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Demo

Dr. Schrempp's Chem Lab

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Original air date:

12.26.07

Building Fire with Chemistry

Strong acids are cool; fire is even cooler. Combine the two and you can destroy your math homework without leaving the faintest trace of its existence. In this WIRED SCIENCE demo, Los Osos High School chemistry instructor Chris Schrempp is back in the studio to show us how to create nitrocellulose, a material with some pretty explosive properties. But don't try this experiment at home—we don't want anyone to lose any fingers.

The concept is this: By adding some cellulose—really, anything made of paper, plants or cotton will do the job—to a mixture of sulfuric and nitric acids, chemists can create the stuff once used to make smokeless gunpowder. The cellulose (in this case, a cotton ball) needs to soak in the acid solution, then be rinsed and then dried, after which point it becomes extremely flammable and will react explosively to even the tiniest touch of fire or smoke, leaving no ash. Nitrocellulose was once used to make billiard balls, film and cufflinks because it was strong but cheaper than ivory—but people soon realized its pitfalls when these items would often accidentally ignite.

Watch Dr. Schrempp and Chris Hardwick illustrate the pyrotechnic properties of nitrocellulose in the WIRED SCIENCE studio—it's a miracle, really that they didn't burn the place down. If chemistry doesn't light your fire after this exciting segment, then, well, we may just have ourselves a problem.

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12.26.07 6:42 PM PST

Liam Taylor

I am a high school chemistry teacher and I loved your nitrocellulose demo. I will demonstrate it for my classes when we return from Christmas break. Dr. schrempp explained it very well.

12.26.07 11:25 PM PST

Ruben Nunez

This can be used as a propelant for ojives in the bullets for all the G.I's abroad?

12.29.07 5:23 AM PST

JW

I actually did this when I was growing up (using a fume hood at the University of Virginia) and when I was in college. I also used red fuming nitric acid which is what results if you make the mixture properly to clean my glassware in analytical chemistry class. It is a cherry red color and evolves nitrogen dioxide which is a deadly gas if inhaled. I'm not sure your rock star chemist got it right. The purpose of the sulfuric acid is to put the nitrogen into a highly reactive valence state. The nitration is a direct replacement reaction. Red fuming nitric acid (RFNA) is also used in rocket and torpedo fuel as an oxidizer. Not only is the blending of the acids exothermic and must be done in the correct order, slowly adding the sulfuric acid, the reaction with the cellulose is also exothermic and if you add too much cellulose you will end up with carbon instead of nitrocellulose and end up with acid all over the place. So, keep a box of baking soda handy. By the way, baking soda is also an excellent fire extinguishing agent, especially for oil or grease fires. Keep a box by the stove. It also neutralizes odors in the refrigerator. Whenever you're dealing with an exothermic reaction, you need to keep in mind the surface to volume ratio. A reaction that worked fine in a 75 ml beaker might blow up all over the lab if you try it in a 500 ml beaker. That's why commercial nitrocellulose plants who produce smokeless powder for firearms use robotic equipment and buildings designed to direct explosions upward. The Hercules powder plant at Radford, VA used to have a massive explosion about every two weeks. Producing nitrocellulose in large quantities is a risky business. Any little thing can catalyze a massive chemical explosion. You can see this effect in some precipitation experiments just by scratching the bottom of a beaker with a glass rod. Suddenly the formerly clear solution becomes white.

12.29.07 5:44 PM PST

EW

The -OH GROUPS ON THE GLUCOSE MONOMERS OF CELLOUSE NOT REPLACED, THEY ARE NITATED BY THE NO2+ GROUP GENERATED BY AN ACID BASE REACTION BETWEEN HNO3 & H2SO4 WHERE HNO3, THE WEAKER ACID ACTS AS A BASE---> -ONO2 ON ALL MONOMERS OF THE CELLULOSE CHAIN.

1.2.08 11:56 AM PST

dale

what a neat way to liven up a classroom. I am using mostly the IPS series of physical science but these little extras are just great.. Maybe we can produce a new generation of chemists.

1.24.08 7:38 PM PST

ah cooll

what is chemical equation for cellulose react with acid sulfuric and ammonia????

2.27.08 1:15 PM PST

butch

I recently did this demonstration in my chemisty class with my teacher, and when we lit the nitrocellulose it melted instead of combusting. Were our cotton balls not soaked into the acid long enough or dried out long enough?....could it be that the material was not 100% cotton??????

3.3.09 1:09 PM PST

bob

n3rd=mc

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