Did some gold redissolve here? Why?

[Vinny PaisAuno]

Hi, after a very clean drop with SMB (right pic), I washed the gold with HCl and was surprised to see what appears to be some gold redissolving (left pic solution removed from gold). I did not do a water wash first, and wish I had. I did have to use a small amount, 3gm, of sulfamic acid after AR if that matters.

Stannous test appears to be positive, but with a small sample in a test tube gold does not drop with SMB or copperas.

Question 1. Is there gold in solution or other contamination giving false positive?

Question 2. How did HCl dissolve gold? Obviously there would have to be some oxidizer in there. Did the nitric regenerate somehow? Or my beaker cover was not cleaned thoroughly and maybe there were some nitrates on it that condensed down into the breaker?

Question 3. How do I proceed? I think I'm going to try to drop the whole thing with SMB.

Thank you for your help, Vinny

 

[eaglekeeper]

Did you use Sulfamic acid before the first drop?

I did not do a water wash first, and wish I had.

That may have contributed. Multiple small water washes would have removed some of the excess nitric. This happens to me from time to time and I just stock pot it. Looking at the color of your solution,...I wouldn't chase that tiny amount, throw it into the stock pot and recover it later.

I think I'm going to try to drop the whole thing with SMB.

You can try it.....Don't expect much to reduce out.


By the way, the gold powder looks awesome.....but I hope you're not doing this in your garage.

 

[Vinny PaisAuno]

Eaglekeeper thank you for your reply.

Yes I did use a small amount of sulfamic before the drop, a half teaspoon or less was all it took. Not sure if nitric can regenerate after that or not.

But I think I'm starting to understand why it's called sponge..... It hangs on to everything! After 3 water washes it's still acidic! I'll keep washing.

I did try to precipitate the light yellow solution, and as you indicated, virtually nothing came out. Maybe in the 10s to 100s of milligrams. In the stockpot it goes.

I am working in my garage unfortunately, but I did build a decent fume hood that moves a lot of air. I took the beakers out just for photos.

Thanks again for your help

 

[Yggdrasil]

Eaglekeeper thank you for your reply.

Yes I did use a small amount of sulfamic before the drop, a half teaspoon or less was all it took. Not sure if nitric can regenerate after that or not.

But I think I'm starting to understand why it's called sponge..... It hangs on to everything! After 3 water washes it's still acidic! I'll keep washing.

I did try to precipitate the light yellow solution, and as you indicated, virtually nothing came out. Maybe in the 10s to 100s of milligrams. In the stockpot it goes.

I am working in my garage unfortunately, but I did build a decent fume hood that moves a lot of air. I took the beakers out just for photos.

Thanks again for your help

Sulfamic acid needs to be used hot at around 80 Centigrade.
Nice powder.

 

[eaglekeeper]

What was the starting material...e-waste?

Once you get it melted up, post a picture. It's always nice to see recovered gold.

 

[Vinny PaisAuno]

What was the starting material...e-waste?

Karat scrap! E waste is kind of next level it seems. Will do!

 

[Dannysgold]

Hi, after a very clean drop with SMB (right pic), I washed the gold with HCl and was surprised to see what appears to be some gold redissolving (left pic solution removed from gold). I did not do a water wash first, and wish I had. I did have to use a small amount, 3gm, of sulfamic acid after AR if that matters.

Stannous test appears to be positive, but with a small sample in a test tube gold does not drop with SMB or copperas.

Question 1. Is there gold in solution or other contamination giving false positive?

Question 2. How did HCl dissolve gold? Obviously there would have to be some oxidizer in there. Did the nitric regenerate somehow? Or my beaker cover was not cleaned thoroughly and maybe there were some nitrates on it that condensed down into the breaker?

Question 3. How do I proceed? I think I'm going to try to drop the whole thing with SMB.

Thank you for your help, Vinny

I'm pretty sure the hcl disolved it they same happened to me and I couldn't precipitate it again with smb, even when I washed it with water first, I thought hcl would remove any other base metals but it resolved, ah I thought I Lost my precipitate. What I did was add full strength clear ammonia to the redisolved solution till it turns cloudy and brown. Then a little more, just poor it in without measuring till it gets cloudy and brown , the ammonia will neutralize the acid and force out the precipitate instantly. Let it settle, till all precipitate separats from the solution, then siphon off the solution , it's very fine and you will loose precipate if you poor it off, then rinse it several times each rinse let it settle to the bottom till no more settles, then siphon off again most of the watter and use two coffee filters to filter the water left and the precipate will collect in the filters as a brown mud, let it dry in the filters. I use a vacuum pump and flask with filter to remove the solution from the precipate and Wash it lightly in the filter flask.

 

[Dannysgold]

Dryed precipitate

 

[Goldenrod757]

Isnt using ammonia where nitric is present , in danger of forming explosive ammonium nitrate , altho in small quantity....and also are you not in danger of losing some of your gold to a gold/ammonia chemical complex forming?

 

[Dannysgold]

I'm pretty sure the hcl disolved it they same happened to me and I couldn't precipitate it again with smb, even when I washed it with water first, I thought hcl would remove any other base metals but it resolved, ah I thought I Lost my precipitate. What I did was add full strength clear ammonia to the redisolved solution till it turns cloudy and brown. Then a little more, just poor it in without measuring till it gets cloudy and brown , the ammonia will neutralize the acid and force out the precipitate instantly. Let it settle, till all precipitate separats from the solution, then siphon off the solution , it's very fine and you will loose precipate if you poor it off, then rinse it several times each rinse let it settle to the bottom till no more settles, then siphon off again most of the watter and use two coffee filters to filter the water left and the precipate will collect in the filters as a brown mud, let it dry in the filters. I use a vacuum pump and flask with filter to remove the solution from the precipate and Wash it lightly in the filter flask.

You could end up with different color of solution using ammonia meaning there is other metals that were discovered and not known. Question what did you dissolve in the first place gold or chips, pins in ap or ar , ammonia, I tried it both in ar and ap and bleach dissolving ore,. Aqua Rega is mainly for disolving gold only after it's been turned into a solid form and smb should work. Ferrous sulfate will precipate only gold from Aqua Rega even if your gold has copper in it. Chips and other electronics have other metals in when u dissolve them in aqua Reg or acid peroxide, giving you a green solution..

 

[Dannysgold]

You could end up with different color of solution using ammonia meaning there is other metals that were discovered and not known. Question what did you dissolve in the first place gold or chips, pins in ap or ar , ammonia, I tried it both in ar and ap and bleach dissolving ore,. Aqua Rega is mainly for disolving gold only after it's been turned into a solid form and smb should work. Ferrous sulfate will precipate only gold from Aqua Rega even if your gold has copper in it. Chips and other electronics have other metals in when u dissolve them in aqua Reg or acid peroxide, giving you a green solution..

Isnt using ammonia where nitric is present , in danger of forming explosive ammonium nitrate , altho in small quantity....and also are you not in danger of losing some of your gold to a gold/ammonia chemical complex forming?

That's what I was told and read, however I used it. And All acids were neutralized , I made a solution of hcl and nitric acid to dissolve some ore , I over mixed the ratio of nitric, even added 1lb of smb to the solution of about 5-6 ml of solution, got no stanious test for anything, everything in the ore got disolved, but nothing precipitated with the smb, I was furious wondering why, so I decided to neutralize everything and disguard it to a stock pot adding straight clear ammonia, to my surprise I got a cloudy brown precipate formed instantly, wow I thought , so it worked , i got copper my solution turned blue after it settled down i got brown mud, which would need to be melted and refined again but it has gold in it too.,

 

[eaglekeeper]

Then a little more, just poor it in without measuring till it gets cloudy and brown , the ammonia will neutralize the acid and force out the precipitate instantly.

Caution!...if using Ammonia with dissolved metals....It doesn't play well with some, including silver.

 

[Yggdrasil]

I'm pretty sure the hcl disolved it they same happened to me and I couldn't precipitate it again with smb, even when I washed it with water first, I thought hcl would remove any other base metals but it resolved, ah I thought I Lost my precipitate. What I did was add full strength clear ammonia to the redisolved solution till it turns cloudy and brown. Then a little more, just poor it in without measuring till it gets cloudy and brown , the ammonia will neutralize the acid and force out the precipitate instantly. Let it settle, till all precipitate separats from the solution, then siphon off the solution , it's very fine and you will loose precipate if you poor it off, then rinse it several times each rinse let it settle to the bottom till no more settles, then siphon off again most of the watter and use two coffee filters to filter the water left and the precipate will collect in the filters as a brown mud, let it dry in the filters. I use a vacuum pump and flask with filter to remove the solution from the precipate and Wash it lightly in the filter flask.

Welcome to us.
Sincerely, stop giving bad advice.

If you are going to drop all metals as Hydroxides (which is what you do), at least use Sodium Hydroxide.
HCl do not dissolve Gold unless it has an extra oxidizer, simply washing with water will not remove all Nitric,
then you have to roast it to a low red glow.

And when you are finished with drying the Hydroxides, what to do then?
Then you are back to square one.

Study this before you start giving advice:

We ask our new members to do 3 things.
1. Read C.M. Hokes book on refining jewelers scrap, it gives an easy introduction to the most important chemistry regarding refining.
It is free here on the forum: Screen Readable Copy of Hoke's Book
2. Then read the safety section of the forum: Safety
3. And then read about "Dealing with waste" in the forum: Dealing with Waste

Suggested reading: The Library

Forum rules : https://goldrefiningforum.com/threads/board-policy-this-should-be-read-by-everyone.4646/

 

[Yggdrasil]

You could end up with different color of solution using ammonia meaning there is other metals that were discovered and not known. Question what did you dissolve in the first place gold or chips, pins in ap or ar , ammonia, I tried it both in ar and ap and bleach dissolving ore,. Aqua Rega is mainly for disolving gold only after it's been turned into a solid form and smb should work. Ferrous sulfate will precipate only gold from Aqua Rega even if your gold has copper in it. Chips and other electronics have other metals in when u dissolve them in aqua Reg or acid peroxide, giving you a green solution..

Start to study before giving advice to others.

 

[Yggdrasil]

That's what I was told and read, however I used it. And All acids were neutralized , I made a solution of hcl and nitric acid to dissolve some ore , I over mixed the ratio of nitric, even added 1lb of smb to the solution of about 5-6 ml of solution, got no stanious test for anything, everything in the ore got disolved, but nothing precipitated with the smb, I was furious wondering why, so I decided to neutralize everything and disguard it to a stock pot adding straight clear ammonia, to my surprise I got a cloudy brown precipate formed instantly, wow I thought , so it worked , i got copper my solution turned blue after it settled down i got brown mud, which would need to be melted and refined again but it has gold in it too.,

Acids are not a good thing to use on ores, at least not until you have a proper assay.
There can be all kinds of toxic nasty things in ores.
AR are never used on ores, since it is way too expensive.

 

[Vinny PaisAuno]

HCl do not dissolve Gold unless it has an extra oxidizer, simply washing with water will not remove all Nitric,
then you have to roast it to a low red glow.

Thank you all who replied, Yggdrasil, your talking about washing the gold after dropping with SMB right?

After denoxxing with sulfamic acid and dropping with SMB, I was surprised that much nitric remained in the gold powder!

Would you recommend roasting the powder as part of the washing process? after a water wash before HCl wash perhaps?

What would be best practice for cleaning up post drop? I had read here about washing with water, HCl and ammonium hydroxide although the ammonia step seemed to be debatable so I skipped it.

Thank you all for keeping me on track I'm almost done with a second refining

Vin

 

[Yggdrasil]

Thank you all who replied, Yggdrasil, your talking about washing the gold after dropping with SMB right?

After denoxxing with sulfamic acid and dropping with SMB, I was surprised that much nitric remained in the gold powder!

Would you recommend roasting the powder as part of the washing process? after a water wash before HCl wash perhaps?

What would be best practice for cleaning up post drop? I had read here about washing with water, HCl and ammonium hydroxide although the ammonia step seemed to be debatable so I skipped it.

Thank you all for keeping me on track I'm almost done with a second refining

Vin

I replied to the strange procedure of the actual poster. You can see in my reply.
If one have swap between HCl and Nitric with for instance dissolving Tin with HCl and then go to Nitric to take the Copper you will dissolve some Gold.
Or you precipitate Gold from an AR solution, and then decides to wash it in Nitric, you need to roast the powder to drive off the HCl first.

If you have actually deNOxed it properly, there should be no Nitric left.
How do you use your Sulfamic acid?

 

[Vinny PaisAuno]

I see, thanks! I added sulfamic acid to hot AR. 90C. It only took 1 or 2 grams before it quit fizzing. Then diluted and ice bath the AR, filtered, then dropped easily with SMB.

Do you think using a watch glass cover on the wash beaker that had previously been used for AR could have dripped some kind of nitrates into the solution?

I was really meticulously clean and careful, but clearly some oxidizer got in there.

I did have a small bottle of nitric in the fume hood, would vapors possibly contaminate?

In the end it's ok, Ionly lost maybe .001 gms of gold, but I'm just curious for the purpose of learning what I could do better next time.

I sure appreciate everyone's help. Vin

 

[Vinny PaisAuno]

Or you precipitate Gold from an AR solution, and then decides to wash it in Nitric, you need to roast the powder to drive off the HCl first.

Would you recommend washing in nitric for greater purity? I was only planning to wash in water and HCl, many times of course. I've heard some, Harold and others recommend ammonium hydroxide too.

 

[Yggdrasil]

I see, thanks! I added sulfamic acid to hot AR. 90C. It only took 1 or 2 grams before it quit fizzing. Then diluted and ice bath the AR, filtered, then dropped easily with SMB.

Do you think using a watch glass cover on the wash beaker that had previously been used for AR could have dripped some kind of nitrates into the solution?

I was really meticulously clean and careful, but clearly some oxidizer got in there.

I did have a small bottle of nitric in the fume hood, would vapors possibly contaminate?

In the end it's ok, Ionly lost maybe .001 gms of gold, but I'm just curious for the purpose of learning what I could do better next time.

I sure appreciate everyone's help. Vin

Vapours can do that, but it takes time.
HCl can dissolve minute amounts of Gold if the Gold is fine enough, it just takes a bit of Oxygen in the Acid.
But it is nothing to be bothered about, put it in the stock pot and reclaim it there later.