# iridium or rhodium?



## arthur kierski (Apr 24, 2011)

i put some pgms powders from cats in ar-----after doing the denox for 3times with hcl,i filtrated the solution------rh powder was left in the filter paper---------
to the solution i added nh4cl and obtained the yellow (nh4ptcl6) salt-i filtrated the yellow salt out and left the solution to rest for an hour--When i returned ,there was a black salt precipitated in the botton of the beacker------some says that the salt(black) is iridium----as i think that cats do not have iridium,i deduced that could be rh(pd?)-----------question: Iridium or rhodium? 
thanks for replies
Arthur


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## Lou (Apr 24, 2011)

Rhodium usually hitches a ride with the platinum, but iridium often takes longer than an hour to co-precipitate if dilute concentration. If your ammonium chloride precipitant is used in a great excess, it'll come down in an hour, otherwise it can take overnight.

I doubt it's rhodium. 

Pictures?


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## lazersteve (Apr 24, 2011)

Arthur,

I've also seen a deep-red brown to purple colored salt slowly form after precipitating Pt/Pd from cat extract solutions. 

Look at the fine powder in a bright light and determine if it is deep-red brown to purple or if it's black.

Here's a photo of some I've collected:







I also have a lab sample of RhCl3 that I obtained from Lou that resembles this powder in both appearance and solubililty. The salt in the vial is a mixture from several batches that I've collected, so there are some slight variations in color, but it all formed slowly after precipitating Pd and Pt from cat leach solutions.

Lou,

Do you feel like it is a possibility that this is RhCl3 ? I came to this conclusion mainly due to it's solubility characteristics and the source being cat honeycombs.

Steve


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## Lou (Apr 24, 2011)

It's possible, but bear in mind that RhCl3 is relatively soluble in comparison to (NH4)3RhCl6. You can send it up here and I can do elemental analysis if you want...


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## Macgiver (Aug 7, 2011)

Hello Gents,

I have the same issue... from AR at 165F I added ammonium chloride expecting to drop Pt. Instead I got this bright orange, not yellow, BRIGHT orange precipitation. I am thinking it is Ir because I have been told it is the most common PM in the ore but I am surprised and second guessing because of the amounts collected. Any ideas or thoughts?

Thank you.

CW


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## Lou (Aug 7, 2011)

It's not iridium and I'd be VERY surprised to see you solubilize that, and that it's so "common" in the ore. That would be very unlikely. In fact, it's very unlikely that any of that is a platinum group metal. The precipitate looks all wrong to me. Just what type of ore are you working? What is the name of the mineral, and from what part of the world did it come?

Do not precipitate from aqua regia, you must remove the greatest part of the nitric acid. If there are any platinum group metals, the presence of nitric acid guarantees that you will get no where close to a complete precipitation.


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## samuel-a (Aug 7, 2011)

Lou

I'm thinking excess oxidizer caused Pd to precipitate/co-precipitate with any Pt he might have in there. wouldn't you say so ?
color seems fit to Pd...


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## Lou (Aug 7, 2011)

Precipitate looks wrong.


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## Macgiver (Aug 7, 2011)

Hello Lou and Samuel-A,

Thank you for the feedback. I am very confused.

All the nitric was removed prior to precipitation. The solution was kept at 165F under 20 inches of vacuum for approximately 2 hours while being stirred at medium speed. The solution was then poured into a beaker and ammonium chloride was added in powder form, slowly until precipitation was seen. The solution was then allowed to cool and then salts were filtered off.

The ore comes from Nevada and is out of a rhyolitic ash flow, which is also in an area with lots of meteors.

As I mentioned several of the assays we have claim high levels or Ir. I have also be "schooled" that PGMs do not exist in the USA.

Thank you again,

CW


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## lazersteve (Aug 7, 2011)

How about a photo of a stannous chloride test and a DMG test on the salt.

From the looks of it there is a large excess of NH4Cl in the precipitate (note the large glass like crystal formations in the colored salt). If it were me, I would stannous and DMG the colored salt then if it shows Pd (which I suspect it may), I would proceed to repurify it as described here.

Next time around be sure you go easy on the ammonium chloride. I like to do the math on my precipitations and be certain I'm not overloading the solution.

Steve


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## butcher (Aug 7, 2011)

Oregon does have some PGM metals.


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## Harold_V (Aug 8, 2011)

Macgiver said:


> The ore comes from Nevada and is out of a rhyolitic ash flow, which is also in an area with lots of meteors.


What volume of ore is represented by the picture you posted? A ton? A hundred pounds? Three ounces?



> As I mentioned several of the assays we have claim high levels or Ir.


Assays? 

What type of assay?



> I have also be "schooled" that PGMs do not exist in the USA.


It's not that they don't exist. They do. What they don't exist in is commercially viable amounts. I have personally processed samples that yielded indications----but it was clear that one could not make money.

Kennecott Copper, in Utah, produces platinum and palladium regularly, as a by-product of copper. Not much, but it's there.

Harold


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## Macgiver (Aug 8, 2011)

Good Morning,

Yes I will go easy on the A-Ch next time and I think I will make it into a solution rather than just adding it as powder. Thank you for the link.

The represented amount of ore is 350 pounds, ground to between 200-600 mesh, put in AR consisting of 3 to 1 HCL and Nitric, and agitated for three days. When I returned it had been settling in the tank for another four days. I pulled the overhead liqueur off, filtered it and held it under 20 inches of vacuum at 165F for almost 3 hours. With no activity (boiling, bubbles, or vapor - and no indication of nitric acid) I transferred it to a large jar and began the precip with ammonium chloride while still hot. The photo was taken at this point. 

When I get back to the lab in Reno I will test with stannous and will find some DMG to test with as well.

The assays I mentioned are from well known labs. I will get my files out and share that information on my next post.

Thank you all again.

Perplexed,

CW


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## Macgiver (Aug 8, 2011)

The assays we have are both Atomic Absorption and ICP. They show the AG being the highest values with a ratio of 15 to 1 over any of the other metals. 

We also have assays showing good values from http://www.aallabs.com/cms/ in Reno, NV.

CW


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## Lou (Aug 8, 2011)

Post up the assays please.


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## Macgiver (Aug 9, 2011)

Hi Lou,

I am presently bound by NDA and cannot release this information directly. I will find out if I can post the results or a redacted version. I may have to send it directly to you. 

CW


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## Lou (Aug 9, 2011)

Quite alright and very understandable. If there's payable PGMs in an ore here stateside, I'd probably want an NDA signed too!!!

In any case, we can just skirt the confidential part. I like to have an assay sheet to look at (not saying that I don't trust your competence) as it gives me an idea of what to do and where I'm aiming.

You might consider hitting the ore first with nitric to solvate the silver (or else cyaniding it) and then removing that solution for Ag processing with CIP and then going at the more noble stuff with bleach and then HCl/H2O2. Or perhaps melt it all with silver and flux the hell out of it, and pour anodes or granulate...many ways to go.


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## wolverine06 (Aug 27, 2011)

I just joined as a new member tonight and I ran across your photo of orange goo. My first thought was that it looks like a Pb or Cr salt. The reason I say this is because for a long time, many of the red, orange and yellow pigments commonly used in paint were Pb or Cr based. But because of the associated health risks, many of those "old pigments" have been replaced.

Anyway, it is something to consider.


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## wolverine06 (Aug 27, 2011)

It also looks like there is a yellow precip.

PbI2 is yellow.


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