AR Process Carat Jewellery

[jord]

Hi all, I have followed this forum for a year or so now and have learnt to successfully recover and refine gold and silver jewellery. My sources are 9K, 14K, 18K gold and .925 Silver jewellery. I was hoping for advice on my process, there has been nothing gone wrong so far but I would like to know if there is anything I can do better.

I first separate the jewellery into it's allocated carats, weigh the amount of each Carat and work out the amounts needed to Inquart each pile. I use the sterling silver to Inquart down to 6k. I then melt and shot the metal and carry out a 2:1,then 1:1 nitric wash with distilled water filtering the solution after each wash and cleaning it till there is no visible tint to the distilled water.
Afterwards I shot the metal again, cover in hydrochloric acid, and slowly add increments of nitric acid 5ml a time until all the metal is dissolved (also when the reaction dies down I add a small amount of HCI to see if the reaction restarts before adding the nitric). Once dissolved I add a pinch of sulphamic acid then let the solution cool and also add ice. I then filter the solution, afterwards once filtered heat the solution to around 75 degrees Celsius and add the SMB until no more gold drops, continously testing the solution with stannous chloride. Once the solution test negative I decant the solution leaving the gold in the beaker and put the rest of the solution to my stock pot and wash the gold powder with distilled water.

Thank you for taking the time to read this and any advice would be hugely welcomed.

 

[FrugalRefiner]

It sounds like you've learned well.

I don't remelt between the nitric leach and AR. I just go right to the AR.

I would add a wash with HCl before the water wash.

Dave

 

[Martijn]

Welcome to the forum. What Dave said

You could leave the melting it back after nitric wash, fine powder gold dissolves much better than solid shot.

To test if there is silver nitrate in the wash, test a couple of ml wash water with salt water or HCl to see if any AgCl forms. If so, keep rinsing.
I don't heat to drop with SMB. not sure if it's necessary.

Well done. do share some button pictures for us to enjoy!

 

[jord]

It sounds like you've learned well.

I don't remelt between the nitric leach and AR. I just go right to the AR.

I would add a wash with HCl before the water wash.

Dave

It wouldn't be possible without people like yourself and for that I thank you! But also cheers for the tips sounds like it will save me a bit of time! I will try both of these on my next batch. Would you do the HCI for both washes? After the nitric leach and then on the gold powder itself?

 

[jord]

Welcome to the forum. What Dave said

You could leave the melting it back after nitric wash, fine powder gold dissolves much better than solid shot.

To test if there is silver nitrate in the wash, test a couple of ml wash water with salt water or HCl to see if any AgCl forms. If so, keep rinsing.
I don't heat to drop with SMB. not sure if it's necessary.

Well done. do share some button pictures for us to enjoy!

I will definitely leave as a powder from now and go straight to AR.
For the silver nitrate I'm guessing I will stop seeing white crystals form?
And also I will try drop the gold without heat again also cuts out an extra step thank you!

I will make sure to share photos of my next batch!

 

[jord]

I will definitely leave as a powder from now and go straight to AR.
For the silver nitrate I'm guessing I will stop seeing white crystals form?
And also I will try drop the gold without heat again also cuts out an extra step thank you!

I will make sure to share photos of my next batch!

This was my first refined bar(button) haha

 

[FrugalRefiner]

It wouldn't be possible without people like yourself and for that I thank you! But also cheers for the tips sounds like it will save me a bit of time! I will try both of these on my next batch. Would you do the HCI for both washes? After the nitric leach and then on the gold powder itself?

After the nitric leach, go straight to AR. Washing with HCl would create a weak AR and dissolve a bit of gold.

After you've dropped your gold, do a wash or two with full strength HCl, then water. Save the HCl from these washes and use them for a future digestion.

Dave

 

[Martijn]

I will definitely leave as a powder from now and go straight to AR.
For the silver nitrate I'm guessing I will stop seeing white crystals form?
And also I will try drop the gold without heat again also cuts out an extra step thank you!

I will make sure to share photos of my next batch!

Add the nitric slower, it has a lot more surface to work on when in powder form.

 

[Martijn]

Traces of silver chloride looks like milk in solution. Test a bit to see on stronger silver nitrate. If it stays clear you're done rinsing. Store it separate to convert to silver later.

 

[jord]

After the nitric leach, go straight to AR. Washing with HCl would create a weak AR and dissolve a bit of gold.

After you've dropped your gold, do a wash or two with full strength HCl, then water. Save the HCl from these washes and use them for a future digestion.

Dave

Perfect, I am fully with you now. Thanks for clearing that up I will make sure to apply this method

 

[jord]

Traces of silver chloride looks like milk in solution. Test a bit to see on stronger silver nitrate. If it stays clear you're done rinsing. Store it separate to convert to silver later.

Cheers for getting back to me, I am currently learning how to process the silver nitrate to feed into my silver cell but I will also incorporate this method into my process, thank you.

 

[4metals]

All of the suggestions are right on the mark. One easy step you could add is, after you digest the gold in aqua regia, add ice to the solution before you filter it. Silver chloride is exponentially less soluble in cold acid and will drop out as a solid silver chloride which you will catch when you filter the solution before you do the precipitation.

 

[jord]

All of the suggestions are right on the mark. One easy step you could add is, after you digest the gold in aqua regia, add ice to the solution before you filter it. Silver chloride is exponentially less soluble in cold acid and will drop out as a solid silver chloride which you will catch when you filter the solution before you do the precipitation.

All of the advice given is exactly what I was hoping for and is all massively appreciated and will all be used in my next batch.

Could I also ask, I know the nitric leach is 2:1, 1:1 but is there an optimal volume of solution for the amount of weight you are processing as I want to keep my nitric use down to a minimum if possible.

 

[4metals]

I know this works with fire assay parting so it stands to reason it will work for your inquarted karat. The first leach, 2:1 usually is strong enough to leach out the lions share of the silver and the second leach just cleans up what is left. Some assayers take the used second parting acid (1:1) and its rinses (which now approximates 2:1), as the first parting acid for the next batch. You may need to up the quantity of the first acid so it does a complete dissolve of the silver and base metals, but a little experimenting will allow you to determine the volume of 2:1 to use per oz of feed material so the second acid will remain strong enough for a second use.

 

[4metals]

Just a note if anyone wants to use this process for fire assaying, filter the used second parting acid before reusing it. When decanting parting acids it is possible to lose a flake without knowing it. If that flake ends up in another assay your results will be erroneously high. Filtering eliminates that issue.

 

[billgold]

One thing I have not seen mentioned. After dissolving everything possible in aqua regia, add a few ml of concentrated sulfuric acid and stir to precipitate out any lead that was in your starting material.

Filter thoroughly before precipitating the gold. You may need to make two or three passes of the liquid through the filter before it becomes crystal clear.

When doing the AR dissolution and you are down to only a small amount of solid material in the beaker - you may only need to add a drop or two of nitric acid to get the rest to dissolve. This will minimize the amount of excess HNO3.

 

[jord]

I know this works with fire assay parting so it stands to reason it will work for your inquarted karat. The first leach, 2:1 usually is strong enough to leach out the lions share of the silver and the second leach just cleans up what is left. Some assayers take the used second parting acid (1:1) and its rinses (which now approximates 2:1), as the first parting acid for the next batch. You may need to up the quantity of the first acid so it does a complete dissolve of the silver and base metals, but a little experimenting will allow you to determine the volume of 2:1 to use per oz of feed material so the second acid will remain strong enough for a second use.

I will save the acid for a second use, on my volumes I have been watching sreetips and adjusting my volumes from his slightly as he is processing similar weights but I think most will come with time as I refine my refining process haha.

 

[jord]

One thing I have not seen mentioned. After dissolving everything possible in aqua regia, add a few ml of concentrated sulfuric acid and stir to precipitate out any lead that was in your starting material.

Filter thoroughly before precipitating the gold. You may need to make two or three passes of the liquid through the filter before it becomes crystal clear.

When doing the AR dissolution and you are down to only a small amount of solid material in the beaker - you may only need to add a drop or two of nitric acid to get the rest to dissolve. This will minimize the amount of excess HNO3.

Thank you for your comment, I believe I do not need to use sulfuric acid as the sulphamic acid has a double purpose of pushing the lead out and De-Nox the solution.

 

[cejohnsonsr1]

Thank you for your comment, I believe I do not need to use sulfuric acid as the sulphamic acid has a double purpose of pushing the lead out and De-Nox the solution.

Unless you’re using way too much nitric, you shouldn’t need to denox with sulphamic. A few drops of sulfuric during the digestion is much more effective and efficient.

 

[jord]

Unless you’re using way too much nitric, you shouldn’t need to denox with sulphamic. A few drops of sulfuric during the digestion is much more effective and efficient.

I try use minimal nitric as possible, I do not have sulphuric acid on hand either.