Gaps in Hoke Knowledge-Ewaste

Hello,

Ive found this forum very helpful. Thanks to the people putting in the work here.

I have made 2 successful gold drops and have had trouble with a third. I would like to know more about a few specific details not covered by Hoke. Or covered in passing and ive lost the book.
I main

I have questions like How much Nitric to use to dissolve base metals per gram or pound or kilo when working with ash. How can one be sure base metals are sufficiently treated? Ive heard u can add more nitric to see if it reacts. (bubbles or fizzes)

Wen decanting Nitric containing base metals, do you need to wash the remaining solid to make sure to remove residual nitric?


After dissolving Au in AR filtering to new container and evaporating off excess nitric. How much liquid does there need to be to give the precipitation room? I think i have had troubles with evaporating and leaving to little liquid and thus getting trapped in a SMB cycle. Add more wait. Remove copper add more wait. I know there shouldnt be copper left but the this time there was. Ideally id like to add more control to the overall process.

I am at work so sorry if it is rushed or unclear. Thanks

Welcome to the forum.
When it comes to removing base metals the advice is to remove as much as possible to help create a cleaner AR solution to avoid drag down of base metals during precipitation, as to how much acids to use that’s very hard to quantify due to the mix of base metals that can be present, I’d advise using heat when dissolving and adding small additions of acid as the reaction stops.
The advice in dissolving your gold is to start with an excess of Hcl which will cause few if any problems and then small additions of nitric after the reaction stops, if after an addition of nitric you get no reaction always add a little Hcl to check you still have some free in your solution to continue dissolving the values.
If as you say you have copper left after using AR the chances are you have no gold in solution as the copper will cement any gold from your solution which will look like a black powder so no amount of precipitant will drop it as it isn’t in solution, the filter you I used should have your gold on so simply dissolve in AR but use as little nitric as possible.

Thank you for your reply.

I have had gold drop with what i assume to be copper as well (greeny gelatenous crystals) . The solution that kept dropping copper was testing purple with stannous which kept leading me to add more SMB (Cmon drop you). Ill do some more research thanks again.