PG metals and DMG...

Gold Refining Forum

Help Support Gold Refining Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

samuel-a

Well-known member
Joined
Oct 7, 2009
Messages
2,190
Beside Pd, will any other PG metal form an insoluble complex in acidic conditions?
 
Nickel is know to form complex with DMG - "Brunuck-Chugayev" procedure for gravimetric analysis of Nickel. Of course in weak acids(acetic acid and formic) and ammonia. It is forming pink-red voluminous precipitate. Since youre are dealing with mlcc ,for example when you want to precipitate Pd from mlcc with DMG , if you are not careful you might get co-precipitation of Ni. normally Pd-DMG complex is yellow if other color is present then you got some Ni-DMG in it(for mlcc)...
fortunately Ni isn't Precious ;-D
 
Hi Kats12

I'm aware of Ni DMG complex could not exist in highly acidic solution.

At the moment, i'm not working with MLCC's and have no concern with Ni.

At first, DMG dropped the Pd as usual (orange juice pulp - look alike), soon, the precipitation turned very dark brown.

At this point i filtered the Pd-DMG and added again DMG to the filtered solution, this time only a dark brown/dull red precipitate formed, this time it setteled very quickly (similar to AgCl does), pH at 0-1, SnCl show definite black (with no other colors).

I'm really struggling here....
 
Lou said:
Dissolve the ppt in ammonia and filter?

How would you expect it to help in this current situation?

The reason i ask' is that some weeks ego, my small chemical fridge passed away, so i couldn't store my ammonia and the weather here is very hot.
I can make a fresh batch of 3-4N ammonia solution, but i'm thinking, maybe just better go ahead burning the Pd(DMG)2 (and the darker stuff) at 600-650C and further study a sample of sponge...

Penny for your thought...

Thanks.
 
I have an article that mentions DMG and another reagent being used together for detection Rh and other metals.
I'll look up details and post them here.

Steve
 
lazersteve said:
I have an article that mentions DMG and another reagent being used together for detection Rh and other metals.
I'll look up details and post them here.

Steve

Sounds interesting Steve.

I snapped a photo of the dry dark ??(DMG) complex:
dmg.JPG

In the meanwhile, i burned it to remove carbon and melted 0.5g test... it had all the characteristics of Pd.
The rest is back in AR to see if all dissolve or not.
 
Hello Sam,

To me the dark precipitate on your foto from September 7th looks like finely divided [Pt(HDMG)2], formed by slow reaction of dissolved Pt(II) with dimethylglyoxime. A method used at my active refining times to determine Pd and Pt quantitatively after inquartation, was to dissolve the Pd and Pt- containing Ag-buttons in ca. 32% HNO3 and to measure their Pd/Pt-contents by ICP after appropriate dilution. An alternative way was, to determine Pd gravimetrically by precipitation with dimethylglyoxime. This method is rather unsure because dissolved platinum reacts with H2DMG too, forming slowly insoluble [Pt(HDMG)2], which adds to the [Pd(HDMG)2]-precipitate, thus falsifying the result for Pd. Pure [Pt(HDMG)2] forms fine, dark chocolate-brown, nearly black needles with a violet, metallic glister. All three
precipitates, [M(HDMG)2], where M = Ni, Pd, Pt, are isomourphous, i.e. they have the same cristalline structure.

Regards, freechemist
 
Very interesting freechemist.

That's sound reasonable to me, thank you.

The only reservation i have from your description is that the dark ppt, formed instantly right after the orange DMG complex, but who knows... right?

Anyhow,few weeks back, i incorporated the DMG step to all of my solutions after inquartation and before the waste bucket.
I add few drops of DMG solution to each solution, both, nitric + Ag and AR without the gold.

The Pd/Pt really accumulate this way....
 
Lou said:


I should correct myself to say that maybe some platinum complex is formed if the platinum is high in concentration, the solution warm, and it is Pt(II).
It is not typically the case, however.
 
If an alcoholic solution of dimethylglyoxime is used to precipitate palladium, there is ample reductant to reduce Pt(IV) to Pt(II), if not to the metal.

Regards, freechemist
 
Is it safe to say that ALL the Pd will be scavenged as the DMG-Pd compound, but will be somewhat contaminated with platinum ?. :?:

Something similar happens in Au-Pd chloride solutions, i.e.: The DMG forms a compound with gold too if gold is highly concentrated, but all the Pd comes down first, or that's my experience. :oops:
 
Rhodium also has DMG complex. When it is present in solution with palladium the complex will look much less yellow, white-grey hue. Anyone can confirm?
 
Lou said:
Lou said:


I should correct myself to say that maybe some platinum complex is formed if the platinum is high in concentration, the solution warm, and it is Pt(II).
It is not typically the case, however.
I dissolve my pgms in hcl/h2o2 how could I get pt IV rather than pt II, I had the same problem
With dmg
 
I also struggled to selectively ppt Pd with DMG. even in very acidic conditions. stock soln contained Pd/Pt/Rh, and I was aiming to scavenge P for Pt/Rh separation tests and XRF shown that Rh gone with Pd to the ppt.
Rh wasnt detectable in any further step of processing even that it was clearly shown in the stock soln. (0,6%)
and also nearly half of platinum gone as well. i used DMG somewhat suspended in DMSO (aim to try this approach and failed miserably :D ).
i have encountered Pt(II) few times in my short refinig career :) mainly the difficulty to precipitate it with zinc in presence of copper and iron also in solution. processing large batches of old PtPd MLCCs i observed that Pd is immediately dropped by zinc dust when added, but somehow the majority of the Pt in solution wasnt in +4 ox state (no drop of salt with NH4Cl) - perhaps, this idk for sure. Because i added like twofold excess of zinc than usual and still no precipitation and XRF together with SnCl2 shown clearly Pt positive solution. prolonged stirring w zinc dust finally almost completely neutralized the HCl :D not to mention the shit ton of Fe and Cu powders... and then it finally left the solution. addind shitton of HCl to get some of the base metals sludge back to the liquor... :D because of this i clearly remember that strange Pt behavior :)
 
Being below hydrogen in the reactivity series of metals, a metal like zinc can displace the hydrogen from the acidic solution basically in a manner neutralizing the acid forming salts ...
 
Back
Top