# Platinum/Iridium AR problem



## Uljunky (Jul 23, 2013)

I have read all the posts I could find that referenced Iridium. I have platinum/iridium wire of unknown concentrations. I used AR, it was slow but working for about 20 hours, the reaction stopped even with fresh acids and higher heat, 2 days near a boil and no PGs in the solution. I believe that i have a high level of iridium and that the platinum has dissolved leaving an iridium coating on the wire. I tried heating the wire with a torch to convert it to iridium oxide but that was problematic because it burned! Lower temps did not produce oxide that would react with AR. Quartering it doesnt seem viable since it likes to burn bright white. I tried breaking the coating in a mortar, no luck. Tried scraping with a knife blade, no luck. 

Anyone seen this before? Several ounces have been started.


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## butcher (Jul 24, 2013)

Hokes book has the answer.
Read Hokes until you understand it then read it again...

She describes a couple of methods of dealing with Platinum Iridium.
The forum has her book as free download, there is also a print friendly copy fixed up by one of our fine forum members, look in the book section, many members also post links to Hoke's book in their signature lines,


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## Uljunky (Jul 24, 2013)

I did find information in Hoke's book on ways to process the remainder of my new material. When i started i believed my material contained less than 10% iridium. It seems it has much more. I don't want to alloy it since it is volitile under flame at this point. I pulled about 200cc of platinum salt from the batch before it stopped reacting. It is a fairly large amount of material and i do not want to have it go up in smoke, that is the reason i reached out on this forum.


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## Lou (Jul 24, 2013)

How did the iridium start burning?


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## Uljunky (Jul 24, 2013)

I heated one of the coils of wire (0.010-0.012" x 30") in an oxidizing oxylene flame watching for a color change to black idicating iridium oxide which I have dissolved in AR. While increasing the heat it started to glow white like platinum then the ends of the wires snapped back and started shooting tiny sparks and it got brighter, I removed the heat and it continued for a moment very bright, interesting and expensive. The wire after being burned crumbled into an off white powder and pieces that were very brittle.


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## Lou (Jul 24, 2013)

You don't really see the oxidation on the material nor should it spark. I've melted iridium in air, there are no sparks.

It shouldn't crumble into a white powder either.


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## freechemist (Jul 24, 2013)

First question: Did you test the solution with SnCl2? - If there is any dissolved platinum it must show up by testing with stannous chloride.

You write:


> I pulled about 200cc of platinum salt from the batch before it stopped reacting.


Second question: What do you mean by "*platinum salt*"?

There are other confusing points in your posts, like *burning iridium* and *volatility of the material under flame*.

Further on you write:


> It is a fairly large amount of material and i do not want to have it go up in smoke, that is the reason i reached out on this forum.


Third question: What material do you mean exactly? Remaining material to be treated? - The 200 cc platinum salt? - The undissolved material after acid-treatment?


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## Uljunky (Jul 24, 2013)

First question: i tested with ZnCl2, after many hours of treatment with fresh acid there were no valuables, no change in the wire being treated either. (Second batch of fresh AR)
Second question: platinum precipitated with ammonium chloride. 
Third question: i now know that for the untreated metal i must add more platinum to reduce the concentration of iridium PRIOR to treatment. What i would like to know is how to proceed with the material that has been soaked in AR, dropped 200cc of platinum when treated with ammonium chloride which has now stopped reacting to AR. I'm hoping thAt someone has made this mistake before. I would not be in this pickle if I had allowed my first batch to completely dissolve before starting a large batch. The test batch was slow but I expected that because of the iridium.


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## Lou (Jul 24, 2013)

Why separate them? Any refiner would pay the same, really.


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## Uljunky (Jul 24, 2013)

I tried two differnt refiners and received about 50% of the value of what i sent in. I figured if it was separated i could get a higher return rather than being ripped off again.


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## Lou (Jul 24, 2013)

How do you know what it's worth?

These elements aren't exactly easy to analyze...


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## Uljunky (Jul 24, 2013)

One of the refiners had an x-ray spectrometer. It identified 85% platinum.


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## freechemist (Jul 25, 2013)

My first question again:


> Did you test the solution with SnCl2? - If there is any dissolved platinum it must show up by testing with stannous chloride.


Testing with ZnCl2 is nonsense. *Zn*Cl2 is *zinc*-chloride, and doesn't show any reaction with dissolved precious metals. *Sn*Cl2 is *tin*-(II)-chloride, and shows characteristical colour-reactions with dissolved PMs (Au, Pd, Pt).

*@platinum salt:* If I understand you right now, you _"pulled about 200cc of *alleged* platinum salt-solution from the batch before it stopped reacting"_, and precipitated the ammonium salt by adding ammonium chloride to the 200cc-solution-sample.
Did you test this solution-sample with tin-(II)-chloride? What is the colour of the precipitated ammonium-salt? - Pure (NH4)2PtCl6 is a bright yellow, crystalline material, and even trace-amounts of iridium give it a strong red discoloration. Thus, after my experience, impure (NH4)2PtCl6, containing about 1% (NH4)2IrCl6, still shows a reddish colour, reminding of freshly burnt roof-tiles.

*@X-ray-spectrometer:* Personnally, I never trust in X-ray-results, especially those, obtained by so-called hand-held X-ray-guns, if not done by a carefully calibrated spectrometer, by means of appropriate reference-materials of known, certified composition.


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## Uljunky (Jul 25, 2013)

I'm very bored with this thread. I tested my beautiful canary yellow platinum powder and acid baths with stannous chloride with the appropriate results. I am not a fool and have a background in labratory testing. I was hoping for advice to correct my error not a long drawn out silly conversation. 
At this point I will put it in a crucible with what seems to be a good amount of zinc, cover it with an argon purge and hope for the best in the furnace. 

Good day and good bye.


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## samuel-a (Jul 26, 2013)

Uljunky said:


> I'm very bored with this thread. I tested my beautiful canary yellow platinum powder and acid baths with stannous chloride with the appropriate results. I am not a fool and have a background in laboratory testing. I was hoping for advice to correct my error not a long drawn out silly conversation.
> At this point I will put it in a crucible with what seems to be a good amount of zinc, cover it with an argon purge and hope for the best in the furnace.
> 
> Good day and good bye.



Problem is, your terminology. It is a bit strange.
To me, the metal you are describing sound lees like Ir and more like Ti or maybe another refractory metal.

Diluting the alloy with lead or zinc and parting with nitric should have probably be your first step rather than AR.
Give it a go and let us know.


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## Lou (Jul 26, 2013)

Instead of getting bored over people offering help, try to work with us so we can help you. No one called you a fool. We're just asking questions to help us understand what's wrong.

As freechemist said, if your material was truly high in iridium, you'd have some trouble getting a very yellow ammonium hexachloroplatinate. It could be that not enough dissolve. I dissolve 90/10 Pt Ir on a regular basis and I'd rather dissolve that than type B PtRh thermocouple wire. If you're doing solids, either increase the surface area, or melt it with a fifth its weight in copper. That'll be difficult to do with a torch on any great scale, to put it mildly.


Don't mix your ammonium hexachloroplatinate with zinc powder and pack in a crucible. Just decompose it with heat--ZnCl2 is volatile too and you may have platinum losses and the Pt will be a drag to re-dissolve. You can use dilute HCl and slurry the ammonium hexachloroplatinate and then add zinc powder (or better, turnings). It'll go green before it is done as Pt(IV)-->Pt(II). Personally, I'd re-dissolve the yellow salt in aqua regia, concentrate, and then dilute and bring to a boil and add soda until the pH is 7-7.5. Then sparge in chlorine. All the iridium will precipitate as a brown hydroxide. Let that settle, pour off, rinse the cake with freshly boiled water, and then add 50 cc concentrated HCl per liter of Pt solution. Syrupize that and then add ammonium chloride. Then decompose that with heat at about 550-750 C. You should have pretty nice platinum. 


Now if you want to dissolve high Pt material and leave the iridium behind, roll it into a thin foil and dissolve it in aqua regia with sonication. Some of the Ir dissolves, but not all of it. 

Pictures say a thousand words.


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## au-artifax (Feb 15, 2014)

I think there is another possibility. From your account of what happened when you heated the left over material, it is behaving exactly the way a material alloyed with zerconium would. Zerconium is sometimes alloyed with other precious metals for specific reasons and is done so mostly for corrosion resistance and material characteristics necessary for the application. Sometimes this alloy shows up in applications that involve nuclear generation or machines that are powered or use nuclear power/isotopes.

I think you have a substance with a Zerconium byproduct at this point. Zerconium is flammable and is also used in feeder tubes for nuclear reactors. It will burn hotter than any other metal, similar to a thermite reaction.

Read up on Zerconium and specifically as an ingredient in special alloying. The metal is used in varying states throughout industry.


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## au-artifax (Feb 15, 2014)

One more thing, Zirconium pacivates immediately in acids including AR to ZrO2. There are ways to dissolve it, but it would not be of any immediate benefit monetarily. Attached is one link for a quick look at Zirconium and it's byproducts, their uses, and chemistry.

http://www.theodora.com/encyclopedia/z/zirconium.html


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