Sciencemadness Discussion Board - Separating Iridium from Gold

Separating Iridium from Gold

Herr Haber - 1-2-2022 at 09:06

I recently stumbled upon this video about a guy melting gold with a high % of iridium:
https://youtu.be/UgP_UqXUnsc

I'm surprised that iridium is a problem to him but most surprised it's a problem for his refinery !!

This makes little sense to me as iridium a more expensive than gold.
Any opinion on that ? Would separating iridium would be such a complicated endeavour for a refiner that they see iridium as a problem ?

Sure, you cant aqua regia the whole thing.
I dont see how inquartering would help either (though that might be a step in the right direction).

The guy is pretty well equipped (XRF) so I can only assume he knows a thing or two.
What am I missing ?

AJKOER - 3-2-2022 at 10:09

Yes, I agree strange, as Iridium melts at 2,446°C, 4,435°F (see https://www.rsc.org/periodic-table/element/77/iridium) but Gold at 1,064°C, 1,948°F.

Also, per this source https://www.sciencedirect.com/topics/earth-and-planetary-sci... :

"derived from small celestial bodies, are composed mostly of iron, nickel, gallium, germanium, and iridium (Fig. 1.3). The impact of falling on the Earth’s crust causes partial melting and concentration of valuable metals."

Iridium may be a problem in the sense it is harder for his refinery to melt/cast.

Also, if your sample contains highly radioactive Iridium 192 (which emits gamma rays and has a half-life of 74 days that is relatively short) for a plant manager that can be a problem (should be subject to reporting to AEC, plant closing and associated clean-up).

[Edited on 3-2-2022 by AJKOER]

unionised - 3-2-2022 at 10:59

If that was really iridium, and I knew the guy, I'd offer to swap him that mixture for for its weight in pure gold.

AJKOER - 3-2-2022 at 11:34

Unionised:

You may wish, per my revised comment, bring your radiation detector.

If measurable amounts of Iridium 192, an actuary could calculate related storage cost and clean-up along with potential personal future health cost for yourself/others as well a legal fees for any claimed damages, etc., all combined and appropriately discounted to its present value, which would compared to the current price of gold.

I may have missed some issues, see this Time story here http://content.time.com/time/subscriber/article/0,33009,8676... and of course those pleasant conversations you'll have with the Atomic Energy Commission.

Still interested in the gold swap?

[Edited on 3-2-2022 by AJKOER]

Tsjerk - 3-2-2022 at 11:44

Quote: Originally posted by AJKOER

Unionised:
Still interested in the gold swap?

[Edited on 3-2-2022 by AJKOER]

I can't speak for unionised, but for me: any day.

SWIM - 3-2-2022 at 15:41

Yes, the iridium may be iridium 192!
And what if the gold is gold 198!!!!!

I have also decided to stop bathing because the water I use might be trituim oxide!!!

*puts fluorodeoxyglucose F18 in my coffee*

Metallophile - 3-2-2022 at 16:20

Why would it contain Ir192, with a half-life of 74 days? It does seem like separation would be worthwhile though, given the value of iridium. Could this be done chemically? It also contained Ag, Pb, and Fe, according to his XRF.

Herr Haber - 5-2-2022 at 09:43

Quote: Originally posted by unionised

If that was really iridium, and I knew the guy, I'd offer to swap him that mixture for for its weight in pure gold.

XRF says 4% Ir and 4% Ag.
I'd do the swap too !

But I look at foundry slag as treasure, so I might be a little biased

Actual extraction costs might negate any profits for me but it would be a fun project.
And Iridium is missing in my element collection !

"Glencore": Anodes are 92% pure copper
"Me": What's in the remaining 8%?

Quote: Originally posted by Metallophile

It does seem like separation would be worthwhile though, given the value of iridium. Could this be done chemically? It also contained Ag, Pb, and Fe, according to his XRF.

That's my question

His sample is 243 grams at the beginning and 200 grams after melt.
That's still about 8g Ir but I wonder what was really in the 40 grams he lost.

[Edited on 5-2-2022 by Herr Haber]

Rainwater - 5-2-2022 at 12:43

To dissolve, iridium takes some very nasty stuff.
When i suspect a sample, I use an oxy acetylene torch and add 5 times the sample mass in copper or 3 times the mass with silver
Incort the sample which is at the very limits of my torch. Turn it into beads then soak in nitric.
Decant and repeat until no orange NO₂ is produced.
Then a hot aqua regia bath until no orange gas again.
The left overs are probley iridium. Ive only came across it a few times. Could be a better way.
As for the melting step. I find copper to be better. I think the alloy formed has a lower melting point than with silver. But i try to use at least a 4:1 mol ratio so no other metals get trapped

Herr Haber - 5-2-2022 at 13:18

Silly me !
Yes Rainwater, thank you

So not only inquartering (spelling?) is a good approach it's probably the best if not the only.
(Guess who forgot Ir doesnt dissolve in AR...)

Can you confirm what he says about the smell ?
I've come accross weird smells while working with metals so I'm willing to believe anything.

Rainwater - 5-2-2022 at 14:35

I never noticed any smells from pure metals melts. I must add that I do my smelting with lots of ventilation and outside. Ores, though, will stink up the neighborhood

[Edited on 5-2-2022 by Rainwater]

unionised - 6-2-2022 at 03:37

Quote: Originally posted by AJKOER

Unionised:

You may wish, per my revised comment, bring your radiation detector.

If measurable amounts of Iridium 192, an actuary could calculate related storage cost and clean-up along with potential personal future health cost for yourself/others as well a legal fees for any claimed damages, etc., all combined and appropriately discounted to its present value, which would compared to the current price of gold.

I may have missed some issues, see this Time story here http://content.time.com/time/subscriber/article/0,33009,8676... and of course those pleasant conversations you'll have with the Atomic Energy Commission.

Still interested in the gold swap?

[Edited on 3-2-2022 by AJKOER]

I think someone may have hacked AJKOER's account. There's no mention in that post of free radicals.

I'm also concerned that he didn't mention the potential danger of having a sample delivered by a rabid dog (which is more likely that significant radioisotope contamination).

unionised - 6-2-2022 at 03:43

Quote: Originally posted by Herr Haber

Can you confirm what he says about the smell ?
I've come accross weird smells while working with metals so I'm willing to believe anything.

I wondered about that.
I can't see any plausible route from iridium to anything that's volatile enough to smell.
I can explain garlic like smells from selenium, tellurium or arsenic.

So I'm left with the vague dilemma; which do I believe?
His nose or the XRF?

Well, I know XRF machines can get confused...

yobbo II - 6-2-2022 at 10:21

https://www.semanticscholar.org/paper/The-Au-Ir-(Gold-Iridium)-System-Okamoto-Massalski/422052c10cd8f4b160fa44773ff8508624aa1eb1

If you can obtain a phase diagram of Gold/Iridium it may show that the system melts at.

https://dl.asminternational.org/handbooks/book/36/chapter-ab...

Yob

[Edited on 6-2-2022 by yobbo II]

chornedsnorkack - 6-2-2022 at 12:51

Pb is a problem:
https://link.springer.com/content/pdf/10.1007/BF03214762.pdf
By far the largest impurity in refined gold is usually Ag; but it forms a good solid solution to little effect on properties.
The link discusses Pb, Bi, Te and Si as impurities which in small concentrations concentrate at grain boundaries and make gold brittle - small like 100 ppm.

So what are the effects of Ir impurity to gold?

Herr Haber - 6-2-2022 at 13:02

Quote: Originally posted by unionised

I thought about Se, Te and As too but those as Rainwater mentioned are mostly gone after roasting the ores as far as I know.
There's visible smoke being produced and a loss of weight.

It all comes back to his curious looking starting material. The answer for the smell probably lies there too.

Rainwater - 7-2-2022 at 02:44

I would have to say that the limitations of his equipment are causing issues.

He is using a graphite crucible.
Which @ 720c starts outgassing CO/CO₂. And it looks like he used a graphite mold to, as evidenced from the gas bubbles in his final ingot.

His pouring temp was likely to be low, which caused the unsmoth surface and fractures in the final ingot.

All which leads me to subspect that the alloy produced may not be uniform, which will make the xrf very inaccurate.
The very first batch i ever sent off cost me almost 20% because of the impurities the refinery found. Low quantities = higher rates.
Hence my new found interest in chemistry. But i must add, i was drulling a little bit when i seen that coffee cup full. Far more that i run at once.