Thermite made from uncomon chemicals

[whitefox77]

I've been asked to assist with a thermite demonstration for high-school students. The school is apparently concerned about teaching high school students how to make thermite using such common materials as rust and aluminum, so I've been asked to come up with something a bit more exotic.

 

What I need is a thermite composition that isn't made with aluminum, and isn't made with potentially toxic chemicals (no barium or lead).

 

If anyone can be of assistance I'd appreciate it.

[qwezxc12]

Worth a preusal: Science Madness - exotic thermites

 

Also CuO/Al thermite (resonably coarse to keep it from exploding) is very cool. Commercially it's know as "Cad-Weld" as it used for copper welding ground connections.

[whitefox77]

After doing some research I'm thinking

 

60% calcium sulphate

40% course magnalim (60 mesh)

 

Does anyone have any experience with this mix?

[FrankRizzo]

After doing some research I'm thinking

 

60% calcium sulfate

40% course magnalium (60 mesh)

 

Does anyone have any experience with this mix?

 

Yes. I've used it to make orange strobe rockets in combination with ammonium perchlorate. It's fairly reactive, though the 60mesh metal should slow the reaction to an acceptable pace. I'm not sure that calcium sulfate would be considered an "uncommon chemical" though, it's simply Plaster of Paris. Also, sulfate reductions aren't Goldschmidt (thermite) reactions.

 

Here's a great resource for ya:

 

http://www.amazingrust.com/Experiments/how_to/Thermite.html

[Mumbles]

The thermite reactions can be ran with magnesium too. Might be a bit more exotic for you. You could just use the Al, call it a special grade that is unavailable to the public.

[TYRONEEZEKIEL]

use dark pyro al. Its a bit pricey, but to a completely unaware person.. Black metal is really exotic

[FrankRizzo]

NO! Dark pyro aluminum would not be appropriate for a demonstration in front of students. The reaction will be much to fast to be safe.

[TYRONEEZEKIEL]

not if something much lower on the reactivity series is used. like chromium oxide. we arent looking for an explosive copper thermite are we?

 

But if something like that is wanted there is no need to waste money on dark pyro.

 

 

true words frank

Edited July 28, 2009 by TYRONEEZEKIEL

[Seymour]

Ok... Thermite and danger...

 

People seem to think that once you light thermite, everyone dies. It will melt to the centre of the earth and create a black hole, out of which will come communists.

 

Yes, the reds.

 

Ok, sure, it's dangerous, but at the distance that I'm sure the kids will be at, quite likely with a window seperating them, I can not see any reason for all this alarm.

 

Standard thermite using Fe2O3 using dark Aluminium burns fast. Almost as a flash. It also burns very cleanly, so cleanly that all the solid products are in an aerosol (read smoke).

 

Perhaps it is just me, but I do not consider smoke to be a great a danger as a pool of molten metal that results from the combustion of thrermite with coarse metals.

 

What is wrong with using standard atomised Aluminium in a CuO/Al reaction? This is a demonstration, and while it will be supplimentary to the science of redox reactions, it is also there as a treat for the students. Something exiting. A flash, a pink cloud of metallic smoke, and a red stain on the concrete sounds pretty exiting to me, and I'm sure the kids will agree.

 

Personally I suggest the Copper oxide/Aluminium reaction using standard atomised Aluminium. ( sure dark metals are 'exotic', but to an average high school student, any metal powder fits that bill).

 

Secondly I sugggest making Aluminium/Fe3O4 thermite. Firstly because it produces more molten metal in my experience (compared to Red oxide), providing a good contrast to the flash of the copper thermite, and secondly because the students likely to catch on to thermite will be expectiong a red powder, while this one is simply black.

 

The students who figure it out regardless are going to do so no matter what. I think the school's policy is fairly useless, and that by avoiding red Iron oxide one is being very acomodating.

 

Further contrast (and a study of rthe reactivity of Aluminium) can be provided by mixing the CuO with both Aluminium and carbon, showing that charcoal - a recognisable fuel- is far out-energised by a dull grey metal!

 

Just keep the kids away from the commies!

[asilentbob]

I'd just go with the standard aluminum/iron oxide thermite... Double terracotta flower potted and have it drip out into some dry sand. Its classic and been done for probably longer than your teacher has been alive.

 

You could try the titanium one... IIRC Mg/TiO2... however since Ti will burn readily at those temps you wont get much.

 

Chromium oxides can be nasty. Manganese isn't too nice either.

 

In addition... very fine aluminum powders (especially flake) are inferior for thermite. -325mesh flake aluminum is pitiful. High surface area very fine particles will tend to burn up in the air rather than react with the iron oxide... so you will get a pitiful extremely impure nugget of iron and a lot of aluminum oxide as smoke and slaggy crap.

[Miech]

Manganese thermites burn almost like flash powder, similar to copper oxide. If you want something impressing, try TiO/Al, its one of the brightest thermites around. It's realtive fool proof, as it burns very slow and without toxic fumes.

[optimus]

I just realised I have Zirconium Oxide.... a few other too but can't remember off-hand...

 

Should this work? If so anyone care to suggest ratios?

[Miech]

I have no idea on the zirconium thermite. I'd try the stochiometric ratio first, that would make the most sense.

 

Another thermite popped into my mind, being silicon thermite. It's not an actual thermite, as silicon is a transition metal, and it is not self sustaining. To overcome the latter a bit of sulfur is added. It is reported that a mixture of silicon oxide (sand), aluminium and sulfur works fine anywhere between a 1:1:1 ratio and a 100:75:25 ratio. Be aware that a lot of aluminium sulfide is formed which forms H₂S when reacting with water.

[FrankRizzo]

I have no idea on the zirconium thermite. I'd try the stochiometric ratio first, that would make the most sense.

 

Another thermite popped into my mind, being silicon thermite. It's not an actual thermite, as silicon is a transition metal, and it is not self sustaining. To overcome the latter a bit of sulfur is added. It is reported that a mixture of silicon oxide (sand), aluminium and sulfur works fine anywhere between a 1:1:1 ratio and a 100:75:25 ratio. Be aware that a lot of aluminium sulfide is formed which forms H₂S when reacting with water.

 

Miech,

 

Re: Silicon Thermite. Check out that link I posted.

[FrankRizzo]

Ok... Thermite and danger...

 

People seem to think that once you light thermite, everyone dies. It will melt to the centre of the earth and create a black hole, out of which will come communists.

 

Yes, the reds.

 

Ok, sure, it's dangerous, but at the distance that I'm sure the kids will be at, quite likely with a window seperating them, I can not see any reason for all this alarm.

 

Standard thermite using Fe2O3 using dark Aluminium burns fast. Almost as a flash. It also burns very cleanly, so cleanly that all the solid products are in an aerosol (read smoke).

 

Perhaps it is just me, but I do not consider smoke to be a great a danger as a pool of molten metal that results from the combustion of thrermite with coarse metals.

 

What is wrong with using standard atomised Aluminium in a CuO/Al reaction? This is a demonstration, and while it will be supplimentary to the science of redox reactions, it is also there as a treat for the students. Something exiting. A flash, a pink cloud of metallic smoke, and a red stain on the concrete sounds pretty exiting to me, and I'm sure the kids will agree.

 

Personally I suggest the Copper oxide/Aluminium reaction using standard atomised Aluminium. ( sure dark metals are 'exotic', but to an average high school student, any metal powder fits that bill).

 

Secondly I sugggest making Aluminium/Fe3O4 thermite. Firstly because it produces more molten metal in my experience (compared to Red oxide), providing a good contrast to the flash of the copper thermite, and secondly because the students likely to catch on to thermite will be expectiong a red powder, while this one is simply black.

 

The students who figure it out regardless are going to do so no matter what. I think the school's policy is fairly useless, and that by avoiding red Iron oxide one is being very acomodating.

 

Further contrast (and a study of rthe reactivity of Aluminium) can be provided by mixing the CuO with both Aluminium and carbon, showing that charcoal - a recognisable fuel- is far out-energised by a dull grey metal!

 

Just keep the kids away from the commies!

 

I have run *many* Goldschmidt reactions, so I'm fully aware of the issues at hand. Again, dark pyro aluminum as the reducing metal has *NO* place in a demonstration in front of students. The energy is generated too quickly, which results in molten metal being thrown around (the "flash" you referred to). I much prefer the molten metal to be sitting in a pool near the experiment, rather than being tossed somwhere it could cause an issue.

Edited July 28, 2009 by FrankRizzo

[Seymour]

This is all very dependant on the environment in which this demonstration takes place.

 

So long as the chemicals are reletively well mixed I cannot see how any molten metal can cause a hazard from an energetic goldshmidt reaction. In my experience no macroscopic products, solid or liquid are formed by the oxidation of Dark Aluminium with either CuO, Fe3O4, Fe2O3, or MnO2, or CuO with my standard granular 44 micron.

 

I certainly do not want to be questioning your experience, and nor do I subscribe to the argument that 'because I have not observed a phenomenon, it will not occur', but I am keen for a healthy debate, even if it results in my points made redundant!

 

For no reason other than a familiarity of the subject, and an awareness of attitudes to safety in educational facilities, I would expect the discussed reactions to take place with the sudents inside, the reaction outside, and observation to be through a window for protection, or if a suitable fume cupbord is avaliable, in a similarly shielded set-up there.

 

However I have observed goldshmidt reactions in lecture theatres with no shielding from persons at all. If the demonstration is to be in this environment, then I agree fully that no risks should be taken, indeed, I would question the very use of this environment for the reaction in the first place.

[andyboy]

Well, the possibility alone would be enough for me to take every precaution and still make every kid there sign a release form. Wouldn't want to get sued now would we.

 

Coarse particles doesn't mean that it will not spatter, you will need a drain hole like asilentbob said preferably a claypot and sandtrap underneath.

 

Then again, you could set of some CuO/Al

[whitefox77]

First I'll comment on the school's policy. Of course it's stupid, if any of these kids wanted to make thermite they could easily search the internet and find a forum where people listed dozens of different thermite mixtures in a single thread. This is more about the school people making them selves feel like they are taking precautions. That's why the fact that it doesn't matter that calcium sulphate is easily available as plaster of Paris. So long as I call it calcium sulphate, none of the people at the school (except maybe the chemistry and/or art teachers) will know it's plaster of Paris. Certainly the students wont know that (any that do probably already know how to make thermite). It's about perception, so there is little point in mixing reality into it.

 

I think I'm going to go with a mix of magnetite (Fe3O4) and magnalim (can some one tell me the best ratio?). The names will sound impressive to the students, should provide a good show, and they should be suitably exotic enough to convince the school to allow the demo.

[NightHawkInLight]

The problem I see with that is you will have a hard time justifying using magnalium when explaining the chemistry. There will be separate reactions happening with Mg and Al replacing Fe individually in what looks like one reaction. Each will have to be explained and then the obvious question comes up, why did you need to do them together? At which point you will have to reveal that both a Mg and Al thermite work individually. Straight Mg would work better for demonstration purposes, so long as the experiment is conducted safely. With Mg powder now only able to be shipped in bulk freight, they can't just buy a pound off ebay.

[whitefox77]

The problem I see with that is you will have a hard time justifying using magnalium when explaining the chemistry. There will be separate reactions happening with Mg and Al replacing Fe individually in what looks like one reaction. Each will have to be explained and then the obvious question comes up, why did you need to do them together? At which point you will have to reveal that both a Mg and Al thermite work individually. Straight Mg would work better for demonstration purposes, so long as the experiment is conducted safely. With Mg powder now only able to be shipped in bulk freight, they can't just buy a pound off ebay.

 

 

So long as the school principle doesn't realize that, it shouldn't be a problem My intent isn't to cheat the students out of learning chemistry. My intent is to trick the school into letting their students actually learn something.

Edited July 29, 2009 by whitefox77

[NightHawkInLight]

So long as the school principle doesn't realize that, it shouldn't be a problem My intent isn't to cheat the students out of learning chemistry. My intent is to trick the school into letting their students actually learn something.

Well said. It's because students don't see practical use for chemistry that it's considered such a boring subject by many today. Knowing what most of us at this forum know, who here could think of a subject with more exciting applications?

 

Kids aren't going to kill themselves with Al thermite, at worst they would be blinded, but that is why safety should also be taught. Things that are considered by the average American to be dangerous are almost always perfectly safe with $5 thrown at safety gear.

[inonickname]

Nothing too hard..you could use a slightly different appearing iron oxide. Blue/black iron oxide would be ideal (burning/combustion), you can simply burn down very fine steel wool and turn it down as you would for any other chemical. I would suggest a dark flake pyro Al, but it would be unsuitable.. (by the way, blue/black iron oxide tends to work better)

 

Can they be mixed to a homogenous powder before the demonstration?

 

Anyway, if I were a basic kid in a normal class I'd get aluminum powder through sanding or grinding.

1. It would fail

2. Even if by some pathetic reason it could possibly work the amount of material would be very small.

[Mumbles]

Have you guys ever seen the commercial thermite demonstration kits? The Al is coarse as hell. Almost like flitters in one case, or the real coarse atomized needed for breaking glass comets. It takes quite a bit to get them going. We used this super sparkler thing they provided.

[Seymour]

Sorry for pushing the thread off on a tangent, but what exactly are breaking glass comets?

 

All the commercial thermite I have witnessed has used very coarse Aluminium, and considering the high % of products that become sparks when thermite using standard fireworks atomised burns, I'm not at all surprised.

[RUUUUUN]

When we did thermite in high school my teacher used black iron oxide and Al in a clay pot.... it was all fairy coarse so he had to start it with a strip of Mg ribbon...... it was really slow (I thought, so I went home and made some Fe2O3/Al with some really really fine Fe2O3 and spherical Al.... MUCH MORE FUN!!) annnnyyyways, back on topic, he stood the clay pot over a bucket of sand with some metal stakes, shoved the Mg ribbon through the plastic cap on the bottom of the pot(he pre-punched a hole in the cap with a nail), then lit the strip with a match and we watched it burn and burn, then the thermite started and we got to watch molten iron drip out onto the sand... all pretty fun.... I didn't see anything to dangerous about this and the kids thought it was a great reaction, we performed the reaction about 15 feet from the building out in the parking lot, so practically right off the sidewalk.