romazicon - 20-9-2003 at 10:32
Hello there,
I'm a fair bit new to chemistry, though I've been curious for some time.
Can anyone tell me what precautions would be good for thermite beyond safety glasses and lighting it from 10 feet away with a nice long pole? Does it
cause much smoke or noise? I'm planning to either do it in the shed (if there's much smoke), or outside on the driveway if not. The shed
has a chimney, so smoke coming out wouldn't look too suspicious. Also, can it be lit with a roadflare or sparkler? I've not been able to
come accross any of this magnesium that's usually quoted as being needed. If there's much noise, I'll just plan on having a stereo
blaring loudly with music that sounds similar enough that nobody'd notice..
I'm hoping to use it to get the case off of this blasted industrial sized electric motor that I dug out of someone's trash. I want the
magnet wire that's inside for some electrical projects, but it's built like a tank and even breaking the bolts off doesn't loosen the
cover (And the bolts themselves wouldn't move even when i tried hammering on the wrench with a good heavy sledge -- as i said, it's like a
tank). Since I've heard thermite can melt through steel pretty well, I'm hoping to use a small ammount to 'cut' the cover off.
It's the cheapest method I can think of to use, no tools I have can get it off, hacksaw seems out of the question as the angles are just too
akward, and I have plenty of rusty iron and soda cans laying about. Any flaws in this plan that I might want to account for?
DDTea - 20-9-2003 at 10:50
I see some flaws already! Don't light thermite on the driveway, or you will be getting a big pot hole!!!
Thermite reactions take a lot of heat to start, unfortunately, and that is why it is desirable to have Magnesium. Look for some fire starters in the
Camping/Outdoors Store, they tend to have some. You just have to shave it down 
.
If I recall correctly, there isn't smoke in a thermite reaction, unless something nearby is being burnt. And no, it doesn't make much of a
noise either...just the hissing and crackling.
romazicon - 20-9-2003 at 11:37
Why would I wind up with a big pot hole? I'm not using it on the driveway itself, just planning on using it in very small increments until I can
just get through the thick plate casing on the motor. Or did you mean the spalling that might occur if any of it spilled to the driveway in the
process? I'll remember to put a good covering of dirt down first to be safe.
And both sparklers and roadflares do get extremely hot, I believe. They're both much hotter than any ordinary open flame, I know. But if
they're not hot enough still, I'll check out the camping store.
Mumbles - 20-9-2003 at 12:10
Well there's some smoke. Its fine particles of Al<sub>2</sub>O<sub>3</sub>. At least this is what I assumed it to be.
I have heard of people starting the reaction with sparklers, but I never got it to work. Mg ribbon is the way to go. I've also heard some of
the hypergols can ignite the mixture. KMnO<sub>4</sub> and Glycerol is recomended on one of the first search results. http://faculty.kutztown.edu/vitz/NSDL/Thermite/thermite_Proc... It has its own book references too.
kingspaz - 20-9-2003 at 13:09
sparklers work for me. also the 'smoke' is simple water from the iron oxide. it may contain a small amount of Al2O3 though.
Haggis - 20-9-2003 at 13:16
Also, I see a flaw in that if the heat is great enough to melt off the steel, would it not also melt the varnish/copper in the magnet wire? It seems
more like over kill to be using thermite to extract something as delicate as magnet wire.
romazicon - 20-9-2003 at 14:01
Well, there's about an 1/2-3/4 of space between the coverplate and the wire from what I can tell. I'm going to see if I can fit something
underneath the area that I burn, as best I can to provide a little insulation and as a buffer. Perhaps I can fill it in with a layer of soil to
provide some insulation. The magnet wire in question is also of fairly thick guage and very tightly wound, so while there is some risk to the
varnish, I think there is enough copper to absorb the heat well so that it will not melt so long as the thermite or molten steel does not come into
direct contact with it.
I'll test it out on a bit of scrap to get an idea of how it burns, and then use what should be just enough to get through the coverplate
I'm planning on burning it along two thin lines to remove a section, rather than over a large area, confining the melting to very small points.
Along with the soil to act as a buffer, the wire will hopefully be unharmed. And if not, hey, its a good hundred pounds or so of copper that I got
for free anyway. I'll find some use for it eventually.
Perhaps for my test of the thermite I'll mimic the coverplate with something heat sensitive about the same distance behind the scrap piece as I
burn it.
And yes, it may be a bit overkill, but hey, it seems like a good excuse to try an experiment like this.
Mumbles - 20-9-2003 at 20:41
I really don't see the whole water from Iron Oxide thing. Would someone care to explain it? I can see it if you are using Iron Hydroxide.
Fe<sub>2</sub>O<sub>3</sub> + 2 Al ----> 2 Fe <sub>(l)</sub> +
Al<sub>2</sub>O<sub>3</sub>
Thats the reaction, correct? I don't see where the water is forming. The way I've always figured is that the Aluminum Oxide thus produced
in the reaction is forced into the air by the hot air currents. I have came across this on numerous occasions. Has anyone else? I suppose by
looking at the products of the reaction one would have problems telling if there was Aluminum Oxide embedded in the blob of Iron. I always have the
molten Iron drop into a bucket of sand so theres always some mixed in. There is undoubtable some Aluminum oxide mixed in, but it seems as if plenty
is released.
correct reaction
Mephisto - 21-9-2003 at 05:30
The water isn’t formed by the reaction. If the thermite mixture is stored a long time, a very little amount of water gets in it. That’s
the reason, why the both components should be dried (separated) at 150 °C in an oven before use. But the experience shows, that it’s not always
necessary to dry it.
Darkfire - 21-9-2003 at 20:42
You will need alot of dirt, at school my teacher thermite melted right through about 24 inches of sand. You could use kmno4 and glycerine to start it,
im not sure how that will work when using very small amounts though, and the knmo4 can make it spit a lot, my teacher use this method and his kinda
did a bit of an explosion...
chemoleo - 24-9-2003 at 17:34
search threads. there is plenty of information... 