71 replies to this topic

[adamw]

Please be careful with KMNO4 as it is a very nasty oxidiser. It has been discussed before and it was decided that it isn't really safe to use.

[Demented Ferret]

Yep.

...But sure as hell beats paying the rip-off merchants at eBay .

[thewildething]

Just been out today and collected a few pounds of rust from the old piers and railway stuff we have around here , just one question, the rust I use has been picked up from an estuary beach and has been in salt water for 50+ years, no metal left just pure solid rust (in chunks up to 5 pounds!).I wondered if the salt would have any affect on the performance of my thermite, which is sometimes hard to light. I know its forgiving stuff and I can light it normally with sparklers but sometimes it just will not go, could it be the salt??

Anyway, my ball mill is going to be working overtime to grind all that lot up

Marcus.

[adamw]

Well firstly you should 'wash' the rust to remove any traces of salt / other soluble compounds. But with all the stuff in the sea who knows what other non soluble chemicals floating around / formed in the oxidisation process are contaminating your FeO...

[I am a fish]

There seems to be some confusion about the various forms of iron oxide. There are three main types:

• Iron(III) Oxide (Fe2O3) sold by pottery suppliers as "Red Iron Oxide".
• Iron(II,III) Oxide (Fe3O4) which is what you'll probably get from a pottery supplier if you order "Black Iron Oxide".
• Iron(II) Oxide (FeO) which you may get if you order "Black Iron Oxide" from a pottery supplier.

(I have seen pottery websites complaining about the ambiguity of the phrase "Black Iron Oxide".)

I have tried thermites based on the first two types of oxide. In both cases, I have used 5g of 200 mesh aluminium powder mixed with a stoichiometric amount of the iron oxide:

• Thermite based on iron(III) oxide burns vigourously. This is the form that should be used if you simply want to generate heat (for example, to ignite another pyrotechnic composition).
• Thermite based on iron(II,III) oxide burns more slowly, but the reaction is far more spectacular, with globules of moltern iron being noisily spat out.

[Demented Ferret]

Nice, thanks a lot - I'll check it all out.

[Demented Ferret]

Ok, NONE of the thermite compositions worked with magnesium (Finally got hold of about 3 inches, all gone now though).

It could, obviously, only be two things:

The Aluminium or the Iron Oxide.

Now, I bought the Aluminium Powder, I don't know the mesh/micron - but apparantly even granular aluminium works with thermite.

I made the Iron Oxide, however - I did use salt to create conductivity in the water, which I couldn't get out of the final product. The black and the red iron oxide looked as suspected, and showed all the characteristics of Iron Oxide, so I know that the majority of it is Iron Oxide.

So...Any of you guys got an idea what went wrong?

Edit: And I want to add, I used the correct ratios as well.

Edited by Demented Ferret, 19 April 2004 - 04:18 PM.

[paul]

I had problems with selfmade iron oxides, too. So I used commercial iron(II/III)oxide. It cost about 3?/Kg (pottery store)

The Al can be quite coarse. If it is too coarse it is very difficult to ignite. Then you have to use more magnesium to start the fire, or you use a 70/30 mixture of magnesium/thermite

http://deutsch.250x....mit/thermit.htm

For the good effect we did not "collect" the molten mass, but let it drop from the height onto the ground. So the molten iron splattered around (the wood nearby was wet enoug, not to catch fire)

The grey ignition mixture was iron(II/III)oxide with magnesium. (30/70)

I really recomment you to use commercial iron oxides! It gives the best success.



Edit: I think the ammount of chlorides in your ironoxide was too big.

Edited by paul, 19 April 2004 - 04:59 PM.

[Demented Ferret]

Thanks a lot , I did put a lot of salt in (about 50g) and yeilded about 200g of iron oxide...I totally didn't consider the amount of salt being a problem in the end though :-/,

[Demented Ferret]

Yeah, that looks really good. It's a big shame that mine didn't work, but I'll persist.

Edited by Demented Ferret, 19 April 2004 - 06:54 PM.

[Stuart]

If there is salt in your Iron Oxide, why not just wash it out?

[Demented Ferret]

Because it's very messy stuff an very finely powdered, not worth the bother when I can buy some...which spoils the fun, but at least it'll work.

[Stuart]

I would buy it but at least make a batch for the fun and the hell of it. May as well give it a go

[chim-chim]

Red iron oxide is available as Red concrete colorant,
I don't know about across the pond, but over here, it's ony about $3 a pound.

Note: You will not be able to get this stuff out of carpet or clothes, it's tough to clean plastic, etc. Don't work in your Tux.

[Demented Ferret]

Alright, I'll wash by thermite compositions, but I'll have to dry them in a pan (I presume this is okay ?). Again, if anyone in the UK has any magnesium in smaller lengths (1 or 2 meters) then I'll be willing to pay for them, because a roll is just way too much at the moment.