Add NaCl to it.
The Silver will drop as Silver Chloride without adding water to your acid, keeping it concentrated.
Smelting Silver Plate
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The Silver will drop as Silver Chloride without adding water to your acid, keeping it concentrated.
Sulfuric/nitric is a good way to go, if you can source reasonably cheap concentrated sulfuric acid. Advantage is the speed - with 60 °C sulfuric you will go quite quickly. Dosing nitric as it is used up in the process, you can get classic plated stuff (like plated pins, circuit braker parts, or spoons/forks etc.) with 1-3 wt% Ag deplated in 10 or so minutes. Good contact with leaching solution is important, larger pieces can be advantageously put onto copper wire and dipped in.
Just pour the leaching solution, wash the deplated stuff- transfer it into big strainer and spray with water TO THE SEPARATE VESSEL. Then you can take the pregnant sulfuric (still hot) and add new material to it. This can be repeated multiple times with same sulfuric until either junk start to precipitate out or silver sulfate start to precipitate out.
Advantage is that in WARM/HOT concentrated sulfuric acid, silver sulfate is nicely soluble. But solubiility decrease with temperature and also with sulfuric concentration (this is relatively sharp).
After processing the stuff, you can recover by diluting with water and collecting the silver sulfate + crashing out the rest of the silver in solution with brine. Or as silver chloride with bulk.
As it was written by Kurt, base metal (if it is copper or brass, probably also other alloys) will be intact by the acid mixture - allowing you to resell it as is. Also, solder do not pose problem in the process since it usually passivate due to lead sulfate formation on the surface.
Just pour the leaching solution, wash the deplated stuff- transfer it into big strainer and spray with water TO THE SEPARATE VESSEL. Then you can take the pregnant sulfuric (still hot) and add new material to it. This can be repeated multiple times with same sulfuric until either junk start to precipitate out or silver sulfate start to precipitate out.
Advantage is that in WARM/HOT concentrated sulfuric acid, silver sulfate is nicely soluble. But solubiility decrease with temperature and also with sulfuric concentration (this is relatively sharp).
After processing the stuff, you can recover by diluting with water and collecting the silver sulfate + crashing out the rest of the silver in solution with brine. Or as silver chloride with bulk.
As it was written by Kurt, base metal (if it is copper or brass, probably also other alloys) will be intact by the acid mixture - allowing you to resell it as is. Also, solder do not pose problem in the process since it usually passivate due to lead sulfate formation on the surface.
Nah, you beat me by 25 minutes
Practically everything you write is done & also I have done. With exception that plain sulfuric does attack copper, but it is rather slow and product mostly isn´t soluble copper sulfate at first, but copper oxide. It is far more useful to dose in nitric acid and stir the contents. NOx evolution is good indicator. And of course the colour of the items, as the change in appearance is very obvious if it is regular copper or regular brass. High zinc brass alloys can be problematic in sulfuric, but you can always test it first.
With crystallization of silver sulfate... It can be done, but from practical standpoint you probably never reach saturation point even at 60 °C. But that is OK - you will just let the pregnant solution cool, covered with plastic wrap - and when you decide to continue, just decant the leachant into other beaker/barrel leaving eventual crystals on the bottom.
As you mention, base metals also dissolve into the solution and there is always some junk present with your material so the solution will eventually get cloudy and coloured. Not a huge deal, but you will carry contaminants along the way. With prolonged use, you will also take quite a bit of water from the air into the acid - what will cause worse etching of base metal and lower silver holdup.
One option can be addition of fresh sulfuric into existing leaching solution. But after 4-5 or so rounds of stripping, I usually called it done and processed it. Sulfuric isn´t that expensive, and my material (plated pins/plated casings of RF equipment/plated whatever from breakers) was always on the more "dirty" side, not allowing to recycle leachant too far.
The sodium won't affect it either? Does the concentration of sodium eventually lead to excess salt loading (forming sodium sulfate?) I suppose if that doesn't happen until many rounds of leaching, it doesn't matter.
What about converting the silver sulfate that DOES precipitate out? My first test did definitely leave me with a fair percentage of it. What process works best for reducing it to silver?Nah, you beat me by 25 minutes
Practically everything you write is done & also I have done. With exception that plain sulfuric does attack copper, but it is rather slow and product mostly isn´t soluble copper sulfate at first, but copper oxide. It is far more useful to dose in nitric acid and stir the contents. NOx evolution is good indicator. And of course the colour of the items, as the change in appearance is very obvious if it is regular copper or regular brass. High zinc brass alloys can be problematic in sulfuric, but you can always test it first.
With crystallization of silver sulfate... It can be done, but from practical standpoint you probably never reach saturation point even at 60 °C. But that is OK - you will just let the pregnant solution cool, covered with plastic wrap - and when you decide to continue, just decant the leachant into other beaker/barrel leaving eventual crystals on the bottom.
As you mention, base metals also dissolve into the solution and there is always some junk present with your material so the solution will eventually get cloudy and coloured. Not a huge deal, but you will carry contaminants along the way. With prolonged use, you will also take quite a bit of water from the air into the acid - what will cause worse etching of base metal and lower silver holdup.
One option can be addition of fresh sulfuric into existing leaching solution. But after 4-5 or so rounds of stripping, I usually called it done and processed it. Sulfuric isn´t that expensive, and my material (plated pins/plated casings of RF equipment/plated whatever from breakers) was always on the more "dirty" side, not allowing to recycle leachant too far.
There was thread near the beginning of the forum about that process. He stripped in heated Sulfuric and nitric then let it cool overnight.
He poured off the liquid leaving the crystals behind. Made a small nitric addition as needed and reused the acid.
When he was done he used copper to cement the silver out of the container of crystals.
I still prefer electrolysis with sodium sulfite solution. No strong sulfuric to deal with. Not fast but not near as dangerous. Gives you a loose silver sludge that plates out on stainless and settles to the bottom of the container.
He poured off the liquid leaving the crystals behind. Made a small nitric addition as needed and reused the acid.
When he was done he used copper to cement the silver out of the container of crystals.
I still prefer electrolysis with sodium sulfite solution. No strong sulfuric to deal with. Not fast but not near as dangerous. Gives you a loose silver sludge that plates out on stainless and settles to the bottom of the container.
But don't you feel like the electrolysis doesn't pull it uniformly?
When I tried it I would end up with entire areas that were still plated, while I also had other areas that seemed to sit long enough that I"m pretty sure it was eroding the base metal.
I always thought it would work really well with a circulating pump and bag filter.
The process is not perfect. It works better when the substrate is copper. When the solution is getting oxidized to sulfate it starts to attack brass. I have over time received poor quality sodium sulfite that oxidized much sooner than batches from other suppliers.
I processed a few military surplus bus bar and contractor parts and they stripped very clean with no attack on the substrate. With time all the corners and shadowed areas stripped.
You are right that it is not always removing everything. It does occasionally miss spots but removes the vast majority of the silver. My local scrap dealers have never complained about the condition when completed other than the white metal trim and handles which I usually remove.
I have always used the scrap value of the base metals to make my price decisions. That way worst case the scrap could be sold as is without loss.
I am working at a hobby level. For me it is the best option. I tried concentrated Sulfuric and Nitric 15 years ago. It worked, but safety and disposal concerns made it not worth continuing for the small return in my situation.
I was glad to discover the sodium sulfite method to help me clear my 15 year accumulation of estate and thrift store finds.
I have noticed a large variation it the silver content. Some newer items strip for me in an hour or two. Some older and higher quality items have taken 36 hours. That has made me selective in my purchases.
I processed a few military surplus bus bar and contractor parts and they stripped very clean with no attack on the substrate. With time all the corners and shadowed areas stripped.
You are right that it is not always removing everything. It does occasionally miss spots but removes the vast majority of the silver. My local scrap dealers have never complained about the condition when completed other than the white metal trim and handles which I usually remove.
I have always used the scrap value of the base metals to make my price decisions. That way worst case the scrap could be sold as is without loss.
I am working at a hobby level. For me it is the best option. I tried concentrated Sulfuric and Nitric 15 years ago. It worked, but safety and disposal concerns made it not worth continuing for the small return in my situation.
I was glad to discover the sodium sulfite method to help me clear my 15 year accumulation of estate and thrift store finds.
I have noticed a large variation it the silver content. Some newer items strip for me in an hour or two. Some older and higher quality items have taken 36 hours. That has made me selective in my purchases.
