Over saturation?

[Honda350x]

Was wondering if possible to over saturate a solution with smb and if so what is the outcome of the over saturation. Smb was dissolved in water before added to solution to precipitate gold.

 

[4metals]

Welcome to the forum

A saturated solution of sodium metabisulfite will have about 1 pound per liter of solution. That is a lot of solids in a liter. But even if you had a saturated solution to add to your aqua regia, you are still diluting it to below saturation when you add it to your aqua regia. Usually, using SMB dissolved in water, you will not add too much if you agitate and stop adding when the approximate amount of SMB is 1 gram per gram of gold in solution, or close. Then you test with stannous.

Guys who add SMB as a powder are the ones who typically over add. If you make up a standard solution at 1 troy ounce of SMB per 25cc of water it is easy to know how much to add per ounce of gold you are looking for. If you are refining e-scrap go slow with the SMB because there is rarely an ounce in solution.

 

[Honda350x]

Welcome to the forum

A saturated solution of sodium metabisulfite will have about 1 pound per liter of solution. That is a lot of solids in a liter. But even if you had a saturated solution to add to your aqua regia, you are still diluting it to below saturation when you add it to your aqua regia. Usually, using SMB dissolved in water, you will not add too much if you agitate and stop adding when the approximate amount of SMB is 1 gram per gram of gold in solution, or close. Then you test with stannous.

Guys who add SMB as a powder are the ones who typically over add. If you make up a standard solution at 1 troy ounce of SMB per 25cc of water it is easy to know how much to add per ounce of gold you are looking for. If you are refining e-scrap go slow with the SMB because there is rarely an ounce in solution.

Thanks for the response, yes did test with stannous after gold dropped, test was clear. Did a wash with distilled water on the solids after decanting,but now have a purple hue on the solids and in the water, so was wondering if the oversaturation of the smb would cause this, or I need to do some more research on the matter

 

[4metals]

Decanting is never as good as filtering and rinsing. By a purple hue are you talking about the color of a stannous test? Or discolored insolubles after decanting? What were you refining? And how were you refining it?

 

[Yggdrasil]

Thanks for the response, yes did test with stannous after gold dropped, test was clear. Did a wash with distilled water on the solids after decanting,but now have a purple hue on the solids and in the water, so was wondering if the oversaturation of the smb would cause this, or I need to do some more research on the matter

As 4metals say welcome.
You did not by chance spill some stannous?

 

[nickvc]

Purple colored solutions can indicate very fine gold particles, more information as in what and how much you refined and in how much solution may provide some more ideas.

 

[Honda350x]

As 4metals say welcome.
You did not by chance spill some stannous?

No, did not spill any stannous

 

[Honda350x]

Decanting is never as good as filtering and rinsing. By a purple hue are you talking about the color of a stannous test? Or discolored insolubles after decanting? What were you refining? And how were you refining it?

Was refining gold from circuit boards, and was using ar, the purple hue showed up after doing a first wash on the gold particles that dropped out of solution

 

[Honda350x]

Purple colored solutions can indicate very fine gold particles, more information as in what and how much you refined and in how much solution may provide some more ideas.

Was kind of thinking this, the fine gold particles part, hence the question about the over saturation of the smb.

 

[Yggdrasil]

Was kind of thinking this, the fine gold particles part, hence the question about the over saturation of the smb.

You have somehow created nanoparticles of Gold and it has nothing much to do with the SMB.
AR is NOT suitable to use directly on PCBs

 

[Yggdrasil]

By the way I corrected the thread title.

 

[nickvc]

You have somehow created nanoparticles of Gold and it has nothing much to do with the SMB.
AR is NOT suitable to use directly on PCBs

I suspect that the OP had a large volume of dirty solution with very little gold but unless we get full details I’m only guessing.

 

[Yggdrasil]

I suspect that the OP had a large volume of dirty solution with very little gold but unless we get full details I’m only guessing.

Your suspicion sounds likely.