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R

Ryno9000

Member
Joined
Feb 7, 2020
Messages
16
Hello Forum!
Yesterday I took a hodgepodge from several filtrations that tested positive for gold with Stannous Chloride. I added them to a sterilized jar and added SMB. It appears that the gold is now sitting at the top of the solution instead of “dropping.” The container was left outside, temperature around 50F. Is this a temperature problem, a ph problem, or I need to add more SMB? I have used way too much in the past and end up with a horrible gooey filtration process.
 
Cant really tell what is in the top layer ( why is it brown). Are there suspended particles in the top layer or is it a clear brown solution? Did you teat this layer with stannous chloride?
 
I notice a lot of dried metal salts on the glass, this makes me wonder if this solution did not come from HCl and bleach and is due to concentrating the solution.

Also, the large volume of liquid for such a small amount of gold also makes me curious if this did not come from HCl and bleach process...

I do not notice much coloring of base metals in the solution or salts, so I assuming this is a fairly pure solution although a large volume for the amount of gold...

Answering, or discussing these things would be easier if we knew where they came from and what you did to get them, what oxidizer you used to dissolve the gold, what was the source of the gold, the details, and the details of the details...

When I have gold in solution (I will normally notice a small yellow halo at the surface of the solution just where the surface of the liquids meet the glass), I do not see a halo in your picture, so I suspect you are very close to having most of the gold out of solution, (your testing should be used verify), The yellow of the lower portion could be gold going in and out of solution (again your testing should give you clues to what is going on).
An excess of oxidizer can keep the gold or a portion of it dissolving and then reducing in an endless cycle.
have you tested this solution with SnCl2? Considering a test may not show positive if active oxidizer is still in solution to counteract the test being able to reduce the gold...

If testing with stannous you may want to try experimenting with a couple of different tests, on some small samples of the solution, say do one without heating to drive off chlorine and one after driving off free chlorine gas...
a few drops of solution in a test tube with a small gold button and some heat (to de-NOx the sample) before testing with SMB.

You can also try an alternative reagent for testing the gold chloride solution (with some free nitric or NOx gases in solution) I prefer the copperas crystal in a spot dish (as opposed to using the stannous chloride) because the ferrous sulfate will also de-NOx the solution during the test and form the brown ring of precipitated gold...

Have you tried to break the miscible or polar bonding of the solution by changing the temperature, concentration, or stirring the solution?

https://www.google.com/search?bih=705&biw=1024&hl=en-GB&sxsrf=ALeKk01k5uvHVxBqCnQ87XUlbwHPYk3jwQ%3A1588180713658&ei=6bapXs7rJ4OE-gTA-6Uo&q=immiscible+Mixtures%2C+polar+forces+precipitate&oq=immiscible+Mixtures%2C+polar+forces+precipitate&gs_lcp=CgZwc3ktYWIQDDIECCMQJzoECAAQR1D0Dlj0DmCBJGgAcAJ4AIABvAKIAbwCkgEDMy0xmAEAoAEBqgEHZ3dzLXdpeg&sclient=psy-ab&ved=0ahUKEwiOhJuako7pAhUDgp4KHcB9CQUQ4dUDCAw
 
I’m embarrassed to give answers here as I think I’m making glaring chemistry errors but I guess this is how we learn!

The volume is high as it came from an assortment of capture beakers from other refining. The only method I have ever used is HCL + Peroxide on the front end and HLC + Nitric Acid (90% lab grade) and then SMB for precipitation. I use distilled water to rinse the filters and as such this is a “stock bucket” of that process. Volume being high due to distilled water rinsing.

I did a Stannous test on the solution which was a dark brown with some purple hue (sorry I did not take pictures)!
I decided to sort of experiment and added SMB dissolved in distilled water. Adding that, the light green solution produced vertical “waves” of golden brown and a little bit of chlorine gas. I kept slowly adding the H2O/SMB until the reaction stopped and let it settle overnight. It appears whatever “brown crap” is at the top is the metal and nothing settled on the bottom.
 
If your stannous test showed purple then most likely you still have gold in solution. However some people that are newer to refining gold may mistake a false positive stannous test and think they have gold still in solution. A false positive a occur when you have used to much smb. The gas that you smelled when adding this to your AR is sulfur dioxide (SO2). You may also have free nitric in your solution as Butcher mentioned which will just fight with the smb this will eat your gold back into solution as the smb tries to precipitate it. Did you get rid of the excess nitric in your solution? If so how. This is why we need to know exactly what happened from start to finish as each step is just as important as the last.
 
The top portion is most likely reduced gold metal floating around (the clusters of atoms just having not have grown large enough to gain enough weight to overcome the gravity or other conditions of the solution, the lower portion may just be gold going in and out of solution...

I have had precipitations where I have had nitric in solution and could only precipitate about half of the gold from solution (prior to de-NOxing and getting the rest of the gold)...

With the volume of the liquid volume being so large evaporation would take a while, although I evaporate all the waste products I produce, so I would most like take the time and incorporate that some in the de-NOxing process.

Sulfamic acid or a little added gold and heating (even if you do not concentrate the solution that much) should help to de-NOx the solution...
 
Shark - thanks! I’m assuming it’s temperature related. Do I add a tiny more SMB or wait or...open for suggestions haha
 
I am of the opinion that there is still some nitric in solution. Butcher suggested sulfamic acid or adding a gold button with a bit of heat to denox. That would be good advice. Various images of your solution remind me of a similar problem several years ago. Denox worked then. I am suggesting it may work for you now.

Time for more coffee.
 
galenrog makes a good point, and I have seen it happen myself. Denox it anyway, then stannous test it. If positive, then add a small amount of smb. Over time, sitting in the sun your nitric (oxidizer) can begin to fade in strength. This can allow a portion of your gold to drop, but may well keep some hung up in solution. In most of my cases the pointer was in the yellowish color left after the addition of smb (when using nitric, bleach tends to leave a yellowish solution anyway). When I see that odd yellow color I double check everything.

Shameless YouTube posting, this one is mine. Sorry for the quality.

While this is HCl and Bleach it shows how it looks when dropping and redissolving. As it progresses more gold will stay out of solution.

https://www.youtube.com/watch?v=V6DPbGiccNc
 
When you have precipitated a solution and it fails to accumulate nicely on the bottom heating usually does the trick but on the downside if you have any oxidizer left it will also dissolve some of your gold so test with stannous to be sure that hasn’t happened. Once you have a negative result you can even get you solution to a gentle boil to make the powders really hold together.
 

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