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.

 

[adam mizer]

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

At this point I would have boiled my solids in HCl. 10-15 minute boil checking color of HCl if contamination is dissolving.
I watch the color of the gold powder, lighter color the better.
My recent washes I use ph paper that tells me when I'm neutral, I have found that many small rinses were needed more than I thought.
Have a stock pot storage for gold washes.
It appears like you have dirty gold. Contaminated with other metals.
You should AR again, and second drop will most likely be much cleaner.
The cleaner the gold it likes to clump up together, if dirty with other metals in it will be fine type loose particles darker color.
Also your filtration must be crystal clear.

 

[Honda350x]

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

Didn’t use ar on the pc boards, I soak those in mauratic and peroxide with a bubbler first, only use the ar to put gold into solution to precipitate it out

 

[Honda350x]

At this point I would have boiled my solids in HCl. 10-15 minute boil checking color of HCl if contamination is dissolving.
I watch the color of the gold powder, lighter color the better.
My recent washes I use ph paper that tells me when I'm neutral, I have found that many small rinses were needed more than I thought.
Have a stock pot storage for gold washes.
It appears like you have dirty gold. Contaminated with other metals.
You should AR again, and second drop will most likely be much cleaner.
The cleaner the gold it likes to clump up together, if dirty with other metals in it will be fine type loose particles darker color.
Also your filtration must be crystal clear.

Gotcha, thank you

 

[Honda350x]

Thanks all for the input, when some time allows , I will post some pics on the process I did for this batch , so I can be sure which direction to go in, and make it clearer for those that have done it longer than myself to make sure I’m doing this right!

 

[Yggdrasil]

Didn’t use ar on the pc boards, I soak those in mauratic and peroxide with a bubbler first, only use the ar to put gold into solution to precipitate it out

You would be better off using HCl/Bleach or HCl/ Chlorine or HCl/ peroxide for the foils.
How much foils did you have?
How did you prepare your AR?

 

[adam mizer]

Thanks all for the input, when some time allows , I will post some pics on the process I did for this batch , so I can be sure which direction to go in, and make it clearer for those that have done it longer than myself to make sure I’m doing this right!

Yes its a curve to learning to deal with where you are at.
AP leaves foils but the foils themselves are not pure.
My last foils of AP I collected, usually I wait until I collected up some substantial amount of them.
I may make a full AP run more than once.
While this is happening I have foils sitting in HCl for several days/weeks and getting remainders of any metals the HCl can dissolve out.
After a long while the HCl on the foils has no residual color. Blue/Green all gone.
When I process these foils at the end the AR color itself is pretty nice deep yellow.
But I take a lot of time to do this. Lots of patience.
The results are very clean gold.
AR or HCl bleach or other methods should be done again to get gold cleaned up, as many times as it takes.

 

[Honda350x]

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.

OP??