hungry said:
I was wondering if I could some way refine it over again just to see if I could get different results as I am sure there is some PMs there.
Hey Ed,
Well, there's certainly not much standing in your way, and it could prove to be a valuable learning tool to refine the wastes, but I think I'd give the idea some careful thought before jumping in with both feet.
What you've done up to this point is lower the value of the materials, assuming you've extracted any of the gold. Traces now may be worth far less than the value of the time and acid, but perhaps that's what you're trying to determine.
If I was to pursue this adventure, I'd approach it from the standpoint of refining the spoils from the stock pot. What you've done is put back in the elemental state, any metals that were present. You have also contaminated the material with substances that can be troublesome when you attempt to process chemically. It would be in your best interest to eliminate them, so you are sure that when you apply acid again, that the base metals alone go into solution. I'd start with several hot water rinses, to eliminate any chemical compounds that would be soluble, then I'd incinerate, heating each lot to a dull redness, which would eliminate carbonaceous materials.
I'd then take a small sample and digest it with a few drops of water and nitric acid. Don't use any more acid than necessary to dissolve anything that's willing. When fuming stops, if the addition of a drop or two more acid makes no difference, it's work is done. The entire lot should then be taken up with water, allowed to settle, then decanted. Your target would be the remaining, undigested material. That would then be dissolved with very small amount of AR, then the solution tested, possibly after evaporating to limit free nitric acid. That often interferes with the tests you must perform. Hoke's book discusses evaporation
By running a tiny sample, if there are no values to recover, you won't have wasted a lot of time and acid.
I'd suggest testing the nitric solution for silver before discarding. If it's green, test for gold as well. If it's a distinct blue color, almost no chance it would have any values.
One thing to consider. Once you've converted values to tiny particles, they often will be suspended in solution as tiny specs, usually black, or very dark brownish/purple color. Allow your solutioins to settle once digested, and look for a black or dark covering of material on the bottom. It may well be mixed with various white substances, depending on the nature of the material you've processed.
You could also reduce the material in a furnace, fluxing properly. You'd still face the same problem of re-dissolving an amount of metal that may well not have any value at all, however, and furnace reduction tends to be quite hard on crucibles and the furnace lining due to the aggressive nature of the required flux. It's a good method, but costly-----best reserved to high grade wastes if possible.
If each of your questionable samples started with a slight amount of material, so even if you had 100% recovery, you wouldn't get much gold, I'm of the opinion you'd be better off to simply discard the questionable material and chock up the experience to learning. Avoid recovering base metals along with traces of values from future lots by testing properly before hand, then discard things as quickly as possible. Our memories have a way of making us think garbage may well be worth saving, and it's usually wrong. When you come back to a solution, you'll always question your previous decision------and it will drive you nuts. If you test with fresh or proven test solution, and the solution in question is barren, it's time to get rid of it. You'll get more comfortable with this as you progress, gaining the necessary confidence not only in the testing solution, but your own judgment. I fully understand your reluctance to do so at this point.
I mentioned buying the book. It will teach you what to look for regards the platinum group, plus how to properly test. It's the cheapest and best advice you can get from any source. I've mentioned time and again, I am nothing more than a high school graduate that took no chemistry classes------but I learned to refine, and ran a (very successful) commercial refining business for a little more than 20 years, all with knowledge I gleaned from Hoke's book. It's good-----very good------and written so the common man can make sense of everything mentioned.
Keep us all posted.
Harold
:wink: 
