If AR stopped to work ...

[Renaldas]

What is better to do in such situation:
- add a little nitric acid;
- add a little HCl;
- add a little new aqua regia;
- add something else;
- fully replace AR solution.

 

[Anonymous]

Read chapter VI of Hokes Refining Precious Metals Wastes.

Best Regards
Gill

 

[eeTHr]

Renaldas;

If you used concentrated nitric and concetrated HCl for your aqua regia, then try adding some water and see if the reaction starts up again.

If your solution is very dark, and it already has some water from using diluted acids, try adding some HCl and see if it starts again.

The last thing to try is, add a little nitric and see if it will finish dissolving. If it doesn't quite finish, then add a little bit more nitric. This is the best way to use the nitric, so you won't end up with lots of excess nitric to get rid of before testing or precipitating.

Don

 

[goldsilverpro]

I'm assuming you haven't added any water. I'm not big on adding water - even 10% slows things down. Add a little HCl and heat it. Keep it hot. If the HCl produces a reaction, let it work to completion and then add a little more HCl. When an addition of HCl produces no reaction, add a little extra HCl (maybe 20% of the volume) and then add a little nitric. Keep it hot. When an addition of nitric doesn't react, add a little HCl. If you added enough extra HCl above, this will also produce no reaction and you're finished. If the last HCl produces a reaction, start over with the above process. Do it right and you won't have to evaporate or add urea, unless you had an excess of nitric to start with.