VAN said:
AFTER I BOIL THE JEWELRY WITH NITRIC ,THEN POUR OFF EXCESS ACID, THEN THE SLUDGE AT BOTTOM IS THE GOLD? SHOULD YOU WAIT AND LET THE SOLUTION SETTLE A LITTLE? THE SPOURED OFF SOLUTION IS THEN MOSTLY COPPER AND SOME SILVER. HOW DO YOU GET THE COPPER? ADD SALT FOR THE SILVER.
VAN
I expect that you may get varied responses on this subject. Best I can offer is how I dealt with gold filled objects when I ran my refining business.
After dissolving everything that will go into solution with nitric, the solution is taken up with water to dilute it well, then allowed to settle. Once the solution has settled, it is decanted, and a little salt introduced to the decanted solution to precipitate the silver as chloride. The solids that remain in the beaker should all be put in a filter and allowed to dry. Do not discard anything solid, especially if you find the material is purple in color. That's a sign of either silver chloride that has been exposed to light, or colloidal gold. Once dry, the filter and contents are incinerated until all the paper and resulting carbon is burned away completely. That can be accomplished in a discarded stainless frying pan, heated on a hotplate, then additional heat added with a torch when the pan is hot and the paper has quit burning. Heat until there is nothing left that burns.
The remains are then placed in a beaker and washed in boiling HCL and water. That removes substances that make filtration of the gold chloride solution possible. If you skip this operation, there are times when it can take days for the chloride solution to get through the filter.
The HCL/water solution from this operation is discarded after testing. It would normally contain very little aside from traces of copper and iron. Aqua regia is then introduced to the beaker, dissolving the values. After evaporation, the solution is filtered, then the gold precipitated. You can expect one ounce of nitric and four ounces of HCL to dissolve a troy ounce of gold. Don't use any more than you need-----free nitric must be evaporated in order to recover the gold.
When you refine chemically, never discard any filters. They should be incinerated and the resulting ash stored, for eventual processing for values. You'll recover considerable silver from chloride, plus traces of gold that are impossible to wash completely from the filters. Look at spent filters as a savings account. That's what they are.
You can recover the copper from these solutions by introducing scrap steel, which replaces the copper in solution, and precipitates the copper as a fine mud. That is best carried out in a 5 gallon plastic bucket.
Hope this helps. I know of no slick ways to process gold filled material. It's usually quite dirty stuff.
Harold