In what way can gold and silver alloys be dissolved?

When we recycle gold mine scrap, we often refine it into precious metal coarse material, which is then refined further. During refining, the crude precious metal material is first dissolved and then separated. Sometimes it is encountered that some alloys are insoluble in neither aqua regia nor nitric acid. At this time, in order to dissolve them, special methods need to be taken.

This morning, a recent gold mine recycling customer called me and said, "ROSE, I have a piece of material that contains gold and silver. I have been dissolving it for a long time, but I can't dissolve it. Can you help me? See what's going on?"
I asked him, "Did you use nitric acid or aqua regia when you dissolved it?"
The client said: "I tried both, and only a little bit of the surface dissolves, and the whole thing basically doesn't dissolve."
I said, "You first test the spectrum to see how much gold and silver are in the alloy."
"It's about 50/50 between gold and silver," the client said.
I said, "Then you do this, add some silver in to make the ratio of gold and silver to 1:3, and then melt them together."
The customer said: "It's melted, now what to do."
I said, "You can do a water quench now. Then you can use concentrated nitric acid to dissolve the silver."
The customer asked: "How to do water quenching, I haven't done it yet."
I said: "You prepare a large bucket, fill it with 70% water, and then slowly pour in the molten gold and silver while stirring the water. At this time, the molten gold and silver will become granular. This is called water quenching. Then after this step, the silver can be dissolved with concentrated nitric acid, but the gold will not dissolve, and the gold and silver can be separated."

Silver distribution is a method for dissolving gold and silver alloys. We all know that gold is soluble in aqua regia and silver is soluble in nitric acid. But if the gold and silver contents are equal, the alloy is neither soluble in aqua regia nor in nitric acid. In general, if the ratio of gold to silver exceeds 3 to 1, aqua regia can be used to dissolve the gold, and the silver will be converted into silver chloride and precipitated to achieve separation. If the ratio of silver to gold exceeds 3 to 1, then nitric acid can be used to dissolve the silver but not the gold, thereby achieving separation. In actual operation, as long as we encounter gold and silver alloys that cannot be dissolved by aqua regia and nitric acid, we will choose the silver matching method to deal with them, because the price of gold is relatively high, and silver is relatively cheap.
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