brjook said:
Ok i had three batches about 1OZ per batch of Gold filled caps from watches .I added nitric and let it work.I then heated it till no more bubbles was seen.I decanted and added more nitric and split with equal amouts of water.Oh yea I used 100 ml of nitric 70% on each batch .When the bubbleing stopped i heated and it took a while and the batch seemed to go into a runaway reaction that boiled over in one batch. I took the remaining sediment from all three batches and again added nitric and water and boiled till no bubbles was seen.No runaway this time.
That was an indication that one of two things had occured. One was that you had eliminated all of the base metal. The other is that you eliminated all of the nitric. I choose to think that's what you did.
I then mixed up my AR 50 ml of 70% nitric and 400 ml of hcl. I added it to the sediment and it started bubbleing real good for 45 minutes or so.I tried a test bach about 15ml of the solution and added urea to remove the excess nitric.Dilluted with 4 time water and added SMB. The solution was bluegreen not yellow like i expected.
That's most likely because you hadn't eliminated all of the base metals. If you had any white gold caps included, pretty good chance they were on a nickel substrate. Nickel can be troublesome---it's the thing that causes the rapid overflow of a solution, which is a VERY common reaction when processing eye glass frames. All you can do is suffer through the experience until it is all dissolved. It happens only upon the solution reaching a critical temperature, at which time a beaker that is only 10% full can rapidly foam over. I used to control the reaction by adding water. Eventually the nickel is dissolved and the reaction is normal.
Here's a hint that can be very helpful when you're processing gold filled objects. The gold can be attached to the base metal by means that leave a little to be desired, at least from the perspective of the refiner. After you have dissolved all of the base metal, something you ascertain by adding a small amount of fresh diluted nitric, and bringing the material to a boil. If there's any base metal left, you'll see the reaction. If there is not, the solution will only slightly discolor (blue/green), and there will be no brown fumes. At that time the material should be well rinsed with water, then gathered in a filter. When the solids have been extracted and dried, they should be fully incinerated, along with the filter. The resulting solids are then ground in a mortar with a pestle, and then screened. Any large items that won't go through the screen are suspect---they are either base metal that escaped dissolution, or they may be solid gold. If white in color, they may also be stainless. Testing is quite important if you hope to be successful.
Once the items have been screened, they are given a wash in hot HCl, then rinsed until the rinse solution is clear. There is no need to filter, simply allow the solids to settle, so nothing but solution is poured off.
When the solids yield clear wash water, they can then be dissolved with AR, or the solvent of your choice. The resulting solution will have a wonderful yellow color, and will filter without issues.
I added the SMB and the SMB turned akinda red when it was mixing .No darkening of the solution till i let it set for ten fifteen minutes.Upon checking my AR solution i still had a large amout of gold flakes floating around in it.Did it just dissolve the little bit of base metals left over and not the gold I have several grams of gold in solution and don't want to screw it up .What did i do wrong or what am i seeing ?
For starters, I see no mention of testing with stannous chloride. If you haven't, you're certainly not winning any points with me. Testing is important----VERY IMPORTANT, especially when you're trying to learn.
Ok, right now I'm inclined to think that because you hadn't removed all of the base metal (the solution wouldn't have been blue/green if you had), you dissolved some of the values, but they were most likely partially, if not fully, cemented by the remaining base metals. It's very possible that not all of the liberated gold flake was dissolved, so that may account for the flakes you see in suspension. Test the solution to see if it shows positive for gold. If it does, add a small amount of copper and allow it all to cement. When the solution tests barren, you should remove the trace of copper that was added if you can, but if not, don't worry about it. Expect the cementation to be slow unless you add a lot of copper.
When the solution tests barren, add water to dilute and allow the solids to settle. Siphon off the solution (test again to see if there's any values), and rinse well. Repeat until the solution is clear of color, then add some dilute nitric and heat. Your objective, right now, is to remove the traces of base metal you left behind. When that has been addressed, pick up on the process where you rinse well, then filter and incinerate. If you follow these instructions you will recover all of the values. If you try to re-invent the wheel and go off on a tangent, that may or may not be the case.
Harold