After processing a couple of kilograms of Gold Filled, there was a fair amount of tin in the process. I let the ugly gray settle, decanted and filter the bulk of the gold. Looking at the sludge I could see plenty of purple in mixed in. I did a several HCL/Bleach leach processes, with lots of agitation. Result was about 600ml of dilute dirty solution. I evaporated to 250 ml, Stannous was dark purple.
Filtering wasn't going great to clear up the solution. I decided to drop the gold and call it recovery mission. I added SMB, the color turned, but not the dark brown I was expecting. After SMB add produced SO2 fizz, I tested with Stannous, result was light positive. I added a bit more, it fizzed right away. I tested again and still light positive. Walked away, let it settle for 5 minutes. I tested again and got what looks like a false positive (brown.) I am used to SMB acting almost instantly and getting a negative test once it starts fizzing up SO2. This time I went from a light positive to what looks like a false positive after a 5 minute pause. Is this a normal thing? I am wondering if I need to change my process to wait a 5-10 minutes after the SO2 fizz hits to test? Otherwise my thoughts are to recover and refine the gold, stockpot the solution and move on, unless I am missing something.
Any thoughts would be appreciated. Pictures of the drop and the tests attached. Note, in the tests picture the far right, almost out of the picture, is the test right after the last SMB add, the left brown is the test 5 minutes later. The middle is pre-drop.
Filtering wasn't going great to clear up the solution. I decided to drop the gold and call it recovery mission. I added SMB, the color turned, but not the dark brown I was expecting. After SMB add produced SO2 fizz, I tested with Stannous, result was light positive. I added a bit more, it fizzed right away. I tested again and still light positive. Walked away, let it settle for 5 minutes. I tested again and got what looks like a false positive (brown.) I am used to SMB acting almost instantly and getting a negative test once it starts fizzing up SO2. This time I went from a light positive to what looks like a false positive after a 5 minute pause. Is this a normal thing? I am wondering if I need to change my process to wait a 5-10 minutes after the SO2 fizz hits to test? Otherwise my thoughts are to recover and refine the gold, stockpot the solution and move on, unless I am missing something.
Any thoughts would be appreciated. Pictures of the drop and the tests attached. Note, in the tests picture the far right, almost out of the picture, is the test right after the last SMB add, the left brown is the test 5 minutes later. The middle is pre-drop.
