Quandry with Gold powder

[Lightspeed]

I have started a small experiment with what was supposed to be Gold powder. The makeup of which was supposed to be Copper, Zinc, Gold, Silver and Iron as tested by a Gold and Silver dealer friend of mine. I did not witness the test, the result was relayed to me along with the parcel.

My original plan due to the powder makeup was to initially dissolve the unwanted metals in a Nitric/DW 50/50 digestion to put the unwanted metals into solution, before progressing to AR and precip.

The powder was placed into a 5L beaker which was thoroughly rinsed before use, there may have been approximately 10 grams of powder, after rinsing the packaging and washing down the beaker sides I had around 600ml of DW with a lot of the powder floating due to is fineness and surface tension.
I started with 100ml of 68% nitric addition with very little reaction so added another 80ml with a similar result. I stirred the solution then the reaction started as expected with some fuming and the dilution changing to a clear blue colour as I expected. I left the Digestion for less than 5 minutes on very low heat inside the pyroceram safety catchment. When I returned the whole lot had gone into solution.

So no Gold?? I thought gold did not dissolve in nitric, I would have expected the digestion to have gone well due to the lack of concentration of Nitric.

Is it possible the electronic test of the powder was inaccurate and the so called Gold was actually Brass shown by the Copper and Zinc??

Steps forward:
Test solution with stannous, but should be negative according to all I have read regarding Nitric and gold.

If positive and it should not be, where do I go from here to rid the excess of Nitric?

Do I use Sulfamic acid to neutralise, is there another option?

After neutralising solution should i precipitate silver and (gold if existing) with copper?

I am reluctant to go ahead from there and re dissolve in Nitric as if any Gold were present it simply should have stayed as a solid in the initial digestion.

The solution at this stage is clear light blue, with some fine small black bits floating within it. There is no white cloudiness to denote there is a chloride nor settling on the bottom of the beaker.

This is my first experiment in a Gold recovery and refine.

 

[nickvc]

If you added no chlorides and only weak nitric was used then there was no gold in the original material.
If this was tested with an xrf then chances are it was a false reading, ask your customer the source of this material and if there really was any likelihood of gold been present.

 

[4metals]

Refiners see lots of this material, usually from Africa. It appears to be either gold sponge or if melted a karat gold colored bar. In every case there was no gold or silver. I mean if you're going to pass off something as valuable why would you put anything precious in there? It was more prevalent in the pre XRF days, maybe now they have come up with a way to fool XRF too.

Likely someone came into your sources store with the intent to sell this stuff. When the XRF did not show as much gold as the seller expected it to show, it may have been left there awaiting a more "definitive test" when the seller brings in the mother load.

From your perspective, nitric tells the whole story. Add a few drops of HCl just to see if there is any silver in there, indicated by silver chloride, but don't count on it.

 

[Lightspeed]

Reported back to the owner of the parcel, apparently the source was from India, he has had it since 2000 when he travelled there. I had told the owner when he forwarded the parcel that India is well known for high carat gold, but also there was a high likelihood there was no Gold at all due to the composition.

The lack of silver also tested for confirms it was a dud from the very beginning made to dupe people simply from the similar look of powdered brass dust and gold dust.

Thanks for the replies 4metals and nickvc. Nice little experiment anyway and good experience, and I am glad it wasn't my money that bought the powder. I will try some Karat material I have in a small experiment in the near future in between running the silver cell.

Regards
L

 

[nickvc]

Karat gold is in my opinion a good place to start as you have a known quantity of gold to recover from the refining, you don’t have to second guess you got the processes correct but bear in mind you will have a small loss which will be recoverable at a later stage, I wish you luck and keep the forum posted on your progress.