Fluxing gold sweeps

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I have about 500 grams of gold sweeps from Jewellery shop, market jewelries are only 18 karat and 21 karat,so am sure all gold content of the sweeps are 18 k and 21 k.

I remember I read about the process of gold sweeps recovery which is incineration, milling then use nitric acid to dissolve base metals plus silver and palladium if exist, then use AR to get gold.

My question is, how nitric acid will dissolve silver from the sweeps powder? I mean are incineration and milling will change the 18 k and 21 k nature to gold and silver powder that its easy to be parted by nitric acid?
 
Ayham Hafez said:
I have about 500 grams of gold sweeps from Jewellery shop, market jewelries are only 18 karat and 21 karat,so am sure all gold content of the sweeps are 18 k and 21 k.

I remember I read about the process of gold sweeps recovery which is incineration, milling then use nitric acid to dissolve base metals plus silver and palladium if exist, then use AR to get gold.

My question is, how nitric acid will dissolve silver from the sweeps powder? I mean are incineration and milling will change the 18 k and 21 k nature to gold and silver powder that its easy to be parted by nitric acid?
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The Nitric will remove all base metal (bits of steel and what not) and what ever Silver it can reach.
 
Yggdrasil said:
That is why I say what it can reach.
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That mean using this process with karat waste is not effective and we will not get all gold, but I read in CM Hoke book about this process and they didn't mention that we have to smelt to get all gold or if this process can't get all gold.

I believe that this process is very effective specially after I watched couple Sreetips videos dealing with similar sweeps, but I want to know how exactly silver and gold separated or converted to something that can be easily parted by nitric acid after we burn and grind/sift the sweeps.
 
Ayham Hafez said:
That mean using this process with karat waste is not effective and we will not get all gold, but I read in CM Hoke book about this process and they didn't mention that we have to smelt to get all gold or if this process can't get all gold.

I believe that this process is very effective specially after I watched couple Sreetips videos dealing with similar sweeps, but I want to know how exactly silver and gold separated or converted to something that can be easily parted by nitric acid after we burn and grind/sift the sweeps.
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Hold on a bit, cleaning up and dissolving are two different beasts.

I believe 18 and 21 k can be dissolved directly in AR.

But to makes sure it is as clean as it can be, it is run through a Nitric leach to remove Iron, Copper and what ever else is in there.
That is why I say that if there is a chance of Tin bearing soft solder it should be run through a HCl bath first.
Which in turn will need to be roasted to get rid of all traces of Chlorides.
Then it can be leached in Nitric before final AR.

If I'm not mistaken, Hoke even used HF to remove any traces of abrasives and porcelain.
 
Yggdrasil said:
Hold on a bit, cleaning up and dissolving are two different beasts.

I believe 18 and 21 k can be dissolved directly in AR.

But to makes sure it is as clean as it can be, it is run through a Nitric leach to remove Iron, Copper and what ever else is in there.
That is why I say that if there is a chance of Tin bearing soft solder it should be run through a HCl bath first.
Which in turn will need to be roasted to get rid of all traces of Chlorides.
Then it can be leached in Nitric before final AR.

If I'm not mistaken, Hoke even used HF to remove any traces of abrasives and porcelain.
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Hoke book mentioned using HF, but GRF make me get rid of using it.

Anyway, using HCl with sweeps is bad idea,unless we incinerate first then use HCl then incinerate again then use nitric acid, but that mean much work, direct HCl with organic material usually comes with sweeps make HCl foam a lot, MS Hoke mentioned also boiling in caustic soda incase we don't want to go with incineration.

Thanks Yggdrasil, forgot about 18 /21 k dissolved in AR, but I think we have to boil sweeps in AR for long time.
 
Ayham Hafez said:
Hoke book mentioned using HF, but GRF make me get rid of using it.

Anyway, using HCl with sweeps is bad idea,unless we incinerate first then use HCl then incinerate again then use nitric acid, but that mean much work, direct HCl with organic material usually comes with sweeps make HCl foam a lot, MS Hoke mentioned also boiling in caustic soda incase we don't want to go with incineration.

Thanks Yggdrasil, forgot about 18 /21 k dissolved in AR, but I think we have to boil sweeps in AR for long time.
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Even more so if you melt them to shots.
And HCl only if you expect Tin or you can use strong NaOH which will also take some Tin.
 
If the tin is oxidized, for instance by heating it with potassium or sodium nitrate, it will likely form tin (IV) oxide (SnO2), which is insoluble in nitric acid. In this case, the reaction between the tin oxide and nitric acid wouldn't result in the formation of a paste because tin (IV) oxide does not readily dissolve in nitric acid. So start incineration with potassium or sodium nitrate. Then nitric acid leach the remainder of the base materials out. Filter, wash, and proceed with AR. Sreetips has many excellent videos on YouTube on this specific topic.
 

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