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NitrocelluloseEdit

Synonyms: Cellulose nitrate, Flash paper, Gun cottonEdit

Formula: [C6H7(NO3)3O5]n Nitrated cellulose, prepared from various natural fibers.

Description: Nitrocellulose is used as a binder in pyrotechnic compositions. It is also used in some items without any other oxidizers or fuels. In other fields of pyrotechnics than fireworks it is widely used as a propellant, sometimes mixed with nitroglycerin and other materials (so called double- or triple base propellants).

Hazards: Nitrocellulose is subject to detonation using a detonator and a booster explosive, though a large blasting cap may be plausible. It is also extremely flammable and must be handled as if it is a mixed composition (which it is in fact, on the molecular level, unlike most pure chemicals). Pure nitrocellulose is thermally instable and will decompose over time. Nitrocellulose is also impact sensitive. Double and triple base powders contain nitroglycerin and are probably best avoided for use in fireworks.

Sources: Nitrocellulose is sold in gun shops to those with the proper licenses in some countries. Nitrocellulose is the main compound in smokeless gunpowder. Double and triple base powders seem to be most common though. A less nitrated but usable form of cellulose, called celluloid, is also used in some household items: ping-pong balls (see Nitrocellulose lacquer ). This may be a source for small amounts. Celluloid is also used for film but that is getting a little scarce these days with digital cameras taking over the market. It is probably too expensive for pyro uses anyway. Finally, it is possible to make nitrocellulose at home. The procedure is too lengthy to describe well here, but it involves treating cellulose (preferably cotton or paper) with a mixture of sulfuric acid, nitric acid and water. The product is then washed extensively and stabilized. Properly stabilizing the product at home may be difficult and commercial nitrocellulose is preferred for that reason.

Preparation: Nitration of Cellulose

Overview:

Ideally, you could put some of your cellulose source (preferably toilet paper or cotton) in a beaker, and nitrate it with Nitric acid , wash out the Nitric acid , dry it, and be done. Unfortunately there are several problems in doing this:

1. Nitric acid alone can not be used to nitrate cellulose as the process would be too slow to be practically viable.

2. Concentrated Nitric acid, which is used for its production has a tendency to fume when in contact with moving air, leading to suffocation(You may only feel the effects of this hours after exposure); hence the reaction MUST be carried out in a fume hood with proper safety precautions.

3. Nitrocellulose is heat and friction sensitive, which makes drying it by conventional means (heating it) a problem.

Preparation:

Note: Before beginning, all necessary safety precautions MUST be followed, as the process involves dealing with concentrated acids. Safety goggles, gloves, lab coat, fume hood are a bare minimum. It is also expected that the preparation is carried out in a well equipped lab that has all the necessary apparatus by a skilled and experienced person who knows what he is doing.

1. Carefully measure out 5 mL of conc. Nitric acid(70%) into a beaker. Slowly add drop wise, 5 mL of conc. Sulfuric acid (98%) to the above beaker. This process is highly exothermic and the fumes produced during the process are suffocating. Always add Sulfuric acid  to Nitric acid, not vice versa. An ice bath, if required, may be used to keep the temperature under control(~303K-313K). This mixture is called the nitrating mixture.

2. Weigh 0.8 g of generic cotton(a source of pure cellulose) and break into chunks which are easy to deal with. Slowly add these to the nitrating mixture, making sure that each chunk, once added, is completely dipped in the mixture, and no part of it is dry. Failure to ensure that each and every part of the cotton is in contact with the mixture will lead to some cotton remaining un-nitrated, which in turn, will lead to slow burn rate, higher burn temperatures and unnecessary Dross . Failure to maintain a temperature below 313K, during the addition of cotton, will lead to the formation of a gel like substance which is a completely useless product. Let the beaker sit for 20-30 minutes.

3. Prepare a wash bath of a large quantity of COLD water. Take out each chunk of cotton out of the beaker and thoroughly wash it in the bath. It must be ensured that the the entire chunk(including its very center) is in DIRECT CONTACT with water, or else the inner part will heat up leading to the formation of the useless gel like product. Then wash the chunks in a basic solution(Sodium bicarbonate , being cheap is perfect) to neutralize the excess acids. Finally, wash the chunks in a fresh water bath to remove excess Sodium bicarbonate .

4. Once washed thoroughly, squeeze out water, and let dry in cool air. Do not heat to speed up the drying process.

NOTES: Leftover acids can be reused. Upto 1.0 g of cotton can be used, if reuse is undesirable, but it must be made sure that every part of the cotton is completely in contact with the nitrating mixture. Nitrocellulose Lacquer  can be made by dissolving nitrocellulose in Acetone , although, preparing it for this sole purpose is illogical as ping pong balls work just as good. Storage is best avoided, or best done wet if unavoidable.



Use:

Nitrated cotton: Used as Lift charge  for indoor fireworks, or to eject motor from a model rocket.

Nitrated yarn: Used to make things fall down on command .

Nitrated paper: Mainly used by magicians as flash paper to make it disappear in a flash, but also indoor fireworks as Comet .

Nitrated cellulose: Ice fountains, indoor fireworks, for smokeless gunpowder, celluloid, paints (lacquer).


coming soon: a pic or two, and the chemistry of the reaction.


ReferencesEdit

http://www.wfvisser.dds.nl/EN/cheminfo_EN.html

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