overdriv said:
Let me get this straight.... do you start out as Hoke says:
Step1. to by adding the nitric acid first to clean out the base metals? Then pour off the solution after letting it sit for a half hour to an hour.
Because I worked against the clock, I did exactly that, aside from letting it sit for a half hour. I always drove my solutions to the point of boiling. Otherwise, you risked having them cake to the bottom of the beaker. Once that happens, you risk breakage, so I added what I expected to be an adequate amount of nitric and water, and drove the contents to a hard boil. By the time boil was achieved, the nitric had pretty well done it's work. I'd take up the solution with (tap) water, stir, allow the contents to settle, pour off, then repeat with a small amount of nitric and water, again, driving to boiling. Note that I used tap water for processing, except for when working with my silver cell. I didn't care if I created traces of silver chloride. They were ultimately recovered, and I didn't mind the small amount I had to deal with. I do not make across the board recommendations for others to follow suit, depending on their particular circumstances.
Step 2. add HLC instead of N, heat, then add nitric until the NO2 (brown fumes) stop. (?)
This may sound like my ego talking, but bear with me.
Because I ran jewelry wastes on a daily basis, I was very comfortable with the reactions and knew what to expect. Right down to knowing how much acid to apply. Unlike Chris, I did not add my nitric separately---for good reason. Remember, I talked about running against the clock. I was so busy refining that I was putting in twelve hour days just to keep up. That includes working seven days per week.
I'd determine how much acid I figured I'd need, mix the AR at the ratio of 1:4, and pour it on. If I felt I had used too much, I'd withhold a small amount, allow the solution to work until action ceased, pour off the solution than add the small amount remaining. If there was undissolved gold, it was obvious. If not, I knew I had dissolved all of the values, and knew it was safe to move to evaporation.
The small excess that might be present was consumed by the added button of gold. The routine I followed was fast and easy---the button was weighed before and after, so I knew how much gold was added to any given lot.
Step 4. and precipitate of choice
Right.
I started out using ferrous sulfate, but I wanted to keep my solutions as concentrated as possible---I had limited space, so doing so allowed the use of smaller beakers. To that end, not long after I started refining, I started using SO2 gas, from a cylinder. I did so until I sold the refining business and retired. It stands heads and shoulders above all other methods, but is not a necessity.
I hope I can learn more from you.
If reading my ravings doesn't do anything else for you, I have hopes that you take away the importance of being honest with your customers. I treated mine with the utmost of honesty, yet still lost a half dozen through the years because they had unreasonable expectations. In refining, you destroy the evidence, so if the customer thinks you've screwed him/her, there's not much you can do to redeem yourself. Acquiring a reputation for being dishonest certainly doesn't help.
I once was in charge of managing the casting gold for jewelry manufacturer and the stone dept. as well. It was a fun job.
Sounds like it would have been. You likely already have an understanding about one's credibility, having held such a responsible position.
Harold
