# Did I inadvertently make AR and dissolve my gold?



## DHarr (Apr 20, 2022)

This my third and biggest attempt at CPU metal extraction. Started with 5lbs of CPU's this batch, boiled in diluted nitric acid for 3 days switching out the solution daily and vacuum filtering. Saved the filtrate for the next step each time. After the 3rd boil the CPU's were pretty well stripped and I had about 100 grams of what I think was silver nitrate mixed with the gold flakes in 3 cakes. I added the cakes to a beaker and submerged in 37% HCL 3:1 with distilled H20. Left this to boil overnight and came back in the morning to see almost everything was dissolved, including the gold flakes. I did a stannous test and it was positive so I know it dissolved the gold. I started digging around to see if I could find an explanation for this. Here is the best I could come up with. When I added the washed silver nitrate and gold flakes to the HCL the silver dropped the nitrate and became silver chloride. The released nitrate then became nitric acid which then mixed with the HCL making aqua regia and dissolved the gold flakes. Does this sound right? If so, I now have a beaker (currently reducing to target volume of 500ml) that has dissolved gold and silver chloride. For denoxing I intend to boil a gold button until there is no more reaction. What would be the best next move in order to recovery both metals, ideally separately? I don't want to drop in SMB without knowing that its not going to cause an unwanted reaction with the silver chloride. What is a good method to recover the silver from this silver chloride state? Thanks in advance.

David


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## butcher (Apr 20, 2022)

Silver and gold will not be dissolved in solution together too much to any extent, AgCl silver chloride will be pretty much insoluble in a gold chloride solution, in a solution of very high concentrations of chloride ions a very small portion of silver chloride can be soluble in solution as AgCl2, dilution will convert the small bit of silver in solution as AgCl2 back to insoluble AgCl, chilling and letting sit overnight before decanting and filtering will help to further remove the insoluble silver ions from the soluble gold ions. 

You can test for silver in a more dilute solution, by adding the chloride ion, HCl, NaCl. SnCl2 and so on, upon adding the chloride if silver is in solution a white cloud will form, if the solution holds enough silver ions the silver chloride will make a fluffy (slow to settle) White precipitant or salt of silver chloride.

You will most likely need to de-NOx the solution, remove free nitric acid and also convert any remaining base metal nitrate salts to nitric and remove them as NOx gases from the solution before recovering the gold from the solution.


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## DHarr (Apr 20, 2022)

What’s best to denox with in a scenario like this? I do not have any Sulfamic acid but may have all the ingredients and glassware if anyone knows a recipe. I should have at least a couple other substances that would achieve denox’ing. 
Thanks for the reply.


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## Shark (Apr 20, 2022)

Plain heat will do the denox job. Do not boil.


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## DHarr (Apr 20, 2022)

Shark said:


> Plain heat will do the denox job. Do not boil.


That’s easy enough. Been holding it at 80C for 12 hours now. I like this method. Thanks for the info.


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## Yggdrasil (Apr 21, 2022)

Well holding it at a temperature will not destroy the nitric. 
But since the trace amounts you had, probably is already used up, it might not matter. 
What happened was probably that trace amounts of nitric and nitrates formed AR with the HCl and dissolved most or all the metals there.
Make sure all the metals are dissolved by either adding a minute amount of nitric or some bleach or peroxide.
Then you can drop the gold by SMB.


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## DHarr (Apr 21, 2022)

Is sodium hydroxide suitable to add for neutralization?


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## Martijn (Apr 21, 2022)

Forming AgCl from AgNO3 will create HNO3 in solution. You're right about that. 
And there was probably some nitric left in the cakes. 
I would chill and dilute the solution, filter until clear through the same filter to get the AgCl out and then use the solution to dissolve more gold or dissolve a button. 

NaOH will not be good to neutralize only the nitric, it will neutralize all acid and create metal hydroxides. You need HCl to make the SMB work.

You could also neutralize the HNO3 with sulfamic acid. Its done warm and by adding very slowly! So i've heard. 

Martijn.


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## richoc (Apr 22, 2022)

Can I simply ask what kind of processors are working with?
Not much silver in modern processors, but you can have aluminum bonding wires.
For that matter are they pinned or pin less?
that with toss another mess of metals in the mix.
Really need to know what your working with to help, but really sure there would not be as much silver as your thinking.


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## DHarr (Apr 22, 2022)

richoc said:


> Can I simply ask what kind of processors are working with?
> Not much silver in modern processors, but you can have aluminum bonding wires.
> For that matter are they pinned or pin less?


Mostly pinless Pentium's from late 90's to early 2000's. I have only added a handful (maybe 5) pinned CPU's into approximately 100 total. I am not expecting too much silver, maybe a couple grams. I am now suspecting that some of the cake matter was tin, which I am guessing may be playing tricks on my stannous test's? I have reduced the solution to approximately 600ml and cooled in the refrigerator overnight and there is some minor crystallization taking place in the bottom of the beaker. The solution is also very dark green. I am sure there is a whole medley of metals in this beaker. 

Here is what I am thinking I should do:

1) Vacuum filter the solution to get out all the precipitate from condensing the solution.
2) Denox with either urea or boil a gold button until there is no more reaction (open to new ideas or hearing the debate on either method, I do not have sulfamic acid)
3) Cool and vacuum filter
4) Precipitate with SMB
5). Move the remaining solution to a bucket with clean copper flashing to cement anything else of value
6) After a week or so move the solution to a bucket with angle iron to cement the copper


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## Martijn (Apr 22, 2022)

1: Chill with ice before filtering. 
2: Forget urea. It does not help to remove free nitric in solution. Just drive it off with heat. Or sulfamic acid. Do not boil. 
Sulfamic also has the advantage of pushing out any lead before you filter. 
Adding a little bit H2SO4 will do the same. 
Then precipitate the gold out and let it settle well before transferring to the stockpot.


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## Ohiogoldfever (Apr 22, 2022)

I have heard many times to not boil when driving of nitric or chorines. I am curious why? Not to be contrary, I am curious what happens when boiled?


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## butcher (Apr 22, 2022)

Boiling will cause a loss of values in a boiling solution, as bubbles pop they spray a mist into the air, and values can leave the vessel in the bursting mist.

Evaporation will drive off volatile gases without loss of values, if done right it is no slower than boiling at reducing the volume of a solution, a large surface area is helpful to speed up the process.

Boiling would release a spray or mixture of the constitutes of the reaction vessel all of the liquids water, acids, and salts, including values in an escaping mist, would leave at once/

With a lower temperature (below the boiling point of the mixture, at first, mostly water would escape at first as the acids and metal salts concentrate, then the next volatile acid gases would form and escape (like nitric acid, base metal nitrate would concentrate as the NOx was formed from free nitric acid ) after the nitric azeotropes and is either released as gas or form nitrate metal salts, the Hydrochloric acid concentrates (the hydronium from the concentrated HCl acid converts the nitrate base metal salts into nitric acid which is gassed off again as NOx, converting nitrate salts to chloride salts, then the free HCl becomes gas and is released, if any sulfuric it would help to drive off HCl and if enough sulfuric was involved and evaporated base metal chlorides continued they would be converted to sulfate salts, as the HCl gas was driven out of solution by evaporation, sulfuric acid has a very high boiling point is the last acid to go (if the reaction is driven that far), but it would take the heat of roasting red hot 700-800 degrees F, in an environment of air or under oxygen to convert the the dry sulfate salts into base metal oxides


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## Custommetals (Apr 23, 2022)

Miners use Cyanide , but be very careful it is a Poison. Aquarega is also very dangerous. should use a mask and well vented area.


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## Alondro (Apr 23, 2022)

Custommetals said:


> Miners use Cyanide , but be very careful it is a Poison. Aquarega is also very dangerous. should use a mask and well vented area.


I would NEVER advise using cyanide. It's simply too deadly. A single breath of hydrogen cyanide gas will kill you, and accidentally creating that is as simple as dropping concentrated acid into a cyanate solution. Forget it unless you're an expert's expert at the process.


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## Yggdrasil (Apr 23, 2022)

Alondro said:


> I would NEVER advise using cyanide. It's simply too deadly. A single breath of hydrogen cyanide gas will kill you, and accidentally creating that is as simple as dropping concentrated acid into a cyanate solution. Forget it unless you're an expert's expert at the process.


Well, not entirely true.
With the concentrations used for ore the evolution of HCN is quite slow, so if you even do the big NoNo add acid, there is usually ample time to correct the mistakes.
But in concentrated form it is one of the most deadly substances in the world.
So make no shortcuts, if you go into the ralms of Cyanides make sure you know what you do.


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## richoc (Apr 25, 2022)

Wow this thread has gone for a wild conversational turn.....
Can we get back to helping.
With this metal soup you made please stop working on it in a panic.
You need to step back and take a look at what went wrong and why.
You still have many base metals in there to take out before going for a clean Au drop.
Can you post some photos please before going further in to attempting to making colloidal gold by mistake.


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## Geo (Apr 25, 2022)

You explained it to yourself from the beginning. You added silver NITRATE with gold foils to HCl and put it on to boil for the night. When you got up, all the gold had dissolved. 
This is standard operating procedure to me. But I don't understand one thing. When you filtered the foils from the silver nitrate, why not rinse as well as you can then dry and incinerate the filter. Most lab grade filters are ashless and are designed just for the purpose.


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## DHarr (Apr 25, 2022)

Geo said:


> You explained it to yourself from the beginning. You added silver NITRATE with gold foils to HCl and put it on to boil for the night. When you got up, all the gold had dissolved.
> This is standard operating procedure to me. But I don't understand one thing. When you filtered the foils from the silver nitrate, why not rinse as well as you can then dry and incinerate the filter. Most lab grade filters are ashless and are designed just for the purpose.


The silver nitrate was part of the solution that I filtered containing the gold foils. I think it was more other metal nitrates than silver nitrate now.


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## Shark (Apr 25, 2022)

The key word being pointed out is “nitrate”, when combined with hydrochloric make AR. Washing (rinsing your foils very well with water) will prevent this to some extent. Incinerating the foils (low heat) works better. Geo has worked with this very stuff for years, it will help you to follow his advice. 

I do not mean to say the others are not as good, I just have followed Geo’s advice since before I joined GRF. Simply put, it works.


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## Martijn (Apr 25, 2022)

I read your post again and what you have will certainly not be silver nitrate in with the foils after treating only with nitric acid. Unless you diluted with tapwater.
Then tin paste, also known as metastannic acid will be more likely. 

Silver nitrate is very soluble in water and in nitric acid. Add a bit of HCl or table salt solution to a bit of the nitric leach solution and silver will form as silver chloride. If there was any silver, it will be there. Not in the filter.
Or you could test with clean copper to see if any silver cements out. 
To get rid of tin paste, you need to pyrolyze, incinerate and leach the tin out with HCl.
Going straight for AR will also work, but is hard to filter.


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## DHarr (Apr 25, 2022)

Attached are a couple pictures. The green solution is where I am at now, only it is a little darker due to being reduced a few hundred mL. The other picture is when I added the HCl to the nitrate/gold flake cakes. You can see a bunch of the foils floating on the surface. I broke down and ordered some sulfamic acid this morning so hopefully that will help with this situation. What's a good rule to follow as far as quantity of sulfamic acid to add to the mix?


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## DHarr (Apr 25, 2022)

Martijn said:


> Silver nitrate is very soluble in water and in nitric acid. Add a bit of HCl or table salt solution to a bit of the nitric leach solution and silver will form as silver chloride. If there was any silver, it will be there. Not in the filter.
> Or you could test with clean copper to see if any silver cements out.
> To get rid of tin paste, you need to pyrolyze, incinerate and leach the tin out with HCl.
> Going straight for AR will also work, but is hard to filter.


I do think there is a decent bit of tin in the solution. I have put all the waste solution into a bucket with a roll of clean copper flashing and it has been stewing in there for over a week. I started the process of emptying it this morning to see if there is anything good that cemented out, but I ran out of time before I got too far. Its a 5 gallon bucked and I made it maybe 30% through. Hopefully there is something on the bottom.

Thanks all for the responses.


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## Geo (Apr 25, 2022)

Shark is right. It doesn't matter what flavor of nitrate it was. Nitrates are formed when the nitric acid dissolves a metal. The resulting salt is a nitrate. It can dry completely and then when water is added, it is still a nitrate. Anhydrous or hydrated makes no difference. The compound stays the same. It is basically nitric acid locked in a compound with a metal. In the way that it was used caused it to act the way it did. If left at ambient temps, it would have still dissolved the gold but at a much slower rate. When you heated it, the heat energy drove the reaction forward.


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## DHarr (Apr 26, 2022)

New Info:
I attempted to precipitate with SMB, with the solution chilled to 38F and after 12 hours of holding 80C to drive off excess nitric and the precipitate I got was fine and silver in color. I guess my question is will SMB precipitate other metals than gold?


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## FrugalRefiner (Apr 26, 2022)

DHarr said:


> New Info:
> I attempted to precipitate with SMB, with the solution chilled to 38F and after 12 hours of holding 80C to drive off excess nitric and the precipitate I got was fine and silver in color. I guess my question is will SMB precipitate other metals than gold?


Sorry, but holding at 80°C will not drive off excess nitric. Search for information on how to deNOx.

SMB is usually pretty selective, but it depends on what you have in solution, how much you use, etc.

Dave


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## DHarr (Apr 26, 2022)

FrugalRefiner said:


> Sorry, but holding at 80°C will not drive off excess nitric. Search for information on how to deNOx.
> 
> SMB is usually pretty selective, but it depends on what you have in solution, how much you use, etc.
> 
> Dave


Forgive me, my last post was lacking in details. So basically what is in the beaker I am trying to precipitate is what is left of 9lbs of various AMD and Pentium CPU's after 2.5ish gallons of 68% Nitric, filtering the gold foils and whatever precipitated metal nitrates there were at that time (rinsed multiple times with distilled H20), and then bathed the filtrate in 800mL of HCL and 5 mL of 30% H202 (on heat), and then filtered out the chunkies that were left. All visible gold was dissolved. Stannous test was positive. I reduced the the solution down to approximately 400mL. I added approximately 15g of SMB. The reaction was slow but evident. The solution was to dark to really see any colors of the reaction but after the dust settled I poured off the liquid and washed the precipitate and it was a very nice looking grey. I will try to get a picture of it tonight.

Thanks


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## DHarr (Apr 29, 2022)

In Hokes book the primary method of getting rid of excess nitric is to drive it off with heat. Why is this a bad idea now?


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## Yggdrasil (Apr 29, 2022)

DHarr said:


> In Hokes book the primary method of getting rid of excess nitric is to drive it off with heat. Why is this a bad idea now?


It is not a bad Idea, its just the way you do it, will not work well.
You have to evaporate into a syrupy consistency, then add HCl to drive off the nitric.
Then do it again.
Add a bit of NaCl to avoid losses if you evaporate to dryness.

I suggest you read again and contemplate what she is saying, not what you think she is saying.

Edit:
Rereading your post make me thinks you can't have much free Nitric at all.


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## DHarr (Apr 29, 2022)

I followed her description to a T. What I have left resembles some mildly boiled maple syrup. Went from total volume of 2L, to 400mL, back to 600mL, back to 400mL.


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## Yggdrasil (Apr 29, 2022)

DHarr said:


> I followed her description to a T. What I have left resembles some mildly boiled maple syrup. Went from total volume of 2L, to 400mL, back to 600mL, back to 400mL.


Well you said you left it at 80 degrees for 24 hours. 
Not anything about that it reduced to a syrup. 
So you did do the right thing, just forgot to explain it to us.


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