# Silver refining.



## ssharktu17 (Dec 10, 2021)

I am curious when using nitric to melt sterling or 800 silver what is the remaining material at the bottom after the reaction. And when I Pour off the solution what exactly is in it concerning metals? Then when I do the copper exchange silver precipitates. What is now left in solution?


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## Martijn (Dec 10, 2021)

First one: Anything that was in the sterling that could not get dissolved by nitric. 
Traces of gold or some pgm's would stay solid. Impurities maybe? Theoretically insoluble nitrate salts. 
The decanted solution contains all metals that are soluble in nitric. Copper and silver, but also zinc, palladium, and more are possible. 
Look up sterling alloys and what is or is not attacked by nitric. Some tin could be present. That would make tin paste. 
Only the lesser reactive metals than copper will be cemented on copper. 
So after a nitric digestion basically only silver and Pd. 
More reactive base metals than copper will stay in solution.


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## ssharktu17 (Dec 10, 2021)

Martijn said:


> First one: Anything that was in the sterling that could not get dissolved by nitric.
> Traces of gold or some pgm's would stay solid. Impurities maybe? Theoretically insoluble nitrate salts.
> The decanted solution contains all metals that are soluble in nitric. Copper and silver, but also zinc, palladium, and more are possible.
> Look up sterling alloys and what is or is not attacked by nitric. Some tin could be present. That would make tin paste.
> ...


Thank you! Ok that’s what I was wondering if the solution was all of the metals. So all of the metals stay in solution except silver once you precipitate them out with copper. Interesting so the refining may become contaminated with palladium. So technically you might be getting lucky on .99 silver lol.


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## butcher (Dec 10, 2021)

You cannot melt silver alloys with nitric, now you may be able to melt silver alloys with nitrates in your flux but I do not think that is what you are talking about.

Silver jewelry alloys normally are composed of silver and copper mainly and thus both will dissolve in nitric acid, and become soluble ions as metal nitrates of these metals.

Most metals, a very big majority of metals are soluble as nitrates.
Most salts of silver are not very soluble or are pretty much insoluble.

Jewelry or other alloys of silver could have platings (which could be insoluble in nitric) or hard or soft soldering alloys, solders including soft lead...

Some other reactions may be occurring in your reaction making some metal or salt of a metal insoluble, like maybe your water has chlorine or chlorides, making some metal insoluble in the nitric or nitrate solution...

If you only have silver and copper in solution, and then you used copper to recover the silver through cementing the silver out, or a displacement reaction that would leave with a copper nitrate solution.

If other metals are involved in this solution, it would depend on what metal as to whether copper would displace it with your silver... Study the reactivity of metals for more details...

Another option besides using copper to recover silver from solution is using salt, or HCl or some other chloride to precipitate the silver,( although you can expect some drag-down impurities and more trouble in converting it to metal, a normally more pure product of silver can be obtained in the recovery, very few metals are insoluble as chlorides and we normally do not have them in solutions with each other. Study the solubility rules for a better understanding of what we do....

Where we may have a salt mixture of lead and silver here again solubility and temperature can help us to remove most of the lead chloride from the silver chloride with hot water washes because of the solubility differences of lead at differing temperatures.

Not related to this discussion but if we have a mix of insoluble chlorides such as copper, silver and lead, we can change the valence of the insoluble copper salt using HCl to put copper in solution, leaving the silver and lead insoluble, then remove the lead salt with heat and water, to leave us a more pure salt of insoluble silver... 

A study of dealing with waste will help to answer l more questions related to these subjects than I can in a few pages.


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