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galenrog

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Stripping and reclaiming silver plate sound interesting. Have you developed a technique that is economical?

Time for more coffee.
 
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Geo

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Stripping and reclaiming silver plate sound interesting. Have you developed a technique that is economical?

Time for more coffee.
The method is actually an old, tried and true method that is not widely touted due to the use of sulfuric acid and the patent directions for use. Developed to refinish the silver plating on musical instruments without damaging the instruments base metal. The patented method uses heat which increases the danger of any accident that may happen. In my personal opinion, it is no more dangerous than a sulfuric acid gold stripping cell.
 

Geo

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I use the method without added heat, which mitigates some of the danger. Caution should still be used and unless you are familiar with the dangers and safe handling of sulfuric acid, do small experiments safely until you can study and learn what it can and can not do.
 

Geo

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In your video you mentioned a method of reducing silver sulfate to silver. Does one of your videos explain how to do that?
The most reliable way that I know of reducing silver sulfate is smelting. It is much easier to do when all there is in the sample is silver sulfate.
 

kurtak

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The most reliable way that I know of reducing silver sulfate is smelting
Geo - don't you mean sulfide

Silver sulfate (if I am not mistaking) is silver in solution such as plating solutions & picture/x-ray fixer solutions

The silver from sulfate solutions is then cemented out using steel wool reducing the sulfate to sulfide

The (black) silver sulfide is then further reduced to silver by smelting with iron (nails or rebar) and 50/50 borax/soda ash for the flux (producing iron sulfide)

The iron sulfide then slags off to the flux so when you pour the smelt to your cone mold the near pure (if not pure) silver then settles to the bottom of the cone mold with the slag (borax/soda ash/iron sulfide) on top of the silver

The slag is then knocked off the silver after the poured smelt has cooled

Sulfate (a solution) first needs to be reduced to sulfide (a solid) then further reduced in a "high temp" ion exchange --- kind of like cementing silver from a nitrate solution with copper except iron is used as the reducer (ion exchange) in the smelting

Kurt
 

Geo

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Geo - don't you mean sulfide

Silver sulfate (if I am not mistaking) is silver in solution such as plating solutions & picture/x-ray fixer solutions

The silver from sulfate solutions is then cemented out using steel wool reducing the sulfate to sulfide

The (black) silver sulfide is then further reduced to silver by smelting with iron (nails or rebar) and 50/50 borax/soda ash for the flux (producing iron sulfide)

The iron sulfide then slags off to the flux so when you pour the smelt to your cone mold the near pure (if not pure) silver then settles to the bottom of the cone mold with the slag (borax/soda ash/iron sulfide) on top of the silver

The slag is then knocked off the silver after the poured smelt has cooled

Sulfate (a solution) first needs to be reduced to sulfide (a solid) then further reduced in a "high temp" ion exchange --- kind of like cementing silver from a nitrate solution with copper except iron is used as the reducer (ion exchange) in the smelting

Kurt
Yes, Sulfide. Thank you.
 

Helian

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In fact, silver sulfate is a white powder that you can buy from chemical supply companies. I have several bottles of it. In the meantime, I found a Youtube that demonstrates a good way to refine it. It turns out that silver sulfate is much more soluble in boiling water (1.33g per hundred mL) than water at lower temperatures. When it's in solution, you can add HCl or table salt in solution to convert it to silver chloride, which is much easier to refine. My preferred method is to put it in a 1 to 20 solution of dilute sulfuric acid, add a bunch of zinc plated roofing nails, and mix until all the silver cements out (usually about half an hour.) Then you just remove the nails with a magnet. I sold some of this to Manhattan gold and silver, and they gave me nearly the same price for it as they were paying for silver rounds and bars, so it must have been quite pure.
 
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Lou

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SUBSCRIBED! Thanks Geo for taking the time to make these videos.

Silver sulfate is indeed quite soluble in hot water.

As Geo is doing this cold, the recommended approach is to add HCl to precipitate AgCl.

Ag2SO4 + 2 HCl = H2SO4 + 2 AgCl

The reason I say "cold' is because if you're doing it hot, very objectionable fumes of HCl can be produced. If you fume freshly precipitated AgCl with sulfuric acid, you're left with Ag2SO4.

In any event, Ag2SO4 used to be the go to way of refining silver in the cast iron kettle process with hot, concentrated sulfuric acid. The silver sulfate was soluble while anhydrous CuSO4 could be filtered off largely as it would "salt out". This method is part of the reason there's so much gold in Mexican silver from before the 40s and 50s.
 
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snoman701

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The method is actually an old, tried and true method that is not widely touted due to the use of sulfuric acid and the patent directions for use. Developed to refinish the silver plating on musical instruments without damaging the instruments base metal. The patented method uses heat which increases the danger of any accident that may happen. In my personal opinion, it is no more dangerous than a sulfuric acid gold stripping cell.
Are you just talking about the 95/5 method sulfuric / nitric?
 
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kurtak

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In fact, silver sulfate is a white powder that you can buy from chemical supply companies.
Correct (true) like any metal "dissolved" into a solution - it can be evaporated down to produce a solid crystalline "salt" of the metal originating as a solution - it makes for easier/safer/cheaper shipping/handling of the product from the producer to the user where the user can then re-hydrate the solid salt to a solution where a solution is needed (such as for plating or photo fixer ect.)

Other common examples of solutions evaporated to sold crystal salts (by producer) then re-hydrated at (receiving) end user are silver nitrate, copper nitrate, copper sulfate & as discussed here silver sulfate (to name a "few")

Once re-hydrated (back in solution) they still need to be reduced & as we know there is more then one way to skin this reduction cat

Kurt
 

snoman701

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How do you actually recover the silver? I cannot imagine trying to settle silver chloride out of concentrated sulfuric, or filtering silver chloride from concentrated sulfuric. And I have the glass wound filters for it.

The biggest problem I've always had with any anodic stripping method is that it doesn't get in to the grooves well. And most of run of the mill silver plate isn't exactly perfectly flat surfaces. I can see where it would work well on instruments though.
 

Geo

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Geo - just curious - for recovering silver plating why not go with cyanide leaching

Kurt
Cyanide is not for the beginner for certain and I found that trying to make some gold plating solution on my own, cyanide is hard to get without jumping through some hoops. Well, unless you are buying it by the pallet it seems.
 

Geo

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How do you actually recover the silver? I cannot imagine trying to settle silver chloride out of concentrated sulfuric, or filtering silver chloride from concentrated sulfuric. And I have the glass wound filters for it.

The biggest problem I've always had with any anodic stripping method is that it doesn't get in to the grooves well. And most of run of the mill silver plate isn't exactly perfectly flat surfaces. I can see where it would work well on instruments though.
This is not an electrolytic process. The acids used in this combination and quantities allows for the silver to be dissolved but not the base metal by simple immersion. It will strip any where the acid can reach. The silver is recovered from solution by adding HCl in small amount until no more silver chloride forms. The silver chloride settles quickly. Much faster than it would from an AR solution or even nitric acid solution. If the process is done correctly, all of the nitric acid is consumed in the process. The sulfuric acid can be reused by heating the sulfuric acid and evaporating back to the starting volume. This removes any excess liquids from the nitric acid or HCl. Personally, I don't filter. I decant as low as possible. The silver chloride tends to make some nice solid clumps instead of a fine powder.
 

snoman701

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Cyanide is not for the beginner for certain and I found that trying to make some gold plating solution on my own, cyanide is hard to get without jumping through some hoops. Well, unless you are buying it by the pallet it seems.
It's also not cheap enough to be worthwhile unless you are buying it by the pallet quantity (you can get it by the barrel reasonably cheap). Quite a bit of cyanide is destroyed in the process. Then on top of it you have the cost of disposal.

None of the things we do are exactly environmentally friendly, but because of the inherent dangers of cyanide, the restrictions in apprehension make it harder to work with for "under the radar" precious metal recovery.
 

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