# Refining large amount of silver



## Anonymous (Jan 20, 2008)

I have recently bought 5 pounds of metal rings, they are used to solder brass and contain 55% silver. I would like to refine the silver and make some bullions.
I have done alot of research on this, and I know how to refine the silver with nitric acid. My question is, is it possible to dissolve the silver in anything else than nitric acid - it is quite hard to find in Denmark? I know that I can make it myself with sulfuric acid, but are there other ways?
I would like to refine it as "fast" as possible, how large amounts can be refined in one batch?
And how much nitric acid is used pr. gram of metal?

Thank you!


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## lazersteve (Jan 20, 2008)

Christiann,

Silver will dissolve in sulfuric acid.

It takes about 3.6 mL of 70% nitric to dissolve 1 gram of base metal (depending on the metal). Part of this is lost as NOx fumes. In a typical application the nitric is diluted with an equal volume of distilled water when working with silver.

Welcome to the forum.

Steve


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## Anonymous (Jan 20, 2008)

Thanks Steve.
But nitric acid is the only way to do this?
I have 2200 grams of metal * 3,6 ml/g = 7920 ml nitric acid.
In Denmark it is only possible to buy nitric acid in 500 ml bottles, so I need 16 bottles. I would become a terror suspect if I ordered this amount :?


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## lazersteve (Jan 20, 2008)

Christiann,

As I mentioned, sulfuric will also dissolve silver.

One mole of sulfate ions will hold two moles of silver ions, unfortunately silver sulfate is not very water soluble (1.2 g /100 mL @ 60C) so the volume of the solution would be much greater.

You may want to look at dissolving the brass and leaving the silver untouched. Muriatic acid will attack zinc and also copper (slowly).

Maybe some of the other guys will have some more ideas for you.

Steve


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## Anonymous (Jan 20, 2008)

That sounds like a brilliant idea!
Muriatic acid is easier to find and also cheaper.
The rings contain copper, zink and tin (is it called that in english?, Sn atomic number 50). Does anyone know if muriatic acid will dissolve this?
Of cause I can just try it. When I'm done I can dissolve a bit of the "silver" in nitric acid and add NH3 to test for copper, I'm quite certain that zink will be dissolved, but how do i test for tin?


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## lazersteve (Jan 20, 2008)

Tin will dissolve in HCl.

Steve


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## Anonymous (Jan 20, 2008)

Well, that must be the answer then..
Why dissolve and cement 55% silver with hard-to-get nitric acid, when I can just wash away the 45% scrap with muriatic acid.

I will try this tomorrow and give some feedback.
Thanks again!


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## goldsilverpro (Jan 20, 2008)

IMHO, I doubt that muriatic will leach out the copper/zinc, since the silver runs 55%. Nitric is the only way that I can think of that would work.


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## lazersteve (Jan 20, 2008)

GSP,

If the silver content is too high to prevent the dissolution he could always 'inquart' the silver to a lower percentage (25%) with another HCl soluble base metal like zinc. 

Do you think that may work?

Steve


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## goldsilverpro (Jan 21, 2008)

The "inquartation" might work if no silver chloride is formed with the HCl. I know there's no oxidizer there, but the AgCl may form anyway. If you're torch melting, you may have big problems inquarting, due to the formation of copper oxide. I don't like to melt zinc because of the formation of dangerous zinc "cobwebs", that float around in the air. Also, 5# is a lot of material to torch melt. I would experiment with very small amounts. 

Nitric would sure be easier.


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## Irons (Jan 21, 2008)

Cover the Silver alloy with dilute H2SO4 and add a small amount of Sodium Nitrate. When the reaction slows down add a bit more, repeat until dissolved.


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## Anonymous (Jan 21, 2008)

Irons, 
how do you recover the silver from the sulfate? or does it make nitrate since you added the NaNO3?
I was wondering because I was considering doing some contacts that I have this way.

Thanks, 

Jim


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## Irons (Jan 22, 2008)

james122964 said:


> Irons,
> how do you recover the silver from the sulfate? or does it make nitrate since you added the NaNO3?
> I was wondering because I was considering doing some contacts that I have this way.
> 
> ...


It will be a mixture of Sulfates and Nitrates.
Precipitate it out with Copper, then Aluminum to precipitate the Copper after recovering the Silver.

My choice would be to use an electrochemical cell to save on chemicals, but that's more complex.

One summer, some friends and I processed 500 lbs of Silver solder scrap this way.


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## peter i (Jan 22, 2008)

Irons said:


> It will be a mixture of Sulfates and Nitrates.
> Precipitate it out with Copper, then Aluminum to precipitate the Copper after recovering the Silver.
> 
> My choice would be to use an electrochemical cell to save on chemicals, but that's more complex.
> ...



The solubility of silver sulphate is rather low (~2 grams/ litre) and I would expect it to be even lower in sulphuric acid. 
Does it dissolve completely, or do you collect the precipitate, and reduce that, to recover the silver?


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## Irons (Jan 22, 2008)

The key is to use as little chemicals as possible. There will be Copper Sulfate and Nitrate crystals as well. Just dissolve as much as you can in hot water after it is all dissolved an precipitate it with Copper.

This is a quick and dirty way to do it.

The best choice to me, if all you want is cash, to sell it as Silver scrap. Buying the chemicals and your labor is more than what you save from selling it as scrap.

Even if it's pure, the refinery is only going to pay you scrap price anyway.


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