# Reducing Silver Chloride



## snail

I have a batch of silver chloride I want to return to elemental silver.I would like to try the hydrochloric and aluminum method, but can't locate the details, could someone please help. 
Dale


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## goldsilverpro

Harold is the best bet to answer your question, since that was the method he used. I know that the HCl is needed to provide enough chloride ion to dissolve the required amount of aluminum. I just don't know how much is needed. It could be calculated from the reaction equation.


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## Harold_V

Wash your silver chloride well, until the wash water is clear, with no traces of color. You can do that with tap water. Make at least one of the washes with hot water, to dissolve any lead nitrate that might be present. If you make that wash the last, or second to last wash, you'll notice that the silver chloride will settle almost instantly, so you can decant while the solution is still hot. Lead nitrate will self precipitate when the solution cools, defeating the purpose for the hot wash. 

I used a thick-walled Pyrex container for the conversion. There's enough heat generated that your chloride can achieve boiling temperature, so don't use glass that won't tolerate heat. Don't do this indoors unless you have a fume hood. There's a considerable amount of gas and vapor liberated in the process. 

Place your chloride in the container, and cover it with a 10% solution of HCL and water (tap water is fine). A large diameter container with a shallow layer of chloride is best. You need room to stir. If you have access to scrap sheet aluminum, it works best, for it presents a large surface area to the chloride, and is easily recovered when the operation is complete. Smallish pieces that can be stirred work well, for you have to expose all of the chloride to the aluminum. Avoid tiny pieces that would be difficult to remove when the process is finished. 

At first, the chloride will have a tendency to stick to the aluminum, but as it all converts to elemental silver, you'll find that the aluminum will shed it totally. The aluminum goes into solution in this process, so expect it to dissolve as it works. Make certain that the chloride has converted to gray (silver) and there's still some aluminum left. At that point the aluminum will bubble, being dissolved by the HCL, and will be very clean, but there is, otherwise, no action. When you're convinced the chloride has all been converted, remove the rest of the aluminum, checking any place that yields bubbles for small pieces that may be left behind. It's not a bad idea to add a little free HCL after you remove the aluminum, which will insure that the silver is well washed, and will expose any tiny pieces of aluminum that may be left behind. Allow things to sit for a few minutes. If there's any aluminum left behind, you'll see bubbles coming from the location. When you're sure you have all the aluminum, fill the container with tap water and allow it to settle. The solution will appear to be about the same color as the silver, and you'll swear there's silver in suspension, but that is not the case. Allow it to settle for a day, then decant the solution and repeat the wash. The wash will slowly come clear, but it takes a few repetitions. Once the solution is fairly clear, it will filter well, but the dark solution won't go through a filter worth a damn, so don't try filtering until you've washed the silver a few times. 

My policy was to place the well washed silver in a Buchner funnel, where the balance of the solution could be removed and the silver compacted well for drying. It's a lot easier to handle the stuff after it's been compacted. I would then dump the Buchner contents into a large evaporating dish to force dry the silver over a low flame. The silver that comes from this conversion is very fine grained and sticky. It melts well once dry, but flux (borax, without soda ash) is a definite asset. The flux should be saved for future re-processing. It could contain traces of unconverted silver chloride, and possibly some prills. Soda ash would convert the chloride traces to elemental silver, but it would also convert traces of base metal oxides should they be present, so I avoided using it. All depends on your objective. If the silver is headed for a silver parting cell, the cleaner the silver, the longer the electrolyte will be viable. How you'll use the silver will determine how to flux. If you use it for inquartation, over and over, use some soda ash in your flux. You'll achieve a 100% recovery (of chlorides) that way. 

Hope I've covered it well enough for you to proceed. It will take only one attempt at the process for all of this to make sense. 

Harold


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## snail

Thank You Harold, Those are thorough clear instructions, I had no trouble following them. I like the Method.

Dale


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## goldsilverpro

Excellent instructions, Harold.


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## Harold_V

Thanks, guys. I used that process for years with excellent results.

Harold


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## PhillipJ

Harold. As always I try to read what you have to say. You explain things very well. For a month or so now, I have been thinking that YOU should write a book.

I was thinking about the sheet of aluminum that you are converting the silver chloride with. How would it work to put it in a dedicated aluminum frypan or aluminum pot, add the HCL & stir untill done? Also, I was thinking about that aluminum seal on the coffee cans would be good to use as a sheet of aluminum.

I,m reading in Hoke about the cell used to purify silver, but so far I see nothing about the electrolyte that they use in it, and am having trouble finding the recipe here.


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## lazersteve

Phillip,

Check out this patent:

United States Patent 3975244 

It should help clear up the process. There are many other patents on Mobious Cell variations.

Steve


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## Harold_V

PhillipJ said:


> Harold. As always I try to read what you have to say. You explain things very well. For a month or so now, I have been thinking that YOU should write a book.



Chuckle! Well, if I thought I could find a dozen people weak enough in the head to buy a book I'd written, maybe I'd go for it. :lol: 

Actually, I don't know that I'd be able. I've never lost sight of the fact that I don't understand why things work as they do--not having an education in chemistry. Mind you, it's not that I can't do a good job of refining----I can, and a damned good one at that, but I am nothing more than a trained monkey, very reliant on the things I learned by studying Hoke, plus a few other sources. When things go south, if it's not something I've experienced, I'm often at a loss to explain the problem. I don't think I'd feel any too good about having information published that was questionable, but I sure don't mind helping others achieve a level of performance that I achieved. That's why you see me here on this forum. 



> I was thinking about the sheet of aluminum that you are converting the silver chloride with. How would it work to put it in a dedicated aluminum frypan or aluminum pot, add the HCL & stir untill done? Also, I was thinking about that aluminum seal on the coffee cans would be good to use as a sheet of aluminum.



You'd be inviting a bunch of grief if you went the pan route, although I see nothing wrong with using a pan as a source of aluminum. Same goes with any aluminum, right down to aluminum cans if you can eliminate the printing. Just make sure you don't end up with a lot of tiny bits in the silver when it's fully converted. 

The problem with using a pan? 

Remember me saying that the aluminum gets dissolved in the process? That's exactly why it's not a good idea. The pan, in all likelihood, would have one thin spot and spring a leak when you least expected it to happen. Otherwise I see nothing wrong with the idea, so if you happen to have a few on hand (clean, no Teflon), or can pick them up cheaply at a second hand store, use them accordingly. You could even start out using the pan as you suggested, but make sure you have it sitting in something that will catch the solution and silver when it springs a leak. 



> I,m reading in Hoke about the cell used to purify silver, but so far I see nothing about the electrolyte that they use in it, and am having trouble finding the recipe here.



The electrolyte is made of silver, dissolved in nitric acid and distilled water. I don't have the information at hand, but there's a book by, I think, Butts & Coxe, that covers silver refining extensively. If I have the name of the authors wrong, I know GSP knows the book of which I speak and he can make corrections to my information. 

My cell was used on a batch basis, running an anode that weighed about 200 ounces (troy). By the time I had refined that amount of silver, the copper content of the electrolyte had climbed to the point where it could start co-depositing copper along with the silver. That doesn't happen as long as the percentage of copper is low enough. You can tell when there's a change because the silver crystals tend to grow differently, long and hairy. I'd stop the cell when I approached that threshold and remove the electrolyte entirely, recover the silver within, and make new electrolyte from some of the pure crystal that came from the cell. That was an excellent test of the quality of the silver, for if it had any copper within, it showed in the electrolyte. On rare occasion when that was the case, I'd simply place the silver crystal back in the basket, place a new anode on top of the crystals, and go back to work after replacing the electrolyte. The silver came out beautifully that way, and I was assured of purity. 

Running a cell is far more involved than the simple description, but I'm more than happy to give you guidance if you get that far along, including making your electrolyte. 

On the subject of electrolyte, I think you'll read that the big boys don't do what I did, likely because their cells are ongoing, never shut down. Instead of replacing their electrolyte, they are constantly replacing a portion of it with new, keeping the copper/silver ratio at a desirable level. I've read that they actually rely on some copper for conductivity, although I'm having one hell of a hard time believing that's true considering there's a huge amount of silver in solution as compared to copper, and it's a far better conductor. 

Harold


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## catfish

Harold:

You under estimate your technical abilities, vast knowledge base, practical experiences and accomplishments. What you may lack in technical training and formal education, you make up for in having a can do it attitude. 

I came from the corporate world and I always would rather have the guy on my team that had a positive attitude and could make things happen. I learned early on in my management career, that there is no substitute for experience and practical knowledge. I used to have several hundred employees that had numerous degrees and very impressive credentials and some of them did not have sense enough to get out of the rain. If it was not for the folks of your caliber, AT& T would have gone broke many years ago. I’ll put my money on folks like you any day.

I again want to thank you for the many hours of posts that you have volunteered for the folks on this forum. Believe it on not, we listen to you and most of us use the very same ideas and techniques you have so graciously shared with us. My hat is off to you.

Also, if you should ever reconsider and do publish a book in lay person terms on refining, I want to be your very first customer.

Thanks,

Tom Smith


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## aflacglobal

I know exactly what you mean. Give me the street smarts anyday.


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## PhillipJ

Thanks for the info Harold and Steve. Not that I plan to purify any amount of silver, but it is good to know how to do it just in case.

So far today I learned when to clean out the silver cell, or know what to look for when the copper limit is reached. Also that a silver nitrate electrolyte with a ph of 1.5 - 2.5 is used. I am assuming that the cathode can be either 999 silver or stainless steel.

Current density I am not sure of? My plating manual says 1 amp per 16 sq. in. of cathode and air agitation for decorative silver plating.

And Harold. I have allready copy & pasted a small book on your lessons here. Probably others have too. You allready have a good start right here for your book. Think about it.


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## Harold_V

PhillipJ said:


> I am assuming that the cathode can be either 999 silver or stainless steel.



Silver would be a problem in cost and fabrication, and not really necessary. Stainless is very acceptable, although in the process of harvesting the crystals, you must use tools that won't raise burrs, or otherwise scratch the cell surface, and won't precipitate the silver in solution. I built a scraper from green fiberglass board material, about 3/4" thick, which I used to scrape down the crystals when it was time to empty the cell. The scraper had a shank made of stainless steel, with the blade attached with a stainless screw. For me it was no chore, I had a machine shop at my disposal. 

To remove the crystals from the cell, I found one of those scoops used for removing litter from a cat's box worked quite well. It held the crystals without losing many of them, and allowed the electrolyte to drain adequately. The crystals were immediately washed with distilled water once removed from the cell, with the wash water making up the following batch of electrolyte. Crystals were placed in a large Buchner, which made washing easy. Once well washed, they were force dried in a large evaporating dish, with a low flame. 

There's a template above the cell which was used to cut the fabric for the anode basket. You MUST use a bag, which becomes the collector of values that follow your silver. This is the process where you recover the platinum group of metals that follow silver, along with some gold, surprisingly. The cut fabric was sewed to form a square, which was held in place in the basket by the polypropolylene clips you see in the rather poor picture, below. The basket was made from 3/8" polypropylene as well, held together by stainless screws, and had a gridwork in the bottom that supported the anode. The gridwork was a series of ¼" poly rods with 1/8" sheet strips of poly, spaced with some ½" diameter tubes that fit over the ¼" rods, and between the 1/8" strips. Hope that makes sense. 

I ran the cell in that location for about ten years. It's virtually impossible to handle the electrolyte without some splashing, and it stains everything it touches, as you'll see. The cell was fabricated from 304 stainless sheet material 16 gauge, and was TIG welded, then electropolished. You could just as easily use a large stainless container from a steam table, but it would involve some creativity in that you must have a basket that is non-conductive and inert, in which you place your anode. You'd also have to have an anode mold cast so it would be sized according to need. 



> Current density I am not sure of? My plating manual says 1 amp per 16 sq. in. of cathode and air agitation for decorative silver plating.



Voltage and amperage would be determined by the individual cell and its characteristics. Spacing of the anode/cathode come into play, as does anode size, as you alluded. I started out trying to run about 15 amps on my anode, which was, maybe, 9" square (don't recall the dimensions). It ran fine, but deposited fine, long crystals instead of short, compact crystals. They had a tendency to short the anode in only a couple hours. Considering I like to sleep through the night (the cell ran non-stop, and builds a temperature at which it is happy and runs best), I cut back on the voltage, with a corresponding drop of the amperage. I could allow the cell to run unsupervised for a few hours, so I could sleep through most of a night. I benefited by growing larger crystals in the bargain. 

Again, each case will be its own. You could even allow the cell to sit idle when you're not there to tend it, but if you have much silver to process, you'd never get finished. I'd run my silver cell two or three times each year, but I ran a few thousand ounces each time I ran it. 

Don't confuse silver refining with silver plating-----your objective is not the same. The current density, I think, is higher in parting. 

I took the liberty to post a second picture, this one with a series of molds. The large one on the left casts a 100 ounce silver bar, the square one was my anode mold, and the cone mold(s) on the right were used for pouring buttons that came from melting silver, recovered from solution with copper, or from silver converted from chloride. It got a flux cover when melting to absorb any oxides that were present. The cone molds allowed a small surface area on the button from which the flux could be easily removed. Often, once cooled, a tap with a hammer was all it took. The buttons were then re-melted and cast as anodes. Note that the molds are all well blackened. Foundry supplies sell a mold dressing that I highly recommend. It's nothing more than lamp black prepared such that it can be brush applied. Without it, you'll get soldering of silver to the molds. 



> And Harold. I have allready copy & pasted a small book on your lessons here. Probably others have too. You allready have a good start right here for your book. Think about it.



Chuckle! If I keep posting, it will save you the cost of the book! 

I'm highly unlikely to write a book, considering it would be a repeat of Hoke for the most part. I confess, there was a time when I had planned to do so, but realized early on that I was no writer. I've done one hell of a lot of posting since then (early 80's) and have since improved enough to at least make my posts make a small amount of sense. Hope you know that I'm highly flattered, though. It's been real good for my tired ego to have folks respond to my contributions. 

Assuming I were to write a book, I could add more on silver, which Hoke tended to disregard, but otherwise I'm not convinced there's anything new I could add. You'll slowly come to understand why I am such a champion of Hoke's book----almost everything I talk about came from applying what was already in print. I've changed a few things, such as including the ammonium hydroxide wash to the cycle of cleaning precipitated gold, but not much more. 

I've stressed the fact that Hoke was a master at presenting information in such a manner as to allow people like me to understand her instructions. My only disappointments are that the costs referenced in her book don't come close to today's reality, and she was really big on "tossing on the gasoline" when incinerating. It goes without saying that you should *NEVER* use gasoline in that manner. There are other means to the same end, that don't present the horrible risks.

Thanks for your support, Phillip.

Harold


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## lazersteve

Harold said:


> There's a template above the cell which was used to cut the fabric for the anode basket



What type of fabric did you use?

How long do they last?

Great cell design Harold!

Steve


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## goldsilverpro

I wrote the post below before I saw Harold's post but I wasn't able to post it yesterday. The traditional Thum cell I'm speaking of looks nothing like Harold's. When I first saw Harold's, I was taken aback, since it looked so strange. On closer examination, I can see what he had in mind. His cell eliminates the need for sliding the basket back and forth in order to remove the crystals. Also. the entire cell is the cathode and will probably last forever. Actually, pretty darn ingenious. At 10 amps, his cell probably produced about 20 to 25 ozs in 24 hours

Most books suggest using unbleached muslin as a filter cloth. I bought mine from Walmart and used a double thickness. It's only problem is that there's sizing in it and it takes an hour or two before the solution penetrates the sizing and there is maximum current flow. The cloth is used once. The muslin cloth also burns well. I never used only gasoline for burning but often used a safer 50/50 blend of gas and diesel.

The 30 gallon cell mentioned below consists of an flat bottomed outer tank about 30" X 60". It was made from 2" X 10" lumber with a 3/4" plywood bottom. It was coated with several coats of polyester boat resin. The last one I made was coated with PVC that was applied with a chopping gun. A sheet of 1/8" 300 series stainless laid flat in the bottom. The stainless had a 90 deg. bend at one end and protruded out of the tank in order to make electrical contact. 

The inner basket (also coated) was about 28" X 28". The sides were 1" X 6" lumber. Instead of a solid bottom, there were 19 removable 3/4" OD PVC pipes sealed with pipe caps on each end. A length of 3/8" or 1/2" rebar was put into each pipe for rigidity. Each pipe rested on a support on the sides of the basket. The muslin cloth was laid on the row of pipes and the 21 impure silver bars (about 30-35 oz each - about 600 oz total) were placed on the cloth. The bars were all touching each other. The solution level was adjusted so it touched the bottom of the silver bars. To make contact to the bars, I used a 3#, 60/40 copper/silver bar attached to the power cable. This contact bar was simply placed on the silver bars. A protruding wooden crossmember was attached to 2 ends of the basket. They rode across the top sides of the outer tank and allowed the basket to be slid from one end of the tank to the other.

The drawing in the attachment is a cutaway side view of a standard silver cell.

I once made a 5 gallon cell, using a 7 gallon plastic tray as the outer tank. The stainless was the same as in the 30 gallon tank. The basket was made from one of those plastic carrier boxes, with diamond shaped holes, that are used to carry 4 gallons of milk. I cut off the top 1/3 of the basket and ran 2, 3/8" stainless rods through the holes in the basket. These rode on the top of the tray to support the basket. This little cell made about 75 oz. per day and worked great. It was very cheap and fast to build.

In both these cells, the size of the stainless cathode must sit very flat on the bottom. It must also fit fairly snug and the corners must be slightly rounded to fit without cutting into the tank coating. It must be professionally bent and professionally cut with a large shear.
.
The silver in the cell must be harvested at least every 4 hours. If allowed to run too long without harvesting, the silver piles up under the basket and shorts out with the silver bars. This invariably burns a hole in the filter cloth and allows all the grunge collected by the cloth to co-mingle with the solution. Then, the entire 30 gallons has to be filtered and the tank cleaned and re-setup. One doesn't make this mistake twice. If one has to leave for awhile, the power is shutdown or reduced.

To harvest the silver, the power is shut off and the crystals are pushed to one end of the stainless cathode. The basket is slid to the other end and the crystals are removed. I always used a stainless BBQ spatula, with no holes in it, to remove the crystals. The power is then turned back on. The crystals are filtered and rinsed very well. Then they are melted and cast into 9999 bars.

*Yesterday's Post*
Steve, I'm quite familiar with the Hunter patent you linked and I remember the interest it created when it was first released. It is not a patent for a silver cell but, it is a patent for removing the build up of copper from the solution, using solvent extraction. However, the cell solution parameters given (1.5 pH, 60 gm/l silver, 30 gm/l) are valid.

There are two basic types of silver cells, the Balbach-Thum (horizontal) cell and the Moebius (vertical) cell. The Moebius cell is usually used for large volume because it takes up less floor space and doesn't need the nearly 24/7 attention that a Thum cell needs, for maximum production. The Thum cell is easier to set up and use. Both are fairly complicated to build. At least, you have to understand what is required. The dimensions are fairly critical. A standard 30 gallon Thum cell will produce about 500 ozs of 9999 silver in a 24 hour period. The books don't come close to telling the entire story. Also, the info in the books is based on mining operations where the composition of the impure bars run the same, day after day. For us, running scrap silver that is different every batch, the situation is much, much more complex. To adequately cover this subject, it would take at least a 30-50 page report, with drawings. There are lots of ins and outs and lots of variables. Each metallic contaminant may require a little different approach.

Just as aqua regia is the final purification step for much of the pure gold that is produced, the silver cell is what finally purifies the silver. With gold, there are other methods available besides aqua regia. To get pure silver, the silver cell is about the only game in town.

I got 5 years of hands-on experience working in a place that had 12 Thum cells and produced about 5000 ozs per day. Two of the cells were, what we called, breakdown cells. We used them to breakdown silver bars that contained lower amounts of silver. Instead of making up the starting solution with pre-mixed copper and silver nitrates, we started it with only a certain amount of nitric acid and water. As the impure bars dissolved electrolytically and silver crystal was produced, the nitric re-dissolved the crystal and formed the silver solution. This stuff isn't covered in any books.

In almost all impure silver, copper is the main contaminant. For example, sterling is 7.5% copper. As the bars dissolve in the cell, the silver plates out as beautiful loose crystals and the copper remains dissolved in the solution. When the copper dissolves, the silver content of the solution decreases. The copper goes up and the silver goes down. At a certain point of either, the crystal purity suffers. The standard way of solving this problem is to remove cell solution and replace it with silver nitrate solution that contains no copper. Thus, the great interest in the Hunter patent mentioned above. This system continuously removes copper from the solution.

Before even thinking about a silver cell, you must have a pot furnace with all the associated equipment, in order to produce bars from the impure silver: furnace; crucibles; tongs; molds; fluxes; safety equipment; exhaust; etc., etc. Also, you have to melt and cast the crystal.

You also need a variable rectifier to power the cell. For a full size 30 gallon cell, you need at least a 250 amp, 4 volt rectifier. You can run cells in series off of the same power supply (PS). A 250A, 12V PS (approx $2500) will run 3, 30 gal. cells. For smaller cells, the PS needs are proportionally less.


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## Harold_V

The fabric was purchased from a company that specialized in filter materials. It was about as thick as canvas that you may see in daily life, but had one side roughed up, so it was fuzzy. I used that side facing in, and got very good results. Seams were all triple sewed to insure they didn't leak solids. The material must permit the passage of the electrolyte, yet retain the smallest of particles that don't go into solution. I was well satisfied with how the fabric worked, and could run several 200 ounce anodes before replacing. It had a tendency to become clogged over time. Because of the exposure to silver nitrate, once dried, they incinerate very well simply by heating in a pan. 

Because I processed a fair amount of dental gold, I had a strong showing of the platinum group in my silver. It was often so high that the sludge didn't fall away from the anode, but had to be mechanically removed. I used a porcelain spatula, and simply left the sludge in the basket until it was time to drop in a new anode. I'd remove the remnants of the old anode, scrape it well, then scoop out all the sediment from the bag, using an acid dipper. Drop in the old remnant, with a new anode on top, and start the cell again. 

I should have mentioned in my previous post. My cell had a lug welded on the back side for the cathode connection. The anode connection was made via a thick "door knob" cast of silver. It was simply placed on the top surface of the anode, which was never exposed to the electrolyte. That way, should the anode dissolve to the point where the connection was exposed to the electrolyte, nothing was dissolved to add contaminants. I machined the mold that was used to cast the door knob. 

When running a cell such as this, the electrolyte should be kept at a depth that just touches the bottom side of the anode, to prevent premature loss of peripheral size. That way you get a more uniform decomposition of the anode, keeping the surface area relatively constant. 

My cell design was acceptable, but I'd make a minor change should I ever build another. The vertical sides ended up being a bit of a problem, which I eventually solved by adding a strip of wide electrician's tape. The short distance from the anode to cathode encouraged crystals to grow to the basket, creating a direct short. The tape, coupled with knocking down the crystals on a regular interval, solved the problem. It would be better to avoid it entirely. That involves greater anode/cathode spacing, so it gets complicated because you then limit the size of your anode unless you increase, substantially, the size of the cell. 

Harold


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## Harold_V

> When I first saw Harold's, I was taken aback, since it looked so strange. On closer examination, I can see what he had in mind. His cell eliminates the need for sliding the basket back and forth in order to remove the crystals. Also. the entire cell is the cathode and will probably last forever. Actually, pretty darn ingenious. At 10 amps, his cell probably produced about 20 to 25 ozs in 24 hours



Having seen only one other cell in all my years, I had little idea what others had done. The cell I copied was similar to my design, but was tapered on all sides about equally. Once I operated mine, I understood all too well why that was the case. I mentioned the short distance and shorting by crystal growth. That would have been controlled by wider or tapered sides. 

My decision to make the cell as I did was based on the idea that I was not primarily interested in silver, and would likely never run it in large volume. In spite of the restricted volume, I was all too aware that I had a lot of Pt. group metals tied up in my silver, and could recover it easiest in a parting cell, with the benefit of producing pure silver. 

I had to balance the amount of silver I had to run against how much I wanted to tie up in electrolyte, which was a part of the reason I kept the sides straight, and included the tapered ends. That is all non-functioning area and need not have depth. While I don't regret the reduced volume of electrolyte, I'd have preferred to not face the shorting issue. 

Bottom line is my cell turned out to be very well sized for my operation, which is a serious consideration. I gave considerable thought before deciding on size, and was fortunate to hit something that was functional for my circumstances. If one builds a large cell, running it could border on the impossible unless a large volume of silver is handled on a routine basis. Small cells, run continually, are a far better choice when volumes are small, I'm convinced. 

I'd run a +/- 200 ounce anode in two or three days. I don't recall the current density any longer, but the voltage, as you alluded, was very low. I do recall having a target of 15 amps, but the crystal growth was too fast and created rapid shorting, which I mentioned in my previous post. If memory serves, I ran around 9 amps, but I sure wouldn't swear that was true. Could be it was up around 12. Getting old and forgetful really sucks!

The tapered ends are good for reducing the volume of electrolyte, but that's a mixed results kind of thing. Greater volume would have equated to a guarantee that the electrolyte had greater capacity for copper before becoming troublesome. On rare occasion I had to re-run a batch of crystals, which I also mentioned previously. 
Aside from the loss of production, it was a trouble-free proposition. The crystals that grew from the virtually pure silver ware small and dense, allowing prolonged running without knocking them down. The trace of copper contained in the crystals was evident as the process ensued, by the electrolyte changing color ever so slowly. 

As the crystals were knocked down, I'd push them to the ends, and harvest only when necessary. When things ran as desired, crystal was harvested only when the electrolyte was replaced. 

All in all, I'd recommend a cell similar in design, if for no other reason, it was easy to build and maintain. 

Harold


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## PhillipJ

Thanks for all your input here guys. You are all talking much bigger than what I would need. For my purpose, I think that I would suspend my anode vertical, in a bag, And plate onto a vertical sheet of stainless, all in an ice cream pail. I see no reason that that wouldn't work.

One thing I don't remember either Harold or GSP mentioning was the use of any agitation.


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## Harold_V

No agitation is required. There's a minor amount of convection due to heating of the process, which appears to be adequate. Chris may have a different view, considering he operated cells that were significantly different from that which I used. 

There's nothing wrong with the simple design you spoke of. Insure that no copper or iron touches the electrolyte. Titanium, if you can get some, is a wonderful bus system. Stainless will also work, as you already know. 

Harold


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## goldsilverpro

No heat. No agitation. Ideally, the starting solution should be 30 gm/l copper and 60 gm/l silver. You can fudge a little on this but, not much. The purpose of the copper is to make the crystal denser. Without it, the crystal will be fluffy and stringy and will climb all over and soon short out the electrodes.

For the copper, I would dissolve solid, clean (no solder) house wire in 50/50, nitric acid/distilled water. You can dissolve about 120 grams in 1 liter of 50/50 nitric. For the silver, use pure silver coins, US 90% coins, silverware, other types of sterling, etc. You can use US 40% silver coins but, not exclusively. You can also use silver that has been cemented out of nitric with copper, if there's no palladium in it and if it's been very well rinsed. Whatever you use, make sure that the only contaminant is copper. Many other metals will create problems. You can dissolve 420 grams of pure silver in 1 liter of 50/50 nitric. 

When calculating the nitric needed for silver alloys, you'll have to take into consideration the amount of copper in the alloy (s), using the figures above. Also, when calculating the copper wire needed, consider the amount of copper in the silver alloys you're using.

After dissolving the metals, it is best to not have any free nitric left in the solution. It doesn't really hurt anything but, until it's used up, the silver crystal produced will be re-dissolved.

After dissolving everything, dilute to final volume with distilled water. Never use tap water in any part of this process. It contains chlorides and the silver chloride produced will create a cloudy solution and contaminate the crystal.

When the cell is operating, for every gram of copper dissolved in the solution, from the impure silver, the total silver content in the cell will decrease 3.4 grams. If the silver in the cell goes below about 15 - 20 gm/l or the copper goes above 100 gm/l, the crystal purity will be affected. Try to keep records and keep track of how much copper is being dissolved. Usually, you know this by the type of materials you are running. When the silver in solution approaches the danger level, you can build up the silver content in 2 ways.

First, you can calculate how much silver you need and add the equivalent amount of nitric acid. This will re-dissolve some of the crystals. This method will obviously cut into your production. 

Second, you can remove some solution and replace it with silver solution that contains little or no copper.

When I ran cells, I analyzed the solution silver content with a simple titration method. One of these days, I'll post how to do it. Then, I measured the specific gravity of the solution with a hydrometer. From this info, I calculated the copper content using a graph I had created.

The impure silver you run through the cell should be at least 90% pure. Otherwise, the silver in the cell decreases so fast that you can't keep up with replenishing it. The easiest silver to refine in the cell is silver that has been cemented from a nitric solution and melted into a bar. It runs about 98 - 99% pure and the silver replenishment is not needed nearly as often.

At 100% efficiency, you will produce 4.025 grams of silver crystal per amp-hour. However, no electrolytic system runs at 100% efficiency. Therefore, at 5 amps, you produce about 20.125 grams per hour. It is best to not go over 4 volts. If you're using a battery charger, use the 6V setting. It may or may not work at 6V. The crystal density could be severely affected and the crystals may grow all over the place. Never use 12V. If you're handy, you could rig up an adjustable shunt, with a voltmeter, to drop the excess voltage.

When running vertically, the crystal will fall off of the stainless cathode and pile up on the bottom of the container. The worst thing that can happen is if this pile grows to the point where it makes contact with both electrodes and shorts them out. I would suggest that you use a 5" separation between anode and cathode. Keep the electrodes about 4" off the bottom of the container.

When the crystals build up to a certain point, you'll have to disassemble the entire cell and pour off the solution to collect them. A way around this may be to also bag the stainless cathode. Leave a couple of inches of empty bag below the cathode so there will be enough room to catch the crystals. If you use a bag, you'll probably have to figure a way to hold the bag a little bit away from the cathode surface. If you don't, the crystals may grow through the cloth. I've never used a bag for the cathode but, for some reason, I think this might happen.

Since you're running vertically, you'll need some sort of wire to suspend the electrodes. Stainless is the cheapest choice (gold also works). Just remember that stainless is only about 1/35 as conductive as copper. The wire should be heavy enough to not overheat. You can make S-hooks from the wire.

Vertical is not the best way to do this. I think that, after you read this, you will see that horizontal is best. It should be easy to design a very small horizontal cell. I once made a horizontal one, in a one liter beaker, for my nephew's science fair project. I"ll try to remember how I did it. It's been 20 years.

I love silver cells. They're fun and very easy to run, once you get setup and learn the ropes. Pure gold is about the most beautiful thing on earth. Pure silver crystals come in second.

Good Luck!


----------



## PhillipJ

Good info GSP. Thanks.


----------



## Harold_V

goldsilverpro said:


> The purpose of the copper is to make the crystal denser. Without it, the crystal will be fluffy and stringy and will climb all over and soon short out the electrodes.



Nonsense!

Copper is used by major refiners to minimize the amount of silver in solution. It's a matter of economics, and is not a requirement for good deposition. If anything, electrolyte without copper grows crystals that are difficult to remove from the anode because they're so robust. 

I refined silver for well over ten years with electrolyte that started with no added copper, and had nothing but good results. My experience was directly opposite of your claim. Only when the copper level was beyond limits did I grow any stringy silver, and while I don't claim to have processed a huge amount, I did refine several thousand ounces. 

For your perusal, I'm posting a picture of silver crystals that were grown from pure silver, in a pure silver nitrate electrolyte. You be the judge if copper is essential, or not. 

Take note that the coin in the picture is one of the new $1 US pieces. The crystals in question are anything but stringy or small. Sorry for the sulfated state of the crystals. They were grown prior to '84, and have been in storage since. 

Harold


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## lazersteve

Harold,

Those are very beautiful! Is there a way to clean the sulfur discolorations without drastically harming the overall crystal? I think I read somewhere that baking soda and/or vinegar in water ( going from memory here, I may be dead wrong! ) would clean the surface of silver without pitting or additional corrosion. Can you confirm or this? It's been a while since I saw the internet article, but I can find if need be.

Thanks,

Steve


----------



## goldsilverpro

My experience was totally opposite than yours. Without copper, the crystals would sometimes even grow up the sides of the non-metallic tank. It seems like you were running at a lower current density than I was. This could make a difference. You mentioned that you kept the current low so you could leave the cell unattended without shorting it out. I ran max and had to push the cell at least every 4 hours to prevent shorting. Sometimes, every 2 hours.

The crystals in the photo are, no doubt, beautiful. Although I have produced similar large solid crystals, I always thought that they were undesirable, from a production standpoint. According to the literature and, my own experience, the best crystals were about the consistency and size of sand. Heavy, brilliant, small crystals are much easier to filter, rinse, and handle. I have never seen these produced without the presence of copper.

There are some thiourea based tarnish removers on the market. A common one is Tarn-X (I think that's right). I think Walmart has it. You just dip and rinse.


----------



## Harold_V

lazersteve said:


> Is there a way to clean the sulfur discolorations without drastically harming the overall crystal? I think I read somewhere that baking soda and/or vinegar in water ( going from memory here, I may be dead wrong! ) would clean the surface of silver without pitting or additional corrosion. Can you confirm or this? It's been a while since I saw the internet article, but I can find if need be.



Like you, I've read an article on polishing silver without manually abrading. I recall reading about using aluminum foil, which apparently creates the small voltage needed. Never tried anything. Chris already mentioned the commercial product(s) that are available. 

While it's hard to see in the photo. the small crystal looks better with the sulfide coating than it does without. For reasons I don't understand, the sulfide coating is only on the interior, and only on the flat bottom area. It's very light in color, and evenly distributed. It's as if someone had gone out of their way to create a contrasting background. It's nothing short of cool! 

Can't say the same for the large crystals sitting on the pale blue foam. It's obvious the sulfation has been caused by the foam-----and it's not pretty, although certainly not ugly. 

The crystals shown were purpose grown-----not from a refining cell. The point I was making is that copper does not make crystals grow dense and small----it makes then grow weaker, so they shed faster. That makes for small, more uniform crystals. I got to witness that every time I ran my cell. The first deposition was often almost a sheet, which quickly changed to crystals as the copper content increased, and finally started growing hair that shorted the cell, and was contaminated with copper. That was consistent, with the contaminated silver confirmed when it was used to make new electrolyte, or refined a second time in electrolyte made from pure silver. By running without copper, it was obvious what the effect was. 

I would advise anyone making electrolyte for a small cell to make it from pure silver-------add no copper. It's not necessary for good production, and extends the useful life of the electrolyte. It may perform a desirable function on a production level, but serves no useful purpose when used in a cell that is run on a batch basis, as mine was. The only real negative is that the silver, at first, starts out plating a sheet that can be difficult (but not impossible) to remove. 

Also------do not try to part any silver of questionable quality. It if has not been precipitated on copper, or recovered from silver chloride, it likely has too much copper within for the cell to yield pure silver for very long. (Read that "don't try to part sterling or coin silver unless you don't care about the quality"). The objective of the silver cell is to produce high quality silver, with the added benefit of recovering traces of greater values. It makes no sense to do anything to defeat the purpose. 

Harold


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## Noxx

Hey, maybe ultrasonic jewelry cleaner could do the trick ?
Just my taught.


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## aflacglobal

It put my post in the wrong section. :?: :?: :?: 

:evil:


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## Palladium

Awesome thread. :wink:


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## Shecker

Before he died, Walter Lashley of New Mexico's American Society for Applied Technology, discovered that silver chloride will spontaneously reduce to silver metal in the presence of chemically pure iron. The iron will change into ferrous chloride and the silver will be reduced. I use to use this process when I was processing photographic wastes for the silver content.

Randy in Gunnison


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## Sylar

I have a bit more then 1 kg AgCl which I want to refine to pretty pure silver metal.

For this amount I set out to find the best way to do this, and from Harold I got the Aluminium proces. This proces was completed yesterday, and the reduced silver was filtered today, pressed to allmost dryness and fired up in my home made furnace.

So I placed the still slightly damp grey silver powder sample in a quartz cup, placed the cup in my furnace and let 'er rip. 30 minutes later the entire furnace (diameter 80 mm, height 100 mm) was as hot as it would get with the modified butane burner I placed in it. Temperature measured to 1020°C with my type K thermocouple but the inside of the quartz cup was still powder, with a speck of molten metal here and there.

1 hour later (about now) I sit here behind my 'puter ... a little confused. I have a light brown powder, definately not metallic, but shiny silver beads the size of a pinhead in it are smiling my way, still slightly warm to the touch.

What have I made, and why didn't it all melt around 950°C to a wonderful glob of relatively pure silver?


----------



## goldsilverpro

No offense, Shecker, but Lasley was an idiot. I read everything he wrote in the California Mining Journal. He was a spiritualist and not a realist, when it came to PMs. Most of his systems were BS.


----------



## Harold_V

Sylar said:


> What have I made, and why didn't it all melt around 950°C to a wonderful glob of relatively pure silver?


It's silver-----you should have used some borax as a flux. Sorry I didn't make mention. You don't need a lot----a sprinkling on the surface will immediately cause the powder and bits of silver you see to become one. It the flux gets quite dirty, add a little more. An excess does no harm. Heat until it is a common mass, then pour to a well blackened mold. You must have the blackened surface, or the silver will solder to the mold. Make sure the mold is iron or steel. Don't use a lower temperature alloy or copper. 

You would be best served using a small graphite/clay or silicon carbide crucible. Also, small clay melting dishes are readily available from jewelry supply houses. They are not expensive and will serve very well for the purpose. Fluxing your quartz crucible/dish will likely not be the wisest thing you do. 

If your choice becomes either the graphite/clay crucible, or a clay melting dish, be advised that each of them are subject to cracking when they are put to work. If you heat either of them slowly, to expel residual moisture, then put them to work, you will avoid the potential cracking. 

Harold


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## Harold_V

Shecker said:


> Before he died, Walter Lashley of New Mexico's American Society for Applied Technology, discovered that silver chloride will spontaneously reduce to silver metal in the presence of chemically pure iron. The iron will change into ferrous chloride and the silver will be reduced.


You left out the little part where you must include some sulfuric acid, or HCl. That's hardly a secret. He likely learned it from Hoke. Also, it need not be chemically pure, although should that be the case, you wouldn't be adding any contaminants to the silver. Silver and iron will not readily alloy.

Harold


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## Sylar

Aha, that's on my todo list for tonight then, I have several kgs of borax sitting here doing jack anyway.


I have a SiC crucible, but it doesn't fit my oven, and I have a graphite dish, which I don't like in my oven because is will tend to oxidise, right? So I'm likely using thinwalled clay/porcelain then.


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## Harold_V

Sylar said:


> I have a graphite dish, which I don't like in my oven because is will tend to oxidise, right?


I used to own one of those small electric furnaces that use a crucible that is machined from graphite stock. Very handy, but life of the crucible was short. While the cover minimized oxygen exposure, that in and of itself was not enough. The crucible had a short lifespan due to the head burning away. The inner portion of the crucible sustained almost no wear or oxidization---but the crucible was rendered useless because the head was destroyed quickly. As a result, I don't recommend that type of furnace, nor do I recommend a graphite dish of any description. They are an excellent choice in that they help prevent molten silver from absorbing oxygen, but expensive to use. Graphite mixed with clay tends to have a much better lifespan, although anything that you use that is combined with flux will suffer a greatly shortened lifespan. That includes your furnace lining. Truth be told, the clay dishes are the best choice. 



> So I'm likely using thinwalled clay/porcelain then.


Coors? They've extremely sensitive to thermal shock, so handle with great care. I personally avoided them for the most part. 

Do investigate the small clay dishes I recommended, when you get a chance. They're made from a white clay and are available in a few sizes. They even offered white clay crucibles at one time. Don't know if they still do. 

You can melt ten ounces of silver in the largest dish. They used to be marketed under the Vigor name. Don't know if they still are----it's been more than 15 years since I bought any. I used to use them for all my melting, including inquartation and the melting of pure gold. For the money, they are the best possible melting dish available, and have a reasonable lifespan. An added benefit is they're very easy to clean when they're coated with dirty flux. If you get involved with one and need that operation, ask on the forum. It has been well discussed previously, but I'm always happy to post on the subject again. Makes it easier for the new guys to learn some of the useful tricks.

Let us know how the silver goes. You should end up with some nice buttons.

Harold


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## Oz

Harold_V said:


> I used to own one of those small electric furnaces that use a crucible that is machined from graphite stock. Very handy, but life of the crucible was short. While the cover minimized oxygen exposure, that in and of itself was not enough. The crucible had a short lifespan due to the head burning away. The inner portion of the crucible sustained almost no wear or oxidization---but the crucible was rendered useless because the head was destroyed quickly. As a result, I don't recommend that type of furnace, nor do I recommend a graphite dish of any description. They are an excellent choice in that they help prevent molten silver from absorbing oxygen, but expensive to use.



Many years ago when I was looking into investment casting of silver I heard several individuals talk about floating carbon (charcoal) on top of their silver in a crucible while in their furnace to create a barrier between the molten silver and any possible oxygen in the furnace. They would use a bar across the lip of the crucible to skim off the carbon when pouring to give themselves a clean pour without the oxidation problems. I should add that I never did this myself but thought it might be useful commentary considering Harold was talking about the problem of molten silver wanting to oxidize.


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## Harold_V

Oz said:


> Harold was talking about the problem of molten silver wanting to oxidize.


Actually, it doesn't oxidize, but absorbs nine times its volume in oxygen, expelling it as it solidifies. In a sense, the silver is not effected. It can, however, be the cause of a very rough and irregular surface on cast silver. 

The floating carbon prevents the oxygen from entering the molten silver. The addition of even a small amount of copper also controls the oxygen problem-------but that's not a solution for the guy that wants to cast pure silver. 

I think Hoke talks about this very subject. Not sure. My copy is not at hand, and I have not looked at the download as of yet. Readers-----what does Hoke say about silver and oxygen?

Harold


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## Oz

This sounds very much like the problem Louis was talking about with pouring Pd bars. I’m with you on having a physical copy of Hoke. Perhaps I’m just too old, but nothing replaces being able to turn actual paper pages for me. I do like being able to do key word searches in large PDF files though.


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## Lou

You can really cut down on how much oxygen the silver absorbs by melting it in a rich furnace atmosphere. Be exceptionally careful doing this--by richening the flame, you produce carbon monoxide. I can vouch that it works quite nicely.


Harold, if you're talking about those white, fused silica crucibles that are bone white, then yes indeed, those are premium! They work well for gold, silver, and palladium. Platinum is a bit much for them though.


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## Harold_V

Lou said:


> Harold, if you're talking about those white, fused silica crucibles that are bone white, then yes indeed, those are premium! They work well for gold, silver, and palladium. Platinum is a bit much for them though.


No, the dishes I speak of are just clay. They do not have the characteristic straight sides and thick bottom of the ones you reference. Fact is, they look very much like small Coors evaporating dishes, only thicker. 

I used the type you're talking about for melting my platinum, what little I melted, anyway. It was important to remove the button immediately upon solidifying, otherwise the melted silica would trap the button in the dish. The problem with this type of melting dish is they don't have a large capacity, unlike the larger sizes of the one I mentioned. 

I pickled the recovered button in hydrofluoric acid once removed. I had a small platinum dish that served the purpose. Aside from killing a wart, I can't think of another use for the acid, which I still have. 

Harold


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## Sylar

Succes !!!

I have before me now a bead of shiny silvery silverish silver!  
Weight: 9 grams.

What is the black smoke coming from the hot crucible? Silver vapor?

AgCl + borax = bubbling/foaming + Cl + Ag seems to happen at about 800°C, crystalising out metallic silver until temperature rises enough to melt the produced silver.

What's so special about the borax that it helps consolidate the silver into a metallic state? Can anyone explain the physics of that to me?

By the way, all my AgCl was dry. 
The lump I have sound like a brick if tapped and I scrape off the amounts I test with (pretty easy) why does everyone insist to keep it wet?

Other crucibles I found in my stock: Stainless steel.
What are the up and downsides of these?


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## Harold_V

Sylar said:


> Succes !!!
> I have before me now a bead of shiny silvery silverish silver!
> Weight: 9 grams.


Congratulations! I knew you could do it! :wink: 



> What is the black smoke coming from the hot crucible? Silver vapor?


I don't have a clue. Unless you are overheating the silver, there shouldn't be any vapor coming from it, but you may be seeing other contaminants burning off. If you failed to wash the cemented silver well, you may be seeing some of the aluminum that was included. GSP or Lou may have an idea what you're seeing. 



> AgCl + borax = bubbling/foaming + Cl + Ag seems to happen at about 800°C, crystalising out metallic silver until temperature rises enough to melt the produced silver.


I'm short on the chemistry end of things, so I'm at the mercy of what I read, and don't often understand everything even then. In that regard, one of the things I have been lead to believe is that if you heat silver chloride without a reducer, it doesn't convert to elemental silver well, and much of it is lost as vapor, although I have no clue what form it might be.

Regards the above statement, I stand to be corrected, and the subject has come up before, but the evidence at hand, the result of using soda ash in that capacity, is hard to disprove. 

I gathered from my research, long ago, that soda ash acts as a reducer. I've been told I'm wrong, but something has to explain the fact that you can heat an old contaminated dish that is heavily coated with borax, then add some soda ash to the mix and end up with metal that wasn't there prior to the addition of the soda ash.

As it mixes with the dirty borax, you start seeing bits of metal appear. Eventually the color of the dirty borax is much lighter, and a nice sized button of metal has appeared. That, to me, indicates that the soda ash is reducuing the oxides that were absorbed by the borax. If I'm wrong, I stand to be corrected, but it will take a serious amount of lecturing to make me see it differently, considering I recovered well over 200 ounces of gold from waste materials, along with a like amount of silver, using that process. 



> What's so special about the borax that it helps consolidate the silver into a metallic state? Can anyone explain the physics of that to me?


Technically? No, I can't. But it does absorb impurities that might otherwise prevent the silver from fusing. It also "lubricates" the silver, allowing it to flow freely. You'll have to trust the input from others that understand chemistry far better than I do if that isn't correct, or isn't enough information. I gave it my best shot. 



> By the way, all my AgCl was dry.
> The lump I have sound like a brick if tapped and I scrape off the amounts I test with (pretty easy) why does everyone insist to keep it wet?


To prevent you having to scrape off what you need! My normal process was to allow it to accumulate in a jar, even if it got well darkened by exposure to light. No big deal, all I was going to do eventually was recover the silver. By keeping it wet you can readily handle the material. I see no advantage to storing it dry----and scraping it to get it in condition to be reduced seems like a lot of wasted effort to me. I say keep it wet, if for no other reason, convenience. Others may have a different viewpoint. Maybe they'll chime in. 



> Other crucibles I found in my stock: Stainless steel.
> What are the up and downsides of these?


For melting? 

BIG MISTAKE!

Molten metals are strong solvents of other metals. That means that what you melt in a stainless vessel is likely to dissolve a portion, or all of the vessel used for melting. If you were to flux, you'd also solder the lot to the vessel. Assuming it was heated long enough, you'd dissolve the wall to the point where you'd spring a leak, losing your values. You'd also contaminate the values because of the dissolution of the vessel. Makes no sense to purify a metal, only to contaminate it with something different when melting. 

You can dissolve gold in molten lead and never get near gold's melting point. Same applies to other elements. Do all your melting in non-metallic vessels. Even if they don't dissolve, they tend to solder to the vessel. 

Harold


----------



## Lou

Erm, you shouldn't just melt silver chloride by itself?! That is quite hazardous to your health and it just wastes your silver! You'd have better luck adding it to NaOH, filtering the Ag2O and melting that; that works a treat. Just fusing silver chloride with borax won't do much. Some of the silver disproportionates to silver and chlorine gas (so small you won't see the yellow), but the rest of it goes up as that black smoke, because it has a vapour pressure. Bad idea.

Your best bet is to try sodium carbonate, charcoal, and silver chloride. The sodium carbonate doesn't act as reducer in the traditional sense, because carbon's oxidation state remains the same. Instead, it serves to soak up the chloride off the silver, which forms table salt, which melts and volatilizes. There are some free electrons floating about that hit the Ag+ and reduce it; this can come from the chloride (silver is strong enough an oxidizer at those temperatures to oxidize chloride to chlorine). Anyway, really bizarre things happen at those temperatures. Pyrochemistry is never easy to define.

You can also use some copper or iron pieces to cement your silver chloride to silver metal. I prefer the use of NaOH because it will leave fine silver that isn't contaminated after melting (because the sodium volatilizes off).


Lou


----------



## goldsilverpro

Here's 2 patents for the reduction of silver chloride to silver metal, both by Kunda - 4306902 and 4388109. They require blending anhydrous sodium carbonate intimately (requires grinding together - he does it dry in a blender) with silver chloride and heating to a temperature of between 1058 F and 1157 F. If held within these limits, there is little, or no, attack on the crucible. Silver powder (finely divided), mixed with sodium chloride results. The sodium chloride is finally leached out with hot water. In practice, for 143 grams of silver chloride, 106 grams of anhydrous sodium carbonate is needed - 1 mole Na2CO3/1 mole AgCl. In the second patent, it took one hour to completely convert, at the required temperature.

I attended an IPMI refining seminar in 1980. One of the speakers gave a talk on silver chloride conversion and he felt that the Kunda method was the best. Both Harold and I have the same IPMI book that contains the papers from that seminar.

I have never attempted this method, but I have always felt that it sounded viable. The temperature range is critical. So is the intimate blending of the 2 chemicals.


----------



## Sylar

Ah, so the black vapor was actually AgCl ... makes sense.

I tried with the Na2CO3 aswell and that DOES produce far better results! Mind you I'm working on lab scale, yesterdays output was 30 grams silver.

I just figured that, while adding AgCl to the crucible and Cl2 coming out of it that I must be getting full conversion to Ag. When pouring the molten mass in a carbon dish I immedialty saw it was no metal al all. So the chlorine I saw/smelt must have been "free chlorine" in the AgCl. I also read that there exist many forms of AgCl with all slightly varying chlorine contents, so perhaps +1000°C reverts them all to basic AgCl?

Anyway, I placed the still hot black mass in the crucible again on high heat and slowly started adding Na2CO3. It wasn't quite anhydrous, but there wasn't enough crystal water to make for much problems. Bubbling and foaming resulted with some close calls on the crucible level, but steady adding and careful control made out to a nice yield anyway. 
The still unconverted AgCl was separated from the metal and saved for the next conversion run.

Meanwhile I have a bigger batch of AgCl under low concentration HCl (5-10%) with a piece of Al standing somewhere it can't do much harm. Next test on wet conversion will use some sulfuric acid and iron, since I'm fresh out of HCl. 
What I still had was barely enough to neutralise the ammonia in which I tried dissolving some AgCl, only to come to the conclusion that 10% ammonia solution can't really dissolve much AgCl weight per weight.

Knowledge and experience where gathered, with some nice shiny Ag as reward! Life is good 8)


----------



## goldsilverpro

Lou,

I read somewhere, recently, that the reaction between the silver chloride and sodium carbonate, at elevated temperatures, is not a true reduction reaction, even though the silver is obviously reduced. I have looked for the source of that information, but can't find it. Here's the equation:

4AgCl + 2Na2CO3 = 4Ag + 4NaCl + 2CO2 + O2

I don't remember exactly what they said, but I think they said it was an exchange reaction, after the CO3 was broken down by the heat.

What is your take on this, Lou?


----------



## peter i

Harold_V said:


> Technically? No, I can't. But it does absorb impurities that might otherwise prevent the silver from fusing. It also "lubricates" the silver, allowing it to flow freely. You'll have to trust the input from others that understand chemistry far better than I do if that isn't correct, or isn't enough information. I gave it my best shot.
> 
> Harold



Oh, but you could!

Borax is a flux, lowering the surface tension allowing the silver to flow (flux means flow).

It's also a rather efficient solvent for many metal oxides, removing them and forming a glassy compound that's low melting and immiscible with the silver.


@Sylar:
The small nodules (for lack of a better word) on your silver is a result of oxygen liberating from the solidifying silver, making the silver "foam".


----------



## Sylar

Looks explainable ...

4AgCl + 2Na2CO3 = 4Ag + 4NaCl + 2CO2 + O2 

So what happens at about 1000°C:
Na2CO3 can't exist at such high temperatures:
Na2CO3 => Na2O + CO2 
CO2 escapes the reaction at a fairly early stage, starting decomposition at about 400°C. So this is what remains of the equation:

4AgCl + 2Na2O => 4Ag + 4NaCl + O2
The O2 probably gets trapped in the Ag, and the NaCl start to vaporise off ... getting rid of it all with take some time because boiling point is 1413°C according to the msds I found.


Thanks for explanation on borax Peter. I often forget about the solvent properties at such high temperatures. My thermocouple was the first victim of that. It's about 2 cm shorter from stirring the melt with it :roll: Thank god the silver produced a good solder connection or my temp reading would have been useless untill I got a new one. On the downside, my silver is now alloyed with some stainless steel and a bit of Ni and Cr. I guess I'll get rid of those in the series of experiments utilizing electrical current.


----------



## lazersteve

goldsilverpro said:


> Lou,
> 
> I read somewhere, recently, that the reaction between the silver chloride and sodium carbonate, at elevated temperatures, is not a true reduction reaction, even though the silver is obviously reduced. I have looked for the source of that information, but can't find it. Here's the equation:
> 
> 4AgCl + 2Na2CO3 = 4Ag + 4NaCl + 2CO2 + O2
> 
> I don't remember exactly what they said, but I think they said it was an exchange reaction, after the CO3 was broken down by the heat.
> 
> What is your take on this, Lou?



GSP,

Here's how Loewen describes the details of the reaction:

4AgCl + 2Na2CO3 = 2Ag2CO3 + 4NaCl

and via thermal decomposition

2Ag2CO3 = 2Ag2O + CO2

and finally through further thermal decomposition

2Ag2O = 4Ag + O2

Steve


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## Sylar

Either way is fine by me, as long as I get some silver in return for my efforts 

I have taken a liking to the Fe and H2SO4 process for the reduction of AgCl, so everything will be treated this way. Strange thing though, when I stir, I get brown gasses (NOx) bubbling up from the reaction :?: 

What could be responsable for this? Residual Ag(NO3)2 decomposing?


----------



## Lou

Steve, that makes much better sense and* that is a reduction reaction.*

I should've remembered that silver carbonate decomposes immediately to Ag2O. Ag2CO3 is an intermediate and will be transient, the silver oxide less so. The slowest step is forming carbonate from the silver chloride. This reaction is an excellent example of thermodynamics driving a reaction that normally wouldn't occur but for the high temperature. All of the products but the silver are volatile, two being gases, and one being darn close.

Still, it would be naive to assume that even that nice, proper equation is strictly what is happening. 

Also, the silver oxide trick is apparently a very old one indeed. I had great success with it any time I do it, but researching into it, it was known by chemists 500 years ago! Still very convenient.


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## Sylar

Some pictures of my proces:


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## Anonymous

If the tarnished layer is not too thick, then there might be a more simple solution available for you to clean the crystals. The proposed method is to electrochemically exchange the sulphur between the silver and another metal.
This video should explain the principle http://www.youtube.com/watch?v=vGCx9HZwYBo :idea: , it works quite well, except for the surface appearance, it will not usually restore the polish.


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## JohnW

A way to do this that produces no harsh vapors, and little or none hazardous waste is to mix the AgCl with sodium hidroxide (caustic soda) and use Hydrogen Peroxide (H2O2) to obtain the silver. The output (if using very clean AgCL is Ag, NaCL and water.


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## solar_plasma

> Here's how Loewen describes the details of the reaction:
> 
> 4AgCl + 2Na2CO3 = 2Ag2CO3 + 4NaCl
> 
> and via thermal decomposition
> 
> 2Ag2CO3 = 2Ag2O + CO2
> 
> and finally through further thermal decomposition
> 
> 2Ag2O = 4Ag + O2




That's quite beautiful, isn't it? If cementing is like boxing, this is southern style kung fu !!! Who is that Loewen? Books? Articles?


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## Tub Buster

Harold_V said:


> Silver would be a problem in cost and fabrication, and not really necessary. Stainless is very acceptable...



Harold, in this old message thread on "Reducing Silver Chloride", you posted a design for a small silver cell. Apparently a number of people liked the design, but unfortunately the link is broken. This was the original link:

http://goldrefiningforum.com/~goldrefi/phpBB3/download/file.php?id=381
Silver cell-1.jpg
(24.64 KiB) Downloaded 913 times

Would you mind reposting the design, or just sending it to me?

As an aside, I'm a new member, so I spent about 3 months reading old messages and the various texts. In fact, I've produced a hypertext version of Hoke's book that I might release sometime in the new year. Anyway, reading so many old messages, one can't help notice how many bad links there are on this website.

When I ran a website 15 years ago I used a broken link detector. It crawled the site and issued a report on all bad links. I just googled "broken link detector" and there are lots to choose from. Some are free and others are part of commercial packages that generate all sorts of statististics about what page people go to, how long they stay, etc.

Merry Christmas
--
Bob


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## Harold_V

Tub Buster said:


> Harold_V said:
> 
> 
> 
> Silver would be a problem in cost and fabrication, and not really necessary. Stainless is very acceptable...
> 
> 
> 
> 
> Harold, in this old message thread on "Reducing Silver Chloride", you posted a design for a small silver cell. Apparently a number of people liked the design, but unfortunately the link is broken. Would you mind reposting the design, or just sending it to me?
Click to expand...


Here's a picture of the cell in question. It's made of 1/16" thick 304 stainless, with welded corners. After welding, it was electropolished. A lug was welded to the back side to provide an attachment point, as the entire cell becomes the cathode. Anode contact was a silver "candlestick". Anode basket made entirely of polypropylene (I worked as a machinist when the cell was built). Note the two covers for the ends of the cell, intended to keep contamination (dust) out. 

The strange looking device (the cross piece) is a template for cutting filters for the anode basket. They were cut from heavy filter material and sewn at the corners. Held in place by polypropylene clips. 

Sloping sides are desirable, but they create their own problems. I chose to use 4" wide vinyl tape to isolate the sides, as they quickly grow crystals to the anode and create a short. The tape solved the problem. 

I'm open to questions if you have any. 

Harold


----------



## necromancer

Harold_V said:


> PhillipJ said:
> 
> 
> 
> Harold. As always I try to read what yoHomes e to say. You explain things very well. For a month or so now, I have been thinking that YOU should write a book.
> 
> 
> 
> 
> Chuckle! Well, if I thought I could find a dozen people weak enough in the head to buy a book I'd written, maybe I'd go for it. :lol:
> 
> Actually, I don't know that I'd be able. I've never lost sight of the fact that I don't understand why things work as they do--not having an education in chemistry. Mind you, it's not that I can't do a good job of refining----I can, and a damned good one at that, but I am nothing more than a trained monkey, very reliant on the things I learned by studying Hoke, plus a few other sources. When things go south, if it's not something I've experienced, I'm often at a loss to explain the problem. I don't think I'd feel any too good about having information published that was questionable, but I sure don't mind helping others achieve a level of performance that I achieved. That's why you see me here on this forum.
> 
> 
> 
> 
> I was thinking about the sheet of aluminum that you are converting the silver chloride with. How would it work to put it in a dedicated aluminum frypan or aluminum pot, add the HCL & stir untill done? Also, I was thinking about that aluminum seal on the coffee cans would be good to use as a sheet of aluminum.
> 
> Click to expand...
> 
> 
> You'd be inviting a bunch of grief if you went the pan route, although I see nothing wrong with using a pan as a source of aluminum. Same goes with any aluminum, right down to aluminum cans if you can eliminate the printing. Just make sure you don't end up with a lot of tiny bits in the silver when it's fully converted.
> 
> The problem with using a pan?
> 
> Remember me saying that the aluminum gets dissolved in the process? That's exactly why it's not a good idea. The pan, in all likelihood, would have one thin spot and spring a leak when you least expected it to happen. Otherwise I see nothing wrong with the idea, so if you happen to have a few on hand (clean, no Teflon), or can pick them up cheaply at a second hand store, use them accordingly. You could even start out using the pan as you suggested, but make sure you have it sitting in something that will catch the solution and silver when it springs a leak.
> 
> 
> 
> 
> I,m reading in Hoke about the cell used to purify silver, but so far I see nothing about the electrolyte that they use in it, and am having trouble finding the recipe here.
> 
> Click to expand...
> 
> 
> The electrolyte is made of silver, dissolved in nitric acid and distilled water. I don't have the information at hand, but there's a book by, I think, Butts & Coxe, that covers silver refining extensively. If I have the name of the authors wrong, I know GSP knows the book of which I speak and he can make corrections to my information.
> 
> My cell was used on a batch basis, running an anode that weighed about 200 ounces (troy). By the time I had refined that amount of silver, the copper content of the electrolyte had climbed to the point where it could start co-depositing copper along with the silver. That doesn't happen as long as the percentage of copper is low enough. You can tell when there's a change because the silver crystals tend to grow differently, long and hairy. I'd stop the cell when I approached that threshold and remove the electrolyte entirely, recover the silver within, and make new electrolyte from some of the pure crystal that came from the cell. That was an excellent test of the quality of the silver, for if it had any copper within, it showed in the electrolyte. On rare occasion when that was the case, I'd simply place the silver crystal back in the basket, place a new anode on top of the crystals, and go back to work after replacing the electrolyte. The silver came out beautifully that way, and I was assured of purity.
> 
> Running a cell is far more involved than the simple description, but I'm more than happy to give you guidance if you get that far along, including making your electrolyte.
> 
> On the subject of electrolyte, I think you'll read that the big boys don't do what I did, likely because their cells are ongoing, never shut down. Instead of replacing their electrolyte, they are constantly replacing a portion of it with new, keeping the copper/silver ratio at a desirable level. I've read that they actually rely on some copper for conductivity, although I'm having one hell of a hard time believing that's true considering there's a huge amount of silver in solution as compared to copper, and it's a far better conductor.
> 
> Harold
Click to expand...



I would buy that book & I am sure many others here that would do the same.

Hokes is the only book in my refining library, looking to ad more.


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## sharkhook

This thread is an Education in it's self! I would love to see/hear more about Harold's cell and how it is used it.


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## butcher

There are probably thousands of posts on this subject on the forum, Harold, GSP, and many other members have discussed the silver cells extensively, you can find several types of silver cells and learn just about everything you would need to learn to build your own and understand how it works, and how to operate the cell.

It is all here on the forum waiting for you.
just like you found this post, you will find many more that will help to answer your questions, and help you to learn things you would not even think to ask. Just keep digging through the forum and you will find many of these treasures.


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## sharkhook

This and many others I have found very informational!!

I am reading much every day and just trying to understand it. Several, like this one, I have come back to many times, I never seem to get it all the first time. I will just keep recovering the "easy" stuff, saving the more complicated, and studying, while gathering the needed tools and chemicals. Eventually, I will take a shot at the refining aspect of it.

Thanks to all those who contribute the information found here.


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## Tub Buster

Harold_V said:


> I'm open to questions if you have any.


Thank you. Do you recall the dimensions? You mentioned the anode was about 9" square. 
Did you calculate the cathode surface area?


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## Harold_V

Tub Buster said:


> Harold_V said:
> 
> 
> 
> I'm open to questions if you have any.
> 
> 
> 
> Thank you. Do you recall the dimensions? You mentioned the anode was about 9" square.
> Did you calculate the cathode surface area?
Click to expand...

I don't recall the dimensions, but they are not critical. The only pertinent considerations are the anode size and anode/cathode spacing. Even spacing isn't critical, as you'll overcome pretty much any issues (unless you don't have enough spacing) by varying voltage. If memory serves, the target voltage is what it takes to achieve 25 amps/square foot of anode. I chose to operate lower (about 15 amps/square foot), which provided a longer interval between times knocking down the crystals. I ran my cell steady, 24 hours, until I had processed all silver at the ready. I often ran it for a couple months steady. 

You'd be best served to procure a copy of the book written by Butts & Coxe, which discusses silver cells and silver processing extensively. I do not recall the title, but do a search and it will be obvious. 

Food for thought. The typical electrolyte consists of some copper in solution. I chose to use none, as it was introduced fast enough simply by running the cell, as silver recovered by cementation with copper will always contain traces of copper. 

You may read that the lack of copper alters the deposit, which is true---but the reports made by at least of of those who didn't use copper free electrolyte are not correct. I parted tens of thousands of ounces of silver, always starting with pure silver electrolyte. My reason was simple. I got more silver from each lot processed, because the amount of copper in solution is what limits the useful life of electrolyte. The net result (ALWAYS) of not including copper at the outset was a film of solidly adhering silver--not crystals. That was followed by the formation of dense crystals, as the copper content rose. When content was high enough, the crystals, which had previously been rigidly fastened to the cell, now were very easy to remove. Continued operation caused a further rise in copper content, at which time the deposited silver began growing as thin threads. This reaction was characteristic of all my runs, so I had to conclude that copper aids in the stripping of crystals, but should not be allowed to accumulate beyond reasonable limits, as once it's too high, copper co-deposits with the silver, just as palladium will if it accumulates in the system. Armed with this thought, the moment thin threads started forming, I cleaned out the cell and replaced the electrolyte. I also started with a new anode, which was simply placed on top of what remained of the previous anode. As a measure of purity, I'd use the last silver harvested to make the next electrolyte. If it was free of blue coloration, I knew the silver was not contaminated with copper. 

I recommend no less than 2" clearance from the anode surface to any surfaces of the cathode. The more you provide, the longer the cell can operate without attention. It is very important that crystals not be allowed to grow near the anode basket, as the resulting arcing will perforate the filter and contaminate the already processed silver. 

What I recommend, if you're interested in parting silver, is to study until you understand the principles involved, then make a setup and pursue the operation of the cell. Consider your first run a learning experience, and that you may make mistakes. It's easy enough to re-process the resulting silver, which can be as simple as placing the harvested crystals back in the anode basket, even without melting.

Harold


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## FrugalRefiner

Butts & Coxe's book was titled _Silver Economics, Metallurgy, & Use_. I found a used copy online for less than $20.00 delivered.

Dave


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## sharkhook

Thank you Harold, this has been a great read and learn post.

And Thanks FrugalRefiner for the book title. 

I still need more study before trying this, but it has went a long ways toward understanding how it all works.

Edit: correct spelling


----------



## FrugalRefiner

sharkhook,

Keep an eye on this category. There is a new thread called Time for Another Contest?. I expect there may be some interesting posts there in the next month or so. 8) 

Dave


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## butcher

http://www.abebooks.com/Silver-Economics-Metallurgy-Use-Butts-Allison/9130619157/bd
http://www.abebooks.co.uk/book-search/author/BUTTS,-ALLISON;-COXE,-CHARLES-D-?cm_sp=brcr-_-bdp-_-author


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## NeMonstr

Harold_V said:


> Wash your silver chloride well, until the wash water is clear, with no traces of color. You can do that with tap water. Make at least one of the washes with hot water, to dissolve any lead nitrate that might be present. If you make that wash the last, or second to last wash, you'll notice that the silver chloride will settle almost instantly, so you can decant while the solution is still hot. Lead nitrate will self precipitate when the solution cools, defeating the purpose for the hot wash.
> 
> I used a thick-walled Pyrex container for the conversion. There's enough heat generated that your chloride can achieve boiling temperature, so don't use glass that won't tolerate heat. Don't do this indoors unless you have a fume hood. There's a considerable amount of gas and vapor liberated in the process.
> 
> Place your chloride in the container, and cover it with a 10% solution of HCL and water (tap water is fine). A large diameter container with a shallow layer of chloride is best. You need room to stir. If you have access to scrap sheet aluminum, it works best, for it presents a large surface area to the chloride, and is easily recovered when the operation is complete. Smallish pieces that can be stirred work well, for you have to expose all of the chloride to the aluminum. Avoid tiny pieces that would be difficult to remove when the process is finished.
> 
> At first, the chloride will have a tendency to stick to the aluminum, but as it all converts to elemental silver, you'll find that the aluminum will shed it totally. The aluminum goes into solution in this process, so expect it to dissolve as it works. Make certain that the chloride has converted to gray (silver) and there's still some aluminum left. At that point the aluminum will bubble, being dissolved by the HCL, and will be very clean, but there is, otherwise, no action. When you're convinced the chloride has all been converted, remove the rest of the aluminum, checking any place that yields bubbles for small pieces that may be left behind. It's not a bad idea to add a little free HCL after you remove the aluminum, which will insure that the silver is well washed, and will expose any tiny pieces of aluminum that may be left behind. Allow things to sit for a few minutes. If there's any aluminum left behind, you'll see bubbles coming from the location. When you're sure you have all the aluminum, fill the container with tap water and allow it to settle. The solution will appear to be about the same color as the silver, and you'll swear there's silver in suspension, but that is not the case. Allow it to settle for a day, then decant the solution and repeat the wash. The wash will slowly come clear, but it takes a few repetitions. Once the solution is fairly clear, it will filter well, but the dark solution won't go through a filter worth a damn, so don't try filtering until you've washed the silver a few times.
> 
> My policy was to place the well washed silver in a Buchner funnel, where the balance of the solution could be removed and the silver compacted well for drying. It's a lot easier to handle the stuff after it's been compacted. I would then dump the Buchner contents into a large evaporating dish to force dry the silver over a low flame. The silver that comes from this conversion is very fine grained and sticky. It melts well once dry, but flux (borax, without soda ash) is a definite asset. The flux should be saved for future re-processing. It could contain traces of unconverted silver chloride, and possibly some prills. Soda ash would convert the chloride traces to elemental silver, but it would also convert traces of base metal oxides should they be present, so I avoided using it. All depends on your objective. If the silver is headed for a silver parting cell, the cleaner the silver, the longer the electrolyte will be viable. How you'll use the silver will determine how to flux. If you use it for inquartation, over and over, use some soda ash in your flux. You'll achieve a 100% recovery (of chlorides) that way.
> 
> Hope I've covered it well enough for you to proceed. It will take only one attempt at the process for all of this to make sense.
> 
> Harold


Зато , добавление соды в шихту с порошковым серебром переводит ненавистную метаоловянную кислоту (SnO2*nH2O) в станнат. Насчёт восстановления оксидов я не вкурсе, но они растворятся в буре. Разве оксиды содой восстанавливаются?
Можно и к золоту в шихту добавлять соду, всё в той же борьбе с оловом. По моему, хуже от этого не становится. Я так делаю.Harold_V


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## butcher

I Googled the above and it translated to:

But, the addition of soda to the charge powder silver translates hated metaolovyannuyu acid (SnO2 * nH2O) in stannate. About the reduction of the oxides vkurse I do not, but they will be dissolved in the storm. Is soda oxides recovered?
Possible and to gold in the batch add soda, all in the same struggle with tin. In my opinion, worse this becomes. I delayu.Harold_V

But I am still having trouble understanding exactly what it is saying.


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## NeMonstr

OK,
сода is Na2CO3 or NaHCO3,
метаоловянная кислота is SnO2*nH2O
в буре in borax.

Сода add to Ag (and AgCl) is good, and сода kill tin. :mrgreen:


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## butcher

NeMonstr,

I think we are losing information, in trying to translate the languages.


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## NeMonstr

Еvery time I add Sodium carbonate to silver powder. It's good. Sodium carbonate removes tin and recover silver chloride to silver.
Sodium carbonate not recover oxides. Charcoal recover oxides. Borax dissolved oxides.
Sodium carbonate or sodium bicarbonate.

Sodium carbonate also add to gold powder, when melting, that removes tin.


----------



## butcher

Ok I understand now you are talking about melting the metals with flux.

Silver chloride can burn off as smoke in a melt, to keep from loosing silver we can use flux to reduce it to metal.

If we melt silver chloride we need to reduce the silver in the melt, we can use sodium carbonate and charcoal.

But these reducing fluxes can also reduce other metals in the melt.

Tin can oxidize fairly easily, but with carbon or sodium carbonate in the flux, the tin can be reduced to metal.

Sodium carbonate and charcoal are reducing fluxes, basically they can take oxides from metals like tin oxide (that would normally go into the slag glass), and reduce the tin oxide back to metal in the melt.

To get a metal to go into the slag of the melt we want to oxidize the metal.

But in this case we need sodium carbonate and charcoal to keep our silver as metal, and so we can also reduce tin metal with our silver in this flux melt.

It would be best to separate as much tin from the silver as possible with our acids and processing before it is melted.

With gold we could more easily oxidize some of the tin out with an oxidizing flux in a smelt.

But here again if we can get the tin separated from the gold by other means it would be much better, before melting the gold.


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## NeMonstr

Sometimes dirty scrap, sodium carbonate helps. Do not add charcoal. Sodium carbonate not reduce the tin oxide back to metal in the melt. Tin dioxide+sodium carbonate in the melt => sodium stannate. Sodium stannate soluble in water.


----------



## butcher

I am no chemist.
This is just my thoughts

sodium carbonate as far as I know in a melt is somewhat neutral, it can normally act as a weak reducing agent taking oxides from metal oxides.

sodium carbonate is considered a basic and non oxidizing flux, but can become an oxidizing if an oxidizer is added, even oxygen from a torch or furnace where air can be absorbed into the melt can make the melt with sodium carbonate more oxidizing.

This is one reason why a carbon powder cover over a melt of silver chloride powders mixed with sodium carbonate is a good idea to help reduce the silver chloride to silver, the carbon can help to act as a reducing agent, and help absorb oxides or help to lower oxygen being absorbed into the melt.

In a melt with an oxidizer added and sodium carbonate we can oxidize the metal more easily. 
In a melt with a stronger reducing agent (like carbon) we can reduce a metal with the sodium carbonate in a flux melt.
We can make the melt with sodium carbonate an oxidizer or a reducing agent with the other ingredients in our flux.

stannic oxide in a fusion with a strong base like NaOH will give a stannate, which is soluble in water.
(its melting point is below silver). (This fusion can be done in a silver dish as long as the silver dish is protected from the flames of the torch). 
2SnO2 + 2NaOH --fusion--> Na2SnO3 
Dissolving this sodium stannate Na2SnO3 in water gives Na2Sn(OH)6 (aq)

stannic oxide is not completely attacked by a fusion with sodium carbonate (alone).


sodium stannate Na2SnO3 can be formed in a fusion with SnO2 with sodium carbonate and with sodium nitrate added in the fusion.

SnO2 stannic oxide in a melt with sodium carbonate and carbon can reduce the tin oxide to tin metal.


----------



## NeMonstr

Try it and see better with soda.
Stannates, aluminates &etc. receive not only with sodium hydroxide, but also with soda. Saltpeter+
I almost dissolved catalyst car. But, a lot of dirt. And expensive way.


----------



## NeMonstr

Found little information. Sodium oxide obtained by sodium carbonate calcination. Tin oxide reacts with the alkali metal oxides.





Na2CO3 → Na2O+CO2↑ (1000°C)
Na2O+SnO2=Na2SnO3


----------



## Clneal2003

NeMonstr said:


> Harold_V said:
> 
> 
> 
> Wash your silver chloride well, until the wash water is clear, with no traces of color. You can do that with tap water. Make at least one of the washes with hot water, to dissolve any lead nitrate that might be present. If you make that wash the last, or second to last wash, you'll notice that the silver chloride will settle almost instantly, so you can decant while the solution is still hot. Lead nitrate will self precipitate when the solution cools, defeating the purpose for the hot wash.
> 
> I used a thick-walled Pyrex container for the conversion. There's enough heat generated that your chloride can achieve boiling temperature, so don't use glass that won't tolerate heat. Don't do this indoors unless you have a fume hood. There's a considerable amount of gas and vapor liberated in the process.
> 
> Place your chloride in the container, and cover it with a 10% solution of HCL and water (tap water is fine). A large diameter container with a shallow layer of chloride is best. You need room to stir. If you have access to scrap sheet aluminum, it works best, for it presents a large surface area to the chloride, and is easily recovered when the operation is complete. Smallish pieces that can be stirred work well, for you have to expose all of the chloride to the aluminum. Avoid tiny pieces that would be difficult to remove when the process is finished.
> 
> At first, the chloride will have a tendency to stick to the aluminum, but as it all converts to elemental silver, you'll find that the aluminum will shed it totally. The aluminum goes into solution in this process, so expect it to dissolve as it works. Make certain that the chloride has converted to gray (silver) and there's still some aluminum left. At that point the aluminum will bubble, being dissolved by the HCL, and will be very clean, but there is, otherwise, no action. When you're convinced the chloride has all been converted, remove the rest of the aluminum, checking any place that yields bubbles for small pieces that may be left behind. It's not a bad idea to add a little free HCL after you remove the aluminum, which will insure that the silver is well washed, and will expose any tiny pieces of aluminum that may be left behind. Allow things to sit for a few minutes. If there's any aluminum left behind, you'll see bubbles coming from the location. When you're sure you have all the aluminum, fill the container with tap water and allow it to settle. The solution will appear to be about the same color as the silver, and you'll swear there's silver in suspension, but that is not the case. Allow it to settle for a day, then decant the solution and repeat the wash. The wash will slowly come clear, but it takes a few repetitions. Once the solution is fairly clear, it will filter well, but the dark solution won't go through a filter worth a damn, so don't try filtering until you've washed the silver a few times.
> 
> My policy was to place the well washed silver in a Buchner funnel, where the balance of the solution could be removed and the silver compacted well for drying. It's a lot easier to handle the stuff after it's been compacted. I would then dump the Buchner contents into a large evaporating dish to force dry the silver over a low flame. The silver that comes from this conversion is very fine grained and sticky. It melts well once dry, but flux (borax, without soda ash) is a definite asset. The flux should be saved for future re-processing. It could contain traces of unconverted silver chloride, and possibly some prills. Soda ash would convert the chloride traces to elemental silver, but it would also convert traces of base metal oxides should they be present, so I avoided using it. All depends on your objective. If the silver is headed for a silver parting cell, the cleaner the silver, the longer the electrolyte will be viable. How you'll use the silver will determine how to flux. If you use it for inquartation, over and over, use some soda ash in your flux. You'll achieve a 100% recovery (of chlorides) that way.
> 
> Hope I've covered it well enough for you to proceed. It will take only one attempt at the process for all of this to make sense.
> 
> Harold
> 
> 
> 
> Зато , добавление соды в шихту с порошковым серебром переводит ненавистную метаоловянную кислоту (SnO2*nH2O) в станнат. Насчёт восстановления оксидов я не вкурсе, но они растворятся в буре. Разве оксиды содой восстанавливаются?
> Можно и к золоту в шихту добавлять соду, всё в той же борьбе с оловом. По моему, хуже от этого не становится. Я так делаю.Harold_V
Click to expand...



Not sure about translating but the HCL and aluminum worked amazingly well! I will add that the reaction is extremely exothermic! I believe that is the correct term to use. IT GOT EXTREMELY HOT! Almost to hot to hold at one point. My batch is drying right now get ready to melt. It's a nice cool 60 degrees Fahrenheit here and the heat coming out of the glass made me wish I had a slightly longer stir rod. 

My next big project will be a fume hood to operate in the winter.


----------

