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?

If that's rhenium (d=21,02), I'll have to kill you and steal it. Nothing personal, of course. 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.

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.

Tank

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

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.

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?

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.

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...

[Edited on 22-6-2012 by blogfast25]

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... [Edited on 22-6-2012 by blogfast25]

perhaps 'liberated' would fit better

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

Quote: Originally posted by phlogiston

Parts are made out of platinum all the time. Crucibles, filters, etc.

Quote: Originally posted by ScienceSquirrel

It would have been worth a lot less historically when demand for platinum was low. What else can it be?

An Osmium alloy?

Which cylindrical part (an axel?) would require the chemical resistance of Pt/Ir? And how could such a part go 'walkies', left in the basement by a 'forgetful' previous owner, even at today's prices????

I just hope someone's not playing an elaborate prank here!

[Edited on 22-6-2012 by blogfast25]


[Edited on 22-6-2012 by ScienceSquirrel]

Quote: Originally posted by blogfast25

Quote: Originally posted by ScienceSquirrel   It would have been worth a lot less historically when demand for platinum was low. What else can it be? An Osmium alloy? Which cylindrical part (an axel?) would require the chemical resistance of Pt/Ir? And how could such a part go 'walkies', left in the basement by a 'forgetful' previous owner, even at today's prices???? I just hope someone's not playing an elaborate prank here! [Edited on 22-6-2012 by blogfast25] [Edited on 22-6-2012 by ScienceSquirrel]

Quote: Originally posted by phlogiston

It is also a great stroke of luck that you found it, rather than someone who would simply discard a pile of what might look like junk.

Quote: Originally posted by Erbium_Iodine_Carbon

Alright I've accurately weighed it and the density is just over 21.3g/cm3.

Quote: Originally posted by AndersHoveland

Rhenium has been used in nuclear reactors as a barrier between the uranium fuel pellets and the niobium alloy cladding. Rhenium has the second highest melting point of the elements, and is twice as strong as tungsten.

Quote: Originally posted by unionised

I think you should wait until Archimedes has finished his bath, then ask him.

Quote: Originally posted by Eddygp

@unionised The density was already calculated, wasn't it?

Quote: Originally posted by DerAlte

@Unionised If the hand in the photo is a human male hand, I don’t think the poster’s estimate of volume is that far off! I believe the elements are actually bolonium and bullshittium, well known in Lalaland. Their densities are imaginary, approximately 22i and 19i respectively, where i= SQRT(-1). They are made from Al and Fe by a mental transformation process, aided by hallucinogenic. Repost this thread in Whimsy, since we do not have a section for Science Fiction, although many recent posts seem to qualify. Regards, Der Alte

Quote: Originally posted by DerAlte

@Unionised If the hand in the photo is a human male hand, I don’t think the poster’s estimate of volume is that far off! I believe the elements are actually bolonium and bullshittium, well known in Lalaland. Their densities are imaginary, approximately 22i and 19i respectively, where i= SQRT(-1). They are made from Al and Fe by a mental transformation process, aided by hallucinogenic. Repost this thread in Whimsy, since we do not have a section for Science Fiction, although many recent posts seem to qualify. Regards, Der Alte

Wicked, man!

Unionised's point on density stands: accurate measurement of volume may not have taken place yet.

Eddygp - 23-6-2012 at 11:06

OK, put the rhenium/whatever-it-is in a beaker with x cm3 of water. The beaker should now contain (x+y)cm3 of water+metal. x+y - x = y. y = volume of metal

z mass in grams/y = z/y g/cm3

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LanthanumK - 23-6-2012 at 11:54

Use scratch tests with various materials (glass, knife, quartz, etc.) to determine Mohs' hardness. Tungsten has 7.5 hardness, platinum 4, and rhenium 7. If it can be scratched by a knife with difficulty, it is probably platinum.

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phlogiston - 23-6-2012 at 13:13

rhenium dissolves in nitric acid, tungsten and platinum do not.

tungsten dissolves in warm, 30% hydrogen peroxide to give a yellow solution, platinum does not.

If the rod's diameter is uniform over its length, the volume measurement should be sufficiently accurate, and probably more so than typically achieved by immersion.

Quote:

None directly. It was not a rant, merely a little piece of satire based upon the actual likelihood of it actually being true, which is vanishingly small. Have you ever seen a piece of machined pure tungsten? What use would it be?

Unlikely events happen. It is not as if we hear this story on a regular basis.

Although you may not be able to think of any, these things exist and are used. Keep in mind he worked in a pretty unusual place.
Machined tungsten items are easy to find online:

Quote:

People do not have about $9000 worth of shiny Pt rod or large billets of W in their basements.

Apparantly, some people do. You should check out some of the wonderful items some element collectors have.

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Fleaker - 23-6-2012 at 17:01

If you want, you can send it to me. I will use XRF analysis on it and tell you what it is. It's either platinum, rhenium, or iridium (it isn't osmium, I can tell that right away--plus that's so difficult to cast or sinter).

Looks like an iridium rod to me.

Quote:

People do not have about $9000 worth of shiny Pt rod or large billets of W in their basements.

I know people who have way more expensive quantities of PGMs or other elements in their collection. I have a good friend of mine is a metallurgist who has quite the collection of 5 and 10 kg sputtering targets out of Ta, Hf, Re, Zr, Nb, and W.

Attached is a piece of 9995 platinum so you can see its cast.



[Edited on 24-6-2012 by Fleaker]

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unionised - 24-6-2012 at 04:36

Quote: Originally posted by DerAlte

unionised wrote: Any evidence for that rant? None directly. It was not a rant, merely a little piece of satire based upon the actual likelihood of it actually being true, which is vanishingly small. Have you ever seen a piece of machined pure tungsten? What use would it be? Der Alte

Yes, I have.
It was the electrode from a high power flash lamp.
Do you realise that your ignorance doesn't stop other people finding a use for it?
Incidentally, I also have a tin with 5Kg of tungsten sponge in it. It was chucked out as scrap so I git it for free. Not as valuable as a single rod, but quite a nice find.
Also, I rather suspect that they start with lengths of rod to make these.
http://www.google.co.uk/search?q=tungsten+darts&hl=en&am...


[Edited on 24-6-12 by unionised]

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cyanureeves - 24-6-2012 at 04:51

tungsten carbide is not the same as tungsten is it? ebay mostly has tungsten carbide stuff like rings and drill bits but i would like to own tunsten or separate it from the carbide if possible.

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Endimion17 - 24-6-2012 at 05:29

The hardness test is a good starting point. Platinum crucibles are pretty easy to scratch with stainless steel.

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blogfast25 - 24-6-2012 at 05:45

At the end of the day really only XRF will lay this to rest easily and conclusively.

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unionised - 24-6-2012 at 07:28

For a given definition of "easily" - specifically one that includes having access to an XRF rig.

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blogfast25 - 24-6-2012 at 07:58

Quote: Originally posted by unionised

For a given definition of "easily" - specifically one that includes having access to an XRF rig.

Quite a few jewelers have portable Niton XRFs today. If the suspicion is that Ir or Pt might be involved they would willingly oblige, I think.

My own suspicion is that we won't hear from our original poster again...

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Erbium_Iodine_Carbon - 24-6-2012 at 16:23

I could scratch the rod with a kitchen knife. I also took some pictures with the measurements. I did weigh it on a scale accurate to 0.01g and got a mass of 185.61g.




[Edited on 25-6-2012 by Erbium_Iodine_Carbon]

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Sedit - 25-6-2012 at 00:05

Sorry if this has been asked but have you done a specific gravity test on it yet?

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Organicus - 25-6-2012 at 02:29

Quote: Originally posted by Erbium_Iodine_Carbon

I could scratch the rod with a kitchen knife. I also took some pictures with the measurements. I did weigh it on a scale accurate to 0.01g and got a mass of 185.61g.

So whats the density now?

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Erbium_Iodine_Carbon - 25-6-2012 at 03:55

Density was 21.33g/cm3

V=h*pi*r^2
V=10.65*3.14159...*0.51^2
V=8.70cm3

Density=mass/volume
D=185.65/8.70
D=21.33g/cm3

[Edited on 25-6-2012 by Erbium_Iodine_Carbon]

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blogfast25 - 25-6-2012 at 05:02

On photo 5 the rod seems slightly scratched, which would indicate the metal to be 'softish'. And you're certain that the rod isn't tapered, right?

With the suspicion being indeed in the direction of Pt you should really consult a jeweler, preferably one with a Niton XRF. Or take off a small piece and have it XRFed by Fleaker...

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hyfalcon - 25-6-2012 at 06:06

Close enough for Platinum allowing for measurement error. Man, I would LOVE to have THAT for a perchlorate electrode!

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Erbium_Iodine_Carbon - 25-6-2012 at 06:36

The 5th pic was indeed meant to show where I scratched the rod. I wouldn't use it as a perchlorate electrode by itself because it's surface area is tiny compared with the actual amount of platinum. I'm toying with the idea of dissolving some in aqua regia and plating it onto some other substrate, of course if it does turn out to be Pt.

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blogfast25 - 25-6-2012 at 08:18

Quote: Originally posted by Erbium_Iodine_Carbon

I'm toying with the idea of dissolving some in aqua regia and plating it onto some other substrate, of course if it does turn out to be Pt.

Sure. Add saturated NH4Cl to the solution (assuming you get one) to get yellow (NH4)2PtCl6. Boy, you are one lucky %^$%&%$&(^ if this turns out to be a majority Pt alloy!

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plante1999 - 25-6-2012 at 08:22

Quote: Originally posted by blogfast25

Quote: Originally posted by Erbium_Iodine_Carbon   I'm toying with the idea of dissolving some in aqua regia and plating it onto some other substrate, of course if it does turn out to be Pt. Sure. Add saturated NH4Cl to the solution (assuming you get one) to get yellow (NH4)2PtCl6. Boy, you are one lucky %^$%&%$&(^ if this turns out to be a majority Pt alloy!

I already said this one in this thread. but test for other PGM could be done.

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Fleaker - 25-6-2012 at 08:36

Neat. It's platinum then, or an alloy thereof.


FYI, don't ever use a mixture of ammonium nitrate and HCl to try and dissolve platinum--it does not work.

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Swede - 25-6-2012 at 09:03

Interestingly, 187 grams equals 6.012 troy ounces... pretty close to a round number of troy ounces.

At $1440 / oz $US, IF the bar is Pt, then it has a value of approximately $8,640.

I see no reason for it to NOT be Pt, at least in terms of its shape. A solid bar rules out nothing. Big research firms start with all sorts of shapes to turn out finished products. The bar may be the starting shape of any number of Pt objects/devices. And a huge firm, or a government entity, might conceivably have dozens of these stashed away, years ago. The $$ would be piddling to them, and the temptation to lift one would be huge.

Cool find, it'll be interesting to find out what it is.

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unionised - 25-6-2012 at 11:42

Humour me.
Take a long thin bottle of water, deep enough to put the rod in.
Put it on the scales and zero them. Tie a thread round the rod and lower it into the water so it is covered but not touching the bottom.
See what the scales read.

The water will exert an up thrust on the metal equal to the weight of water displaced (i.e. the volume of the rod). Since something has to provide that force, there's a downward force on the scales.
Since the density of water is practically 1 g/ml, the weight registered on the scales is the volume of the bar.

Even if this gives you exactly the same value as the measurements with the calliper gauge it will be useful confirmation (always a good thing in science) and it also lets me explain the easy way to measure the volume of an irregular solid.

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smaerd - 25-6-2012 at 18:43

Really cool idea unionised. I'll need to take note of this.

Who knows maybe the guy was raised in the great depression and instead of hiding his cash under the mattress due to a mistrust in banks he decided to invest in a superfluous platinum rotor. Another interesting idea to take note of.

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condennnsa - 26-6-2012 at 00:07

Yeah, that's really cool unionised, I didn't know that!

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Panache - 28-6-2012 at 06:55

Platinum will carry a magnetic field, albeit more weakly than fe or ni, if you have a rare earth or strong magnet leave it attached overnight and see if it magnetises it slightly by morning. I believe this separates the other Pgm possibilities.

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DerAlte - 29-6-2012 at 10:55

@Panache – AFAIK, Pt is paramagnetic in bulk so your test will not work. However, in alloys it is indeed ferromagnetic in combination, eg, with cobalt. Also, apparently in nanoparticles:
http://www.phantomsnet.net/files/abstracts/TNT2005/TNT05_Fer...
Also see www.platinummetalsreview.com/pdf/pmr-v8-i1-009-011.pdf
The presence of even small amounts of the ferromagnetic metals may thus show ferromagnetic properties.

@unionised: you wrote

Quote:

Yes, I have. It was the electrode from a high power flash lamp. Do you realise that your ignorance doesn't stop other people finding a use for it? Incidentally, I also have a tin with 5Kg of tungsten sponge in it. It was chucked out as scrap so I git it for free. Not as valuable as a single rod, but quite a nice find. Also, I rather suspect that they start with lengths of rod to make these. http://www.google.co.uk/search?q=tungsten+darts&hl=en&am...

Both your electrode and the darts are probably alloys, not pure tungsten. It does not take much alloying metal to quickly reduce the density of W. I was referring to pure tungsten.
And yes, I do realise that my ignorance doesn't stop other people finding a use for things. Otherwise the world would have come to a stop long ago!

Your Archimedean idea is a good one. As a further demo of the principle I would add suspending the thread via a spring balance to show the effect of buoyancy, also showing where the apparent weight gain is compensated. Your idea is far more accurate than measuring the displaced volume of the liquid which I have often used.
The principle is very easily shown mathematically.

@ Erbium_Iodine_Carbon
I am still very skeptical (~4σ but congratulate you either way. This is either one of the best hoaxes ever perpetrated on the members of this forum or a really lucky find. You win both ways!

Der Alte

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Eddygp - 30-6-2012 at 02:13

Let us know if it's platinum... Wow... O.o

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unionised - 30-6-2012 at 05:04

Mass of electrode 19.94 +/- 0.01g
Mass of water displaced 1.04 +/- 0.01 g
density 19.17 +/- about 1%
lit value 19.25

With the available equipment it is not possible to distinguish the density of this lump of metal from that of pure tungsten.

As you say " It does not take much alloying metal to quickly reduce the density of W. "

Re the darts, the reason for using tungsten is that it has a very high density and, as you say " It does not take much alloying metal to quickly reduce the density of W. " so it would be counter-productive for them to alloy it.

So the actual evidence shows, in one case, and strongly suggests in the other that pure tungsten is a reasonably common commodity.
Incidentally, when they make light bulb filaments they start with tungsten rods and draw them.

To give some idea of the value of this find you may want to look at this
http://www.ebay.co.uk/itm/4-Pure-Tungsten-Rod-Electrodes-1-4...

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vmelkon - 3-7-2012 at 07:10

If you really think it is a PGM, then perform this simple test:
1. Shave off a small piece using a knife.
2. Heat it in a flame
3. Does it form a layer of oxide?

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