gold pin removal

Dissolving the base metals and leaving behind the gold foils for further refining is the way to do this. You can do this several different ways, some better than others. Before that however, you should read whatever books that pertain to these types of reactions first, join GRF and read the posts pertaining to the processes you will be using, and do familiarity tests so that you understand the reactions. Not only that, but these types of reactions MUST be done either outside in a well ventilated area so that no other people or animals are able to breath in the NOx fumes that are given off, or under a fume hood, or best in an enclosed reaction system connected to a wet fume scrubber. The rusty colored red/brown NOx gas that is created can cause serious harm, or even death, sometimes days later. It's bad stuff to say the least, I wouldn't play around with it unless you know what you are doing and have some chemistry under your belt.

I was speaking with someone not long ago about platinum refining. This particular person, who has some experience refining gold under his belt made a very simply yet potentially deadly mistake. He added a substance in an attempt to neutralize the excess nitric acid, this created a highly explosive and volatile solution, then he added another substance to the solution to bring the PH down which caused the solution to explode. Imagine if you can, a highly acidic solution, in glass, exploding with such violence that it throws acids and glass shrapnel all over the place. Fortunate for him he was doing this in a five gallon bucket and most of the solution was contained. Even still, he did get some on his skin and had to neutralize it, he probably will wear the scars for many years to come. To say the least he was extremely lucky it didn't turn out far worse than it did.

Refining using these methods is extremely dangerous even for those experienced. You have to have a process, understand the different reactions and know what to do in case things go wrong. I would strongly suggest, if you are interested in this type of work, that you head my advice above and seek out others, read books, join GRF, etc before attempting anything.

Just a side note, what you dissolved was probably not copper. To dissolve copper with HCl you either need an excess of oxygen in solution, or the HCl has to be so hot that it's almost boiling, not generally the best way to do this. If the pins you were doing were of the type we have been talking about on this thread, then the metal was probably iron or kovar or perhaps both, which both would dissolve in HCl.

Scott