Gold dropped without SMB?

[Ohiogoldfever]

I have a curious one I’d like some input from people smarter than I am.

This batch is from about 1lb black poly top duel leg transistors. I removed the legs in a previous step using AP. After leg removal I was left with the plastic D shaped tops.

Tops were incinerated, crushed in a mortar and pestle. The crushed material was rinsed in a bucked to separate the ash from the heavy materials. Once rinsed all material was put into a 2 liter beaker and digested using 1 tablespoon potassium nitrate and roughly 300 mL HCl. The reaction was allowed to take place in the sun over the course of about eight hours.

After all visible gold had been digested I filtered the material and de Nox with Sulfamic acid. At this point I rinsed all the remaining materials several times using distilled water. The rinse water was filtered and used to dilute the pregnant solution (stannous test positive for gold) . Once diluted I filtered one more time (coffee filters) to try and remove some final haze in the solution. I left this over night to filter intending to drop this morning with SMB.

This morning the solution is crystal clear though slightly green. A fine layer of material has settled to the bottom. Slightly gray in color. Probably super fine ash mixed with gold mud is my expectation.

Stannous test now shows negative.

I don’t need advice on recovery as I am comfortable with that. I am just curious if anyone can help me understand why the gold dropped without SMB treatment.

 

[Yggdrasil]

I have a curious one I’d like some input from people smarter than I am.

This batch is from about 1lb black poly top duel leg transistors. I removed the legs in a previous step using AP. After leg removal I was left with the plastic D shaped tops.

Tops were incinerated, crushed in a mortar and pestle. The crushed material was rinsed in a bucked to separate the ash from the heavy materials. Once rinsed all material was put into a 2 liter beaker and digested using 1 tablespoon potassium nitrate and roughly 300 mL HCl. The reaction was allowed to take place in the sun over the course of about eight hours.

After all visible gold had been digested I filtered the material and de Nox with Sulfamic acid. At this point I rinsed all the remaining materials several times using distilled water. The rinse water was filtered and used to dilute the pregnant solution (stannous test positive for gold) . Once diluted I filtered one more time (coffee filters) to try and remove some final haze in the solution. I left this over night to filter intending to drop this morning with SMB.

This morning the solution is crystal clear though slightly green. A fine layer of material has settled to the bottom. Slightly gray in color. Probably super fine ash mixed with gold mud is my expectation.

Stannous test now shows negative.

I don’t need advice on recovery as I am comfortable with that. I am just curious if anyone can help me understand why the gold dropped without SMB treatment.

This bold text made me wonder.
Did you digest all metals in there?

 

[Ohiogoldfever]

Thinking it’s cemented on fine copper maybe?

After the multiple processes it had been through I wouldn’t have expected much to have avoided digestion.

I suppose that could be. Given the color it leads me to think it’s still got some copper in the solution. I’d just planned to deal with any of that in further refines.

That makes sense.

 

[Yggdrasil]

Thinking it’s cemented on fine copper maybe?

After the multiple processes it had been through I wouldn’t have expected much to have avoided digestion.

I suppose that could be. Given the color it leads me to think it’s still got some copper in the solution. I’d just planned to deal with any of that in further refines.

That makes sense.

If there still are undissolved metal in there you will get only parts of the gold since it cements back to the base metals. That is why I asked.

 

[Ohiogoldfever]

If there still are undissolved metal in there you will get only parts of the gold since it cements back to the base metals. That is why I asked.

Right. I’m aware of cementing though wouldn’t have expected it. I suppose it’s possible. I’ll get back at it tomorrow and see what I find as I decant and re-digest the sediment.

Thanks for the help!

 

[Ohiogoldfever]

I made it back into the shop. I syphoned the clear solution off and did another stannous test.

I got a very pale orange with a moderate black just along the edge of my drooping filter paper.

I’ll add SMB and see what drops. It’s not nearly the instantaneous dark result it was giving me during my first stannous test.

I’ll also post what happens when the mud in the beaker is re- refined.