# Gold is stuck it will not drop



## tom341 (May 18, 2007)

I worked all day trying to drop the gold out of my aqua rega mix of sodium nitrate and Hcl. I dissolved mil-spec gold plated pins in aqua rega and no matter what I do with Urea, the MSB will not drop the gold. Stannous chloride shows gold present but it’s still in there. The Aqua rega is very dark and the pins are completely desolated in the mix. The PH level is reading 2.56 I understand that a Ph of 1.0 is the threshold, and ready for the MSB, but I kept adding urea and got up to the 2.56 before I just gave up. I checked it this morning and the pot is about half full or half empty of urea hehehe. I checked the pins wile they were in process and they appeared to have cleaned all the gold off the pins I guess maybe I should have pulled the pins at that point OUT, but instead I left them in the Aqua Rega over night and the pins totally dissolved. Is there too much copper and the gold will not drop? I thought copper would not dissolve into Aqua Rega. I don’t think there is any silver in there because these pins were mil-spec non soldered unused new pins, and appeared to be a base metal of copper. I called the people at Shor and the guy said to drop all the metal out of the aqua rega with aluminum foil and rerun the dropped metal in a fresh batch of aqua rega mix, but won’t the same thing happen? He also sad jested using a plastic spaghetti strainer or mosquito netting to place the pins in the Aqua rega, and as soon as the gold is gone off the pins pull the spaghetti strainer or mosquito netting out with the left over base metal pins before they dissolve into the aqua rega solution. Well guys will I end up with gold being able to drop if I rerun what the left over stuff in the bottom of the Aqua Rega aluminum foil produced sludge or not? ..THX..<*\\\><..TOM  :?: :?:


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## lazersteve (May 19, 2007)

tom341 said:


> I thought copper would not dissolve into Aqua Rega



Tom,

AR will dissolve copper. If you used an excess of AR as compared to the amount of dissolved metals you may not have all the nitric acid gone or it is also possible that you may need to dilute the solution with water to get the gold to drop.

If it were my gold, I would start by testing small samples with a variety of tests to determine what solves the problem most effectively.

For example:

Pour out four small pint sized jars 1/4 full of the reaction solution. 

Number the jars 1-4.

A) In the first test jar add enough water to double the volume. 
- Now try to drop the gold in this jar using SMB. 
- Be sure to let the solution settle overnight to get an accurate test.

B) In the second jar add an equal volume of Urea saturated water. 
- If get fizzing then you still have nitric in the solution.
- Add Urea until the no fizzing occurs when urea is added.
- Try dropping the gold with SMB and settling.

C) Heat jar 3 until the liquid is reduced to a syrup. 
- If you see brown fumes then add HCl and continue heating until no more brown fumes are emitted.
- When you have no brown fumes dilute with water to twice original volume and attempt to drop with SMB.

D) To jar 4 add Aluminum foil to drop a sample of the metal powders.
- Redissolve the dropped metals powder in AR 
- Neutralize the nitric using Urea
- Drop the gold using SMB

The results of these mini test batches will give you the answer you seek.

Good Luck,

Steve


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## tom341 (May 19, 2007)

Thank you Steve,
I already used the foil on the whole batch, but I did filter all the solids out, BOY WHAT A MESS this stuff was practically totally black. I heated and dried out the filters and I will run through nitric acid (½ pound sodium nitrate, and 32 ounces sulfuric acid) and take out all the copper leaving the gold hopefully. Than run the gold through Aqua Rega (½ pound of sodium nitrate, and 32 ounces HCL). I’m hoping this will work. Pins are somewhat moor different than CPUs and Fingers. I had no trouble getting 40+ Grams from them. ..THX...<*\\\><...TOM


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## Kreis412 (Wednesday at 10:39 PM)

lazersteve said:


> Tom,
> 
> AR will dissolve copper. If you used an excess of AR as compared to the amount of dissolved metals you may not have all the nitric acid gone or it is also possible that you may need to dilute the solution with water to get the gold to drop.
> 
> ...


If the answer is jar 1, what is the reason the smb has no effect? Is the copper "taking" the place of the gold? Thank you for your suggestions.


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## orvi (Wednesday at 11:22 PM)

Kreis412 said:


> If the answer is jar 1, what is the reason the smb has no effect? Is the copper "taking" the place of the gold? Thank you for your suggestions.


This is very complex thing, I will some time give it a go and write thread about AR chemistry of base metals and PMs, in connection with oxidation and reduction what is going on inside.

Reason why lazersteve suggested doubling the volume = diluting the solution, is that oxidation potentials are not only fixed numbers - but they can be altered with temperatures and concentrations. If you have nitric acid residues in the pot - it can redissolve the gold back into the solution very easily. But if you dilute the whole pot (but I am not certain if only doubling the volume would help), you dilute these residues and cause nitric oxidation potential to drop - and eventually inhibiting reaction with gold. 

This technique is used by some folks, but I do not have good feeling about it, regarding control and some standardization. And of course, producing more waste which need to be treated


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## goldshark (Wednesday at 11:31 PM)

Did you make your AR by simply putting the Sodium Nitrate into HCL? I don't believe that will work. That is not AR. Please describe exactly what you did to make"AR", please.


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