# wrong process....



## alex303 (Sep 28, 2017)

Hello!

I tried to work with a "unknown" button, (Cu, Ag,Au,...), of 200 grams.
1) I used 750 ml of Nitric Acid to sissolve base metals
2) after filtering, I had a Blue solution of base metal and a red/violet mud (see the pictures)


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## alex303 (Sep 28, 2017)

3) i add some HCL to the red/violet mud (see the picture)
4) I added just some Nitric( drop by drop) to the solution to create AR
The becker on the left is before adding HNo3, the becker on the right is after adding HNo3.
After adding HNO3, the red mud became a white mud.
I did the stannous test and it was positive (gold was in solution)


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## alex303 (Sep 28, 2017)

5) i heated the solution and I added some sulfamic solution untill it stopped frizzing (see pictures)
Sulfamic solution (200 ml H20 + 40 g of sulfamic crystal)
6) I used an hot solution of SMB and water to precipitate the gold.

Now after 4 hours,the stannous test continues to be positive (gold is in solution) and if I add step by step the smb, it continues to frizzing a little bit and there is no precipitation.

the question are:
1) do I continue to add smb?
2) adding Smb, do I have to heat the solution?
3) Where are my mistakes?

Thank you!!!


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## Topher_osAUrus (Sep 28, 2017)

If the stannous result is more brown than purple it is a false positive

The white mud is most likely silver chloride. After nitric leach, a good few rinses is needed before HCl.

You can slowly heat snd evaporate the solution, it will remove the SO2 and any gold left in solution will end up on the bottom of the beaker


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## g_axelsson (Sep 28, 2017)

If there was any tin in the original metal it would convert to metastannic acid when dissolving base metals with nitric acid. It would end up in your mud.

I never saw filtering mentioned in your description, but I will assume that you did filter the solutions somewhere along the line. Did you find any silver in the blue base metal solution?

Adding SMB into acid creates SO2 so it only tells you that your solution is still acidic. The SO2 in solution will give a brown stain with stannous chloride, just as Topher pointed out.

What was the source of the metal? I know you wrote unknown composition, but you must have an idea where it came from at least to suspect silver and gold in it.

Göran


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## Topher_osAUrus (Sep 28, 2017)

g_axelsson said:


> If there was any tin in the original metal it would convert to metastannic acid when dissolving base metals with nitric acid. It would end up in your mud.
> 
> I never saw filtering mentioned in your description, but I will assume that you did filter the solutions somewhere along the line. Did you get any silver in the blue base metal solution?
> 
> ...



Excellent point Göran, I assumed his feedstock was gold and silver and completely overlooked the fact that tin sludge is a very real possibilty. -how shameful of me  

I was going to mention filtering too, but his last picture looked significantly clearer than the previous. Which, upon futher thought, may not have been filtered, but just put on the hot plate and all of the particles allowed to settle. -conjecture, but, a possibility when dealing with this particular unknown.

I guess its all guesses until he comes back and tells us whats what.


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## snoman701 (Sep 28, 2017)

But...the false positive is sometimes starts clear, then turns brown...but will turn clear again after the sulfur dioxide in solution evaporates off.

You used too much smb. That's ultimately the reason for the false positive.


Sent from my iPhone using Tapatalk


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## alex303 (Sep 30, 2017)

Thanks for you help!
I had precipitation on the night, just waiting and heating.
But in the center of becker there is white dust and on the contour there is brown powder(gold).
After filtration i had a grey mix.... how do i have to do now?


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## alex303 (Sep 30, 2017)

See the picture


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## alex303 (Sep 30, 2017)

See the white dust before filtering


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## alex303 (Sep 30, 2017)

I try to answer to all your questions.
1-The button becames from bourning 1,5 kg of pins.
2-after i used HNO3 i filtered the solution and I obtained the red/violet mud. The strange thing was:
- the mud was very fine and the color was red/violet
- i tried to precipitate from the nitric solution the silver with NaCl, but nothing precipitated, no silver was in the blu solution
- probably the silver was concentrated in the red / violet mud
3- i added Hcl to the red/violet mud and after i added drops of Hno3 to make AR. At this point i had the white dust and the yellow solution. I filtered many times but some white dust was in the yellow solution( not so much)
4- i used sulfamic to denox and to neutralize tin... probably after using sulfamic and before using Smb, do you think is it better to use some sulfuric (drops) to neutralize tin?
Any other question?
Thanks


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## FrugalRefiner (Sep 30, 2017)

alex303 said:


> 1-The button becames from bourning 1,5 kg of pins.


I'm going to assume you mean the button came from melting the pins. The pins have a very thin plating of gold. Pins are often copper based, though some can be other metals.



> 2-after i used HNO3 i filtered the solution and I obtained the red/violet mud. The strange thing was:
> - the mud was very fine and the color was red/violet
> - i tried to precipitate from the nitric solution the silver with NaCl, but nothing precipitated, no silver was in the blu solution
> - probably the silver was concentrated in the red / violet mud


The mud was very fine because the gold content was very low, so once the base metals were dissolved, the particles of gold that remained were very, very tiny. The red/violet color was probably because the gold was so finely divided. Colloidal gold can exhibit red and violet colors for this same reason, just as we see the purple color when testing for gold with stannous chloride. No silver precipitated because there was probably no silver present. The solution was blue because as mentioned above the pins were probably a copper alloy. There would be no practical reason for using silver in these pins.



> 3- i added Hcl to the red/violet mud and after i added drops of Hno3 to make AR. At this point i had the white dust and the yellow solution. I filtered many times but some white dust was in the yellow solution( not so much)
> 4- i used sulfamic to denox and to neutralize tin... probably after using sulfamic and before using Smb, do you think is it better to use some sulfuric (drops) to neutralize tin?


When I use sulfamic to deNOx, I filter after I use it. One of the byproducts of using it is a bit of sulfuric acid. If there is any lead in the solution, it will precipitate as insoluble lead sulfate. Neither sulfamic nor sulfuric acid will "neutralize" tin. Then filter till the solution is crystal clear. Keep pouring the solution through the same filter until it is clear. Some very fine precipitate can make it through fresh paper, but as the larger particles are trapped, they create smaller and smaller openings, so pouring the solution back through the same filter will catch smaller and smaller particles until even the smallest particles are trapped.

Dave


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## nickvc (Sep 30, 2017)

Depending on what exactly the alloys of the pins were or if they had any solder on them it's possible you have tin in the mix, if that's so then collect the powder put it into a filter and wash through with water, then you need to incinerate the powder, allow to cool, place in a beaker and add Hcl to remove the tin.


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## anachronism (Oct 8, 2017)

If it was me I would take that last beaker with the black/brown/gray concentrate, add 100ml of HCl. Then I'd warm it and add drops of Nitric until there's no more reaction.

Dilute it with 100ml of water and this time filter it mercilessly after de-noxing until you have a crystal clear solution before dropping it. Then your powder will be both cleaner and easier to work with. 

You don't seem to have any major problems or errors you are simply working with a low amount of gold from a large amount of base metal. It looks like you've effectively concentrated your pms from the large 200g bar into a smaller volume.


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