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Topic: Chemical Element Collection - Is this really pure tungsten?  (Read 2538 times)

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Offline MarkMardon754

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Chemical Element Collection - Is this really pure tungsten?
« on: April 27, 2017, 07:00:51 PM »
I like to collect chemical elements, especially exotic/weird ones.
I bought a sample of Tungsten from AliExpress, the dealer said it was 99.95% pure.

- It's a small rod, measuring roughly 4.5-5cm in length and weighing 76g. (pretty heavy for its size).
- The rod does not stick to magnets but moves if a magnet is passed quickly over it.


But is Wolfram supposed to leave a metallic iron-like smell on your skin when touched?

I'll also leave a photo of the sample.

Offline Borek

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Re: Chemical Element Collection - Is this really pure tungsten?
« Reply #1 on: April 27, 2017, 07:36:58 PM »
Simplest thing you can do is to measure it as precisely as you can, weight it as precisely as you can, and check how the density compares to that of the W.
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Offline MarkMardon754

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Re: Chemical Element Collection - Is this really pure tungsten?
« Reply #2 on: April 27, 2017, 08:35:24 PM »
Simplest thing you can do is to measure it as precisely as you can, weight it as precisely as you can, and check how the density compares to that of the W.

I have calculated the cylinder's density, it's 19.35g/cm3. So, it really is W.

Offline Borek

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Re: Chemical Element Collection - Is this really pure tungsten?
« Reply #3 on: April 28, 2017, 03:17:57 AM »
I have calculated the cylinder's density, it's 19.35g/cm3. So, it really is W.

That's hardly a definitive test, but there are not many metals with that high density (and most of them are much more expensive), so you are probably right.

The best technique for a sure determination of the composition I can think of in the case of your sample would be an arc spectroscopy, but that requires quite expensive hardware.
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Offline Corribus

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Re: Chemical Element Collection - Is this really pure tungsten?
« Reply #4 on: April 28, 2017, 09:51:44 AM »
Aside from all that, I would recommend you don't handle your samples without gloves, as finger oils leave residues that can tarnish or otherwise blemish many elements.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline MarkMardon754

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Re: Chemical Element Collection - Is this really pure tungsten?
« Reply #5 on: April 28, 2017, 11:16:59 AM »
What about the metallic smell on my hands if I handle the sample? Is near-pure Tungsten supposed to do that?
Also, i read that W has a Mohs hardness of 7.5, but i was able to scratch the sample using a quartz crystal (7.0 Mohs Scale), how is this possible?

Offline Enthalpy

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Re: Chemical Element Collection - Is this really pure tungsten?
« Reply #6 on: April 28, 2017, 05:57:35 PM »
How accurate was the density determination? At RT, the litterature gives 19250kg/m3, not 19350. A micrometer would be accurate enough to make the difference.

If you access a Geiger counter, you can distinguish tungsten from cheaper depleted uranium. The resistance to corrosive mediums would differ a lot too.

Offline MarkMardon754

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Re: Chemical Element Collection - Is this really pure tungsten?
« Reply #7 on: April 28, 2017, 08:27:29 PM »
Sorry, i don't know how accurate the density measurement was... I just measured the rod's height and radius using a ruler, its mass using a kitchen scale, and used an online calculator to do the more complex math.

I also saw many pages stating tungsten's density as 19.35g/cm3. Higher than that of Uranium. One of these pages even rounded the density to 19.4g/cm3.

I'm pretty sure this is tungsten... It's just weird that it makes my fingers smell like iron...


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