Polverone
Now celebrating 21 years of madness
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Lanthanum fun
On a whim, I bought some lanthanum oxide (among other things) from the Al-Chymist since it was on sale. I have just now started to explore its
interesting properties.
I'm at home away from the library, and the only reference I have for lanthanum compounds is Sidgwick's Chemical Elements and their
Compounds. Sidgwick is usually a great one-stop reference for information about the elements, but it doesn't have a lot on lanthanum. One
thing it does say is that lanthanum oxide reacts strongly with water, heating and hissing like calcium oxide; I have seen this information repeated in
some MSDS with almost identical wording. The substance I have does not seemt to react with water at all. Other MSDS said that it readily absorbs
carbon dioxide from the air. A wet sample of my lanthanum oxide left out overnight did fizz some on the addition of HCl, while material straight from
the jar dissolved without bubbles.
Does anyone else have some lanthanum oxide, and can the "reacts vigorously with water" assertion be confirmed/disproved? I'm wondering
what I actually have, if it is not indeed lanthanum oxide.
I discovered that the oxide when heated directly with a propane torch flame glowed a bright white with a tinge of violet; the intensity of light
emitted reminded me of lantern mantles (though it was not quite that bright). Doing a little searching online, I found that some early gas mantles did
indeed use lanthanum oxide. But the lanthanum oxide was mixed with other materials that may have raised the intensity of light output. Actually, given
the timeframe, I would guess that those early "lanthanum" mantles contained small amounts of other lanthanides too. Would pure lanthanum
oxide be expected to glow brightly in a flame as mine did? Would technical grade lanthanum oxide (bright white powder like powdered sugar) be expected
to contain only lanthanum oxide, or other rare earth oxides too?
There was another interesting thing about the flame-heated lanthanum oxide. Whenever the flame was removed after heating the oxide, there was a brief
flash of brighter light emitted. I assume it wasn't actually emitting more light, but that for a brief portion of its cooling it was emitting
wavelengths that the eye is more sensitive to. It took some seconds for the last visible light to stop glowing from the center of the oxide,
presumably because it emits light readily when heated and the powdery oxide is a good insulator.
After some small scale experiments burning sulfur and potassium nitrate with the oxide, the much-abused oxide was dumped out of the spoon where I had
been heating it, crushed and mixed with aluminum powder, replaced in the spoon, and taken outside for ignition. Given its impressive emission of light
at even modest flame temperatures, I expected the oxide to really dazzle me among aluminum powder, but it seemed no brighter than burning aluminum
usually is (pretty bright). The porous nugget that was left was crushed, part being dissolved in alkali and part in acid (the dissolution is still
ongoing).
I noticed while web searching that lanthanum is used to make phosphors and fluorescent materials, so I subjected some of the remaining porous nugget
and the burning spoon itself to a mineralogical UV lamp. In some areas, there was an orange fluorescence under long-wave UV and there was orange,
yellow, and green fluorescence under short-wave in various areas on the nugget and spoon. Plain lanthanum oxide did nothing at all.
In conclusion, lanthanum oxide is a fascinating material and if you can pick up a kilogram of it for $20, you should. It will no doubt provide me with
many more hours of enjoyment.
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Quantum
Hazard to Others
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Very interesting! Sadly my cash is in the hands of UGT as of now and soon I will get my 24/40 kit; I can't get any fancy metal oxides.
This seems like an area of DIY chemistry that has been overlooked somewhat. No need for complex organic chemicals to satisfy the thrillseeker here.
Making simple salts and observing their cool properties is cool with new never before seen(on a DIY scale) elements.
What if, what is isn\'t true?
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JohnWW
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Actually, the uses of lanthanum and compounds are quite limited, mainly motion picture studio lighting and one or two catalysis applications. The
other rare earths, which have 4f electrons and in several cases variable valences, have many more uses, both chemically and as alloys (especially
magnetic).
John W.
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David Marx
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I have a bit of lanthanum oxide, unfortunately I have not explored its heating characteristics and can't comment on your observations. I am
actually most interested in creating LaBr3 but have not had the time to look seriously into the bromination method.
alea iacta est
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Polverone
Now celebrating 21 years of madness
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Registered: 19-5-2002
Location: The Sunny Pacific Northwest
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Sidgwick, speaking generally of the lanthanides, says "The halides nearly all crystallize with 6 or 7 H2O or both; the anhydrous halides are made
by heating the hydrates in a stream of hydrogen halide to 350-600 C."
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