Difference between revisions of "Synthesis of nitrocellulose"

Latest revision as of 11:18, 7 May 2016

This page details the synthesis of nitrocellulose, or guncotton, a low explosive, via the nitration of cotton. Because this page represents an individual's own work as it was written by them, it is asked that the text of this article detailing the synthesis not be edited except for clarity's sake.

Nitrocellulouse from nitrate salts and concentrated sulfuric acid by alexleyenda

WARNING : This preparation deals with concentrated sulfuric and nitric acids and NO_x gases. Both acids are extremely corrosive and can burn and blind a person. In addition, gloves made of nitrile or most other plastics do not provide adequate protection and should not be used, especially given that nitric acid can instaneously ignite such materials . Oxides of nitrogen produced by this experiment are extremely toxic (more so than chlorine). This experiment should only be attempted by an experienced chemist.

NC can be prepared by nitrating a source of cellulose with nitric acid and concentrated sulfuric acid. The main source of cellulose used is cotton, as it is almost entirely made of cellulose. For the acids, it is possible to use a mixture of concentrated nitric and sulfuric acids, or to directly dissolve a nitrate salt in excess concentrated sulfuric acid, forming the nitric acid directly, thus saving the need to distill the HNO₃. Many procedures using different proportions exist to prepare nitrocellulose. Here are some of them: This preparation have been tested and works very well, burning in a flash leaving almost no ash behind.

1. Prepare 2,5 g of cotton, 0,25 mol of a nitrate salt ( for example, 25 g of KNO₃) and 50 mL of concentrated sulfuric acid.

1. In a beaker, dissolve the 0,25 mol of a nitrate salt in 40 mL of the sulfuric acid. You may need to stir a lot and wait up to 30 min for the salt to completely dissolve.

1. Add the cotton and soak it in the solution using a glass rod.

1. Remove the beaker from the ice bath and let it sit for 25 minutes.

1. Add the remaining 10 mL of concentrated sulfuric acid and mix to make sure all the cotton is completely soaked once again. Be careful, it might be so hard to mix that it'll break your glass rod.

1. Let it sit for 1 hour.

1. Rinse the cotton with an huge ammount of water to dilute and flush out the acids.

1. Add the cotton to a solution of NaHCO₃ (sodium bicarbonate) to neutralise what is left of the acids. Once the bubbling stops, let it soak an additional 30 min to make sure the acids are completely neutralised.

1. Rinse with a lot of water to flush the NaHCO₃.

1. Let the nitrocellulose dry completely before use.

Additional notes and tips :

- Use very pure and smooth cotton, if the cotton is a cheap brand and has just a few small knots in it, it will still work but it will burn more slowly and leave more ash behind.

-Even with a good brand of cotton, a negligible amount of ash is left behind. You won't see them if you burn it in your hands or in the air, but you will if you burn it on something white.

-An ice bath is often used in nitrations to prevent runaway reactions. However, using this approach with KNO₃, I found that the temperature does not change much. In fact, the ice bath just freezes the mix and it is a real pain to work with a frozen nitration mixture with cellulose in it. That is why I do not recommend an ice bath.

Notes