# Purifying Palladium Salt extracted with DMG



## kadriver (Aug 23, 2013)

Here is a short video I made showing the process I used to purify the impure palladium salt extracted with DMG from my silver nitrate electrolyte.

This is my first time doing this so I hope I got it right.

Any critique would be welcomed - I have not burned the product yet.

I'll make another video when I burn the Pd salt in a quartz dish.

kadriver

[youtube]http://www.youtube.com/watch?v=btvN9KIghHc[/youtube]


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## kadriver (Aug 23, 2013)

I goofed the title - misspelling the word "Purifying"

If one of the moderators could change the word "Purifting" to "Purifying" in the title on this post then it would be greatly appreciated!

Might help someone who is trying to use the search block.

kadriver


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## JHS (Aug 23, 2013)

Nice thanks


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## 9kuuby9 (Aug 23, 2013)

Thanks for sharing!

You're really mastering Pd refining


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## chemdom (Aug 23, 2013)

Very instructive. Thank you for sharing.


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## Lou (Aug 23, 2013)

Kevin,

Suggestion: just digest the DMG in aqua regia, dilute, filter off any AgCl that might have been entrained in the filter, then treat as per normal.

Best,


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## jimdoc (Aug 23, 2013)

kadriver said:


> I goofed the title - misspelling the word "Purifying"
> 
> If one of the moderators could change the word "Purifting" to "Purifying" in the title on this post then it would be greatly appreciated!
> 
> ...



I think you can edit the title yourself. Give it a try.

Jim


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## Lou (Aug 23, 2013)

I got it for him 


Also, Kevin...Pd is one of those metals that it is inadvisable to calcine, especially in quartz. It forms palladium silicides which embrittle the metal.


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## 9kuuby9 (Aug 23, 2013)

Lou said:


> I got it for him
> 
> 
> Also, Kevin...Pd is one of those metals that it is inadvisable to calcine, especially in quartz. It forms palladium silicides which embrittle the metal.



From the Chart I can tell that Pd2Si only forms in a hydrogen environment with a temperature of 1100°C and Calcination takes place at around 550°C.

I still might be wrong since I do not have as much knowledge in platinum refining as you do; And If I even read the Chart Correctly.

Thanks for the Chart it really does have some valuable information in it; I guess the catalytic properties of platinum metals makes is much more harder to refine :mrgreen:


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## Lou (Aug 23, 2013)

It happens as low as 550*C in quartz under H2.

In vacuo, it occurs over 1000C.


Cheers,


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## 9kuuby9 (Aug 23, 2013)

Lou said:


> It happens as low as 550*C in quartz under H2.
> 
> In vacuo, it occurs over 1000C.
> 
> ...



That explains it all :mrgreen:


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## solar_plasma (Aug 23, 2013)

@Lou



> Suggestion: just digest the DMG in aqua regia, dilute, filter off any AgCl that might have been entrained in the filter, then treat as per normal.



First time I read this: Digest the yellow palladium-DMG in AR? How is that done, does it take heat and much time or will it easily digest? And then treat as if you had dissolved palladium directly in AR?


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## kadriver (Aug 25, 2013)

Lou said:


> Kevin,
> 
> Suggestion: just digest the DMG in aqua regia, dilute, filter off any AgCl that might have been entrained in the filter, then treat as per normal.
> 
> Best,



Lou,

I was wondering about this because the appearance of the yellow precipitate, once it dried, did not look very clean.

As I was doing the experiment I mused that even after rinsing the DMG Pd salt with plenty of distilled water that some silver would still be in the Pd salt.

I didn't know if the ammonia dissolutions would remove the silver or not - judging by the appearance, I would guess that there is some silver chloride in with the Pd.

Thanks for the tip, I'll dissolve the impure yellow Pd salt in AR, then filter out the silver chloride.

I would guess that it would be a matter of course to treat any Pd recovered with DMG with AR and filter to ensure purity.

kadriver


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## kadriver (Aug 25, 2013)

solar_plasma said:


> @Lou
> 
> 
> 
> ...



solar_plasma,

I think the Pd salt that I recovered from the ammonia with HCl could be dissolved in nitric acid only.

By using AR instead of just nitric acid, it will ensure that any silver will precipitate out as silver chloride.

Then the silver chloride can be removed by filtering the resulting solution over and over through the same filter paper until the solution is crystal clear.

I have dissolved other Pd salts in AR. I put the Pd salt in a covered beaker then added concentrated HCl on low heat. Then added nitric acid in small doses until it all dissolved.

kadriver


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## solar_plasma (Aug 25, 2013)

> I think the Pd salt that I recovered from the ammonia with HCl could be dissolved in nitric acid only.
> 
> By using AR instead of just nitric acid, it will ensure that any silver will precipitate out as silver chloride.
> 
> ...



Yes, I got that, I just wondered about the Pd-DMG salt, since I thought DMG would precipitate Pd also from AR. But when you guys now tell, that Pd-DMG complex as well can be dissolved again in AR, it seems to depend on the acid concentration?


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## niteliteone (Aug 25, 2013)

solar_plasma said:


> Yes, I got that, I just wondered about the Pd-DMG salt, since I thought DMG would precipitate Pd also from AR. But when you guys now tell, that Pd-DMG complex as well can be dissolved again in AR, it seems to depend on the acid concentration?


Wouldn't this be similar to Re-disolving gold precipitated with SMB with a second treatment of AR ???

The way I see it the DMG that "pushed" palladium out of solution is still in that solution and not a part of the precipitated palladium recovered from that solution.
Similar to the gold we precipitate with SMB and the Silver we precipitate with copper.

I hope I got this correct. Brain good not function today.


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## FrugalRefiner (Aug 25, 2013)

niteliteone said:


> solar_plasma said:
> 
> 
> > Yes, I got that, I just wondered about the Pd-DMG salt, since I thought DMG would precipitate Pd also from AR. But when you guys now tell, that Pd-DMG complex as well can be dissolved again in AR, it seems to depend on the acid concentration?
> ...


It's a different reaction. When you precipitate gold with SMB, the gold is reduced by the SO2. Only electrons are exchanged between the gold and SO2. Metallic gold is the result. Silver cementation is a somewhat different reaction, but the result is the same with an exchange of electrons between the copper and silver, the result being metallic silver.

When you precipitate palladium with DMG, the DMG chemically combines with the palladium, so it is part of the precipitate. If you use HCl to precipitate your silver instead of cementing it with copper, you'll have a similar result as the Cl- ion combines with the Ag+ ion to for solid AgCl. In both cases the precipitant doesn't push the target cation out of solution, it combines with it.

Dave


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## niteliteone (Aug 25, 2013)

In laymen's terms then, Gold and silver are pushed out of solution and palladium "Bonds" with the DMG to come out of solution ???


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## FrugalRefiner (Aug 25, 2013)

You could say that.


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## Lou (Aug 25, 2013)

Reduction of gold with sulfite is just that, a reduction. Precipitation as the PdDMG complex occurs with no valence change.

I am not a big believer in the ammonia treatment of Pd-DMG. 

If you must recover via DMG, oxidize away the organic ligand with aqua regia. Then you can proceed as normal. Just trying to dissolve in ammonia is wasteful of reagent, plus, where does the DMG go from the complex. What makes you so certain that you'll get the diammine and not your DMG back?


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## niteliteone (Aug 26, 2013)

Lou or FrugalRefiner,
I am fascinated by and interested in learning more about the actual actions and\or reactions of the processes we use here on the forum.
Would you by chance know the name and author of a good beginners Chemistry book or web site where a person can learn enough basic chemistry so these processes will be understandable ???

A lot of the terms used here on the forum are confusing to me since I do not have a chemistry back-ground.


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## FrugalRefiner (Aug 26, 2013)

nitelite,

I don't have any specific recommendations and I don't have anything on my hard drive. I googled beginner chemistry and it looked like you might find something there. Hopefully, some of the other members will have some suggestions.

Dave


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## kadriver (Aug 26, 2013)

Here is a website that is free - the chemistry course is geared towards a beginner with zero knowledge of chemistry. I need to get busy and start this myself:

http://www.ck12.org/student/

kadriver


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## niteliteone (Aug 26, 2013)

Thanks FrugalRefiner and Kadriver. Now I have something to read while taking a break from C.W. Ammen's "Recovery and Refining of Precious Metals 2nd edition" I bought last week.

I appreciate this much
Tom C.


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## freechemist (Aug 28, 2013)

Lou writes:


> Pd is one of those metals that it is inadvisable to calcine, especially in quartz. It forms palladium silicides which embrittle the metal.


Where I worked, we analyzed Pd-concentrations of various PM-solutions in HCl quite often by gravimetric determination of their Pd-content, especially in order to validate/calibrate the usually ongoing ICP-measurements. This was done by first precipitating Pd with H2DMG as [Pd(HDMG)2], and then calcining the washed and dried precipitate to pure Pd-metal in an unglazed porcelain crucible. We never observed false Pd-results, caused by uptake of silicium from the crucibles.

In a following post (August 25th, 2013) Lou writes:


> I am not a big believer in the ammonia treatment of Pd-DMG.
> If you must recover via DMG, oxidize away the organic ligand with aqua regia. Then you can proceed as normal. Just trying to dissolve in ammonia is wasteful of reagent, plus, where does the DMG go from the complex. What makes you so certain that you'll get the diammine and not your DMG back?


Like Lou, I don't believe in the ammonia treatment of [Pd(HDMG)2]. Sure, some of the bright yellow precipitate may dissolve in a big excess of aqueous 10% ammonia, and boiling away the ammonia, together with water, from the solution-phase, lets re-precipitate dissolved [Pd(HDMG)2].

Dimethylglyoxime, which I prefer to abbreviate as H2DMG, contains two acidic protons, and thus can form a mono-anion, HDMG- and a dianion, DMG2-. It is an only weakly acidic organic compound, and therefor practically insoluble in water, but it can be dissolved in aqueous alkaline solutions, e.g. aqueous NaOH, and, may be, to some extent in concentrated aqueous ammonia.

H2DMG <==> HDMG- + H+ and	HDMG- <==> DMG2- + H+ or
H2DMG + OH- <==> HDMG- + H2O	and HDMG- + OH- <==> DMG2- + H2O

The actual active reagent, precipitating Pd, is the mono-anion, HDMG-, forming the very stable, uncharged complex "inner salt" [Pd(HDMG)2], insoluble in water, like an organic molecule.

In recovering Pd via [Pd(HDMG)2], I always preferred calcination to the metal, followed by dissolution in HCl/H2O2; HCl/NaClO3; HBr/H2O2, avoiding the use of AR, where ever possible, because of some very nasty boil-over-experiences on dissolving finely divided Pd-metal in HCl/HNO3.

After my experience, it is neither necessary, nor useful, to oxidize away the organic ligand with aqua regia, and chances are, that a mess results. E.g. Pd stays dissolved, but you don't know, in what form, in which oxidation-state (II, IV?). In addition some quite nasty, small organic molecules may be formed on breaking down H2DMG in aqua regia.


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