Chemical Aqua Regia Completion

[IThinkSilver]

I used AR to process some RAM chips. Since I didn’t know how much gold was there, I added aziotropic nitric acid drop by drop. In total I added about 10 drops, less than 1/2 ml. I filtered the AR and ended up with about 1000 ml after hydration with distilled water. I took a 100 ml sample of the AR and tried to precipitate with SMB but nothing happened except solution turned colorless. Assuming there was excess nitric, I added about 6 spoons of clean gold foils until no more would dissolve. Again, I took 100 ml sample and same results as first try. Upon consulting Hoke, I boiled the AR down to about 150 ml of thick brownish golden liquid. Then, I added HCL to react with any remaining nitric. So here I am now at this point, not sure how to proceed. Solution is in 2 L beaker. I have seen some recommend using sulfamic acid to correct pH I think. What steps are left to get the AR solution ready for SMB?

 

[Yggdrasil]

I used AR to process some RAM chips. Since I didn’t know how much gold was there, I added aziotropic nitric acid drop by drop. In total I added about 10 drops, less than 1/2 ml. I filtered the AR and ended up with about 1000 ml after hydration with distilled water. I took a 100 ml sample of the AR and tried to precipitate with SMB but nothing happened except solution turned colorless. Assuming there was excess nitric, I added about 6 spoons of clean gold foils until no more would dissolve. Again, I took 100 ml sample and same results as first try. Upon consulting Hoke, I boiled the AR down to about 150 ml of thick brownish golden liquid. Then, I added HCL to react with any remaining nitric. So here I am now at this point, not sure how to proceed. Solution is in 2 L beaker. I have seen some recommend using sulfamic acid to correct pH I think. What steps are left to get the AR solution ready for SMB?

Welcome.
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[Yggdrasil]

I used AR to process some RAM chips. Since I didn’t know how much gold was there, I added aziotropic nitric acid drop by drop. In total I added about 10 drops, less than 1/2 ml. I filtered the AR and ended up with about 1000 ml after hydration with distilled water. I took a 100 ml sample of the AR and tried to precipitate with SMB but nothing happened except solution turned colorless. Assuming there was excess nitric, I added about 6 spoons of clean gold foils until no more would dissolve. Again, I took 100 ml sample and same results as first try. Upon consulting Hoke, I boiled the AR down to about 150 ml of thick brownish golden liquid. Then, I added HCL to react with any remaining nitric. So here I am now at this point, not sure how to proceed. Solution is in 2 L beaker. I have seen some recommend using sulfamic acid to correct pH I think. What steps are left to get the AR solution ready for SMB?

I'd like some clarification on your material.
Ram Chips, means in this setting the whole stick or the only the chips?
How many was there?

AR is not suitable for PCB stripping.

 

[IThinkSilver]

I'd like some clarification on your material.
Ram Chips, means in this setting the whole stick or the only the chips?
How many was there?

AR is not suitable for PCB stripping.

Only the chips, about 200 grams. They were calcined and then ground and filtered in distilled water. Then base metals were removed in nitric boil. Material then washed with distilled water. Then boiled in Aqua Regia and that was filtered to get a clear golden AR solution.

 

[Yggdrasil]

Only the chips, about 200 grams. They were calcined and then ground and filtered in distilled water. Then base metals were removed in nitric boil. Material then washed with distilled water. Then boiled in Aqua Regia and that was filtered to get a clear golden AR solution.

Was it ashed properly so there were no more black in the material?
You added enough Nitric to dissolve around 0.5 grams of pure Gold.
If there were still base metals left, less, since the base metals usually need more Nitric.
And at 1000ml the drop might have been invisible.
Did you let the solution stand over night to let it settle?

 

[IThinkSilver]

Yes, no precipitate and then I added about 4-5 grams of gold foils on heat in 1/2 gram increments to use up excess nitric until the foils stopped dissolving. Remember, I was only using 100 ml samples to check precipitation so as not to screw up the AR.

 

[Yggdrasil]

Yes, no precipitate and then I added about 4-5 grams of gold foils on heat in 1/2 gram increments to use up excess nitric until the foils stopped dissolving. Remember, I was only using 100 ml samples to check precipitation so as not to screw up the AR.

When the solution turned colorless it was probably due to the Gold salts turning into metal.
But since the solution was very dilute you will not see it and it will not be very visible when settling.
Try to evaporate down to 50-100ml and try again.

And make sure the solution is sufficiently acidic.

 

[IThinkSilver]

Ok, I made this post because I am at this point where the AR has been evaporated down to a thick golden brown liquid of about 150 ml. I am unclear about how to go from here to a point where I can do a good precipitation. I know there is at least 4-5 grams Au. Do I just rehydrate with about 800 ml of distilled water and then check pH?
What pH am I shooting for? It was close to 1 before I did the reduction. You have recommended using sulfamic acid in another post. Does this increase the pH?

 

[Shark]

What did the stannous test show?

 

[IThinkSilver]

The test showed gold in solution before the reduction.

 

[Yggdrasil]

Ok, I made this post because I am at this point where the AR has been evaporated down to a thick golden brown liquid of about 150 ml. I am unclear about how to go from here to a point where I can do a good precipitation. I know there is at least 4-5 grams Au. Do I just rehydrate with about 800 ml of distilled water and then check pH?
What pH am I shooting for? It was close to 1 before I did the reduction. You have recommended using sulfamic acid in another post. Does this increase the pH?

Don't rehydrate.
Just add HCl until you are sure it is acidic, say 50ml or so filter well and then add SMB or Iron Sulfate (Copperas) or what ever your precipitant is.

And I do not think you have 4-5 grams of Gold even if you added 4-5 grams of foils.
0.5 ml Nitric simply is not enough for that and usually there are a layer of Nickel or similar under the foils.

 

[IThinkSilver]

Followed instructions, precipitating with Copperas. Mixture turned dark, looks like Au coming out of solution. Thanks so much for the help.