# Gold back in solution when washing?



## AndrewSuperD (Aug 28, 2022)

Hi all. Did a 440g+ batch of DDR2/3 memory. I followed this process:

1. Incineration
2. Magnetic separation
3. Gravity separation
4. Hot nitric acid with stir bar
5. Decanted and washed after No reaction
6. Dissolved with AR
7. Tested with stannous with decent purple stain
8. Added Sulfamic acid
9. Filtered and dropped with SMB
10. Began washing with HCl

At this point I noticed the solution turning yellow so I stannous tested and got light purple stain on paper after two minutes. Pics attached. The volume of powders also decreased. 

I then went and reread Harold’s process and I forgot to add tap water to the wash. I assume at this point it wouldn’t have made a difference because I had left over nitric in the powders and I’ve formed a weak Aqua Regia? I thought I added plenty of sulphamic. So I’m not sure how this is happening unless I really over added nitric and I didn’t add enough sulphamic. I got little to no reaction with sulphamic. I probably should have added a gold bead to consume all nitric. Nonetheless…at this point I assume I should carry on with Harold’s process and drop the gold wash with SMB again (it’s all I have to use). Thoughts on my assumptions?


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## AndrewSuperD (Aug 28, 2022)

Adding a picture of gold after 1/3 of Harold’s process. I stopped before Ammonium Hydroxide as I don’t have any and it’s not worth it to me yet. I need more material. As it stands, this is the clumpiest gold I’ve ever had. I was hoping for ~2g but I don’t think I’m going to get there.


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## AndrewSuperD (Aug 29, 2022)

.78g. Disappointed with the weight. I thought these ddr2/3 bga memory chips were .5% by weight?


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## Yggdrasil (Aug 29, 2022)

AndrewSuperD said:


> Hi all. Did a 440g+ batch of DDR2/3 memory. I followed this process:
> 
> 1. Incineration
> 2. Magnetic separation
> ...


Whole sticks including chips?


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## Martijn (Aug 29, 2022)

How did you add the sulfamic acid? Decsribe the process in detail. 
Things of importance are volume and temperature, agitation, amounts and time.


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## AndrewSuperD (Aug 29, 2022)

Yggdrasil said:


> Whole sticks including chips?


Just the chips. The gold fingers were processed separately.


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## Yggdrasil (Aug 29, 2022)

Do what Martijn said.
So can we see if anything jumps out at us.


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## AndrewSuperD (Aug 29, 2022)

Martijn said:


> How did you add the sulfamic acid? Decsribe the process in detail.
> Things of importance are volume and temperature, agitation, amounts and time.


I add the sulphamic acid when the solution is hot ~80C - 90C. I place some sulphamic in the cap of the sulphamic bottle and add that way. It sometimes clumps and I don’t want a big clump to fall into the solution. I watch the solution for any reaction (fizzing) and will add again in same manner if solution has a reaction. Then I’ll stir the solution. I’ll add in the same manner again until I see no reaction. I dont measure as I think I’m careful adding 2ml of nitric at a time to the AR until I have no reaction. Once I’m done adding Sulphamic I set a 15 min timer and when done I remove from heat and add some tap water ice. Then, when cool, I filter with cotton ball in funnel. I wash through with water till clear.


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## AndrewSuperD (Aug 29, 2022)

Yggdrasil said:


> Do what Martijn said.
> So can we see if anything jumps out at us.


Thanks so much for the review/help.


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## Yggdrasil (Aug 29, 2022)

AndrewSuperD said:


> I add the sulphamic acid when the solution is hot ~80C - 90C. I place some sulphamic in the cap of the sulphamic bottle and add that way. It sometimes clumps and I don’t want a big clump to fall into the solution. I watch the solution for any reaction (fizzing) and will add again in same manner if solution has a reaction. Then I’ll stir the solution. I’ll add in the same manner again until I see no reaction. I dont measure as I think I’m careful adding 2ml of nitric at a time to the AR until I have no reaction. Once I’m done adding Sulphamic I set a 15 min timer and when done I remove from heat and add some tap water ice. Then, when cool, I filter with cotton ball in funnel. I wash through with water till clear.


How was the Stannous after SMB?


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## AndrewSuperD (Aug 29, 2022)

Yggdrasil said:


> How was the Stannous after SMB?


The stannous test after the first SMB drop was negative. I put the beaker on heat and let it settle for almost a whole day.


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## Yggdrasil (Aug 29, 2022)

Well maybe there was no more Gold.
The amount of Gold depends on age and design of the chips.
And some has Aluminum bonding wires in stead of Gold.


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## AndrewSuperD (Aug 29, 2022)

Yggdrasil said:


> Well maybe there was no more Gold.
> The amount of Gold depends on age and design of the chips.
> And some has Aluminum bonding wires in stead of Gold.


Maybe not. It’s just frustrating. I’ll keep all waste just in case I (or anyone) think of something. It might be that my incineration was inadequate? I’ll take another look at that material this weekend. Oddly enough after I added the tap water (recall I did 1/3 Harold’s process) to the HCl I added for washing, the stannous test which was positive with no tap water, resulted negative after the tap water add. Why might that be? Too diluted? Thanks for your time.


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## Yggdrasil (Aug 29, 2022)

We always keep our waste solutions in a stock pot.
And from time to time we process it with cementing on copper with heavy air bubbling or stirring,
before treating it for waste disposal.
It will drop any PMs that has managed to sneak by.

Edit for spelling


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## Shark (Aug 29, 2022)

How did you separate your metallic's from the ash?


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## AndrewSuperD (Aug 29, 2022)

Shark said:


> How did you separate your metallic's from the ash?


I take small scoops of material at a time and lay them in a flat plastic container. I use a device like the magnetic grabber (attached picture) multiple times over the same material. I drop the magnetic material from about six inches onto a clean plastic surface so the dust scatters off the materials, then use the magnetic grabber again. I’ll then put the dust back in with the main materials. 

I’m hoping the problem I have here is that my sifting procedure left a good amount of material which I’ve done nothing with yet. I did look at it under a microscope and saw no gold but maybe I should take another crack at it. Wash it, sift again, etc…


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## AndrewSuperD (Aug 29, 2022)

Yggdrasil said:


> We always keep our waste solutions in a stock pot.
> And from time to time we process it with cementing on copper with heavy air bubbling or stirring,
> before treating it for waste disposal.
> It will drop any PMs that has managed to sneak by.
> ...


Yep, as do I. I was referring to the sediment left in the filter after the AR process. Maybe something still in there or maybe like you said, that’s all there was.


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## orvi (Aug 29, 2022)

It happen to me quite often, that after washing dirty gold drop (pins digestion in AR - so heavy copper/tin/lead solutions), some trace ammount of it re-dissolve into the solution. I always check after first wash with stannous. It seems like a lot - but when you are washing the gold, you use little ammounts of HCL - thus overall it isn´t that bad  Personally, I keep the first washing (HCL) and add it to the next batch I process. If you are after the exact yield, you can cool the solution, and bit of SMB and boil it again to the final negative test. Boiling it helps to agglomerate newly formed gold particles.

We discussed this in our shop a bit... But we did not came to any certain conclusion about how this happen. 
It could be that boiling in HCL together with atmospheric oxygen can be sufficient to oxidize some gold in these conditions... Also, there could be some impurities adsorbed onto gold surface, which alter the oxidation potentials and make it easier to oxidize the gold. Because - I always seen redissolved gold only in the first wash. No matter how violently I was boiling the gold powder afterwards in HCL nor ammonia, no gold redissolved.


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## Martijn (Aug 30, 2022)

AndrewSuperD said:


> Maybe not. It’s just frustrating. I’ll keep all waste just in case I (or anyone) think of something. It might be that my incineration was inadequate? I’ll take another look at that material this weekend. Oddly enough after I added the tap water (recall I did 1/3 Harold’s process) to the HCl I added for washing, the stannous test which was positive with no tap water, resulted negative after the tap water add. Why might that be? Too diluted? Thanks for your time.


That is weird. Water should not hold back a stannous test result, it should only be lighter. 
You said you had a purple result before the SMB. That indicates a very low gold concentration to start with. You usually need to dilute to see the dark stain turn purple.


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## AndrewSuperD (Aug 30, 2022)

orvi said:


> It happen to me quite often, that after washing dirty gold drop (pins digestion in AR - so heavy copper/tin/lead solutions), some trace ammount of it re-dissolve into the solution. I always check after first wash with stannous. It seems like a lot - but when you are washing the gold, you use little ammounts of HCL - thus overall it isn´t that bad  Personally, I keep the first washing (HCL) and add it to the next batch I process. If you are after the exact yield, you can cool the solution, and bit of SMB and boil it again to the final negative test. Boiling it helps to agglomerate newly formed gold particles.
> 
> We discussed this in our shop a bit... But we did not came to any certain conclusion about how this happen.
> It could be that boiling in HCL together with atmospheric oxygen can be sufficient to oxidize some gold in these conditions... Also, there could be some impurities adsorbed onto gold surface, which alter the oxidation potentials and make it easier to oxidize the gold. Because - I always seen redissolved gold only in the first wash. No matter how violently I was boiling the gold powder afterwards in HCL nor ammonia, no gold redissolved.


Thank you so much for the reply. I appreciate the detail and the sharing of experience. As outlined above, I kept the first wash and tested with stannous with a positive result. I then added tapwater and tested with stannous resulting in negative. Curious about this, I began to evaporate the excess liquid volume. I forgot to turn off the hot plate and all the liquid evaporated leaving a glistening and brown bottom of the beaker. I added 100 mL of hydrochloric acid and the brown bottom and glistening material went nowhere. So I added 1 mL of nitric and redissolve all material in the beaker. I again tested with stannous with a positive result. Picture attached. The camera Flash washed out how dark the test result was. In my natural light, it looks darker. I then added so Fama Cassett (hahahahaaa talk to text - added sulphamic acid) in the manner I described above and that’s where it’s sitting right now. It’s covered with a watch glass waiting for my next drop with SMB. That will be tonight.


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## AndrewSuperD (Aug 30, 2022)

Martijn said:


> That is weird. Water should not hold back a stannous test result, it should only be lighter.
> You said you had a purple result before the SMB. That indicates a very low gold concentration to start with. You usually need to dilute to see the dark stain turn purple.


Thank you Martjin, there is very little gold in this wash water. I was editing, while you were editing, please see above for my description of what happened.


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## Martijn (Aug 30, 2022)

With that little nitric, just go for SMB. It will use up the excess nitric, also by redissolving the precipitated gold.


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## Shark (Aug 30, 2022)

I have seen this several times as well. Mine went back to my store brand distilled water. The amount going back into solution was very small but annoying. I would add a very small amount of smb to the wash and it would drop right back out. I then would continue the wash as usual, only changing the water, with no further problems.


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## orvi (Aug 30, 2022)

Shark said:


> I have seen this several times as well. Mine went back to my store brand distilled water. The amount going back into solution was very small but annoying. I would add a very small amount of smb to the wash and it would drop right back out. I then would continue the wash as usual, only changing the water, with no further problems.


I collect the "dirty" HCL from washings to separate bottle, and when I am about to process next batch in AR, I use this acid for the start. Then I have three separate beakers in the hood - one for gold "waste" (washings, last traces of powder from second settling etc...), second for silver waste (mainly AgCl from various tests of material etc., AgCl contamined with PdCl2, Sn oxides etc..) and third for Pd waste/dilute washings. Anytime the container fill up, I process it - usually by lye/sugar (Ag) or by cementation with copper dust (Pd, Au), dispose barren liquid and collect further


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## olawlor (Aug 31, 2022)

Could the tap water have enough Fe2+ to precipitate the gold? My well water is packed with Fe2+ right out of the ground (it oxidizes to annoying rusty Fe3+ after sitting in air for a day), and iron pipes are common in city water systems.

If you had a very dilute gold solution, and added ferrous sulfate (the active ingredient being the Fe2+), you'd expect to have a clear solution that tests negative with stannous chloride, because the gold is no longer dissolved ions, but sub-micron dots of inert metal swirling around. 

Dissolved ions are the big reason distilled water, or at least deionized or clean dehumidifer water, is preferred to tap or well water in refining. Depending on the process, chloride ions can drag down silver, ferrous ions could reduce and precipitate gold, calcium ions can precipitate sulfate giving a hard to filter and valueless precipitate, etc.


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## 608927101la (Sep 1, 2022)

olawlor said:


> Could the tap water have enough Fe2+ to precipitate the gold? My well water is packed with Fe2+ right out of the ground (it oxidizes to annoying rusty Fe3+ after sitting in air for a day), and iron pipes are common in city water systems.
> 
> If you had a very dilute gold solution, and added ferrous sulfate (the active ingredient being the Fe2+), you'd expect to have a clear solution that tests negative with stannous chloride, because the gold is no longer dissolved ions, but sub-micron dots of inert metal swirling around.
> 
> Dissolved ions are the big reason distilled water, or at least deionized or clean dehumidifer water, is preferred to tap or well water in refining. Depending on the process, chloride ions can drag down silver, ferrous ions could reduce and precipitate gold, calcium ions can precipitate sulfate giving a hard to filter and valueless precipitate, etc.


That's interesting. Think all wells are the same in that regard?


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## Rhpos (Sep 1, 2022)

AndrewSuperD said:


> Hi all. Did a 440g+ batch of DDR2/3 memory. I followed this process:
> 
> 1. Incineration
> 2. Magnetic separation
> ...


AuCl3 , soluble in Et2O. Easy separation. Avoid flames.


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## Lou (Sep 1, 2022)

Well, it would be [AuCl4]- but yes, there are better things than E2O for it, though I personally love the smell of ether in the morning.

In any event, the issue is the HCl. It will dissolve gold because air gets into it and makes small amounts of chlorine. Two ways around that are 1. small amount of SO2, 2. small amount of ethyl alcohol. This removes the Cl2 from the HCl.

Lou


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## orvi (Sep 1, 2022)

Lou said:


> Well, it would be [AuCl4]- but yes, there are better things than E2O for it, though I personally love the smell of ether in the morning.
> 
> In any event, the issue is the HCl. It will dissolve gold because air gets into it and makes small amounts of chlorine. Two ways around that are 1. small amount of SO2, 2. small amount of ethyl alcohol. This removes the Cl2 from the HCl.
> 
> Lou


I also love ether smell... And many more, which I certainly shouldn´t be smelling  but it happens from time to time... Accidentaly, not intentionally. Benzene and methyl chloride both has interesting sweet smell too, but in high concentration very annoying... Don´t ask how I know this  

Ethanol "trick" is good one  I think you mean that you first treat HCL with bit of EtOH and then use it for gold washing. Did I get it right ?


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## Lou (Sep 1, 2022)

yes, the plan being to kill off the oxidant.


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## Yggdrasil (Sep 1, 2022)

So the EtOH is a good Oxygen scavenger?


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## orvi (Sep 1, 2022)

Yggdrasil said:


> So the EtOH is a good Oxygen scavenger?


I wouldn´t say it is oxygen scavenger, but it is a good reducing agent for many strong oxidizers, like chlorine, which the EtOH is supposed to react with. Either oxidizing alcohol to acetaldehyde/acetic acid, or by radical chlorination of carbon chain, if the mixture is somewhere on direct light. But radical chlorination is I think much slower, giving more room for it to proceed on oxidation to ethanal/acetaldehyde - which could then be again chlorinated to form chloroacetaldehyde etc...

I do not think oxygen reacts with alcohol under normal conditions at appreciable rate. In HCL, the equilibrium between ethanol and ethyl chloride is established, but since there is plenty of water in HCL, equilibrium is shifted towards reagents - EtOH and HCL.

But since EtCl has low boiling point, and bad solubility in water, it evaporates and slowly push the equilibrium forward.
Complex issue to be resolved by just thinking about it  One would need some GC-FID or better GC-MS to find out what is created by this reaction for sure  

But important conclusion is - chlorine gets used up. So there is none to react with gold


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## Yggdrasil (Sep 1, 2022)

Aah I se now, I read the origin post wrong.
My bad.
I think my glasses need glasses


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## Shark (Sep 1, 2022)

Yggdrasil said:


> Aah I se now, I read the origin post wrong.
> My bad.
> I think my glasses need glasses


I know the feeling all to well……


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## Ultrax (Sep 4, 2022)

If the precipitation was completed with metabisulfite without its hydrolysis (prelilminary dissolution in water), part of the gold could be redissolved in the sulfate complexes. (SO) gold complexes are very strong and mask the tin chloride test - it will be negative for such gold compounds. The only simple test option is complete evaporation and heating above 400C.
Or, long (more than 8 hours) electrolysis with graphite electrodes at low potential.


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## 608927101la (Sep 5, 2022)

Ultrax said:


> If the precipitation was completed with metabisulfite without its hydrolysis (prelilminary dissolution in water), part of the gold could be redissolved in the sulfate complexes. (SO) gold complexes are very strong and mask the tin chloride test - it will be negative for such gold compounds. The only simple test option is complete evaporation and heating above 400C.
> Or, long (more than 8 hours) electrolysis with graphite electrodes at low potential.


So can't just add more water later anyway and heat it?


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## Ultrax (Sep 5, 2022)

If you're asking about SMB, no you can't add water later. SMB (Na2S2O5) should be hydrolyzed to NaHSO3 before adding it to the acidic solution. Because reducing agent for gold is SO2 in this reaction. If you're talking about evaporation, you don't need additional water anyway.


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## Yggdrasil (Sep 5, 2022)

Ultrax said:


> If you're asking about SMB, no you can't add water later. SMB (Na2S2O5) should be hydrolyzed to NaHSO3 before adding it to the acidic solution. Because reducing agent for gold is SO2 in this reaction. If you're talking about evaporation, you don't need additional water anyway.


I have never used SMB other than as powder, and it has worked fine for me.


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## Ultrax (Sep 5, 2022)

Hello,
I wrote "part of the gold could be redissolved in the sulfate complexes" 
It depends on SMB quantity, solution pH, HCl-HNO3 proportions and concentrations, and availability of copper (Cu) or nickel(Ni) ions which significantly decreases Au oxidation potential.
I have often seen solutions of gold sulfate complexes thrown into waste after precipitation with non-hydrolyzed metabisulphite. Especially when someone trying to use a multi-stage process with different acids and get gold specifically from electronic components with large quantities of base metals (not from ore).


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## Shark (Sep 5, 2022)

I have had problems off and on for a long time. When I stopped doing much waste it got better. Then I got to doing a good bit of gold filled and started seeing it at random again. This is why I got to testing other precipitants over time. I never use smb anymore with out water, and very rarely with out heating both the AR and the smb.


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