Answer 1:
Here is a first-person account from a
Post-Doctoral Chemist at UCSB: I've done a
thermite reaction on a 1 kg scale using aluminum
powder and magnetite (mixed iron oxide
Fe3O4). I used magnetite
because it's quite cheap and comes finely divided,
though red oxide should be fine or better if less
fine. The reaction is faster if the powders are
finer, so I recommend not using fine reactants in
a school setting and the scale should be less than
100g.
The reaction should be done outdoors and on
a disposable, fireproof surface (I used a
paving slab) in a disposable container which will
be obliterated during the reaction (I used a
family sized soup can).
For ignition the surface must be fresh
(otherwise absorbed dampness from the air puts out
the fuse) and ignited using a magnesium ribbon
fuse extending down into the mixture. This fuse
itself needs a fairly good gas flame to light (a
bunsen, a blowtorch or one of those blue flame
cigarette lighters should do the trick).
When reacting, the effect is somewhat like a
Roman Candle firework (lots of vertical sparks
leaping about 2 feet into the air). I have never
had a problem with explosions, but the reactants
should be thoroughly mixed to give smooth burning.
I have never got a good metal sample out of the
reaction, just some semi-metallic slag. I
recommend a small scale test reaction (i.e. 1g of
material) to get a feel for it before attempting
anything too spectacular . For extra safety, a
bucket of dry sand for covering burning metals and
a bucket of water for first treatment of any
accidental burns.
Spectators should be at least 6 feet away
from a small reaction and a anchored piece of
perspex as an explosion shield between the pot and
the spectators might be a good idea. I have never
gone to such lengths as this to protect my
audience, but they were all consenting adults in a
very informal setting.
THIS IS NOT TO BE TRIED BY SCHOOL STUDENTS.
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