Contaminated Nitric?

Yggdrasil · Jun 21, 2022

Hi.
I have been involved in helping a friend with some ore refining.
So far we have smelted with Lead, Silver and Copper.
There is a couple of assays saying that it have significant gold in it.
The problem is that every time we are parting the button it dissolves completely.
It tests positive for Gold in Stannous.

If we drop the Silver as Chloride the Chloride become brown, clean/wash it in AR and it is Crystal white.

After some head banging we decided to test the Nitric on Gold foils, poof no more foil.
So we have reached to a conclusion that the Nitric is somehow compromised.

But how?
Have anyone else had this challenge?
It can’t be chlorides, the AgNO3 is crystal clear?

Regards Per-Ove

Jimbriese · Jun 21, 2022

I’m not sure but I think I had some AP on some gold fingers inside the fume hood and then started a batch of silver contacts in nitric the next day the gold was gone from the fingers. I think the fumes for the nitric was absorbed into the HCL and caused my issues.
Don’t know if it would go the other way if the bottle was left open in the same vicinity but is an option to look at.

orvi · Jun 21, 2022

Solubilities could be very different in various solvents. AgCl is insoluble in water, but soluble in HCL (to some extent). Nitric is another solvent, where It possibly could be soluble. Maybe.

But tech grade nitric is many times contamined with some chlorides, which can help to dissolve gold. And as it was said above, if it isn´t tightened well, or stored in vicinity of HCL, vapors can mix and this could happen.

Justincase · Jun 21, 2022

A problem with basic parting?
Have you tied a sample that you know to be pure silver?
If there are chlorides present in your nitric you will see the AgCl.
Then you have to work out if it is the fault of your supplier or if you mixing up storage containers.
But either way, it is a very basic and necessary point of separation.
To even be able to do this you would need a very low silver content.

BlackLabel · Jun 22, 2022

Did you use tap water?

Yggdrasil · Jun 22, 2022

No, he has distilled water for this.
He is scratching his head and wondering if he used the wrong pipettes at one time in the future.
But that should be minute at best.