved.  At this point, the cotton is neutral or slightly basic, and will no longer be reacting with the acid mixture.  Any further solution can be poured down the drain.
8. Rinse the nitrocellulose well with water, to make sure that it is as clean as possible.
9. Squeeze excess water from the nitrocellulose.
10. Allow the nitrocellulose to dry for several days (without heating) so that it is absolutely free of water.  If possible store the nitrocellulose in a dessicator.

Outdoors, nitrocellulose can be ignited with a match or even a glowing splint.  It releases hot gasses, and should burn extremely quickly.  Care should be taken to keep water from coming into contact with the nitrocellulose.  Although it is not soluble in water, it will not burn properly if wet.

Cleanup:

It is important never to pour acid of such high concentration down the sink, because it can react with pipes and almost anthing.  The oxidized nitrocellulose can be thrown away in a trash can, as long as it is sufficiently cool.  If it is desired to dispose of nitrocellulose, simply burn it in a safe manner.