Unknown residue from AR

[LawrenceP]

Hi,

This is the first time I am doing this on this scale.

I had about 10 ounces of gold skins from computer pins that I had been collecting and they were removed using concentrated Nitric acid overnight.

I read that 1 Litre of AR will dissolve about 6-7 ounces of gold so I dissolved the 10+ ounces in 1.5 litres of AR and got a greenish solution. I know that this is due to the presence of copper that was not completely removed by the Nitric acid.

After filtering through a coffee strainer and settling down, there was a layer of light coloured residue. The green liquid tested very positive with stannic chloride.

Is this gold due to the dilution of the AR or was there insufficient AR? Or will the gold still be in solution?

What do I do about the residue as I am afraid to discard something valuable or precipitated gold.

Please help!

Lawrence

 

[FrugalRefiner]

Lawrence,

You might have been better off doing a smaller, test batch to see how your material would react. Then you could have scaled up knowing a little more of what to expect. It's hard for any of us to know if there is any gold left in the sediment.

At this point, I would probably treat the solution and the sediment separately. Add a small amount of sulfuric acid to precipitate any lead that might be in solution. Dilute your solution with 2 to 3 times its current volume of water (or ice) and chill the solution. Filter the solution until it's perfectly clear. Then precipitate the gold in solution with your choice of reducing agent.

Then take a small sample of the sediment and add some fresh AR to it. Test this new solution with stannous chloride to see if there was any gold remaining in the solids. If it tests positive, treat the remaining solids with additional AR. If it tests barren then you know it can be disposed of PROPERLY as hazardous waste.

Dave

 

[LawrenceP]

Hi Dave,

Thanks for the tip. It worked!

The sediment turned out to be tin as it turned out to be grey sludgy sediment and did not dissolve when some AR was added to it.

Cheers :lol:

Lawrence