Blue crystals on ugly silver bar?!

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Owltech

Well-known member
Joined
Sep 13, 2015
Messages
116
Parted silver, reduced with sodium formate
the crystals remind me of the ones you get on galvanised steel

SAM_6282.JPGSAM_6309.JPGSAM_6337.JPGSAM_6338.JPGSAM_6356.JPG
 
Blue? I see a tan cream colored crust. To me, it looks like a slag of melted silver chloride. Silver chloride melts long before the silver but doesn't boil off the molten silver and when you pour your bar it ends up on top just as a slag would. I assume you used a clean crucible and no flux at all.

I think you didn't rinse the remaining silver nitrate out of the formate solution and converted it to chloride when rinsing with tap water. Whatever was retained in the silver metal crystals ended up looking like the tan slag.

But if that really is blue, I have no idea what it is.
 
4metals said:
Blue? I see a tan cream colored crust. To me, it looks like a slag of melted silver chloride. Silver chloride melts long before the silver but doesn't boil off the molten silver and when you pour your bar it ends up on top just as a slag would. I assume you used a clean crucible and no flux at all.

I think you didn't rinse the remaining silver nitrate out of the formate solution and converted it to chloride when rinsing with tap water. Whatever was retained in the silver metal crystals ended up looking like the tan slag.

But if that really is blue, I have no idea what it is.
Spot on! Never fired, brand new, SiC crucible, no flux at all... just the stock glaze the crucible comes with:SAM_6321.JPG

The silver cement was not bone dry, but just a wee bit moist

SAM_6320.JPG

the crucible after pouring:

photo 2.JPG

the blue glitter I was talking about:

silver blue crystals.jpg

as for the tan coloured crust (which a pinch of borax should have taken care of), was caused (IMHO) by the crucible''s original glazing, or by the rusty steel mould used to pour the silver into:

photo 4.JPG

I'm excluding the presence of Cl as I've used de-ionised water throughout the whole process. The rinse water was tested for silver nitrate presence with diluted HCl and no cloudiness was observed. Final rinse water pH was 7. And finally, the silver powder remained unchanged after prolonged exposure to sunlight.
 
Hi!
Are you sure it is actual coloration or just reflections from crystalline boundries like multi crystalline silicone or as you say, Zinc has. To my eyes, on this picture, that is what strikes me.
 
Yggdrasil said:
Hi!
Are you sure it is actual coloration or just reflections from crystalline boundries like multi crystalline silicone or as you say, Zinc has. To my eyes, on this picture, that is what strikes me.

the glitter occurs when the silver bar is placed at a certain angle to the light
 
Ok.
Then it is some kind of reflection or frequency modulation of the light at crystal boundries. But to what causes it or why. I think we are on the correct place to get an answere :)
 
Nice pics. Did you follow the exact procedure initially posted by 4metals for the formate reduction or added/changed something?. With a graphite ingot mold, your bar appearance would be much better.
 
cuchugold said:
Nice pics. Did you follow the exact procedure initially posted by 4metals for the formate reduction or added/changed something?. With a graphite ingot mold, your bar appearance would be much better.

I followed patent US5000928A by Kodak Co (very similar to the procedure laid out by 4metals) with small changes,

Following your advice, I re-melted the bar and poured the silver into a graphite mould and this is the result: (please note that the tan coloured crust and the "blue glitter" remained even after addition of borax)SAM_6387.JPGSAM_6389.JPGSAM_6395.JPG

the bar (in the middle) compared to two other bars refined by cupellation (the surface on all bars is smooth despite appearing rough)
SAM_6429.JPGSAM_6432.JPG
 
I'm not really sure about the colors. Perhaps some Pd oxide or even Pt contamination?. 4metals or Lou will probably know better. It usually pays to scavenge with DMG in those Pd++ and Pt++ nitrate solutions, before reduction of silver. Very cool pics. Thanks for posting.
 
cuchugold said:
I'm not really sure about the colors. Perhaps some Pd oxide or even Pt contamination?. 4metals or Lou will probably know better. It usually pays to scavenge with DMG in those Pd++ and Pt++ nitrate solutions, before reduction of silver. Very cool pics. Thanks for posting.

Thank you, DMG was the "small change" prior sodium formate addition
 
When highest purity is required, evaporation to crystals, and then fusion of the crystals in a furnace at above 250 C and less than 444 C (If I remember correctly) is what is required to make oxides of all contaminants. After cooling, dissolving in distilled water, the oxides can be filtered out, and then go for formate reduction. Really fine silver can be obtained, with 2 iterations, 999995 for sure. :G
 
The blue crystals show up in high purity silver and appear as holographic crystals.
Their is something else going on here with that other layer. What was the source materials?
Formate will reduce platinum and palladium if you don't control the ph and the temp.
Try dropping the silver first and then going after the pd or pt if you suspect that. DMG before the drop may be your problem. Lou and 4metals are the best when it comes to these problems!
Try washing a sample of the powder in hcl and then melting it and using graphite.
 
Thank you all for helping me out! Starting material was the nitrate solutions of these:
(dore on the left, the recovered metal on the right)
grf2.jpg

After raising the nitrate solution's pH to 6 with KOH:
AgNO3 pH6.JPG
 
If GSP tells you that your silver is good, that's as good as mint stamp.

Now for the tan colored crust: Maybe you can fix that by adjusting your pouring technique. In minute 1:04 of the video below, you will see someone slagging the pour of an already refined gold bar, to make the surface better. Try to hold the 'floating stuff' inside the crucible with a ceramic or graphite rod, and your bar will be smoother. Great pics!.

https://www.youtube.com/watch?v=nQ37SFKahc0
 
Yes, the crystals are what you get when the silver is pure.

Bigger the crystals, the purer the silver. Gold does same thing but less iridescent.
 
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