Strange reaction with SMB

[Swissgoldrefiner]

Hello,
I have a solution which contain gold and probably other PM.
It looks green/yellow.
I started to add SMB few spoon (probably too much) and the solution turn totally to brown.
Does anyone have this issue befor? It's maybe it miss HCl?

 

[FrugalRefiner]

Well, at the risk of having missed something, it's supposed to turn brown.

Was the solution concentrated or dilute?
Assuming you added the SMB dry, did it all dissolve?
Is the SMB fresh or old?
Have you added a bit more HCl?

Dave

 

[Swissgoldrefiner]

Well, at the risk of having missed something, it's supposed to turn brown.

Was the solution concentrated or dilute?
Assuming you added the SMB dry, did it all dissolve?
Is the SMB fresh or old?
Have you added a bit more HCl?

Dave

I mean it turn brown, but whole the solution...not cloudy brown and when i left it lets say 30 min, it stay cloudy.
My stanous chloride test show nice concentration of gold...as well as Pt...but it s old test, tomorrow i will try to make a new SnCl solution. Dont know if old solution can give fake positive...but it may.
SMB all dissolved well, no feezing. SMB should be 1 year stock...
I didnt add more HCl...i will try this things tomorrow.

 

[orvi]

Hello,
I have a solution which contain gold and probably other PM.
It looks green/yellow.
I started to add SMB few spoon (probably too much) and the solution turn totally to brown.
Does anyone have this issue befor? It's maybe it miss HCl?

It is normal that AR solutions turn nearly black in colour when treated with excess sulfite. Strange that you test positive for gold even after addition of SMB. Maybe some residual oxidizer is present.
Sometimes when you are dropping gold from dirty solutions, it take quite a bit of time to settle down.

My experience is that old testing solution do not have much reducing power - tin is oxidized to +IV oxidation state by oxygen. So opposite situation.

 

[Martijn]

If still positive for gold after smb, add more smb and test again.
If the gold won't settle, heat it with a bit of sulfiric acid added.

 

[Martijn]

And make reference gold test solution to verify your stannous is working or not.

 

[Swissgoldrefiner]

Yes, guy i will do all this tomorrow...i am fed up with SMB...haha

But i was thinking maybe i have some organic compound which may interfer. The item come from milling chips of swiss watch and contain lot of oil. First batch i didnt burn the oil, so i was thinking it may come from that. My solution looks positive to Pt and Au...but with my old SnCl2...
Thanks for your support.

 

[orvi]

Yes, guy i will do all this tomorrow...i am fed up with SMB...haha

But i was thinking maybe i have some organic compound which may interfer. The item come from milling chips of swiss watch and contain lot of oil. First batch i didnt burn the oil, so i was thinking it may come from that. My solution looks positive to Pt and Au...but with my old SnCl2...
Thanks for your support.

Most organics together with dissolved gold act as reducing agents for gold. Or they are inert. Oil is just painful to deal with when refining, but overall it do not react with anything in the mixture. Maybe at elevated temperature some of it get chlorinated with chlorine evolved from AR. Maybe
And not to forget, gold chloride and chloroauric acid tend to be somewhat soluble in some organic solvents. Not heaps, but it should be considered and being aware of.
You can also dissolve the oil from the material with some solvent like acetone or toluene, even paint thinner will work. But burning is cheap

 

[Swissgoldrefiner]

Most organics together with dissolved gold act as reducing agents for gold. Or they are inert. Oil is just painful to deal with when refining, but overall it do not react with anything in the mixture. Maybe at elevated temperature some of it get chlorinated with chlorine evolved from AR. Maybe
And not to forget, gold chloride and chloroauric acid tend to be somewhat soluble in some organic solvents. Not heaps, but it should be considered and being aware of.
You can also dissolve the oil from the material with some solvent like acetone or toluene, even paint thinner will work. But burning is cheap

The probleme with the oil is that it make some "protective layer" which avoid acid to attak metal correctly. Another batch of that mess, which have oil floating, i added IPA and it dissolve a little the oil and then the metal restart to react.
Another batch, i used EtO2 to separate oil and metal mess...this works...i will let the Ether evaporate and then add some solvent to flame everything. It's small test of 20 gr, so no matter of fume, etc...

Another batch which i preburned and removed the oil dont want to precipitate as well...but i think it's because it contain too much nitric...it dont feez...but i smell the stong smell of Sulfite/Hcl smell when i add more SMB....i mean the acidid carecteristic...
What is strange is that i added huge amount of urea and SMB, but nothing happen. Maybe it's because it's too cold in my place (probably 5-10°C...i need to do it in my lab, but too lazy to go there...). In past it happen to me that i add SMB and nothing happen and i wait 2 days and then the Au come out.

 

[orvi]

Yes, that is an obvious issue. You can burn it out with torch and than properly burn also all carbon that is produced primarily. Washing with some solvent is very elegant solution, but more expensive of course.
Do not mix IPA or any other solvent with AR or nitric, it can be very dangerous in terms of unstable and toxic compounds produced.

"Smell test" is my primary test when dropping gold if you can smell SO2, gold is most probably reduced completely. Maybe it just need time to equilibrate.

 

[Rick & Carrie]

Hello,
I have a solution which contain gold and probably other PM.
It looks green/yellow.
I started to add SMB few spoon (probably too much) and the solution turn totally to brown.
Does anyone have this issue befor? It's maybe it miss HCl?

The brown is the gold dropping out of solution. The brown will settle as a sludge at the bottom of your container. Decant the bulk of your Solution And rinse the remaining solution with the brown gold sediment into your filter in your filtration system. Rinse the sediment with hot distilled water, then let dry. Melt this with borax in a melting dish to produce the familiar yellow metal as a bead.

 

[Swissgoldrefiner]

Update:
So the batch who have oil and looks brown now looks green and the gold is precipitated. I think the brown color was due to the oil. It should make like an emultion (like oil in milk) and probably avoid gold to go down.
The other batch i got the gold in the bottom as well. However, i have too much SMB: I can see some crystal forming. So i add more whater.
What i find strange:
1. As SMB have high solubility, it's strange that i have crystal (i dont think i reached the saturation).
2. For fun, when gold was coming out and i was heating the solution i added some HCl...the precipitate disapeared!

I still have some doubt about other PM inside it. So i will try to dissolve 1g of platinum 9995 inside AR and use it as testing solution.