Hello forum. I am currently dissolving some Sterling scrap jewelry in nitric acid and distilled water. The necklace dissolved the other bits of that I put in their dissolve but the ring which I thought was silver 925 isn't dissolving. It's a heavy man's ring and stamped 925 but doesn't look like much if any has dissolved after being heated and probably 20ml of nitric in total. The total weight of items was 25.6g. so I'm pretty sure that should be plenty to dissolve that little bit of silver. I took out the ring brushed it off with a toothbrush to get the top coating off and I clipped into it and seen no other color such as copper or I don't know any other color so it seemed to me like it was pure silver. But like a dummy I didn't bother to do a scratch test. Should I just do that now? What couldn't be the problem that it doesn't dissolve if it was indeed pure silver?