# Iodine/Iodide & Rhodium



## Comanche (Oct 2, 2007)

*Does anyone know how efficient the Iodine/Iodide leach is for dissolving Rhodium either out of ores or out of electronics? 
If it works, I wonder what would be the best precipitant for the Rhodium?
Thanks!  *


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## goldsilverpro (Oct 2, 2007)

The first thing you would have to do is find some very, very rare type of electronics (or, ore) that contains rhodium. In 40 years, the only electronics I have seen that were guaranteed to contain rhodium were some fingers plated in the early '70's. I have heard lots of stories about rhodium being on some of the more modern electronics, but I've never seen or heard of any results. With the price, rarity, and working difficulty of rhodium, it would only be used in a particular application where nothing else would work, such as gold, platinum, palladium, nickel, etc.

I would doubt very much that I2/KI solution would dissolve Rh. I would doubt that you could find any common chemical(s) that would dissolve rhodium, unless it were very, very finely divided. Commonly, rhodium is dissolved in certain fused salts (molten chemicals) or, I believe, high temp chlorination, usually performed in a tube furnace.


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## Comanche (Oct 3, 2007)

*Well, I suspect that I may have some ore and also some concentrates that may have natural rhodic gold in them. 
At this time, it is my belief that a lot of rhodium in ores is missed due to the insolubility problem with most leaches, as well as probable other causes. Once the gold in the rhodic gold has started dissolving, then the rhodium becomes the outer surface and stops any further dissolution by leaches.
So, my intention was to find out if anyone knew if the iodine leach would dissolve the rhodium along with the gold in such an ore or piece of jewelry made of a gold-rodium alloy.
I apologize for not being more succinct and direct in presenting my query to begin with.
Now if I can locate some gold-rhodic alloy jewelry to experiment with, that would be the real ticket! Also some known rhodium would also be great to also test with.*


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## Harold_V (Oct 3, 2007)

Comanche said:


> Now if I can locate some gold-rhodic alloy jewelry to experiment with, that would be the real ticket! Also some known rhodium would also be great to also test with.



In all my years of refining (for jewelry manufacturers), numbering just over 20, I never encountered any alloy of gold/rhodium. The closest I came was rhodium plated items, often white gold, or even sterling, to prevent tarnish. 

What advantage would there be in alloying with rhodium for jewelry that couldn't be addressed just as well, for 1/10, or on today's market, much less, the cost of palladium? I'm not convinced there is such a thing. Could you enlighten me if you are aware of such an alloy? White gold is typically alloyed with nickel, and on rare occasions, palladium. 

Harold


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## Comanche (Oct 3, 2007)

Harold, I cannot dispute you. I am not a jewelry man by any means. It just made sense to me that very wealthy individuals would enjoy having very, very expensive pieces of jewelry made of a rhodic/gold alloys, as they do of other platinum metals.

In any case, it appears that the only way that I am going to get to the bottom of this is to just go ahead and begin doing some tests on known rhodium samples, including some Rhodite, the mineral of rhodium and gold that is worth a fortune when located!

This field has hardly been touched yet by mainstream sources. I do suspect that there are certain very clever individuals or groups that operate in secrecy (with very good reason) that have all the answers I am seeking. This would also explain why the sparse information on this mineral and subject!

A quick and interesting read on the platinum group of metals and their association with gold and silver that piqued my interest to investigate it further is located at:

http://www.minsocam.org/ammin/AM22/AM22_1016.pdf 

With Rhodium at $6,000+ oz. and gold rising, I must pursue this avenue at this time in conjunction with my other works! :lol:


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## Irons (Oct 3, 2007)

Comanche said:


> *Well, I suspect that I may have some ore and also some concentrates that may have natural rhodic gold in them.
> At this time, it is my belief that a lot of rhodium in ores is missed due to the insolubility problem with most leaches, as well as probable other causes. Once the gold in the rhodic gold has started dissolving, then the rhodium becomes the outer surface and stops any further dissolution by leaches.
> So, my intention was to find out if anyone knew if the iodine leach would dissolve the rhodium along with the gold in such an ore or piece of jewelry made of a gold-rodium alloy.
> I apologize for not being more succinct and direct in presenting my query to begin with.
> Now if I can locate some gold-rhodic alloy jewelry to experiment with, that would be the real ticket! Also some known rhodium would also be great to also test with.*



I have seen native Gold/Rhodium alloys. They're not very common.

I've also seen a mixture of Platinum and Rhodium digest and at the end of the day, the Platinum is in solution and the Rhodium looks just as bright and shiny as when it was put into the digester.

The easiest solution to a Gold/Rhodium alloy that passivates is to inquart it with sufficient Gold so that it can be digested, leaving the Rhodium as a precipitate.

Refiners take a steep discount on Rhodium because of the labor and materials it takes to refine it.

My suggestion is to save up any Gold that doesn't dissolve until you have enough to inquart it or get a quote from a refiner once you have enough to make it worthwhile.

At the end of the day, you're going to have to sell it to a refiner anyway, and they are going to get their pound of flesh, regardless.

This is why Rhodium is so expensive. It's like trying to get blood out of a turnip, as the old saying goes.


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## Irons (Oct 3, 2007)

Comanche said:


> *Does anyone know how efficient the Iodine/Iodide leach is for dissolving Rhodium either out of ores or out of electronics?
> If it works, I wonder what would be the best precipitant for the Rhodium?
> Thanks!  *



To answer your question:

Check patents on line. There is one using Iodine, Iodate and Oxygen under high pressure.

Looks like an expensive process.


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## Comanche (Oct 7, 2007)

*One last thing on this topic. Powdered Rhodium will dissolve quickly in hot concentrated Sulfuric Acid H2SO4, and solid rhodium will also dissolve but takes a lot longer. But it is gradually dissolved over time in pure H2SO4 at just under boiling.  *


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## mike.fortin (Oct 7, 2007)

Comanche--if sulferic digests honeycom then is rodium in same soluton? How do we take them two apart to make money on rodium? Mike.


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## lazersteve (Oct 7, 2007)

Mike,

Check this post:

Rhodium Metal

Steve


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## Comanche (Oct 7, 2007)

*Steve, which post specifically are you referring to? And which part of the post?

Mike, what do you mean about dissolving honeycom (honeycomb?) in sulfuric acid, then is rhodium in the same solution? I don't follow what you are asking here at all! :lol: *


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## lazersteve (Oct 7, 2007)

Comanche,

The link I posted should take you directly to a post concerning Rhodium. It's in the PGM section under "Rhodium Test".

Steve


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## Comanche (Oct 7, 2007)

Steve, 
I must presume that you are referring to fusion with sodium bisulphate ( I use the spelling bisulfate). I was not aware that rhodium minerals would dissolve in a fusion of sodium bisulfate.....I am glad to learn that!  

My method is to fuse the mineral or powdered unknown metal with POTASSIUM BISULFATE completely. Dissolve in DW, filter and then treat the clear solution with ETHYL ALCOHOL which drops only the pure rhodium metal as a very fine black powder. It works great for me!  

Potassium Bisufate is a much, much stronger oxidizer than sodium bisulfate.


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## lazersteve (Oct 7, 2007)

Comanche,

I posted a reference to the potassium bisulphate method earlier in the same thread, but did not include the process to precipitate the rhodium.

Steve


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## Irons (Oct 7, 2007)

Comanche said:


> Steve,
> I must presume that you are referring to fusion with sodium bisulphate ( I use the spelling bisulfate). I was not aware that rhodium minerals would dissolve in a fusion of sodium bisulfate.....I am glad to learn that!
> 
> My method is to fuse the mineral or powdered unknown metal with POTASSIUM BISULFATE completely. Dissolve in DW, filter and then treat the clear solution with ETHYL ALCOHOL which drops only the pure rhodium metal as a very fine black powder. It works great for me!
> ...



If you have time on your hands, the Rhodium usually drops out on its own on standing. It's one of the problems of making stable Rhodium solutions, any impurities will cause the Rhodium to drop out.


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## Comanche (Oct 7, 2007)

Yes Irons, 
However, I use the ethyl alcohol (Everclear) method because then I am sure that all the rhodium has been reduced out of the fusion solution, and of course, like you said, there is no waiting around to filter and wash it off!


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## Comanche (Oct 7, 2007)

One of the reasons that I brought this topic up, was because I recently did an Iodine/Iodide uptake on some ore that I got in New Mexico this summer on a prospecting expedition.

The area is a know gold area and pgms have long been suspected to be inherent in some of the ores there also.

Anyhow, I did a zinc drop on the solution. After rinsing the precips with strong HCL Acid to remove the zinc residuals, I had good gold and quite a lot of another metal. Under microscopic examination the gold was metallic gold crystals of course, and the main other metal was a very silverish white metal with a very strong rose tint, which led me to believe that good rhodium was present also.

However, I did not know if this leachant of Iodine/Iodine would dissolve Rh or any of the platinum group elements out of an ore. Apparently a 7% solution will dissolve some of the pgms along with the gold and silver also.

So, I am left with the option now of doing a larger batch, and getting enough precipitates to send off for spectrographic analysis before I make any further judgements or come to any real conclusions on this final precipitation product.

Another test that I plan on doing to these precipitates is to fuse them with about 4 to 5 parts of pure silver powder inquarted, then take that alloy and do the nitric acid bath to remove the silver and any palladium present and see what is left then besides the gold.

Slowly but inexorably, I shall find the truth! :lol:


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## Irons (Oct 8, 2007)

As Harold mentioned elsewhere, PGM loss can occur when Silver is Alloyed with PGMs and Nitric Acid is used.
Gold is the recommended iquarting material for Rhodium.

I know it's a pain but Gold has been proven to give the best recovery.

Since you have the recovered material in a fine powder to begin with, why not just dissolve the Gold away, leaving the Rhodium?

Rhodium is usually the last metal to be recovered because, after everything else is dissolved, it remains as a residue.

I wish you the best.

Another thing you might look at is using Nickel Sulphide as a flux to extract any PGMs, it's what many commercial refineries use to leach PGMs from the Gold melt. It works best when the Gold contains a small percentage of PGMs and saves having to dissolve the Gold to extract them.


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## Comanche (Oct 9, 2007)

Thanks for the ideas Irons.

When dealing with pgms, I always digest the silver, copper, etc. with sulfuric not nitric. Works for me.


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## Comanche (Oct 9, 2007)

I should have said that some of if not all of the rhodium also dissolves (most of it) in the sulfuric, but you have your gold and platinum etc. left.

Actually, the best thing of course is if you know exactly how much pgms you have with your gold, then you can send it directly to a refiner you trust, even though you may take a small hit on the price, it will save you that much and more on time, chemicals, and etc.


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## Comanche (Oct 9, 2007)

By the way, worth mentioning is to always roll out as thin as possible the alloy button or metal and make a "cone" before digesting with acids, as this really helps the precious metals left to stay together instead of having just a fine powder laying all about.


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## Harold_V (Oct 9, 2007)

Comanche said:


> Thanks for the ideas Irons.
> 
> When dealing with pgms, I always digest the silver, copper, etc. with sulfuric not nitric. Works for me.



Can't be working real well. Because copper is insoluble in sulfuric, it is commonly used as a pickle. Copper oxide, unlike elemental copper, is soluble in sulfuric, so it's very effective. 

Harold


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## Comanche (Oct 9, 2007)

My deepest apologies. I know better than to post when I am give out and not half thinking! 

In the first place, I don't always do everything a certain way! :lol: That was a really dumb statement! :lol:

What I did inadvertently, was get into some methods done on just a small assay type scale, not a larger type scale that I would use to extract and separate the precious metals out of. :wink:

I let this topic get way out in left field from what I originally intended it to do. Like I did say, this topic was only for the express purpose of discovering if any of you knew if Iodine/Iodine leach would dissolve the rhodium minerals.....and since I do not think that we really came to a real conclusion or answer to that question.....my best option now is to get out in my lab, grind up some ore and start testing myself! :lol:

In the second place, when I say it works for me, that does not necessarily mean that the entire process works for me, but the part that I I wanted to accomplish works for me! :lol: 

Irons, I believe that if you will try putting some copper wire or any copper in some concentrated hot sulfuric acid and bring to almost boiling , you may discover that indeed the copper will dissolve very neatly into the Hot, Saturated H2SO4 quite rapidly. Different strengths of sulfuric acid and temps will dissolve copper at different rates. This is also one of the reasons that sulfuric acid is the accepted electrolyte for making purified copper cathodes, of course again a certain strengths, temps, amps, etc.!  

Anyhow, my apologies to all, if I have offended any or such.  Which I never try to do intentionally.

I am now ready to move on to another subject, at least until I have the answers to this I/I problem that I will pursue shortly in my lab work! :lol:


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## lazylightning (Jun 30, 2008)

Hi All!

As I see this subject has been untouched for a while, I would still like to put my question forward here because I think someone here could steer me right. 

So I went to the labshop today and instead of potassium bisulfate they accidently sold me something a little different. Actually, on one German chemistry forum I accidently ran accross a reference about dissolving Rh with the help of the stuff I accidently got which is K2S2O7. Below is a qoute of the reference:

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"The dissolution of rhodium in an acidic salt melt functions quite well, if you let react the metal with a mixture of potassiumdisulfate; K2S2O7 and sodium chloride; NaCl. This mixture melts at fairly deep temperatures, so you actually can use pyrex-beakers as reaction containers. Another possibility is, to use porcelain dishes. Reaction is best done in an oven at 500-550o C. Usually in 1-2 hours about 80% of the metal has dissolved in the molten mixture. Prolonged reaction does not lead to significant more dissolution, because the salt melt itself decomposes slowly at these temperatures, probably by releasing gaseous SO3 and/or SO2Cl2. The presence of chloride in abundance leads to the formation of Rh(III)-chloro-complexes, clearly evident by the deep red color of the resolidified melt after cooling down. The combined effects of a molten mixture of NaCl and K2S2O7 on platinum group metals can be compared to the combined effects of HCl and HNO3 in aqua regia on metallic gold. So even metallic iridium, which does not react with molten K2S2O7 alone, is dissolved in a similar way by the molten salt-mixture.

Here an example for a rhodium batch of 20 grams, which I did myself for a few times: 20 g of rhodium powder, 136 g NaCl and 296 g K2S2O7 are intimately ground together in a mortar. The grey powdery mixture is placed in a porcelain dish or into wide Pyrex or Jenaer-glass beakers. The beaker(s) or dish(es) should only be half filled. They are put in an oven, heated to 500-550oC and held at this temperature for about 1-2 hours. After cooling down the deep red solids are dissolved in a mixture of 1600 ml water and 400 ml of concentrated HCl. Any undissolved rhodium metal, usually about 4 grams, is filtered off and can be reused again. The deep red filtered liquid contains about 16 grams of rhodium and can be treated further to precipitate Rh(OH)3."

The text is from this forum page: http://www.mathematik-forum.de/forum/showthread.php?t=106496&page=1
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So judging by the text written above, if I add the table salt to the melt mix then it will dissolve the Ir too. I probably have Ir in it. Do I want to do that? Or will Ir precipitate out with the Rh when I add the alchohol? Maybe I should do it without the table salt to insure that the Ir isn't dissolved? They didn't mention whether or not the K2S2O7 will work on the Rh without the table salt, if you look at it carefully. If I add the table salt and it dissolves the Ir too, then it the Ir could precipitate out with the Rh, and then I've done all this for naught. 

Also, I just noticed that they do not refer to using alchohol as a precipitant, perhaps it will not work in this case? Though I dont see why, it's still a Rh sulphate water solution.

The site is in German though they're posting in English. I'd just join that forum but all the registration process is in German. Ich nicht forschtehen.

Any ideas? 

The material I have is electroprecipitated sulfides(a red color) which contains Rh, Ir and perhaps other pgm's (but no Ru or Os, they are already removed). There may be base metals also. I can roast them to get oxides, but that will make it harder to dissolve, I assume. Then I will have to reduce the oxides under hydrogen first to make it metal again and easier to dissolve. What about putting these sulfides (ground up) into this melt mix. Again, these sulfides dissolve easier in AR than the metal forms and hot AR can dissolve the Rh sulfides pretty fast too. I think they would dissolve pretty easy in any salt melt at all. Then the problem I will face again is the prospect of Ir being in the solution as a water soluble sulfate. Again, will it come out of solution as a precipitate along with the Rh when I add alchohol, or will only Rh do that? Rh is my target material of choice because it seems to be highest along with the Ir in concentration.

Thanks in advance for any thoughts on this.


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## Shecker (Jul 10, 2008)

Older Reed switches had a coating of gold/rhodium as the contact point. Never ones have ruthenium.

Randy in Gunnison


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