OK. Here is my reasoning. In the beginning, I really dumped a lot of Sodium nitrate into my HCl because not all of the gold would dissolve. As a result, I ended up with a huge excess of Nitric, and still not all the gold dissolved. Since the gold was in the form of placer nuggets, I now assume that somehow they became oxidized causing them to turn black and preventing them from dissolving completely. Then, I tried my first precipitation. I DID get some brown powder settling to the bottom and my solution turned almost clear with the exception of the powdered gold which had yet to settle. I kept adding SMB hoping the solution would show that all the gold had precipitated. Did not happen. Next morning, there was still brown powder in the bottom of the beaker, but the solution had turned to its familiar yellow color. At no time, when I tested the solution did I ever get a negative for gold. It was ALWAYS positive, which I took to mean not all the gold had precipitated.
Let me say here that I purchased Gold Chloride solution online from a chemical supplier and use it as my "standard" for testing my Stannous Chloride solution. Would really cause a lot of problems if my stannous gave me a false negative when in fact, there was gold in my solution. I dip a Q-tip into my standard gold chloride solution and then drop a single drop of my stannous chloride solution on it. So far, my stannous chloride has always turned the end of the Q-tip a rich black color.
Now, I knew I had added way too much NaNO3 and way too much SMB. I felt certain I needed to get rid of excess Nitric, so I hung another gold nugget (1 ounce of 22k) into my solution. Only 1.64 grams of gold dissolved from it. I added a very small amount of SMB and nothing happened. Still thinking the problem was excess Nitric, I started to evaporate it as per almost everyone including Ms. Hoke. I evaporated for several days. next morning (for each of several days) there was a white sediment. At first it looked like crystals, and then it started to look more like a powder. Then, according to Hoke, I added more HCl to reconstitute the solution. I figured it wouldn't hurt anything at this point to try to precipitate any gold that I could, so I carefully added one small spoonful of SMB. The white SMB looked like a snow storm swirling around in the yellow solution. Then, the snow storm turned brown, so I shut off the stir and heat functions and let it rest overnight.
I carefully decanted the solution from the sediment. The sediment went into a beaker with the sediment I got from dissolving foils using HCl/Chlorox. The solution, still yellow has only been evaporated 1 time. As per members on the forum (and Ms. Hoke), I plan on repeating the evaporation process up to a total of three times, or until the solution shows no gold is dissolved in it. If there is still gold in the solution, there must have been nitric there to cause it to dissolve. As some gold precipitates, there has to be less in the solution. Once all the nitric is gone, the gold cannot re-dissolve. Before I start evaporation for the second time, I WILL add H2SO4 to it. Again, anywhere from a few drops to a few ml should do the trick. The original gold was placer gold and not from escrap. I would expect that while it may contain some lead, I wouldn't think it would be that much.
The stannous test has always been a deep black. Both when testing my "standard" solution and my dissolved gold solution. Once I set the Q-tips down, they were indistinguishable.
If I follow Ms. Hoke, I need to evaporate more (at least once or twice). I can precipitate all that will come out right now, but if I wait for it to settle, and there is any nitric left, some will re-dissolve. As long as it's re-dissolving, there must be nitric. Get rid of the nitric and the problem should be solved. Dang, WHAT A ROOKIE MISTAKE!
