Element Collection

Element Collection

Saturday, March 27, 2010

Experiment: Manganese Dioxide Thermite

This old post serves as the Video Companion to  this video.

For this experiment, I used manganese dioxide and a much finer aluminum powder than in my other thermites, at a ratio of 2.42:1 MnO2:Al by weight (40g total). I've done this reaction before (but forgot to photograph it), and using my normal aluminum it produced a reaction similar to the iron thermite. It was a little brighter and produced more sparks. With the finer powder, things went a little differently. The small flower pot erupted in a pillar of flame about 6 feet high, with the sound of a rocket engine and heat that was felt a good 15 feet away. This is a great demonstration of the importance of particle size in thermite and most other reactions. I plan on posting a direct comparison, complete with pictures, sometime in the future.

Full reaction: 4Al + 3MnO2 -> 2Al2O3 + 3Mn

The reaction produces pure manganese metal, but I couldn't recover much of it because it was blown out in the ensuing fireball. I'd say it was worth it. Click the pictures for larger versions.































9 comments:

  1. I have reasonably pure manganese dioxide If I took 40 grams of it stuck it in a flower pot and stuffed a sparkler into it would I produce about the same reaction.

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  2. Not quite - it won't burn by itself. You need to mix your MnO2 with a stoichiometric ratio of aluminum powder. In this case, 2.42:1 ratio by weight of manganese dioxide to aluminum powders. A sparkler should be fine to ignite it, but could be tricky like magnesium ribbon has been for me.

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  3. can u tell how to make an explosive with a dry cell

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  4. From your manganese dioxide thermite experiments, what parameters would you say worked best for producing manganese metal? For example, does extra fine or normal aluminum powder work better, etc. Also, did you use manganese dioxide from batteries? Thank you for your help.

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    1. In a thermite, ideally you want everything to be molten at the end to afford good separation of your metal. The problem with manganese thermites is that manganese's boiling point is very close to aluminum oxide's melting point, so you always lose quite a lot of metal no matter what you do. I would say a coarser Al powder might be better, just so the products don't all blow out of the crucible.

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  5. What you wrote here is that if I do a bunch of washings to maganese dioxide from a dry cell battery, add some aluminum powder, and light it up it would be a thermite reaction..?

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    Replies
    1. I didn't say that. Dry cell electrolyte MnO2 is contaminated with a lot of graphite, which won't come out just by washing. You have to dissolve the MnO2 to chemically purify it, which isn't easy. NurdRage on YouTube has a good video on how to do this. Using straight battery paste will be extremely hard to ignite and sustain as a thermite.

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