I don't think that any electrolytic stripper will work on a mass of wire because I don't think that the current will "throw" into the center of that mass. In my experience, it will only strip the wire on the outside surface of the mass.
If you did shred it (good idea, by the way), you would need (in my estimation) to tumble it in the stripper in a barrel plating machine. They make polypropylene barrel platers with "herringbone" panels that would prevent the small pieces of wire from falling out. Here's one for sale on eBay. It doesn't say what it's made of or whether herringbone panels are used or not. It also doesn't say what type of contacts are in the barrel. There are 3 types of contacts available - center bar, button contacts, or danglers. In sulfuric, they would have to be made of lead or some harder lead alloy. All might work, but I would probably use danglers or buttons. I'm not saying to buy this one - I only wanted to show you what they looked like. When new, they're much higher priced. I used a Poly pro one in the sulfuric stripper. The plastic surface did degrade over time (became powdery) but I still was able to use it for several yearshttp://www.ebay.com/itm/SINGLETON-BARRE ... 3f1a034a66
If you did shred it and used a barrel plater, I would consider using an electrolytic cyanide solution instead of the sulfuric stripper. It would contain about 50g/l sodium cyanide and about 150g/l of sodium hydroxide and run at room temperature at about 4 volts - you'd have to experiment with the voltage and/or current density, though, for best results. The barrel construction is not as critical with the cyanide solution and it's much easier to get the silver out then with the strong sulfuric stripper. The high sodium hydroxide prevents attack on the copper and the silver plates out on 2 (one on each side of the barrel) fairly large 300 series stainless sheet cathodes about 3mm thick. The solution can be used over and over by periodically analyzing the cyanide and the hydroxide and making needed additions. I really haven't worked with this much. I proved it in beakers in the lab. We then set up a 50 gallon solution of it but we didn't have a barrel plater. We just put a bunch of silver plated flatware in a steel basket. It worked, but only on the outside of the mass. The stuff in the middle wasn't touched. A tumbling barrel plater would solve this problem.
A note on the "herringbone" plastic barrel panel. The plastic is quite thick. On one side of the panel, they drill angled holes half way through. They repeat this on the other side and the drilled holes meet in the middle of the plastic. The result is that the holes are v-shaped (like this > but with a much less severe angle). Therefore, small wires won't fall through the holes.
A note on "dangler" contacts. These are 2 flexible insulated cables with a heavy metal slug mounted on the ends. They enter the barrel from holes in the ends of the barrel. When the barrel turns, they flop around and make electrical contact to whatever is in the barrel.
It would be nice to use a solution the would strip the silver by simple immersion. That would allow you to retain all of the copper in a simple manner. From the figures you gave, from 0.5-1% silver, the copper is worth about the same as the silver.
I don't know how this would work but I did find a very interesting 2007 patent application for an immersion stripper. See the attachment. (Note: the rolled gold one is also interesting because they melt rollled gold or, gold-filled, and run it through a copper cell). It uses sodium persulfate as an oxidizer, sodium hydroxide to raise the pH, and ammonia to complex the silver. The problem I see with this is that, under normal circumstances, when you combine an ammoniacal silver solution with NaOH, you can create an explosive compound. Maybe the persulfate eliminates this possibility but I'm not enough of a chemist to know. It would be appreciated if one of the chemists would answer this question. If it's safe, it could be an answer for a lot of people on the forum. To precipitate the silver as AgCl, I would think one could simply acidify with HCl.
You might be able to use the common 95/5, H2SO4/HNO3, by volume, to strip the silver. If you think about it, it is similar to the electrolytic sulfuric stripper, except it uses the nitric as an oxidizer instead of providing oxidation from an anode. It is dangerous, especially when hot, but, since the silver is thin, it might work well at room temperature. As it slows down, you can add a little more nitric. When it is saturated, you could dilute it and drop out the silver as AgCl. Read this thread, especially the posts by henos. He runs it hot (80C+) and then lets it cool. Most of the silver crystallizes out as silver sulfate. He separates out the crystals and then reuses the solution, with some nitric additions, I assume. A good thing about running it hot is that no moisture from the air would be absorbed and dilute the solution, as would happen at room temperature. A problem with running it hot is, what sort of vessel do you heat it in? In the old days, they used white, fine grained cast iron, I believe. Heavy stainless might work but I'm not so sure about that. Titanium might work. Glass would work but you would be severely limited as to size, in order to keep things safe. viewtopic.php?f=50&t=16166&hilit=sulfuric+nitric+silver
First of all, it was indicated that some of the wire might be brass. If the wire is used for electrical purposes, I can't see how this is possible due to the reduced electrical conductivity of brass as compared to pure copper. If there is brass, this could cause cathode deposition problems due to the zinc. I did find a patent and and article that seemed to somewhat solve the zinc problem. See attachments (note that the rolled gold one is also interesting for melting gold-filled and running it through a copper cell). In general, since the copper preferentially plates out first, before the zinc, the copper content must be analyzed and kept at a high level in order to prevent the zinc from co-depositing. Also, the zinc content in the solution must be controlled
Small copper wire is notoriously difficult to melt due to the formation of copper oxides on its large surface area. However, since this wire is coated with silver, this problem would seemingly be reduced. Most references I found packed the wire into the crucible and some first compacted the wire into blocks. One shredded the wire first into small pieces so it would better fill the voids. In all cases, they covered the copper with about an inch layer of charcoal chunks. This reduced any copper oxides that formed.
To avoid melting, I thought about packing the wire tightly into bagged titanium anode baskets. An alternative would be to somehow compress the wire into small blocks that would slip into the baskets. This would only work if the silver were thin enough so than the acid would penetrate through the porosity. I think this is worth a try. First, ball some up any try it in a beaker to see in the solution will penetrate and dissolve the copper.http://www.ebay.com/sch/?_nkw=titanium% ... 6134127402
I just thought of this, but, with shredded wire, a barrel plater might work in the copper cell. Here again, though, the solution would have to be able to get to the copper through the porosity in the silver. I would probably get a barrel with button contacts or danglers and they would probably have to be made of hardened lead to prevent being dissolved or cut up.
Here are some threads on the copper sulfate/sulfuric cell. If you do go this route, I would suggest setting up to analyze the solution constituents so they can be adjusted when needed.viewtopic.php?f=45&t=5396&p=46132&hilit=anaconda#p46132viewtopic.php?f=37&t=6652&p=59443&hilit=copper+sulfate+sulfuric+acid+formula#p59443
Hope this helps. Unless I think of something else, that's about it for ideas. It took more than 3 hours to write this and I'm worn to a frazzle. Whatever
you do will require experimentation. What you're trying to do isn't easy.
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