SSn with iodine

[rhodiumfever]

I'm doing the tests in a test tube, don't have a testing plate and yes I'm using as much stannous as solution. It appeares that I don't have Rh here but will try again today as yesterday the ore hadn't been leached for very long,
Thank Lino and Platdigger.
There's still Rhodium somewhere in them hills.
Anyone come up with a reason why adding Iodine to SSN is a good idea?

 

[Platinum]

http://www.scribd.com/doc/16798901/SSN-Leach

 

[lazersteve]

I'm doing the tests in a test tube, don't have a testing plate and yes I'm using as much stannous as solution. It appears that I don't have Rh here but will try again...

I performed all of my tests in a test tube also.

My small test tube is 5 mL , my larger ones are 25mL. I used drops from an eyedropper to perform the test. The important thing is that the solution must be acidic, hence the indication to use three drops of HCl to one drop of the solution being tested and one drop of stannous. The test is pretty sensitive so very little is needed. If the solution being tested is very diluted you may add another drop of it.

If you have solid Rh powder you can get some to go into solution using a boil in hot concentrated (98%) sulfuric acid. I have also posted photos of positive results for this test in the reactions list post.

If you are struggling to see the color changes while heating and after the solution cools, you don't have Rh. The color change is pretty pronounced even in the presence of Pt.

I would have to agree that you have not put any Rh into solution.

Steve

 

[rhodiumfever]

Thanks Platinum for the input, unfortunately that document is the one by the American Soc. for Applied Tech. and it seems to be the only thing out there that directly addresses SSN. I did find a US patent 5156721 which seems to be barking up the same tree but includes using an electrolysis cell - if that's the correct way to describe it (cathodes and anodes). I got a chemistry A level at school but I wouldn't give myself one now!
And Lazersteve, a rock as always, in the test I found, http://goldrefiningforum.com/phpBB3/viewtopic.php?p=16869&#16869 you don't mention adding HCl but you do add water. I've made my stannous according to your directions 2g Sn : 30HCl so I guess I don't need the extra HCl? Also since my leach is 7 parts water to 1 part HNO3 then I guess I could leave out the step adding 3 drops of water as per your directions.
Yesterday material is still being leached so will have a more concentrated solution to work with this time.
Oh yes I would still like to Know if I would have oxidized the Rh (had it been there) when I roasted the ores.

 

[lazersteve]

Here's the sulfuric acid test results:

Testing for Rhodium with 98% Sulfuric Acid


Steve

 

[rhodiumfever]

Thanks for the reply Lino.
With the 2nd batch, I raised the pH to 1.5 - 2.0 which is what the SSN paper by the American Society for Applied Technology suggest.
I then dropped with zinc and this time got black/brown sludge which is taking ages to filter.
I'm primarily looking for Rhodium so I intend to to dissolve in hot AR and if there is anything left then it should be Rh!?
Have you ever used SSN (saturated saline and nitric acid)? I haven't heard anything negative about it but there doesn't seem to be a lot of information available. Some sites suggest adding iodine if you want the leach to be extra aggressive. I'm not sure how that would help, but thought it may act as a buffer to keep the pH very acidic. I would like to understand what advantages it lends to the leach.
SSN is sometimes referred to as SWAN (salt water and nitric).
Will see if I can start the AR stage now!

The final step of the above procedure was to filter off the Rhodium but there just seemed to be a few bits of dust in the bottom of the filter. The original ore was about 1oz of my super concentrates ( depleted to 5g) and it had leached for 4 days.

Anyway I hadn't thrown the filter paper away so I took the grey dust section of the filter paper and put it in a test-tube. Added concentrated Sulfuric and immediatly got and opaque black residue. No change visible on boiling. Couldn't see any red so pored a bit onto a filter paper and could see bit of brown mingled with black.

Maybe to much Rhodium I longingly hoped so I went to my 5g parcel and put about 0.3g into a test tube. Added conc. H2SO4, no change. Boiled for about 2 minutes and a grey color has appeared and made the solution less translucent. Cannot find any discernable red color in this.

The original ore has a whole mix in it but the filter paper residue was after dropping with zinc and then boiling in AR. What do you think Steve?

 

[lazersteve]

From you descriptions of the colors I'd say no Rh is present or it's locked up in silicate or an alloy if it is there.

My gut feeling is that it's just not there.

It took some time for me to get familiar with the Rh tests. The eureka moment came when I performed the tests using known Rh samples that I got from Lou. Once I saw a real positive test with my own eyes, it was easier to recognize when I saw it again.

Hoke teaches this familiarization process very well in her book that Harold pushes so much. Working with known samples instead of unknown samples to learn takes a lot of the hope an guess work out of your tests. Once you can properly identify a known sample using these test then you can graduate to the unknown samples.

Steve

 

[rhodiumfever]

I was hoping you weren't going to say that but it has been dawning on me that without having observed a positive reaction its going to be impossible to draw any complete conclusions from my basement chemistry. I'm getting flashback to school when even with good chemicals and clean equipment one didn't always get the desired result from a test. I shall have to wait until I next visit my safety deposit box and get my 20% rhodium sample, that in itself will not be so easy because I also have stored there the other 2 or 3 samples that I bought which contain no pms. However one out of the four samples should react sufficiently differently to determine it the odd man out and therefore Rh. I wished I had been more diligent about labels.
I ave since tested the .3g sample of super concentrated ore and although no visible reaction on heating, when cooled I can definatly see an orange/brown hue. The tests with the filter paper were so strong I thought I had found something but if you say this is an indication of no Rh I shall accept the mans word.
Just lastly if you had half a gram of superfine Rhodium and poured 2cc of concentrated H2SO4 on it, what would you expect to happen. Also can you give me an equation for what is happening in this reaction and is the final product soluble in water or is there a further test I can do on the final product (black suspension after H2SO4).
Thanks for everyone's help and I hope to be able to report something new and enlightening in the near future

 

[lazersteve]

The final product is Rhodium sulfate and is in the acid.

Sam just asked a similar question here:

Rhodium Sulfate Solution

Remember the sulfuric acid will not completely dissolve all of the Rh so several treatments are required.

The sulfuric acid needs to be boiled to put the Rh in solution. You see the color of the solution change when the Rh begins to go in. The solution will darken like when you make tea.

Steve

 

[WIZZARD]

Hope I don't make a posterior of my self, but hears a thought.

Flux and fuse the ore with low melting collecting metal (maybe Ag) . Part the alloy with Mobius cell, collecting metal goes to the CAT and the anode bag fills with NM and base metal mud. No over voltage as NM will also go to the CAT. This takes forever! Roast the mud to ensure zero valance, use AR for Au, Pt, Pd, residue is Ag, Rh, Ir, Ru. Parting this stuff in steps solves a lot cross NM contamination. Leave the Ag alone until you get your Rh. Fuse residue with sodium bisulfite to make Rh soluble in H2O, filter, drop with sodium hydroxide to black powder still salts of Rh and Na. An old guy told me when I was a young guy, that PGM's can be locked in the host rock as salts, thus soluble in simple acids? If you make Rh salts they need to be stabilized and brought to zero valance, by slow ignition, then they are not soluble any more? Pre roasting some ore can drive off the soluble PGM salts. Not theory been there done that! Iodine used on the whole thing will collect all the iodine soluble metals and minerals, now you got to figure out to selectively part the solutions? Don't tell me someone has that on a thread, send it to me, I have a lot to learn.


WIZZARD

 

[Lou]

Where there's rhodium, there will almost certainly be its sister metals (at least in natural sources).

Harold meant that rhodium and cyanide don't get along--under normal conditions, it won't complex rhodium metal (nor platinum).

Sounds like you're on an epic tail chase!

 

[rhodiumfever]

Thanks Lou for clearing that up, you can see that it was fairly cryptic to my newbee brain. The point is that the original miners were not even considering getting the PGM values, they were only after gold. I was sold the concentrated tailings as "white gold" but they didn't know how to recover it. Now cyanide is not used so the method is almost entirely amalgamation which again wont touch PGMs so somewhere there's a huge pile of Rhodium tailings to be had! I'm just about out of samples now so will have to wait until I restock to continue my quest.

 

[Wyndham]

Now this idea may be in totally the wrong direction and please slap it down if it needs it. I seem to remember that some costume jewelry is first plated with Rhodium then gold plated. I don't know if this is still the case or if it ever was.
If it was/is then if one could find this stuff, deplate the gold, wouldn't that be a reasonable way to get a test material for Rhodium??
I also think there is some ceramic lusters(liquid) some are gold some are platinum and one might be Rhodium.
Just a thought to get a pure test material or maybe not. Wyndham

 

[Harold_V]

It would be unusual for gold plated jewelry to be first plated with rhodium. The purpose for the base plating is to prevent migration of gold to the base metal. Nickel has been, and is, the metal of choice for that purpose.

Harold

 

[depperl001]

Now this idea may be in totally the wrong direction and please slap it down if it needs it. I seem to remember that some costume jewelry is first plated with Rhodium then gold plated. I don't know if this is still the case or if it ever was.
If it was/is then if one could find this stuff, deplate the gold, wouldn't that be a reasonable way to get a test material for Rhodium??
I also think there is some ceramic lusters(liquid) some are gold some are platinum and one might be Rhodium.
Just a thought to get a pure test material or maybe not. Wyndham

Hi,

Anno about 1979 some silver jewellry was plated with Rhodium so that it would not discolour.If you could find some it would give you a strong idea.
Regards,
depperl001

 

[goldsilverpro]

I see no reason why gold plating would ever be put on top of rhodium plating.

 

[Harold_V]

I see no reason why gold plating would ever be put on top of rhodium plating.

I'm afraid I'd have to agree. The barrier that is required to keep gold from migrating has been, for years, nickel. I can't begin to imagine why they'd use a metal that cost hundreds of dollars per ounce when one that costs just a few bucks per pound serves the purpose perfectly well.
Not too long ago, rhodium wasn't very expensive. Even then, it wouldn't have made sense to use it in place of nickel. Not unless there was a specific reason.

Harold

 

[goldsilverpro]

Like Harold intimated, THERE HAS TO BE A REASON for everything, when it comes to the usage of precious metals. They are, and always have been, too expensive just to use them where ever you want to based on a whim. This is an extremely important concept. When this finally soaks in, you will be able to analyze the materials you are dealing with in a more intelligent manner. I guarantee you that no manufacturer has ever wasted these metals, except maybe through ignorance. They always only use what is absolutely necessary - no more, no less. This has been true for 1000s of years.

 

[Harold_V]

Like Harold intimated, THERE HAS TO BE A REASON for everything, when it comes to the usage of precious metals. They are, and always have been, too expensive just to use them where ever you want to based on a whim. This is an extremely important concept. When this finally soaks in, you will be able to analyze the materials you are dealing with in a more intelligent manner. I guarantee you that no manufacturer has ever wasted these metals, except maybe through ignorance. They always only use what is absolutely necessary - no more, no less. This has been true for 1000s of years.

The point of all of this is when you finally come to terms with the idea that there's not a huge amount of any of these metals used, you are on your way to realistic expectations.

How many, here, have clipped pins, thinking they are gold through and through, due to being made of yellow brass? It's a common mistake, often leading to poor investments.

It really pays to look at everything with skepticism. It's hard to screw a cynic.

Harold

 

[rhodiumfever]

Just received some samples from another area which is not widely known for PGMs however I would still like to check for them.
3 samples are from within a 20 miles radius. They are tailing samples. All 3 of the samples have gone through amalgamation with Hg. And one of the samples has been leached with cyanide. (I know I said its illegal but appears to be going on in some areas)
I roasted the 2 mercury only samples over charcoal for about one hour and then dropped into cold water. I think this prevents any rhodium present from oxidizing which would then be very difficult to leach.
I was a bit leary about roasting the cyanidation tailings so omitted that step.
Now I have 3 samples of 100g each in a solution of 7:1 saturated saline and nitric acid. No iodine to complicate things more than necessary.
Several questions, would cyanide have done anything to any PGMs which happened to be present? Lou and Harold mentioned that it doesn't affect Pt or Rh.
Is 100g such a small quantity that I can't expect to see any results?
Does anyone know how to measure the ORP of the leach because a meter will quickly get corroded and cease working? It should be kept between 400- 900 mv for some reason
Does anyone apart from The American Society for Applied Technology have any experience with leaching PGMs with SSN.
I may well be on a tail chase but like a puppy I'm still not convinced I can't catch it. This forum, by the way, is quite amazing and although my brain hurts I think if I keep reading some of the stuff will eventually sink in.