April 7 2012 7 07 /04 /April /2012 15:58
I have become interested in mini-thermites, thermites that are relatively safe and interesting. Magnesium, being more reactive than aluminium and still quite stable, appears to be the reducing metal of choice. The heat wave created by a magnesium thermite is so intense that it blows the chemicals apart after ignition, prevent any coalescing of liquid metal. This is bad for most thermite applications but good when intense heat is quite undesirable. Grinding magnesium on a file is relatively easy; the provided scraper with the firestarter makes larger pieces (less desirable) with more difficulty than the file.
I had previously prepared iron(III) oxide hydrate by electrolytically oxidizing iron in aqeuous solution and filtering the precipitate formed. The powder is mixed and ground with the magnesium dust to form a brown mixture that looks to be highly reactive and a lot of fun. The following sentence is not true, but was written initially: Ignition will be with a magnesium strip, not the dangerous mischmetal flint, because of the decreased size of the magnesium.
This thermite failed with titanium thread ignition, steel wool ignition, and mischmetal - magnesium ignition. This was because first, there was too much excess iron(III) oxide. Second, the iron(III) oxide was hydrated, making it unlikely to burn.
So I made a new mixture. I heated the iron(III) oxide to dehydrate it. I then mixed it with an excess of magnesium shavings, since they will burn even when no iron(III) oxide is present. I then scraped up a large amount of magnesium shavings and powder. I placed the thermite mixture on a brick, then piled the shavings on top. On top of that, I placed the easily ignitable powder. I then ignited the powder. Since the shavings take a second to ignite, it gave me enough time to retreat before the reaction began. I ended up using a mischmetal flint just because it was the easiest way at the time. The reaction was quite silent and slow compared to copper, but it was much hotter because of this.
Here is the video of the second trial.