False positive stannous from too much SMB?

[Nevadayote]

So, I'm reading Hoke, reading posts here, and still experimenting with what I have. I used AP to get some gold foils and then again used the HCL and bleach solution to dissolve the foils. All good! My stannous test showed dilute gold in solution. It turned purple/black after a few seconds but was very thin looking. That's why I describe it as very dilute.

I decided to drop what was there and added SMB. I got a lot of reaction and added more smb. Then, I did another stannous test. Immediately the solution turned dark black!

Now, I think I added much too much smb and am getting a false reading since the test before smb was very dilute and this test after smb is so reactive and so dark.

If it is the case that I have too much SMB, is there a way to remediate it?

 

[Yggdrasil]

So, I'm reading Hoke, reading posts here, and still experimenting with what I have. I used AP to get some gold foils and then again used the HCL and bleach solution to dissolve the foils. All good! My stannous test showed dilute gold in solution. It turned purple/black after a few seconds but was very thin looking. That's why I describe it as very dilute.

I decided to drop what was there and added SMB. I got a lot of reaction and added more smb. Then, I did another stannous test. Immediately the solution turned dark black!

Now, I think I added much too much smb and am getting a false reading since the test before smb was very dilute and this test after smb is so reactive and so dark.

If it is the case that I have too much SMB, is there a way to remediate it?

Did you test the pH?
When you are using HCl/Bleach it is very easy to add too much bleach.
This will push the pH too high and even neutralize the solution.
I personally do not like the HCl/Bleach method for this reason, I prefer to use HCl/Peroxide or HCl/Pool Chlorine for this reason.
The solution needs to be at 2-4 the lower the better.
Stannous also need to be done in a low pH milieu, not that critical but still.
Add a bit of HCl and see what happens.

 

[anachronism]

A false stannous test isn't black. It's browny coloured.

 

[Nevadayote]

OK. I found my pH test strips and checked. The pH is showing at 1. I also did another stannous test, and it darkened up a lot. Maybe it has a brown tint? It's hard to tell since the result is so dark. I've got undissolved SMB lying on the bottom of the beaker, too. The solution looks fairly clear with a nice yellowish tint to it.

I haven't taken any other actions yet.

 

[FrugalRefiner]

Take a drop of your solution, dilute it with a few drops of water, and try the stannous test again. If you still can't tell, try another drop and dilute it more till you can see the true color.

Dave

 

[Yggdrasil]

OK. I found my pH test strips and checked. The pH is showing at 1. I also did another stannous test, and it darkened up a lot. Maybe it has a brown tint? It's hard to tell since the result is so dark. I've got undissolved SMB lying on the bottom of the beaker, too. The solution looks fairly clear with a nice yellowish tint to it.

I haven't taken any other actions yet.

Take out a ml or so.
Dilute it by 2 and test that one.
If it is still blackish, add 2 more ml and test.
When you get to a level it becomes not dark, the real color will be visible.
Anyway, it may be wise to add a slab of Copper into the solution and cement out any values.
Redissolve and try again.

 

[Yggdrasil]

Take a drop of your solution, dilute it with a few drops of water, and try the stannous test again. If you still can't tell, try another drop and dilute it more till you can see the true color.

Dave

Dave beat me to it

 

[Nevadayote]

Take out a ml or so.
Dilute it by 2 and test that one.
If it is still blackish, add 2 more ml and test.
When you get to a level it becomes not dark, the real color will be visible.
Anyway, it may be wise to add a slab of Copper into the solution and cement out any values.
Redissolve and try again.

I'm liking the "try again" idea a lot. So, here's my plan that I'll try starting on my next day off work:

1. Take the solution as is and dilute it with distilled water enough to dissolve all of the excess SMB.
2. Put copper into that dilute solution to cement out any gold, silver, etc.
3. Take the cemented out values and start the refining over again with HCl and nitric. By this time, my nitric acid should have arrived so that I can stop using bleach!
4. denox the AR before using SMB!
5. Drop the gold...I haven't settled on the exact method yet. I'm not set up to generate gasses to bubble into the AR, so it may have to be more careful use of SMB.

 

[galenrog]

Before you start, flesh out your plan a bit. At each step, add what the expected result should be and a plan of what to do it results are unexpected.

The expected results are easy to move to the next step from. The unexpected, no so much. That is why such a plan is needed. Even for the experienced.

Time for more coffee.

 

[Nevadayote]

Before you start, flesh out your plan a bit. At each step, add what the expected result should be and a plan of what to do it results are unexpected.

The expected results are easy to move to the next step from. The unexpected, no so much. That is why such a plan is needed. Even for the experienced.

Time for more coffee.

Great advice! I'm still mulling the plan over for sure.

 

[Nevadayote]

OK. After much thought and some research and some advice here, I modified my plan. Step ONE became cementing out any "values" from the solution by adding copper.

I did that and ran another stannous test... Completely clear! WOHOO!

Next, I decanted the liquid into my temporary stock pot, leaving all the solids behind.

After that, I consolidated all of the solids into one beaker, added distilled water, and stirred! My current objective is to dissolve all that excess SMB and remove it entirely from the mix. I expect to end up with clear distilled water and a mix of solids in a beaker. Some solids will be metal, and others just junk.

By the time I've got the above step completed, it is highly likely that my order of nitric acid will have arrived. If I have my expected results from above, I'll decant off the water so that I can add nitric. I plan to let that have a good long time to work on dissolving metals other than gold.

When the above step is complete, I'll filter off the nitric, put the remaining solids, filter and all, in a clean beaker, and start washing it with distilled water. There will still be some waste solids, such as ceramic chips, plastic, and silica, but those shouldn't pose a problem.

After all that, I may just put it all in a clear bottle and admire the view for a while!

 

[Nevadayote]

Hmmm...dissolving the SMB proved to be much easier than I had anticipated! The SMB had crystalized but, couple of liters of distilled water later and it was all gone.

I rinsed the remaining solids with distilled water and filtered them well. Right now, it's sitting in about 250ml of distilled water. The solids are not quite as mixed up as I had thought they would be! It's a fine brown sludge about 1/4 inch thick on the bottom of a 500ml beaker.

I don't want to get my hopes up, but it resembles the gold precipitate I've seen. No doubt there has to be other junk metal in it! Once my nitric arrives and I can use it to dissolve the junk metals, I should have a better idea of what I've got! After that, it's just a matter of getting the gold into solution using HCl and =nitric...very little nitric...in very small increments!

 

[Yggdrasil]

Hmmm...dissolving the SMB proved to be much easier than I had anticipated! The SMB had crystalized but, couple of liters of distilled water later and it was all gone.

I rinsed the remaining solids with distilled water and filtered them well. Right now, it's sitting in about 250ml of distilled water. The solids are not quite as mixed up as I had thought they would be! It's a fine brown sludge about 1/4 inch thick on the bottom of a 500ml beaker.

I don't want to get my hopes up, but it resembles the gold precipitate I've seen. No doubt there has to be other junk metal in it! Once my nitric arrives and I can use it to dissolve the junk metals, I should have a better idea of what I've got! After that, it's just a matter of getting the gold into solution using HCl and =nitric...very little nitric...in very small increments!

That kind of sludge lends itself to HCl/bleach or HCl/Peroxide perfectly.
Use ample HCl and drip in the Bleach or Peroxide by the drops.
When it is dissolved, simply let it sit in an open container for a day or so to let the Clorine gas off.
No need for destroying the Nitric.