So a month into working on SIMs, I have over 30 lbs of processed foils (plastic backings removed by hot 20% NaOH solution, plus frequent mechanical stirring in a 16 Gal steel drum, all over 2-3 hours in 5 lb batches).
I added enough HCl to cover a 4 lb sample, with heat, and then added HNO3 a few ml at a time. Some red gas came off, likely because of all the copper. Stannous test is positive, but cannot drop any gold.
Is there too much copper and other metals present?
Is there an ideal pH to aim for (with what?)
Should Denox be done with sulfamic only, or would urea help here because of the other nitrates?
Thanks for any tips.
I added enough HCl to cover a 4 lb sample, with heat, and then added HNO3 a few ml at a time. Some red gas came off, likely because of all the copper. Stannous test is positive, but cannot drop any gold.
Is there too much copper and other metals present?
Is there an ideal pH to aim for (with what?)
Should Denox be done with sulfamic only, or would urea help here because of the other nitrates?
Thanks for any tips.