Using Au to rid solution of excess HN03

[AUH-R]

Hi all,

Finished off some 486 bottoms yesterday, my process to date:

1. Bottoms left in HCL in a jar outside for about 6mths, swirled now and then, green solution changed for fresh HCL several times.
2. Incinerated with torch until glowing red.
3. Added H20 and a few drops of HN03, no reaction after 5mins.
4. Added HCL Au went into solution.
5. Added a 0.72 Au bead to solution instead of using evaporation technique to try.
6. After reaction stopped I left it on the hotplate for another hour, just to be sure.
7. Weighed Au bead 0.42.
8. Dropped with SMB.
9. Will do usual washes today.

My question, the Au bead I used to rid the solution of excess HN03 looks like it has Cu cemented onto it now. Can someone please explain how this is possible?

Thanks,
AuH-R

 

[butcher]

Just a guess here, the gold bead was not pure gold to begin with.

Another possibility, a saturated solution when hot, will hold more metal salts, than when cooled, it could be possible that when cooled maybe the gold bead has become coated with some of these metal salts.

 

[AUH-R]

Just a guess here, the gold bead was not pure gold to begin with.

Another possibility, a saturated solution when hot, will hold more metal salts, than when cooled, it could be possible that when cooled maybe the gold bead has become coated with some of these metal salts.

I think your 2nd suggestion is more likely, thanks.