Platinum/Iridium AR problem

[Uljunky]

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.

 

[butcher]

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,

 

[Uljunky]

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.

 

[Lou]

How did the iridium start burning?

 

[Uljunky]

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.

 

[Lou]

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.

 

[freechemist]

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?

 

[Uljunky]

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.

 

[Lou]

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

 

[Uljunky]

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.

 

[Lou]

How do you know what it's worth?

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

 

[Uljunky]

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

 

[freechemist]

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. ZnCl₂ is zinc-chloride, and doesn't show any reaction with dissolved precious metals. SnCl₂ 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.

 

[Uljunky]

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.

 

[samuel-a]

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.

 

[Lou]

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.

 

[au-artifax]

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.

 

[au-artifax]

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

 

[Connie Saxe]

Even though this thread is quite old, so are books in the library - people still search the internet for answers.

Here, when dealing with Iridium, it is important to understand Iridium as it exists. If it is in the metallic form such as incorporated into a man-made object, then it is metallic and usually alloyed. Under normal conditions metallic Iridium is not readily converted back to Iridium Oxide - that is why even less Iridium Oxide is found in nature than Metallic Iridium - but don't forget our friend Iridium Chloride - the "green" intermediate between Iridium Oxide and Iridium Metal. Iridium ore derived from Meteor craters have much more Iridium Oxide and Chloride than other sources on earth because of the temperature and pressure related to Meteors and their resting places.

The below photo shows highly-refined Iridium Ore transitioning in a crucible at 1200C where dark spots are Iridium Oxide, Green are Iridium Chloride and Silver is Iridium Metal Specks that will not melt together for another 2,200C.



Iridium Chloride can exist as both a solid and liquid depending on the number of chlorides etc. The reason I bring this up is because if Iridium Metal or something thereto, does ever give in to Aqua Regia - low and behold, you get a green solution of Iridium Chloride. Iridium Chloride solution is not difficult to produce from Iridium Oxide found in nature that is partially converted to Iridium Chloride solid. In nature very few Metals exist as 100% something or other.

If I am dealing with Iridium ore, I can always get a green solution to evolve from a few morsels of ore/soil containing Iridium Metal, Oxide and Chloride by soaking them in Aqua Regia - but dissolution is hardly ever noticeable except under microscope. Two weeks later, the morsels are still there. Don't forget, HF Acid can dissolve Iridium Oxide. But everyone hates HF Acid, except me.

Simply heating Iridium Metal does not usually produce Iridium Oxide. If it did, our spacecraft would fall apart before they get passed Mars. Besides, who would want to create Iridium Oxide if you already have Iridium Metal? We work hard enough and destroy tons of the earth's surface to create Iridium metal, why work backwards?

Given these things, if you have Iridium in any form, no one other than a scrap-refiner experienced in Iridium can refine it - and even they have a really hard time trying to un-do Iridium. Trying to melt anything containing Iridium requires 2,466C and will likely destroy whatever it is the Iridium is attached to (as well as you) and once everything is melted together then you have a bigger mess than what you started with.

 

[Yggdrasil]

Even though this thread is quite old, so are books in the library - people still search the internet for answers.

Here, when dealing with Iridium, it is important to understand Iridium as it exists. If it is in the metallic form such as incorporated into a man-made object, then it is metallic. Under normal conditions metallic Iridium is not readily converted back to Iridium Oxide - that is why even less Iridium Oxide is found in nature than Metallic Iridium - but don't forget our friend Iridium Chloride - the "green" intermediate between Iridium Oxide and Iridium Metal. Iridium ore derived from Meteor craters have much more Iridium Oxide and Chloride than other sources on earth because of the temperature and pressure related to Meteors and their resting places.

Iridium Chloride can exist as both a solid and liquid depending on the number of chlorides etc. The reason I bring this up is because if Iridium Metal or something thereto, does ever give in to Aqua Regia - low and behold, you get a green solution of Iridium Chloride. Iridium Chloride solution is not difficult to produce from Iridium Oxide found in nature that is partially converted to Iridium Chloride solid. In nature very few Metals exist as 100% something or other.

If I am dealing with Iridium ore, I can always get a green solution to evolve from a few morsels of ore/soil containing Iridium Metal, Oxide and Chloride by soaking them in Aqua Regia - but dissolution is hardly ever noticeable except under microscope. Two weeks later, the morsels are still there. Don't forget, HF Acid can dissolve Iridium Oxide. But everyone hates HF Acid, except me.

Simply heating Iridium Metal does not usually produce Iridium Oxide. If it did, our spacecraft would fall apart before they get past Mars. Besides, who would want to create Iridium Oxide if you already have Iridium Metal? We work hard enough and destroy tons of the earth's surface to create Iridium metal, why work backwards?

Given these things, if you have Iridium in any form, no one other than a scrap-refiner experienced in Iridium can refine it - and even they have a really hard time trying to un-do Iridium. Trying to melt anything containing Iridium requires 2,466C and will likely destroy whatever it is the Iridium is attached to (as well as you) and once everything is melted together then you have a bigger mess than what you started with.

There is no structural Iridium in a spacecraft.
Too heavy and too difficult to form, so the spacecraft would be safe.

Iridium are if it is melted, melted in exotic equipment like a electron ray furnace or similar.