Very weird reacting after failed AR precipitation

Gold Refining Forum

Help Support Gold Refining Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Bluebloomer

Well-known member
Joined
Jul 7, 2014
Messages
140
Location
Netherlands
I had 4 filters with some preciptated gold, but as it was a very fine black powder, I wanted to refine it so I could have a gold button for future AR which had an excess of nitric acid.

- Started with 150 ml 35% HCL
- Brought it to a simmer and added the filters untill they desolved
- Added 4 shots of 1.5 - 2 ML of 53% Nitric Acid.
- Added a few grams of Sulfamic Acid to the hot AR untill it didn't react anymore, asuming the excess nitric was gonne.
- Added 1 ML of 96% H2SO4
- Added ice and waited to cool it down, then used a vaccuum filter.
- Added 2 scoops of 2 grams SMB
- No reacting took place other than the disguisting SMB smell.
- After 30 minutes still no color change (solution was cooled with ice)
- More SMB added 5 scoops in total, and the solution turned from yellow to clear brown but still no precipiate.

Next day after storing in a mini bar too cool the solution hoping it would precipitate the gold, still noting.

So I added copper, and let it sit for another 24 hour. The copper was black, and when shaken thick crusts came off the copper, asuming it was cemented gold and or other metals.

Redissolved the precipitate in 35% HCL, (cold) and after 30 minutes I added just 3 ML of nitric. Then the weirdest thing happened;

It formed a floating precipitate clogged together and allmost looked like a molten piece of plastic or something, also a very heavy chlorine smell appeared and the AR turned a clear brown. The preciitate I tried to dissolve was the thick black crust from the copper cementing from the failed AR.

I have no idea what it is, upon adding the first 1.5ml of nitric I saw the black precipitate on the bottom form this floating precipitate with a heavy rotten egg smell, and later turned to a very heavy chlorine smell.

Could it be that the excess SMB in the AR clinged to the copper and the precipiate was more sulphur based than metals ? I have never seen it before and I forgot to take any pictures, also I cannot explain why this reacting occured but I am beginning to dislike sulfamic acid to denoxx becasue I seem to have more problems precipitating the gold from AR with SMB. It's very difficuld to make sure not to get any excess of nitric. The preganant solution had to containt at least 6-8 grams of gold but no gold dropped in any way.
 
I can’t explain all of your questions but the point where you explained the yellow solution turned to brown suggests to me you had very little gold in the first place and the brown color you were seeing was that small amount of gold in very fine particles in suspension. In all honesty it takes a lot of filter papers to give a reasonable amount of gold unless your careless or processing large amounts of gold.
 
There was enough gold in there to precipitate at least 2 grams.

The copper had this thick black crust on it, I asumed cemented metals. But the joke was on me, the black crusted precipate, was dissolved in HCL, and it turned to deep dark green lumps of copper I asume.

My guess is that the excess SMB somehow cemented on the copper forming some copper complex.
All this trouble and misery because I overshot my nitric again. But I would still like to understand what the reacting was turned the black precipitate into a floating spunge like substance and the rest turned a deep greep, and stayed in the HCL like a droplet.
 
A simple question, did you test your solution with stannous to confirm there was any gold there? and have you tested the supposedly dropped solution?
 
Back
Top