Did I inadvertently make AR and dissolve my gold?

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Martijn

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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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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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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.
 

Geo

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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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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?
 

FrugalRefiner

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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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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.

ThanksGrey precipitate.jpg
 
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Yggdrasil

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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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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.
 

Yggdrasil

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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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