I have done three previous batches of fingers in AP and currently am processing the fourth batch, each with 500 grams of fingers.
The first batch was done with 2:1 HCL (31.45%) and H2O2 . I noticed on it quite a bit of black sediment. I was not able to obtain 3% H2O2 so I prepared it from 35% strength (86mls of 35% H2O2 and 914mls of water) to come up with 3% peroxide in 1 liter solution.
The subsequent two batches were done, in the same solution from the first batch, without adding anymore HCL or H2O2 but with continuous aeration from an air pump. Complete removal of gold fingers occured within 36 hours in both cases, as well as in the first one.
I noticed in the second batch that the gold was composed of a rather large percentage of small/ very small particles and am still observing black sediment. The third batch had a lot less amount of small/very small particles, but still observed black sediment.
My questions;
From a previous post by Steve, I read that gold will not dissolve in the solution when you are using aeration instead of peroxide. I believe the black sediment observed be gold from the first run, or is it being also formed in the subsequent batches; or is it another material?
When gold is re-dissolved back into a reactive solution after adding SMB and not promptly removing it from the solution in , will it precipitate using SMB again?
What can be causing the formation of the small gold particles? The fingers were the same type in all cases. Nevertheless, these particles precipitate with SMB but a lot end up in the filters when you are washing and filtering.
Thanks