# Dissolving & Precipitating Pallidium From Nitric Acid



## Tomac1 (Oct 26, 2011)

Hey guys,

I was going over hokes book again, hoke says that pallidium is the only platinum group metal that will go into solution when refluxed in nitric acid alone. I also observed that it seems as some metals do not like to drop when nitric acid is present, like gold for example. 

I have an object that is basically pure pallidium and platinum(no base metals to worrky about), I'd like to use nitric acid alone to dissolve & precipitate the pallidium first, so that but I don't what chemical to use to precipitate from nitric acid (sodium chlorate like with AR?), or even if precipitation of pd from nitric alone is possible, or is possible in this case. 

My idea is that because AR looses its potency relativly quikly over time, I'm trying to push back the introduction of the HCL into the process for as long as possible. 

After I dissolve pallidium in the nitric will I be forced to add HCL to the solution of nirtic and pallidium to create a AR solution anyway before I can precipitate it? 
I'm figuring even if this is the case, it will still save me some time, because the AR solution wont be concerned with dissolving the pallidium, because the nitric alone will have taken care of that. 

One problem I see it that if I allow the nitric to dissolve the palladium, weather or not im able to precipitate and filter off the palladium directly from the nitric, when I got to add HCL as to extract the platinum will the nitric be somewhat spent so that I dont save much time anyway.

I'm sorry it this is poorly written and confusing I can't think of a more direct way to ask... I think this is gonna be one of those things I'm just gonna have to experiment with.

Best Regards


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## eeTHr (Oct 26, 2011)

Tomac---

What is the percentage of palladium in this object?


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## Tomac1 (Oct 26, 2011)

I have one that is 20%, and one that is 40%.


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## Tomac1 (Oct 26, 2011)

Keep in mind that I am not worried any base metals,they are not present, so the problem that hoke had in his book does not apply.


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## qst42know (Oct 26, 2011)

Tomac1 said:


> I have one that is 20%, and one that is 40%.



I don't have your answer but I think knowing what other non base metal this is alloyed with would be important even vital to success.


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## butcher (Oct 26, 2011)

Is the palladium a plating on the outside of the metal, or an alloy with the platinum, if these were an alloy your nitric may have a hard time getting the palladium out of the mixture of metals, how much base metals would also be a factor,you might need to add silver to help. just a thought I really do not know what your working with.


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## niteliteone (Oct 26, 2011)

He's not working with anything but an imagination. :shock: He is trying to learn all the "ins and outs" without any real world material. :shock: 

This is a hypothetical question dealing with a metal he has a desire to start refining. 8) 

No disrespect intended just wanted to let responders know whats going on so they can respond accordingly to hypotheticals.
Tom C.


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## eeTHr (Oct 27, 2011)

I may be mistaken, but I seem to remember someone posting about inquarting platinum. Only it was much more than a quarter of platinum which was required. I think it was one-tenth, if I remember correctly. So if you had the 20% platinum piece, you would take the remaining platinum weight times ten, of added silver, I guess.]

Does anyone recall that thread?


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## philddreamer (Oct 27, 2011)

I think TomC might be right. After reading other posts by Tomac1, I side with TomC.
I was following his thread: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=11822

Maybe he's trying to find fluxes for smelting the crushed cat ceramics? :roll: 

Hummm...


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## Tomac1 (Oct 27, 2011)

Yes, you guessed right, caught me red handed, I don't like to mention cats because people on the web as people have a tendency to get sketchy when the subject comes up. 

So my real question is, what can someone suggest a flux formula to try when smelting crushed ceramic from a 60%pt,20%pd,20%rh honeycomb style autocatalyst?

Here is my idea, and it might be a stupid one, you tell me. One man named Graham on finishing.com claimed to have pulled off something similar to this. 

Crush up the ceramic honeycomb, smelt with suitable flux in order to effect a separation of the ceramic and PGMs, that is PGMs in a conglomerate at the bottom and ceramic on top, let cool then break the ceramic and PGM conglomerate apart probably with a hammer, dissolve PGM conglomerate in AR, use usual methods as described by Hokes book from there. 

PS: I do this stuff just for the recreational aspect, not in it for the money, don't care if its profitable or not : )


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## Tomac1 (Oct 27, 2011)

15% Kryolite
35% Borax (anhydrous)
25% sodium nitrate
12 1/2% soda ash
12 1/2% slaked lime


I was thinking about the above flux formula for this experiment, I've been snooping around and it seems like this formula might not do enough to make the melt wetter, aka to minimize the bead hang up, how can it be improved to lower the overall viscosity of the melt.

Regards


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## qst42know (Oct 27, 2011)

Do a search using the spelling "cryolite". 

You will find some information on melting ceramics.


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## 4metals (Oct 27, 2011)

The flux you listed will be liquid enough if used in the proper proportions to the ground ceramics. My concern is that with the typical low quantities of PGM in cats, you will have to use a metallic collector.

If I were doing this as a hobby, that collector would be silver, for a business venture I would choose copper.


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## philddreamer (Oct 27, 2011)

What would be the ratio of silver needed?


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## Tomac1 (Oct 27, 2011)

Hey,

In response to 4metals, what ration of silver should be used, also what ratio of copper?


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## samuel-a (Oct 27, 2011)

Tomac1 said:


> 15% Kryolite
> 35% Borax (anhydrous)
> 25% sodium nitrate
> 12 1/2% soda ash
> ...




http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=46&t=10931&p=115002&hilit=+collector#p115270


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## Lou (Oct 27, 2011)

It would be wise to keep the sodium nitrate out of the mixture as it can oxidize the Pd. You will need the fluorspar and cryolite to ensure fluidity. Nickel would be a good collector. Nickel-PGM alloys are great in aqua regia. 80% Pt bal nickel dissolves 5-10X faster than Pt alone in AR.


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## philddreamer (Oct 27, 2011)

Thanks Lou!


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## 4metals (Oct 27, 2011)

I have found that powders with at least 10% by weight of total metals react favourably to the flux above. Wether that metal is gold, or copper or silver , or nickel for that matter, it will collect more effectively and pool the PM's in the melt. 

While it is totally intuitave that the Pd will report to the slag with the sodium nitrates oxidiziing power, I have used this blend on dental scrap running high in Pd and never have seen the Pd in the slags (which I always assay).

The reason I like silver for a collector when doing this as a hobby is because you can separate all of the metals in the slimes of a silver cell. And there is plenty of support for that process here on the forum.


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## Harold_V (Oct 28, 2011)

eeTHr said:


> I may be mistaken, but I seem to remember someone posting about inquarting platinum. Only it was much more than a quarter of platinum which was required. I think it was one-tenth, if I remember correctly. So if you had the 20% platinum piece, you would take the remaining platinum weight times ten, of added silver, I guess.


You are well served to avoid mixing silver and platinum. Once alloyed, both will dissolve in nitric. (If the resulting metal is targeted for the silver cell, not directly parting by nitric, that is not true. The platinum will report in the slimes, as 4metals suggested.) 

Harold


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## samuel-a (Oct 28, 2011)

If not intended for the cell, the next best thing would probably be to collect Pt/Pd/Rh with Lead and part it in boiling nitric to remove Pb+Pd.

All that remeains is the Pt/Rh powder.
Pretty good method for Pt/Ir and Pt/Ru jewellry alloys separation to...


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## eeTHr (Oct 28, 2011)

Thanks, Harold. I guess the guy was doing something other than platinum. Or using something other than silver? Do you recall that thread? It seems he was suggesting a process, and had done some experiments with various percentages.

Since I wasn't planning on using it, my memory of it is vague---so I don't know if it would help with cats or not. (?)


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