Platinum > palladium > rhodium
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SMB is not a good way to reduce Nitric.
So where did you read about this?
On this site it said to drop the gold first then boil the solution down. Then add ammonium chloride to drop platinum etc etc.
There is a blue salt in the bottom and when I add water, the water turns green. I’ve watched a bunch of videos and this is rhodium right?
Yes, but you do not use SMB to drop/ destroy Nitric.
You seem to have read a lot but you need to digest it so you understand why you do the different things.
There is no way to tell, since we don't know what it originated from and how it has been treated.
And in Refining there is no such thing as yes or no to a process it is always: Yes but... or No but...
Regarding PGMs it is even more so as separation is quite tricky.
Information is your/ our friend.
Have you read this text from Raleigh Gilchrist?
A Procedure for the Separation of the Six Platinum Metals from One Another and for
their Gravimetric Determination
I think you will find it here on the Forum.
Or search Google for it.
To understand strange behaviour of platinum group metals in solution, you need to understand bit more about chemistry and other methods to see the issues connected with PGM chemistry. Most of the times, when refining gold nad silver, it is very basic chemistry, simple redox reactions and that´s it.
However, PGM chemistry is coordination chemistry. PGMs in solution form complexes, mainly complex anions coordinated with numerous ligands such as chlorides, but also water, residues of nitric acid and so on. There is never just one of these complexes in solution, ligands switch places, bonds dissociate and reform etc...
And every one of these complexes has unique reactivity, redox potential and preferential conditions regarding pH/ligand concentration, when it´s existence is most probable.
Yup, this is simplest pathway to get some separation.But not the one which will give you sharp separation. To be honest, gold and silver refining techniques are well known and documented. PGM chemistry is not - as most of the best procedures on how to refine these metals were developed by handful of companies, which like to keep them proprietary. There are bits of info here and there, but nothing as whole procedures on how to effectively separate these metals. I wish I had this kind of information few years ago - but it is simply not available to the public. We may dislike that, but it isn´t gonna change because of some small scale guys want that to be the case.
More advanced techniques involve resin adsorption, selective special chelating agents and liquid liquid (SX) extraction methods. There is immense number of possible routes and combinations on how to create flowcharts and separation strategies. All possible combinations of steps...
I´ve been there, I sacrifieced two years of my free time looking for viable route on how to separate PtPdRh feed into constituents. To be honest, I learned a lot. To be honest again, I failed. Together with my partner in refining, with both of us having PhD. degree in chemistry. That wasn´t because we were incapable, but because we lacked crucial bits of info that is simply missing in literauture.
I shared quite a bit of info here on the forum, just search my older threads and replies. Not some assumption chemistry, everything was backed with at least some XRF measurements.
Some notes to this:
1. Every precipitation, either ammonium chloroplatinate, or potassium hexachloropalladate, anything precipitated from concentrated solutions (meaningful concentrations to get reasonable yields) will drag down some of the other PGMs and contamine the precipitate. You need to fine-tune the balance between efficacy of the drop and purity of obtained metal salt (Pt or Pd). In my case, I aimed for rhodium concentration from the feed that contained around 1-2% Rh to at least 15% Rh fraction with as high efficacy as possible. My ballpark number from the experiments was 90%. I explain. 90% efficacy of Pt drop with NH4Cl was "sweet point" where I still removed sufficient Pt from the feed without unnecessarily diluting the remaining Rh fraction. In my case, around 20% of Rh followed to the Pt precipitate. I was able to get nearly 99% pure Pt (metal basis) with one carefully adjusted precipitation with NH4Cl, however, in that case I was getting only like 75-85% yield of platinate.
2. Nitric acid can dissolve also platinum and sometimes even rhodium. It depends on particle size. Solid Pt and Rh won´t dissolve in nitric, but cemented Pt somehow can, and if you force it enough, even Rh can. It is also dependent on the morfology of cemented PGM powder and also on the PGM ratios in that powder. Same apply to alloys with Pd and Pt and nitric dissolution. For example silver alloys with Pt content and Au content. Inquartation of AuPtAg alloy will cause some Pt to dissolve into solution, even if this should not be the case according to textbooks.
3. Palladium do not precipitate with SMB. Best precipitants for Pd are formates, ascorbic acid, hydrazine, hydrogen and DMG (my personal experience, there are many more). Every one of them has unique selectivity and drawbacks.
Golddigger76
Well-known member
Here's some post from a long time ago but it has excellent pictures.
You should study for a long while when it comes to platinum group metals, they can and will kill you if you are doing sloppy experimenting !!!!
Thread '• Refining Palladium concentrates.' • Refining Palladium concentrates.
Thread 'Seperating Ag as AgCl from Pd(NO3)2 in a nitrate solution' Seperating Ag as AgCl from Pd(NO3)2 in a nitrate solution
You should study for a long while when it comes to platinum group metals, they can and will kill you if you are doing sloppy experimenting !!!!
Thread '• Refining Palladium concentrates.' • Refining Palladium concentrates.
Thread 'Seperating Ag as AgCl from Pd(NO3)2 in a nitrate solution' Seperating Ag as AgCl from Pd(NO3)2 in a nitrate solution
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Golddigger76
Well-known member
Also Lazersteve has some excellent posts covering the testing for Rhodium and other PGM's, you can search the forum for his post
Hey guys! I need a little advice on processing this blue rhodium salt. Should I process it just like the yellow salt or is there a special way I need to do it? I can’t find any info on processing it. Hardly any info on it at all accept how to make it.
Dissolve in water.
Add formic acid and ammonium chloride to turn into a metal.
Then melt.
Would that be the process?
Dissolve in water.
Add formic acid and ammonium chloride to turn into a metal.
Then melt.
Would that be the process?
Why do you think it is Rhodium?
Have you had it tested?
When I washed it with water the water turned green. I believe that’s as strong indicator that’s it’s rhodium. Do you know how to process blue Rhodium salts?
That hardy makes out as a test.
I have not even heard of blue Rhodium salts.
What about laying out in detail where your salts come from and how it was processed?
Man I’ve been doing a lot more research and these PGMs are pretty hard to separate and , depending on the concentration they can all have the same color. When I test with stannous it comes out a dark brown. One solution is a dark green and the other is a bright yellow. The dark green solution doesn’t turn as brown with the stannous. I’m guessing it’s to dilute? Or is mixed still? I dropped off tones of yellow salts until they started turning red/yellow then stopped in the green bucket. I haven’t been resaturating the solution with ammonium chloride mabye that’s the cause for the , I’m guessing, palladium dropping out?
This is how the stannous is supposed to look like. Courtesy of LazerSteve
Brown is not one of them
Huh I thought Pd could be brown aswell?
