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Author: Subject: Melting tellurium powder
Texium
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[*] posted on 11-12-2023 at 14:09
Melting tellurium powder


I have some tellurium powder, and I was hoping to melt a couple grams of it into a little ingot (or at least a blob) to have as an element sample. I searched the forum, but couldn't find any information about melting tellurium. I assume either inert gas or a flux of some kind will be needed to prevent oxidation.

Due to its relatively low melting point, I thought perhaps I could put the powder into a borosilicate glass ampoule, purge with inert gas, and seal it. Then I could heat the entire ampoule above the melting point of Te, which is still well below the softening point for borosilicate. Has anyone tried something like this before?

[Edited on 12-11-2023 by Texium]




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[*] posted on 11-12-2023 at 16:13


I would be hesitant to heat a sealed ampoule. Gas expansion could ruin your sample.

Easier to neck a test tube, melt the Te with an argon flow, then seal.
Or, if it is just for an element sample, I have a nice crystalline piece Zi could give you.
(I can't really see that I will get into Te chemistry.)
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[*] posted on 11-12-2023 at 16:33


A friend who sells chemical elements melts selenium powder regularly to get nice samples to sell and does it in the air!Of course he covers the crucible with a sealing lid.I think he uses a corundum crucible. But he complains,even when he does the work outdoors and with a mask,that he always smells a bit of selenium,he likens it to a sulphur-like smell.He has a degree and exam in toxicology and knows the dangers of selenium compounds.If you want to try it,I can ask him for details,tellur is selenium-like,so it should work similarly...
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[*] posted on 16-12-2023 at 12:46


Goodness gracious, you couldn't pay me enough to melt Se or Te in air!



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[*] posted on 16-12-2023 at 14:15


Quote: Originally posted by Fleaker  
Goodness gracious, you couldn't pay me enough to melt Se or Te in air!


I've also heard about thallium smelting and the emerald flame that appeared during it, but the details were withheld from me, that they don't talk about such things...I would never go for it either, but there is always someone who knows that they will make a very good profit and do it:(That's life...
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[*] posted on 22-7-2024 at 01:42


Quote: Originally posted by Fleaker  
Goodness gracious, you couldn't pay me enough to melt Se or Te in air!

Se and Te are different matters.
SeO2 is quoted as subliming at 315 degrees. TeO2 is quoted as boiling at 1245 degrees.
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[*] posted on 22-7-2024 at 07:56


Quote: Originally posted by chornedsnorkack  
Quote: Originally posted by Fleaker  
Goodness gracious, you couldn't pay me enough to melt Se or Te in air!

Se and Te are different matters.
SeO2 is quoted as subliming at 315 degrees. TeO2 is quoted as boiling at 1245 degrees.


Doesn't matter. It's not about oxides or even toxicity (in strict sense). From Wikipedia:
Quote:

Humans exposed to as little as 0.01 mg/m3 or less in air exude a foul garlic-like odor known as "tellurium breath".

And tellurium is more volatile than selenium. When melting tellurium some of it will evaporate. If that vapor reaches the brave experimenter, their social life is damaged in next several months. Can be very annoying, even for hermits like me, I suppose.

Selenium causes selenosis with similiar symptoms.




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[*] posted on 22-7-2024 at 12:31


Quote: Originally posted by EF2000  
Quote: Originally posted by chornedsnorkack  

Se and Te are different matters.
SeO2 is quoted as subliming at 315 degrees. TeO2 is quoted as boiling at 1245 degrees.


Doesn't matter. It's not about oxides or even toxicity (in strict sense). From Wikipedia:
Quote:

Humans exposed to as little as 0.01 mg/m3 or less in air exude a foul garlic-like odor known as "tellurium breath".

And tellurium is more volatile than selenium.

Under which conditions?
Not generally true:
Se vapour pressure is 100 Pa at 344 degrees, and 1 Pa at 227 degrees (still above melting). Te vapour pressure is 100 Pa at 502 degrees.
Then again, at 100 Pa, the vapour density of Te is several g/m3.
You should not inhale 502 degree or 450 degree air either. Here the key question is what exactly do these few g/m3 of Te do as the air cools down to breathable temperature. Is it condensed and caught on the apparatus walls, or is it condensed as fine aerosol that passes out of your apparatus and into your lungs?
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[*] posted on 23-7-2024 at 01:38


Quote: Originally posted by chornedsnorkack  
Quote: Originally posted by EF2000  

And tellurium is more volatile than selenium.

Under which conditions?
Not generally true:
Se vapour pressure is 100 Pa at 344 degrees, and 1 Pa at 227 degrees (still above melting). Te vapour pressure is 100 Pa at 502 degrees.

You are right. I wanted to say that vapor pressure of tellurium at its melting point is more than vapor pressure of selenium at Se melting point, but phrased it incorrectly. Thanks for pointing out.

About what happens with vapor, I think that it's the same as with heavy metal fumes. Lead fumes are also dense and condense into aerosol, causing occupational lead poisoning in workers. (When the same fumes are still hot, they cause metal fume fever).
Whatever the mechanism, I don't think it's advisable to melt tellurium in open apparatus, at least without breathing protection/fume hood/really good breeze outside. (Another scary thing comes to mind: Can it be absorbed through skin?)




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[*] posted on 23-7-2024 at 06:34


Quote: Originally posted by EF2000  
Another scary thing comes to mind: Can it be absorbed through skin?

Even if it doesn't, it would slowly detach from your skin as you move and form a fog of tellurium around you. The same thing happens with our dead skin cells.




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[*] posted on 23-7-2024 at 08:18


Melting tellurium open to air is certainly out of the question.



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