mitchd said:
Hi, This is my firt post so I hope that I don't get beat up to bad. My thought is that you should melt the gold fill as is first and then let the nitric acid do it's work. what is left should be darn near 24 karat gold. There is not much gold in gold fill and should be well under the 6 karat that you would make 10K 12k etc to do the same thing.
Welcome to the forum.
Not to fear about being beat up. People with manners do quite well here.
A little bit of advice on gold filled materials.
There is no need, and, especially, no benefit in melting. Because the layer of gold alloy is generally very thin, it can be processed perfectly well without melting. Simply incinerate, to remove oils and other unwanted substances, then digest directly in dilute nitric acid. The gold alloy will be returned as a thin sheet, possibly even as fine particles, depending on how badly it was worn. They settle rapidly, unlike the yield from melted gold filled objects.
When you melt gold filled materials, the gold percentage is too low for the gold to remain in a honeycombed piece. As a result of the fine distribution of gold in the base metal, it is released in microscopic particles that can be difficult to settle. The net result is a prolonged waiting period, with no real benefits, plus the real possibility of losing some of the gold, depending on how you deal with the resulting solution. All in all, I would discourage you from melting, for any reason, unless you use the gold filled material as feed for inquartation.
The gold that is released, while alloyed, is generally partially leached of base metals and silver. It will readily dissolve in AR, for recovery by precipitation. It can also be well washed with HCl, assuming you have incinerated a second time to eliminate traces of nitric. That often performs a valuable service in removing traces of tin, often found in conjunction with gold filled objects.
Harold
Edit: None of this would apply to watch bands, which contain stainless in various ways. I had the best results with such items by stripping with cyanide, in a cell. That is most likely beyond the ability of most folks here, due to the difficulty of buying and dealing with cyanide, which is as it should be. Sell them, or strip them by hand, which is a slow process.