This blog is my attempt to reconnect with the world of chemistry. I have a PhD in Inorganic Chemistry and make a living doing research for a large company in Michigan. As times have changed, that company has changed its focus and I no longer have as much chance to do the basic, fundamental research which I most enjoy. Through this blog, I am hoping to recapture the magic which I felt during my graduate (and undergraduate) days in college. Expect topics on chemistry and alchemy along with some non-chemistry related items which I think might be interesting.

"The chymists are a strange class of mortals, impelled by an almost insane impulse to seek their pleasure among smoke and vapour, soot and flame, poisons and poverty; yet among all these evils I seem to live so sweetly that may I die if I would change places with the Persian King."

Johann Joachim Becher (phlogistonist)
Acta Laboratorii Chymica Monacensis, seu Physica Subterranea, (1669).

Tuesday, January 6, 2009

Home Grown Titanium

Although my current lack of posting might not indicate it, I've actually come across quite a few interesting articles lately. Unfortunately, they all involve nanochemistry, and since I've already talked too much about nanochemistry recently, I'm imposing a moratorium on that subject for awhile. Fortunately, I do have something else to talk about.

The Goldschmidt reaction.

Not familiar with the Goldschmidt reaction? Perhaps you have heard of it referred to as "the thermite reaction."

Surely everyone who has ever taken a freshman chemistry course has read or heard about the thermite reaction. Most of you have probably seen it in action. The pyrotechnics are impressive and most freshman chemistry lecturers simply cannot resist demonstrating it in front of a class. In its most common incarnation, aluminum and Fe2O3 (or Fe3O4) powders are mixed and ignited. The aluminum is converted to Al2O3 while the iron oxide is reduced to the metallic state. Significant quantities of heat are released, and if the experiment is set up correctly, molten iron will drip out of the bottom of the reaction vessel. Although iron oxide is the material most associated with the thermite reaction, copper and manganese oxides can also be used.

In a continuation of "the type of experiments I'd like to try at home when my wife is away" category, I recently came across a method for generating titanium metal in your garage using TiO2 and the thermite reaction. A full description of the technique as well as a video of the pyrotechnics are included. Metallic titanium was actually recovered, which is amazing since titanium tends to oxidize in air at temperatures near its melting point. In order to generate the temperatures necessary to melt the titanium, CaSO4 was added to generate additional heat. CaSO4 reacts with aluminum in its own version of the thermite reaction to form CaS. A more detailed description of the process involved can be found here.

This would have been an awesome experiment for alchemists to have performed back in the day. Simple, yet impressive. Perhaps the substitution of iron oxide with some form of gold oxide (or other suitable gold compound) might have resulted in the appearance of molten gold, always a good way to impress the wealthy patrons upon whom the alchemists depended. Unfortunately, although aluminum salts were known to the alchemists as far back as ancient Greece, aluminum metal was not produced until the 1800's. And it's the chemical energy stored in the metal which drives the whole reaction.


Ψ*Ψ said...

much love for thermite <3 :)

Gert said...

Thanks for linking to my blogpost.

As regards running a thermite reaction with gold (III) oxide, it would be rather pointless: the oxide is so unstable that it's practically endothermic. It decomposes at about 160 DC, no reductant required. The thermite reaction Au2O3+ 2 Al ---> 2 Au + Al2O3 is in all likelihood a flash powder: the heat of reaction would be approx. ΔH ≈ - 1675 kJ/mol, probably enough heat to heat the reaction products to above the BP of the gold!

AuCl3 would be the next best bet but unfortunately AlCl3 is highly volatile, so again this is a recipe for a flash powder, not nuggets of gold...

A fellow thermite enthusiast tried it with Ag2O and found it difficult to keep it going: presumably the moment the reaction starts the silver oxide started decomposing but the released oxygen couldn't react with the Al because the temperature was too low to combust the Al. So, somewhat quizzically this reaction fizzled.

Much, much more interesting IMHO are the thermites with very stable oxides, like the oxides of Cr, Ti, Nb, V, Zr, Th, U and such like. There, getting the balance of enthalpies right to obtain both the metal and alumina in the molten state, can be quite a challenge...

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