Color change (poor mans AR)

[Tankman]

Hi all,

I have been recovering gold from pentium 1 processors over the last few weeks (320+ in all). The last batch that was done, were all the pieces that were not fully dissolved from the previous recoveries. The method that was used was to add HCL and a little water to the 1.3 pounds of the ceramic processors, with small introductions of potassium nitrate. Once the brown fuming stopped after the last addition, I let the solution simmer for one hour before turning of the hot plate and letting cool to room temperature. The solution was a very dark green color, but when I poured it into the beaker with ice, it turned a muddy yellow color, which after letting settle overnight turned to a clear yellow color, with the silver chloride sitting at the bottom. This was filtered, and 5 grams of smb dissolved in 50mils of warm water was added to the solution which turned it a rusty yellow color. The solution still is a rusty yellow color after letting it sit after twelve hours.

 

[Barren Realms 007]

Have you tested your solution with stannous chloride?

Not sure what question you are asking on this?

 

[Tankman]

Yes, I have tested with sn and it tested positive for gold. The questions are, why did the solution change from a very dark green to yellow? and when I added the smb it went a rusty yellow color instead of dropping the gold powder out?

 

[jeneje]

If it were me, I would add Ice to the solution and cover it with a watch glass and set it up somewhere until the gold finished coming down.

Ken

 

[bswartzwelder]

If your solution tested positive for gold, you aren't through with the precipitation process. There's still more gold which you need to drop. Once the solution tests negative, all the gold has been dropped.

 

[Anonymous]

One thing I would say is that if you used a mere 5g of SMB in a solution that you dissolved 320 Pentium 1 processors into then there's no surprise that it's still pregnant.

You have at least 30g of gold in there so why under use the precipitant?

edit: some people recommend 1g of SMB for each gramme of gold. I always think to works out at more so you need to add one heck of a lot more 8) 8)

Jon

 

[Tankman]

Sorry, should have made myself a bit more clear on this. I have been doing the pentiums in batches of 40 at a time. The last batch, (which is the one about this thread) was all the left overs that were not fully dissolved during previous recoveries.

 

[MarcoP]

Since its a batch made from leftovers and probably set aside for a while could it be a consequence of a poor rinse leaving some acid that with air and time oxidized the leftover metal creating this color change?

Basically you have now been dissolving metals oxide too.

Marco

Edit: clarity.