Question regarding chemical sequence / what did happen?

[theduke_646]

It seems i had a kind of accident, resulting in gold mud and gold crystals.

The sequence was:
a) I did solve gold contining dust in poor mans aqua regia made of KNO3 and HCl. The dust was produced by milling ceramic ICs (Side Brazed Ceramic Dual Inline Packages, SBCDIP). Base metals were eliminated/solved by HCl+ H2O2 and thrown away.
b) Result was a solution of: AuCl3 (Tetraaurumcloro...), K+, NO3-, H+, Cl-, Water.
c) I neutralised the Cl- with Na2CO3. Expection was: result will be a clear yellow liquid.
d) But: at some point it was to much Na2CO3, and the solution morphed to a brown liquid. Resulting in brown mud and some gold crystals. The brown mud is: Gold dust and AgCl, I guess.

But why did this happen, why Na2CO3 reduced the gold? (AgCl is result of some side effects I do not worry about)

 

[FrugalRefiner]

You should not try to "neutralize" the acids once you've dissolved into solution. You want to deNO_X the solution, that is you want to eliminate any excess nitric acid and nitrates. The most commonly used method is to use sulfamic acid.

By neutralizing the acidic nature of the solution, many metals will start to precipitate as oxides, hydroxides, etc.

Redissolve the precipitates with AR again. Add only enough nitrates to get the precipitate to dissolve. Then proceed to drop the gold with the reducing agent of your choice.

Dave

 

[Yggdrasil]

It seems i had a kind of accident, resulting in gold mud and gold crystals.

The sequence was:
a) I did solve gold contining dust in poor mans aqua regia made of KNO3 and HCl. The dust was produced by milling ceramic ICs (Side Brazed Ceramic Dual Inline Packages, SBCDIP). Base metals were eliminated/solved by HCl+ H2O2 and thrown away.
b) Result was a solution of: AuCl3 (Tetraaurumcloro...), K+, NO3-, H+, Cl-, Water.
c) I neutralised the Cl- with Na2CO3. Expection was: result will be a clear yellow liquid.
d) But: at some point it was to much Na2CO3, and the solution morphed to a brown liquid. Resulting in brown mud and some gold crystals. The brown mud is: Gold dust and AgCl, I guess.

But why did this happen, why Na2CO3 reduced the gold? (AgCl is result of some side effects I do not worry about)

Here is a few things to mention.
1. HCl/ H₂O₂ will dissolve Gold, so if you threw away that, you have lost some Gold there.
Dave has covered the rest.

Anyway, why do you just invent such stuff, or have you seen it somewhere?
What about study and the follow proper protocols??

Here is for your studies:

We ask our new members to do 3 things.
1. Read C.M. Hokes book on refining jewelers scrap, it gives an easy introduction to the most important chemistry regarding refining.
It is free here on the forum: https://goldrefiningforum.com/phpBB3/viewtopic.php?f=54&t=19798
2. Then read the safety section of the forum: https://goldrefiningforum.com/forums/safety.47/
3. And then read about "Dealing with waste" in the forum: https://goldrefiningforum.com/threads/dealing-with-waste.10539/

Suggested reading:
https://goldrefiningforum.com/forums/the-library.101/
https://goldrefiningforum.com/threads/when-in-doubt-cement-it-out.30236/
https://goldrefiningforum.com/threa...le-read-this-before-you-post-about-ore.33333/


Forum rules is here.
https://goldrefiningforum.com/threads/gold-refining-forum-rules.31182/