# So here's my idea for a Pt Rh based black powder



## tel (Oct 22, 2014)

So I have approximately 200g of black powder, which the bottle says is Pt Rh based. I've done an NF leach on a small sample and scanned it, finding fairly low levels of a handful of non-precious metals, totaling to about 3% by wt. At any rate, I'm sure this doesn't necessarily mean that its 97% precious metals, but what I plan on doing is leaching the powder in aqua regia on a hot plate for a few days to take care of the Pt and any potential Pd, Au, etc., then filtering, rinsing, drying, and leaching in hot concentrated sulfuric for a few days to take care of the Rh. What I do after this depends on what remains of the powder I suppose, but as for both the remaining solutions, my plan was to scan them both to see what they contain, and then to precipitate the Pt with ammonium chloride, worrying about any remaining PGM's if they exist, and adding ammonium hydroxide to the sulfuric solution until the Rh drops. This may all be the straightforward stuff, but I'm new to all this and welcome any and all input on the subject. I may or may not update this as I go, depending on if anyone seems interested or not.


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## patnor1011 (Oct 22, 2014)

Why do you want to waste time and resources doing something you never did. If that is for the sake of learning and you have steady supply of such material coming in then go ahead. If not, why don't you just sell it?


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## tel (Oct 22, 2014)

Apologies, I never did mention my intention with the final product. I can get more of this material intermittently, so I was looking to stockpile up on some of these extracted materials and make a ring out of mixed precious metals and propose to my long-time girlfriend with it. Of course I could just sell the material and buy one, but I thought it would be much more thoughtful if it was custom made. As for how I would make it, I'll cross that bridge when I get to it (perhaps paying a jeweler?), as my biggest obstacle is melting down the metals with the higher melting points. I have access to induction melting, but I'm not sure it's powerful enough.


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## Platdigger (Oct 22, 2014)

Just curious what this powder may be from? Someone leaching cats? If it were from pt/rh thermocouple wires there wouldn't (or shouldn't) be any base metals.
Or it could be just someone pulling your leg. 
Interesting.


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## nickvc (Oct 22, 2014)

I suspect cat material as they do contain both Rh and Pt but in low percentages. As to using the recovered and or refined metals I doubt that will work.


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## tel (Oct 22, 2014)

I'm not sure where the material itself comes from, but the description on the label states "Pt leach material".


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## tel (Oct 25, 2014)

Just an update, but I've gone and leached this powder in hot NF to remove base metals (hopefully), which I then filtered and rinsed, then leached in hot aqua regia for a day. I filtered the remaining solution and boiled down and denoxxed the filtrate, then drew out the Pt salt. After this, I filtered it again to retrieve the salt, which I then calcined into sponge - pretty much routine stuff, if my reading on here is accurate. At any rate, I ended up with 6g of Pt sponge, which I melted into an ingot. I have the remaining powder leaching in hot sulfuric right now, which I'll check out tomorrow and update when I see if any Rh is actually present. Any and all filtrates have been kept, which I intend to check for other PGM's at some point. Once again though, any and all suggestions and advice is welcomed.


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## Harold_V (Oct 26, 2014)

tel said:


> I filtered the remaining solution and boiled down


You just pushed one of my buttons.  DO NOT MAKE REFERENCE TO EVAPORATING BY SAYING BOIL! * That sends the wrong message to our readers, perpetuating an undesirable method of evaporating. * If you mean evaporate, SAY evaporate. If you boiled, perhaps you should review your procedures. Boiling solutions for the purpose of evaporation leads to losses. 

Harold


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## tel (Oct 26, 2014)

Then it would appear that I need to review my procedures, as I did actually boil this down. Makes sense to simply heat to evaporation, but I've read equal amounts of conflicting information on this regarding boil vs evaporation myself. I'll keep that in mind though, as it was not my intention to mislead anyone - there's simply an infinite amount of information on the subject, and you know the risks of reading how to do something on the internet...


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## Harold_V (Oct 27, 2014)

tel said:


> Then it would appear that I need to review my procedures, as I did actually boil this down. Makes sense to simply heat to evaporation, but I've read equal amounts of conflicting information on this regarding boil vs evaporation myself. I'll keep that in mind though, as it was not my intention to mislead anyone - there's simply an infinite amount of information on the subject, and you know the risks of reading how to do something on the internet...


This lesson came to me the hard way. I evaporated a gold solution too fast, a low boil at worst. This was many years ago, early 70's (early in my learning curve), when I worked from my garage with a fan in the window (no fume hood at this point). Outside the window stood my travel trailer. A few days after evaporating I noticed a large round pattern of purple on the trailer. Purple that was removed by rubbing compound, as it had stained the finish. The lesson learned was taken to heart. My hoods all had a filtration system for recovering values, which paid off handsomely. 

There's not a doubt in my mind that you lost values. How much is the only question. 

There are those who do boil to evaporate, but they have controlled conditions and can reclaim anything that is lost. It's faster, but not a wise choice for the guy working with rudimentary equipment. 

Harold


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## tel (Oct 27, 2014)

Yeah, I use a hotplate that I refurbished myself (well, sort of...). It broke at work so I asked if I could keep it and they had no problems with it, so I did some work on it at home, but now it only operates at max temperature (450°C). After reading this, I'm sure I lost a lot, and it sounds like that hotplate isn't a good idea for this application.


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## tel (Nov 15, 2014)

So this project went untouched for a while, but I just filtered out the remaining powder and rinsed rinsed it clean. So about half of this stuff won't dissolve in either nitro-fluoric acid, aqua regia or sulfuric acid - quite puzzling. At any rate, I took the sulfuric leach solution and added ammonium hydroxide until it was neutralized (in the hopes of dropping Rh out). A brownish salt started to precipitate, so I thought this must be the Rh, however, upon calcining and dissolving a small sample to scan, I discovered that there was in fact no Rh in this, but instead Pd, and more Pt.

As for the remaining powder that doesn't seem to be dissolving, I'm clueless as to what it could be. It doesn't seem to be organic material, as 800C doesn't seem to do anything to it, but I have quite a bit of it left, so I'll hold on to it until I figure out something I suppose. Maybe just let it leach in aqua regia and set aside for a good long time?


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## Harold_V (Nov 16, 2014)

Have you considered that the undissolved black powder may be rhodium?

Harold


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## tel (Nov 17, 2014)

Perhaps it could be. I'm actually heating 0.1g of this powder in aqua regia and seeing what it does over a few days. From what I understand, Rh is pretty chemically resistant stuff, so it could very well be, but not even high pressure u-wave digestion works. Rh can't be THAT resistant, can it?


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## Lou (Nov 17, 2014)

It'll go in the microwave after a few hours in a FEP pressure vessel. Better results with HBr/Br2 under pressure. That'll get it fairly quickly.

Alternatively, it can be put into molten cyanide (more reactive than Ir)and then put into oxidative pressure leaching to eat away the CN. Hardly pleasant.
Or you can fuse it with NaCl/Cl2; alkali bisulfate, etc.

Heck, so corrosion resistant are Rh and Ir that sometimes its best just to melt with another metal like one is doing an inquart, and get them into a fine surface area and leach out everything but the Ir or Rh. Using pressure and different acids, one can obtain fairly high quality Rh or Ir; at least good enough to go for zone refining or ebeam purification, after sintering of course.

FYI, all that the N/F leach did was remove silica, alumina, and refractory metals. Fluoride is pointless on PGMs...fluorine on the other hand...more useful.


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## tel (Nov 17, 2014)

Yeah that was my intention with the NF leach - to strip any base metals prior to working with the Pt and Rh. I was just noting that this stuff even made it through that step, something that makes sense if this remaining powder is in fact Rh. As for the steps which you just went over, I must admit I have zero experience with them, so I'll look into those a little more closely. Luckily, out of the material I can get intermittently, this is the lowest yield stuff, and also the only stuff I cannot dissolve yet. The rest of it is rather straightforward (Ni-Pt, Ni-Ti-Pt mixes, etc.) and has anywhere from 20-70% Pt in them. Of course, I say lowest yield before being able to dissolve it fully yet. I suppose that could all change.


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## Lou (Nov 17, 2014)

Or you could always just sell them....to me


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## tel (Nov 17, 2014)

Heh, perhaps for these powders I'll consider just that. This isn't a monetary motivation (at least as of right now), so when things get impractical I almost want to let them get thrown out like they used to be before I started grabbing them. At least this way someone will get something out of them...

Anyway, I'll have some more powder in a few weeks. Perhaps I'll message you if I don't feel like tackling it.


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## nickvc (Nov 17, 2014)

tel said:


> Heh, perhaps for these powders I'll consider just that. This isn't a monetary motivation (at least as of right now), so when things get impractical I almost want to let them get thrown out like they used to be before I started grabbing them. At least this way someone will get something out of them...
> 
> Anyway, I'll have some more powder in a few weeks. Perhaps I'll message you if I don't feel like tackling it.




Take my advice for what it's worth just sell it to Lou.


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