# what kind of a cell I have to make to refine the silver



## PreciousMexpert (Jun 25, 2009)

For the past few days I have been trying to find a post in this forum that will explain eaxtly what I 
would like to do,i saw many but I could not find the exact formula for makng a cell

I have seen silver bars that measured 8 inches x 3 inches
They were thick about 3 inches.
They were silver but they looked impure
I know that i would have to do a stannous test to determine exactly what metals are in there
I dont have this bar but i have seen it and for now I would like to go on the basis of what i know
I dont want to approach this person until I open my business
Maybe it is premature but it is something I would like to know


My guess would be that it is about 90% silver and with 10% being copper 
I think this is from photo processing liquid 

Can someone tell me what kind of a cell I have to make to refine the silver to make it pure.
Harold an GSP had some intresting items reagarding this subject.
I know where they are.
Please try to use terms that are easy to understand because I dont know all the 
terminology tin this field
Thanks


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## goldsilverpro (Jun 25, 2009)

If this silver comes from photo processing solutions, it is usually of 2 types - electroplated silver (probably the most common, at least in the US) or silver that has been cemented onto steel wool, neither of which should contain any copper. They will also not contain any gold, platinum, or anything else that can be tested with stannous chloride. The most important thing is to have the bar(s) accurately analyzed for silver content.

The silver on film is very pure to start with. Therefore, unless someone has contaminated it stupidly (should never happen) with some other metal, a silver cell is absolutely not necessary. With electroplated silver (silver flake), all you have to do is flux melt it and it should be pure (at least 99.9%). With cemented silver, it may be contaminated with iron. This can be removed by flux melting.

The appearance of the surface of a silver bar can be misleading, even when pure. The expulsion of oxygen, while cooling, can produce an ugly appearance. There may be slag on the bar. Maybe the bar was not melted properly to remove all the sulfur or iron.

If the silver does not come from photo solutions, it could be most anything. To refine silver in a silver cell, the silver has to start at a bare minimum of about 90% pure. At that level, however, one has to be an expert to correctly run it. For a novice, the silver going into the cell should be about 98% pure. Even then, you need quite a bit of knowledge to operate it. Here again, you need to have the silver assayed.

There is quite a bit of silver cell info on the forum. Here's an example. On this thread, I put a drawing of a silver cell which doesn't seem to exist any longer. I'll try to find the drawing and put it on again
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=732&hilit=silver+cell+thum


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## PreciousMexpert (Jun 25, 2009)

Hi GSP!
How are you.
I really appreciate your reply.
I know its hard to give an answer to these kinds of questions but you were nice enough to do that.


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## PreciousMexpert (Jun 26, 2009)

How would I find out what metals are in this bar.
In the Hoke s book there is stannous chloride,but thats for precious metals.
How about in this case
Thanks


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## goldsilverpro (Jun 27, 2009)

Here's the drawing of a typical Balbach-Thum silver cell that I promised. I drew it 20 years ago and I admit that I could have done a better job. It's the exact silver cell I made and used for many years. One place I worked had 12 of these. There are a lot of ways to build cells, if you understand the basic concepts. This one is fairly traditional. The outer box is about 60" long x 30" wide x 10" tall. It holds 30 gallons of solution, 4.75" deep, and will produce about 500 oz of silver per 24 hours. It was made of wood and then sent out to be totally coated with PVC applied with a chopping gun. It can also be coated by hand with several coats of polyester boat resin, using fiberglass cloth reinforcement in the corners and seams. The cathode was 1/8" thick 300 series stainless and was sent out to be cut and formed - it must sit perfectly flat on the bottom of the outer box. Stainless is used because the crystal won't stick to it, assuming everything is run properly. The ends of the wooden anode tray have arms that ride on the top edges of the outer box. This allows the anode tray to be slid from one end of the outer box to the other, so that the crystal can be scooped out. It was run at about 225 amps, 3 volts. Several cells can be run in series off the same power supply. You can run 4 cells off of a 250A, 12V plating rectifier. Notice that, in series, the voltage is additive and the amperage is constant, assuming each cell has the same resistance. In practice, this isn't possible, although it is close enough if each cell is the same and you keep the connections clean. 

The cell can, of course, be made smaller, but the 4.75" solution depth should be maintained.

A simple 5 gallon (or, so) cell can be made as follows: The anode tray is one of those plastic boxes with diamond shaped holes that hold 4 gallons of milk. The top half is cut off and discarded. The outer box is a plastic tray about twice as long as the milk box. It's sides must be strong enough to support the weight of the cell bars. The tray's width is slightly wider than the milk box. Two 3/8" stainless rods are run through the holes in the milk box and ride on top of the outer box, in order to suspend the bottom of the anode tray 4.5" above the cathode. The cathode is cut and formed so it sits flat on the bottom and is bent up at one end (it sticks up out of the solution) so as to make electrical contact to it. If the cathode does not sit flat, the crystal will work it's way underneath it. It runs at about 40 amps, 3 volts and will produce about 75 oz of silver per 24 hour day. 

Theoretically, at 100% efficiency, one amp will produce 4.025 grams of silver per hour. However, no electrolytic system runs at 100% efficiency.

The solution I started with was 4 oz/gal copper and 6 oz/gal silver. On the forum, there has been several discussions as to whether or not copper is needed to start the solution. From my experience, I believe that it is best to use it and I won't debate the point any longer. I used stripped clean (no solder) house wire for the copper and shotted 100 oz bars for the silver. They were both dissolved in just enough 50/50 nitric to dissolve them, with no excess. This was added to the tank and enough distilled water was added to bring up the level so it just touched the bottom of the cell bars. The anode tray was lined with 2 layers of unbleached muslin obtained from Wal-Mart. The impure bars were poured so they were about 3" x 9" x 3/8" thick. They were placed on the cloth, making sure they all touched each other. The 30 gallon cell held 27 bars.

The crystal must be removed at least every 4 hours or the pile will grow too high and will short out against the bars. This can burn the cloth and the undissolved sludge from the bars will fall down and contaminate the solution and the crystal - a huge mess. If you don't want to come in every 4 hours at night to push the cell, simply turn it off when you leave and turn it back on in the morning. The crystal was removed with 2 tools, a pusher and a scoop. The pusher was a 1" x 6" piece of sheet stainless welded to the end of about a 30" stainless rod. The handle was bent slightly so I could push it all the way under the anode tray. The scoop could be a long-handled, all-stainless barbecue spatula. All of the crystal was pushed underneath the anode tray. The anode tray was slid to the other end of the outer box and the crystal was scooped out, filtered, rinsed, and melted. The silver was usually 9999.

There's a lot more to this and I could write 10 pages on it's proper operation and control.


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## PreciousMexpert (Jun 27, 2009)

Hi GSP!
How are you.
You are a man of your word.
I really appreciate that
Thanks


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## goldsilverpro (Jun 27, 2009)

PreciousMexpert,

We're going to get you going, one way or another. You're my project of the week.

Keep us posted. If you're totally confused as to what to do, let us know. Ask questions. We'll work it out. You may end up deciding that the best thing to do on this deal is nothing.

I repeat my questions. Is this one bar all there is? If not, how many can you get now and in the future?


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## PreciousMexpert (Jun 27, 2009)

Hi GSP
Thanks for your help.

I would say about 6 bars every few months


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## PreciousMexpert (Jun 27, 2009)

Hi GSP
I am reading over your instructions and its look quite complete .
When I start to actually build one of these cells I am sure I will have a few specific questions.


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## dick b (Jun 27, 2009)

Chris (GSP):

I have a question. Does the cathode degrade? or could the box be made as a 300 grade SS tray with TIG welded corners that maintained the 4.50" solution depth and had insulated bars that the anode box road on?

That way there would be no way for the crystals to get under the cathode.

Thanks for reposting the drawing, looks like a simple solution.


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## goldsilverpro (Jun 27, 2009)

dick b said:


> I have a question. Does the cathode degrade? or could the box be made as a 300 grade SS tray with TIG welded corners that maintained the 4.50" solution depth and had insulated bars that the anode box road on?
> 
> That way there would be no way for the crystals to get under the cathode.



No, the cathode doesn't degrade at all. What you propose would work. However, the crystals will plate onto all parts of the box that are in the solution. That is similar to Harold's cell. There is, or was, a photo of it somewhere on the forum. I don't think his anode tray slid back and forth. I think he removed it when he harvested the crystal. Harold could probably give the pros and cons of his design.

The solution depth in a traditional cell is about 4.75". That is the distance from the top of the cathode to the bottom of the cell bars. If it were less, the pile of crystal would short the bars in less time and the cell would have to be pushed more often. If more, the voltage would be higher because of the increased distance between anode and cathode. Banks of silver cells were, and are, used by major silver mining companies. I'm sure that the 4.75" solution depth was determined as the ideal compromise to maximize production after data from 150 years of it's history. Actually, most any other depth could be used, but there would be a sacrifice, one way or another.

When designing your cell, I would also keep in mind the distance between the bars and the sides of the tank. Sometimes, under certain circumstances, very long thin crystals can grow, which can bridge from the tank to the bars. The worst thing that can happen is to create a short. It can start a fire. If a hole burns in the cloth, the undissolved sludge (gold, slag, etc.) can dump into the solution and drastically contaminate it. The solution will require filtering, the tank will require disassembly and cleaning, and the silver crystal will have to be melted and rerun. 

We have been discussing a Balbach-Thum horizontal cell. There are also Moebius vertical cells that are widely used mainly because they take up less floor space. However, they are more complicated to use and the anode stubs have to be remelted and rerun. Also, removing the crystal is more difficult. The Balbach-Thum (usually just called a Thum cell) horizontal cell is the simplest to set up and use.


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## dick b (Jun 27, 2009)

Chris ( GSP ):

Thanks for the reply. 
I guess I misread the information when I said 4.50" to the anode tray. I was thinking about the 5 gal size or a little smaller. I thought to use plastic for the tray and fiberglass rods to support the tray and as the rods for the silver to sit on. Then connect the anode directly to the silver bar that was being consumed. Like it's done in lazersteves sulfuric cell.
Trying to scale it down for the hobby refiner.


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## Harold_V (Jun 28, 2009)

goldsilverpro said:


> I don't think his anode tray slid back and forth. I think he removed it when he harvested the crystal. Harold could probably give the pros and cons of his design.


My tray could slide, but not without raising a portion out of the electrolyte. That was very acceptable because the cell is inactive when scraping down the crystals. I used to park it at the far end while scraping the crystals. The bottom of the tray sat on the end of, but inside the cell, therefore catching any drips. 

As far as my design is concerned, I would likely do a few things differently, although the cell functioned perfectly well. The only negative aspect of my cell was that the sides were in close proximity to the anode. That resulted in shorting of the cell prematurely. I dealt with the problem by applying a band of black vinyl tape along the top edge, which then wrapped around the inside down about 1½" beyond the depth of the electrolyte. That discouraged shorting adequately. You can see the tape in the photo that is posted, below. 

The design had two positive aspects, which is the reason it was chosen. The only cell I ever witnessed was almost identical to mine, aside from having four sides that sloped away from the center. That eliminates the premature shorting, but also increases the volume of electrolyte, plus it makes sealing the cell all the harder. I kept plastic covers on both ends of my cell when it was in operation, to minimize the possibility of contamination dropping in with the silver. 



> I'm sure that the 4.75" solution depth was determined as the ideal compromise to maximize production after data from 150 years of it's history. Actually, most any other depth could be used, but there would be a sacrifice, one way or another.


I'm afraid I'd have to agree. My electrolyte depth was only about 3 or 3½". Shorting was a distinct possibility. Because the cell ran continuously, I cut back on amperage so the deposit was slower, thus extending the time intervals between knocking down the crystals. Added depth, coupled with a greater distance to the sides of the cathode would certainly be beneficial, but as Chris stated, every change is a trade-off. Pretty much ANY design will function to some degree. 

My advice is to design a system around the projected volume that is to be processed. You are far better served to operate a small cell for extended periods of time, requiring small amounts of silver for electrolyte, than to operate a large cell, which may produce profusely, but requires a huge amount of silver for the electrolyte. Should volume increase in the future, it's easy enough to add a second cell. 



> When designing your cell, I would also keep in mind the distance between the bars and the sides of the tank. Sometimes, under certain circumstances, very long thin crystals can grow, which can bridge from the tank to the bars. The worst thing that can happen is to create a short. It can start a fire. If a hole burns in the cloth, the undissolved sludge (gold, slag, etc.) can dump into the solution and drastically contaminate it. The solution will require filtering, the tank will require disassembly and cleaning, and the silver crystal will have to be melted and rerun.


Yep, what Chris said. I experienced shorting, enough to burn a hole in one filter bag. I was fortunate in that there was no fire. Be advised that cotton, when soaked in silver nitrate, is very eager to burn, and will do so even when wet. Fire is a real possibility, although not to be feared under normal conditions. 

The one place I differ is crystal. Impure crystal can be run perfectly well in a cell without melting, is so desired. I re-ran crystal a few times when I found I had run my cell too long and had copper co-deposited with my silver. Simply wash the crystal well (distilled water), then place in the filter, covering with an anode. You'll discover that the crystal will process perfectly well, and create very nice new crystal on the anode. Bottom line is there is no need to melt the crystal. I would NOT advise cement silver be processed the same way. Too much garbage is removed in the melting process, for cement silver is rarely of high quality, unlike crystal that has already been through the cell once. 



> We have been discussing a Balbach-Thum horizontal cell. There are also Moebius vertical cells that are widely used mainly because they take up less floor space. However, they are more complicated to use and the anode stubs have to be remelted and rerun. Also, removing the crystal is more difficult. The Balbach-Thum (usually just called a Thum cell) horizontal cell is the simplest to set up and use.


Chris and I are in lock-step on this issue. The cell described is the fastest and easiest to build and to operate. 

Nice job, Chris. 

For the record, my tank was made of 304 stainless, with TIG welded corners. 316 would be slightly better for chemical resistance, although that is a non-issue for a silver cell. Either material is an excellent choice. I had it electropolished after it was welded. Unseen in the photo, there is a lug welded to the back side upper right hand corner, to which the cathode lead is connected via a large clip. Contact with the anode is made with a silver "candle stick" electrode. I made a simple cast iron mold that poured a round disc of silver, roughly 3/4" thick x 1" diameter, with a ¼" stem, to which the anode lead was attached with a clamp. 

Harold


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## Anonymous (Jun 28, 2009)

Hope you guys don't mind that I made your posts with attached files into pdf files, so that others may download for future reference.


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## PreciousMexpert (Jun 28, 2009)

I am overwhelmed with this information.

Special thanks to Chris and Harold.


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