How to Make Nitrocellulose (Gun Cotton)

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Introduction: How to Make Nitrocellulose (Gun Cotton)

Nitrocellulose is the same chemical ping pong balls, fingernail polish, guitar picks, and fine wood varnish is made of. It is also the primary chemical in smokeless gunpowder. The raw cotton form, known as flash cotton or gun cotton, is used for magic tricks and small special effects. It also has a number of uses in the production of fireworks.

As you will see in the following video, nitrocellulose has a fairly unusual property to be able to ignite on an open hand without passing enough heat to the skin to leave a burn. This can only be done if the nitrocellulose has been very well made or it will burn too slowly and the heat will be in contact with the skin long enough to cause damage. Needless to say, I do not recommend trying this for yourself:



Before I go any further there are some things that must be taken into consideration...

Safety Notes:

This process involves concentrated sulfuric and nitric acid in solution, and acid vapors in the air. It must be done outside on a windy day with nothing downwind, or in a fume hood. Nitrocellulose may only be made in the quantity described or smaller, never larger. If a larger quantity is attempted, or if the ice salt bath is not used, a runaway reaction is likely to occur that evolves a lot of very toxic nitrogen dioxide gas. If a runaway starts to occur (as evidenced by red colored nitrogen dioxide gas), avoid the gas, and drop the reaction beaker into a water bucket standing by. This will dilute the reactants and stop the reaction.

Even when a runaway reaction is not occurring, the solution will constantly give off colorless acid vapor which should also be avoided.

Safety glasses and chemical resistant gloves must be worn at all times to protect from acid splash that occurs from stirring. Should any acid come into contact with your skin or clothes, the water bucket that should be standing by in case of a runaway may be used to quickly wash.

So lets get to it...

Step 1: Synthesis

Nitrocellulose is a nitrated form of cotton made by submersion in nitric acid. Sulfuric acid is typically used to stabilize the reaction and the resulting nitrocellulose. There are several processes to achieve the same end result. The first is to simply form a solution of concentrated nitric and sulfuric acid straight from the bottle to then use as a nitrating bath. A second process, and the one I most often use, is to nitrate the cotton with a solution of potassium or ammonium nitrate and sulfuric acid. The nitrate forms nitric acid when introduced to sulfuric acid, skipping the intermediary step of distilling pure nitric acid. This is the process I will be describing here.

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40 mL sulfuric acid (~95% conc.) is measured into a beaker, and 25 grams of potassium nitrate dissolved into it. The nitrate will be difficult to dissolve, but it can be done with much stirring. At this point the solution will begin to evolve clear acid vapor which should be avoided.

The beaker is then placed into an ice salt bath and let cool down to temperature. The salt will allow the water to cool to a lower temperature than if it were filled with ice alone.

4 cotton balls (~2.5g) are then added to the beaker, and worked into the solution with a stir rod or spoon. This may be difficult because the solution will have turned syrupy from the cold. A step that may be taken which will make the nitrocellulose easier to work with later, is to unroll the cotton balls before adding them to the nitrating bath. When the cotton is well worked in, the reaction is left to sit for a half hour. When that time is up, the beaker is removed from the ice salt bath and left at air temperature.

Another 10-15 mL sulfuric acid is added and the cotton is well worked over again with the stir rod. Any hard knots felt in the cotton must be worked with the rod to allow access to the solution. The beaker is then left to sit for an hour or more.

At this point the cotton is removed and placed in water. It must be washed several times with water to remove most of the acid within them. When washed as well as possible, the cotton is then placed into a sodium bicarbonate (baking soda) solution and worked with the hands until no more bubbles form. It may have to be washed with bicarb several times to fully neutralize. Several more washes with water to remove excess bicarb and the nitrocellulose is complete.

Step 2:

The nitrocellulose will now be very tangled and knotted. For best performance, it must be pulled apart and made fluffy as cotton once again. This is a very tedious job to do by hand, but is necessary to make it burn quickly enough to not harm the skin. Untangling the cotton will be much easier if the cotton balls are unrolled before nitrating them. The nitrocellulose must be fully dry for use. From the 2.5 g of cotton that is used in this experiment, approximately 5 g of nitrocellulose should be produced.

This process can be done to cotton in any form. Thin fabric or paper may be used to make flash paper, though it is difficult not to rip it during nitration. A glass tray may take the place of a beaker to nitrate sheets of cotton more effectively. A demonstration of such a process using cotton fabric is demonstrated below:


The process demonstrated in the video yields lesser quality nitrocellulose than the above written synthesis will yield, so that should be taken into consideration should top quality be desired.

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32 Comments

Where can I get potassium nitrate

Would you be able to use something like bullitt drain cleaner, which contains 96% sulphuric acid, or would this impurity affect the formation of nitric acid from the nitrate?

96% should be adequate. There is no nitrate that survives, but much of the sulfuric acid should remain in solution. There will still be some sulfates that are the remainder of the nitrate and sulfuric acid reaction gelling the slurry, but they are nothing to be concerned about.

One more question: when the nitrate reacts with the sulphuric acid, is there any nitrate or sulphuric acid left or is it all converted to nitric acid and other stuff?

sulfuric acid is neetly disguised as liquid drain cleaner.. available at most hardware stores.
Pottassium nitrate is also know as salpeter and can be purchased at many drugstores.
along with sulfur...*wink*... now I dont have to tell you were to get charcoal!

user

im sorry but whats that reaction vessel?

question where did you get your sulfuric acid.

I've got to wonder if "Homeland Defence" will be at your door when you try to procure what is required.

they can go to you door for just about anything. i had a friend who was playing air soft with all of his friends and some genius saw them and thought they were real gun. in minutes swat was at there door.