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Author: Subject: Mystery Metal: ~21.25g/cm3
Erbium_Iodine_Carbon
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[*] posted on 21-6-2012 at 16:36
Mystery Metal: ~21.25g/cm3


Hello all,

Tonight I was looking in my basement for some metal pieces for use as milling media in a ball mill I'm constructing. The guy who built our house was a collector of odd things plus he worked at the nearby nuclear research lab so there are some strange things down there.

With that said, I came upon this very dense rod about 1cm in diameter and 10.65cm in length. Using a caliper the volume was determined to be 8.70cm3 and the mass found to be around 185g by my digital kitchen scale (my 0.01g scale only goes up to 100g) The rod is shiny with a slight golden tint.

Although the weight isn't accurate there are only a few elements in that density range, and the accuracy of the method was proven which I will explain later.

I've tried immersing the rod in 3% hydrogen peroxide but no decomposition was observed. I figure this would rule out platinum (however nice that would be).

Anyways, after showing this to my parents they mentioned something about a labelled tungsten rod that also came with the house so I had to investigate that as well. It turns out the thing is huge, weighing just over 2kg! The color was very different of my other sample so that narrows down the possibilities even more.

Using the same measurement method the density of the tungsten was found to be 19.13g/cm3 which is very close to the theoretical density of 19.3.

I'll attach pics of the 2 metals; apparently the tungsten was labelled and taped to a wooden rod at some point but the label has disappeared.

Basically my question is: what tests can I use to determine the unknown metal's composition?

Picture0156.JPG - 46kB Picture0155.JPG - 47kB
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Lambda-Eyde
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[*] posted on 21-6-2012 at 18:10


If that's rhenium (d=21,02), I'll have to kill you and steal it. Nothing personal, of course. :P Unless your technique or calculations are wrong, it has to be either that or maybe Os or Ir. All of them are of course hideously expensive.



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Rogeryermaw
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[*] posted on 21-6-2012 at 18:30


is it possibly an alloy?
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Erbium_Iodine_Carbon
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[*] posted on 21-6-2012 at 18:48


I have a chemistry exam tomorrow so I'll bring it in and afterwards weigh it accurately. It could very well be an alloy but probably of those platinum group mentioned by Lambda-Eyde. If it were Pt-Ir would that account for it not decomposing the peroxide?
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m1tanker78
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[*] posted on 21-6-2012 at 18:55


Assuming the rod is solid (not tubular)... If you tap it against a hard object, does it thunk, ping, ting, ring, spring??? H2O2 alone isn't a good test; an acidic solution would give you a better idea if it dissolves/discolors or tints the solution a certain color.

I love a good whodunnit or a whatsit in this case. :D

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[*] posted on 21-6-2012 at 23:28


it is probably genuine 95% + tungsten.

i had the opportunity to buy a 100 pound block of 99% tungsten and i passed it up :(

hang onto it, it is hard to find pure tungsten these days
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[*] posted on 22-6-2012 at 03:53


The thing is the other rod I have (the larger one) I know is tungsten and the smaller one looks nothing like it. Also the density is considerably higher than that of tungsten.
I do feel very lucky to just find 2kg of tungsten though!
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[*] posted on 22-6-2012 at 04:23


Take it to a jeweler shop: many are equipped with portable XRF today.



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[*] posted on 22-6-2012 at 04:24


What a find! It may turn to have been a very affordable house :)

Apparently, tungsten dissolves in hydrogen peroxide at an appreciable rate:
http://pubs.acs.org/doi/abs/10.1021/ac60176a021

Perhaps the reaction with only 3% H2O2 would be not so fast as to dissolve much, but you might see at least see something happening.

Although it is a fun project to try to identify the metal, it is probably worth getting a XRF analysis on it. Perhaps you can get someone to do a quick measurement for you at a local metal scrapyard.




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[*] posted on 22-6-2012 at 05:32


Quote: Originally posted by Erbium_Iodine_Carbon  
I have a chemistry exam tomorrow so I'll bring it in and afterwards weigh it accurately. It could very well be an alloy but probably of those platinum group mentioned by Lambda-Eyde. If it were Pt-Ir would that account for it not decomposing the peroxide?


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[*] posted on 22-6-2012 at 05:38


Given the very high density I suspect it is something like rhenium.
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[*] posted on 22-6-2012 at 06:35


Yes, the rhenium-osmium-iridium are the (apparently) possible ones. However, it is quite strange to find 900$ worth of rhenium in your basement...



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[*] posted on 22-6-2012 at 06:43


Quote: Originally posted by ScienceSquirrel  
Given the very high density I suspect it is something like rhenium.


Let him first determine density again. Then we'll talk... ;) My money's still on W.




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[*] posted on 22-6-2012 at 07:06


Fair enough, but I think his method of measuring the density is pretty good and it is quite a bit too dense for tungsten, also it does not look like tungsten.
The guy could have been a bit of a squirrel and just 'collected' it from the lab where he worked.
Not many houses come with a 2kg tungsten rod, so why not a rhenium rod as well?
If you want a small amount of pure tungsten it is used for fishing weights;
http://www.ebay.co.uk/itm/ACE-Tungsten-Beads-SML-0-37g-3-5mm...
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[*] posted on 22-6-2012 at 07:23


Thanks for the W tip. I've been religiously hording kaput incandescent bulbs for years. Must have about 100 g of W by now. Must crack them open some day...



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[*] posted on 22-6-2012 at 07:25


Alright I've accurately weighed it and the density is just over 21.3g/cm3. That pretty well narrows it down to Ir, Os, or Pt since those are the only elements with density greater than 21.0g/cm3. I don't think it's osmium (unless it's plated with something else) because of its color. Again in my measurement I used a scale accurate to 0.01g and a caliper accurate to 0.01cm, so I don't see much room for error there.
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[*] posted on 22-6-2012 at 07:42


I think the likeliest candidate must be platinum, it is the closest at 21.45.
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[*] posted on 22-6-2012 at 07:43


You'll have to chemically test it. Apparently Re can be dissolved in nitric acid:

http://www.espimetals.com/tech/rhenium.pdf




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[*] posted on 22-6-2012 at 07:46


Quote: Originally posted by ScienceSquirrel  
I think the likeliest candidate must be platinum, it is the closest at 21.45.


C'mon Squirrel: how desperate would one have to be to design a part in solid Pt??? And how would such a part manage to 'escape' from a factory??? No one just finds huge lump of Pt in their basement, that's as sure as death and taxes, as far as I'm concerned... :o

[Edited on 22-6-2012 by blogfast25]




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[*] posted on 22-6-2012 at 07:51


Quote: Originally posted by blogfast25  
Quote: Originally posted by ScienceSquirrel  
I think the likeliest candidate must be platinum, it is the closest at 21.45.


C'mon Squirrel: how desperate would one have to be to design a part in solid Pt??? And how would such a part manage to 'escape' from a factory??? No one just finds huge lump of Pt in their basement, that's as sure as death and taxes, as far as I'm concerned... :o

[Edited on 22-6-2012 by blogfast25]


Good point, though I would recommend to dissolve a part of the metal In aqua regia, and add ammonium chloride to test for platinum I have other test For PGM if you want.

[Edited on 22-6-2012 by plante1999]

[Edited on 22-6-2012 by plante1999]




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[*] posted on 22-6-2012 at 07:55


Electrical resistivity of elements varies by purity/shape. If you have an ohm meter available it would be a quick and easy test to try and eliminate some contestants or possibly give you more fodder to prove your point. I warn you however that there is some math involved since the resistivity varies on shape as well.



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[*] posted on 22-6-2012 at 07:56


Parts are made out of platinum all the time. Crucibles, filters, etc.
And some people find chunks of radium salts in their basement. Incidentally, ErIC, you should be carefull too, especially because you mention the guy worked in a nuclear research lab and apparently also forgot about the fortune he left in the basement when he sold the house. Did the former owner die or suffer from dementia or something?

The 'escape' part is suspicious though.




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[*] posted on 22-6-2012 at 08:10


perhaps 'liberated' would fit better :)
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[*] posted on 22-6-2012 at 08:11


If you have any aqua regia available, you could try dissolving part of the sample in it, to determine whether or not it's platinum.
That being said, I would try less destructive measures of identification first :D
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[*] posted on 22-6-2012 at 08:20


It would have been worth a lot less historically when demand for platinum was low. What else can it be?
If the density is correct then things like tungsten etc are ruled out.
I only half believe it myself but facts are facts.
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