# Electrolytic silver refinig



## hrushi (Dec 30, 2008)

Need some help regarding construction of parting cell

For processing 5-10kgs of silver per batch what shud be the capacity of power supply like how many volts or Amps


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## goldsilverpro (Dec 30, 2008)

There's lots of silver cell info on the forum. I would suggest you start here
http://goldrefiningforum.com/phpBB3/viewtopic.php?t=732&highlight=silver+cell+thum

The simplest to use is a horizontal Thum cell (pictured in the link above). Keep this in mind when designing your cell: No matter what the capacity is, the solution depth should be about 4.5" to 4.75" (11.4-12.1 cm)

The amperage is only dependent of the bottom surface area (that facing the cathode that covers the bottom of the tank) of the anodes - between 25 to 50 amps per square foot. At this amperage, you will require about 3 to 4 volts, assuming there is no unnecessary resistance in the system. With one 12V rectifier of adequate amperage, you can run 3 cells in series.


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## hrushi (Jan 17, 2009)

Can i use steel basket instead of titanium basket as anode


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## goldsilverpro (Jan 17, 2009)

There is no metal anode basket in a horizontal Thum silver cell. Contact is made directly to the top of the impure silver bars.

I suppose you could use a titanium basket in a vertical Moebius cell to hold silver shot, rather than hanging silver bars.

We may be talking about different cells. Are you talking about a nitrate silver purification cell or a sulfuric cell or, what?


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## hrushi (Jan 17, 2009)

> I suppose you could use a titanium basket in a vertical Moebius cell to hold silver shot, rather than hanging silver bars.


Can I use SS basket instead of titanium basket



> We may be talking about different cells. Are you talking about a nitrate silver purification cell or a sulfuric cell or, what?


True I am talking about Moebius cell and nitrate silver purification


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## Harold_V (Jan 17, 2009)

hrushi said:


> Can I use SS basket instead of titanium basket


Absolutely not! Stainless will be broken down and transferred by the cell. I am speaking from experience, whereby a stainless screw that became a part of the circuit degraded rapidly. Avoid using anything conductive (like titanium)--it can lead to depletion of your electrolyte, even if it does not transfer. Stainless (300 series), as long as it is used for the cathode, is perfectly acceptable, and is commonly used. 



> True I am talking about Moebius cell and nitrate silver purification


Make your basket from polypropylene, which is inert. It can be fabricated from stock, and assembled with stainless screws, assuming you can keep them isolated from the circuit. Mine was so constructed, and shorted only because of some bridging of silver. That can be avoided by careful design and proper cell operation. 

Harold


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## hrushi (Jan 18, 2009)

Here what I have to do

I have cemented Ag using copper which is of purity 99.50 and I want achieve 9999 purity of it. So what I am trying to experiment is to reduce the time required for electrolysis and also cost of producing 9999 purity Ag.

I have planned to take cemented Ag and put it in anode basket which may be of titanium or put Ag into PP bag and suspend a graphite rod into it.

According to me if use cemented Ag time taken for electrolysis will be less and cost of production will also be compartatively low.

Hrushikesh


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## Harold_V (Jan 18, 2009)

I'm curious how you know your silver is already 9995. If you've used copper for recovery, I have serious doubts that it is any better than 99. 

I didn't read any melting procedures in your post. Are you going to eliminate melting the cement silver? If so, I do not recommend you do so. Silver is best melted and cast as an anode. By fluxing (borax only, no soda ash) the silver, you will remove a considerable amount of material that you do NOT want to get in your silver cell. 

Again, do NOT use anything of a metallic (or conductive) nature for your basket system. Only silver should be exposed to the electrolyte. If you do otherwise, you can expect to deplete your electrolyte and fail in the intended purpose. Melt your silver, cast a flat anode, then place it in a non-conductive basket that has a dense cotton fabric filter, which will collect traces of silver, along with any residual traces of precious metals. Only the bottom surface of the anode should be in contact with the electrolyte, to minimize the amount of silver that is eroded from the anode, thus maintaining a more constant surface area. 

Harold


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## goldsilverpro (Jan 18, 2009)

I have never used titanium baskets in the silver cell and have never run a vertical Moebius cell, although I know how it works. However, titanium and tantalum are used routinely as anode baskets in many acidic plating solutions. I see no problems in using them in this weak nitric matrix. They should hold up indefinitely. Make sure they are bagged to hold the anode sludge. 

I repeat, though, that I have never tried this and am guaranteeing nothing. I always ran horizontal Thum cells and always ran the silver as ingots. I have thought about running granulated silver shot in the Thum cell, but have never tried it. I think there are some patents that use shot.

Don't use stainless. Use only titanium or tantalum.

I might mention that the Ti and Ta baskets are made of expanded metal. If you put shot in them, it will probably fall through the holes. Actually, only the shot next to the basket will dissolve. The shot in the center of the mass won't get any current. It would probably be better to cast bars, cut the bars into about 1" chunks with a shear, and put the chunks in the baskets. Also, use cathodes on both sides on the anode baskets.


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## Harold_V (Jan 19, 2009)

Chris,
On rare occasion, my silver would be lightly contaminated with copper after refining. I made that determination by using the recovered crystals to make my next batch of electrolyte. If the silver nitrate had a tint of green, I knew it contained copper, so I'd use the electrolyte for re-processing the same lot of crystal. I had excellent success simply placing the recovered crystals back in the basket and placing an anode on top, to which I applied my "candlestick" silver electrode. No need to melt to shot, but I can't help but think that recovered cement silver would be troublesome. 

Harold


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## goldsilverpro (Jan 19, 2009)

Harold,

I agree. You would probably have to melt the cement silver and shot it or cast bars in order to add it to the cell.

In my cell, per batch, I added 21 bars, each about 3" x 8", all snugged together making contact with each other. This formed a square of about 24" on a side. Sometimes, a bar or two would dissolve on the side and separate from each other and lose contact. I would reconnect them by sprinkling a little crystal between them.


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## Harold_V (Jan 19, 2009)

Wow! My anodes were only about 8" square, and were ran individually. You really did crank out the silver! 

I liked your method of connecting the errant pieces of anode. 

I kept the amperage well down on my cell, so it wouldn't bridge quickly. I could sleep a few hours before having to knock down the crystals that way. It ran 24/7 for as long as the anodes held up, but I then put it away until I had a few thousand ounces to part once again. 

On the average, I parted about 100 ounces daily. Hardly a drop in the bucket compared to your production, but it seemed to be a good amount for the nature of my operation. While I didn't encourage silver, it was, as you know, a very necessary evil considering I used it exclusively for inquartation. It became the carrier of the majority of the platinum group for me, so parting was important. 

Harold


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## goldsilverpro (Jan 19, 2009)

Harold,

I had 4 cast iron molds and could pour the 21 bars in 30-45 minutes, or so. Each bar only weighed about 40 oz - about 3/8" thick. I just poured until the bottom of the mold was completely covered. I used a thin coat of motor oil to coat the molds. The big guys cast one big 1" x 24" x 24", 200# slab, but they need a hoist to lower it into the cell. That would also take a hell of a mold. It was a lot easier for me to make a bunch of individual bars. Starting with 99% silver, I got 500-600 oz/day/cell. With sterling, I got a lot less.

Actually, your 100 oz/day was pretty darned good for an 8" x 8" anode. That's 1/9 of the area of my anodes. One amp for one hour (1 amp-hour) can deposit about 4 grams of silver. A constant 32 amps for 24 hours would theoretically produce about 100 oz. You must of run about 50 amps during the day. I ran 200 amps, but that is only 50 amps/square foot of my anode area. You had to be running a lot higher.

What material did you use for your candlestick? Instead of a candlestick, I drilled a hole near each end of a 1/4" x 2" x 5" long piece of buss bar. Then, I had somebody hold it upright, with tongs, in the center of the bottom of a mold while I poured molten 60/40, Cu/Ag alloy around it, about 3/4"- 1" deep. The 1/2" hole locked it all together. The bar was about 3" x 8". The other hole was for the cable connection. Lots cheaper than gold and it lasted a couple of years. As you probably know, the big boys use gold candlesticks for both the anode and cathode connections.

Just making conversation.

Chris


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## Oz (Jan 19, 2009)

I have slowly been putting the pieces together for a silver cell and have wondered about the reactions of the platinum group metals. As Harold mentioned above they are often used to recover more valuable PMs from inquartation silver. I am also aware that platinum (I assume perhaps rhodium as well?) will go into a nitric solution to a degree when alloyed with silver. Inquartation silver will have low percentages of these which favors their dissolution with silver in nitric. 

The only difference in a cell that I can see that could mitigate this is that you are keeping a fine balance or equilibrium with your free nitric. Do you notice a significant difference as to how much of these are left in your anode bag compared to a regular nitric digestion?

While discussing PGMs it is my understanding that Pd contamination of the electrolyte becomes critical at lower grams per liter concentration than the Cu. At what concentration of Pd would you become concerned with co-deposition? 

As I do not have practical experience running a silver cell the above are assumptions on my part, by all means correct me.


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## Harold_V (Jan 19, 2009)

goldsilverpro said:


> Actually, your 100 oz/day was pretty darned good for an 8" x 8" anode.


I hope my statement was accurate. It may have been slightly larger, but not significantly larger. Perhaps it was 9" square, tops. I have to apologize, for I really don't remember, but some of your comments, below, are giving me cause to rethink what I said. Please understand that all of this is now, for me, ancient history. It's been 14 years since I refined. I'll address this more, below, and, as you said, just making conversation, but I don't want to say anything that would be misleading. Others may well be hanging their hat on our comments. 



> I ran 200 amps, but that is only 50 amps/square foot of my anode area. You had to be running a lot higher.


The harsh reality is I did not, so I must address the time interval. I am now wondering if I ran the cell longer than I recall. I had learned that I could process a full anode, depending on its weight, without changing electrolyte. While I knocked down the crystals regularly, they were harvested ONLY when I changed electrolyte. It's all a blur to me now, but your hard statements (which I do NOT dispute) make me think I'm simply not remembering what I did, or how long it took. It could well be that I ran much longer between changes, perhaps even five days. I simply can't remember. I do remember that I ran at 12 amps, by choice. Higher amperage, which I tried, caused faster shorting of the cell, so I kicked it back in favor of lower production, but less trouble. That I remember for sure. With your math skills, it wouldn't be too hard to determine how long I ran. Incidentally, while my anodes varied in thickness, they were, on average, 3/4" thick. I seem to recall they averaged about 200 ounces, but, then again, I'm not sure. 



> What material did you use for your candlestick?


I made an iron mold that cast a button that was about an inch in diameter, and maybe that long, too, with an integral shank that was roughly ¼" diameter, and perhaps an inch long. That allowed for a clamp to be attached to the candlestick, which was simply placed on top of the anode, in the center. The center was always the last to go, and was actually covered by a new anode when the cell was cleaned out and started again. Because my amperage demand was low, I didn't have to be overly concerned about its ability to carry much. It worked flawlessly, although I had to suspend the attaching cable overhead, which was not a good feature. I didn't want it touching the filter bag, due to capillary action, electrolyte would wet the insulation, something I didn't like. As far as the candlestick goes, I was still using the original one when I sold the business, so it went with the cell. Only on rare occasion did it ever make contact with the electrolyte, due in part to my system of placing a new anode on top of the old one. Only when I was shutting down, running the last anode, was it ever at risk. Even then, I'd save the last remnant and include it in the next run of silver. 



> As you probably know, the big boys use gold candlesticks for both the anode and cathode connections.


In fact, no, I didn't know that, but it makes sense. That's a lot of money to tie up in a contact, but when you're processing on an ongoing basis, and turning hundreds, if not thousands of ounces daily, it's a small price to pay to insure no contamination. And---in the end, you still have the gold. 



> Just making conversation.


Yep---me too, but I'm having a bit of a time keeping things straight these days. Old age and time is taking a toll! 

Harold


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## Harold_V (Jan 19, 2009)

Oz said:


> The only difference in a cell that I can see that could mitigate this is that you are keeping a fine balance or equilibrium with your free nitric. Do you notice a significant difference as to how much of these are left in your anode bag compared to a regular nitric digestion?


While I never assayed my silver, it was re-dissolved for making new electrolyte, so if there was any contamination present, it was obvious. Silver nitrate that is pure and has been permitted to exhaust all traces of fumes, will be almost colorless. The slightest hint of green or brown is an excellent indicator that there is a trace element present. Generally, if I found anything, it was copper, but on one occasion, one whereby I had allowed way too much palladium and platinum to accumulate in my silver, I co-deposited a trace of palladium. It is obvious when it happens, if by no other means, by the color of the electrolyte. When it shifts to a dark green, you've gone well past an acceptable level of contamination. 

Do keep in mind, I added NO copper to my electrolyte. I had more than enough experience in running without----and had proven that it is not essential, although it did provide for a crystal growth that was much easier to knock down. Silver from my cell, when it was first started after an electrolyte change, would deposit in a film instead of growing crystals. It didn't take long for the copper level to escalate, then crystals would develop instead. With low copper content (in the electrolyte) they were quite rigid----but as the copper concentration grew greater, they grew softer and softer, finally, about the time that copper would co-deposit, the silver grew as hair. 

I ran my cell this way for years----and got consistent results every time. If you get familiar with the characteristics of any given cell, I'm of the opinion that you can fairly well judge the quality that is coming off, and know when it's time to change electrolyte. 

Everything I read indicates industry doesn't do that, they, instead, change a portion of the electrolyte constantly, to keep the copper at an acceptable level. I found it much easier to simply make a wholesale change. That works fine for a small cell such as mine. 



> While discussing PGMs it is my understanding that Pd contamination of the electrolyte becomes critical at lower grams per liter concentration than the Cu. At what concentration of Pd would you become concerned with co-deposition?


I can't address that in terms that are meaningful-----but if you manage to co-deposit palladium, your electrolyte will have long before changed color to the point where you'd be concerned. I would not dwell on that issue unless you have a huge amount of palladium mixed with your silver. 



> As I do not have practical experience running a silver cell the above are assumptions on my part, by all means correct me.


One thing that is good to know is that it is not a good idea to allow too much gold, platinum and palladium to accumulate in your silver. When I processed the values that were recovered from my waste materials, I experienced that very thing. 

I had used my stock pot as a method of saving traces of the pt. group metals, which were commonly found in small quantity in the waste materials from jeweler's benches. The amount was usually way too low to precipitate (remember, they must be concentrated to precipitate), so I just dumped all traces in my stock pot. I also allowed silver chloride to accumulate in my wastes, with the idea of the silver acting as a collector to recover the values mentioned. Turns out that worked exceedingly well, but the doré contained so much of the pt group that it was troublesome in parting in the silver cell. I had to literally scrape the sludge off the anode, often with considerable effort. That lead, in one instance, of depletion of my electrolyte, the silver no longer being able to leave the anode. 

When you have a low level of concentration, your anode will shed the values easily, which can be easily scooped from the basket using an acid dipper. That was my procedure, but it requires that you use a filter that has good integrity. Too light of weight allows the fine particulate matter to go through the filter material. The product I used was made expressly as filter material, and had one side fuzzy, which trapped the fine particles. It was made of cotton, so it was easy to incinerate when it was changed. Being contaminated with silver nitrate, it burned readily, even when wet, and reduced to an ash that was easy to digest with nitric, to recover the residual silver and palladium. Most of the platinum and all of the gold would remain behind as a solid. 

Harold


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## Platdigger (Jan 19, 2009)

Good stuff Harold!.....
Waay interesting.
If it is not too far off topic of the thread, could you tell us how you proceeded with the stock pot to get to the point of "dore" that you
parted in your cell?
Did you just cement everything to iron and then melt it?
Randy


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## Oz (Jan 19, 2009)

Harold,

It is nice to know that the palladium seemed to indicate by a visible brown before you had co-deposition. I have not tested a known purity of Pd in nitric for a reference but I have found that even US mint .999 silver can give me a trace of green from copper.

I had read with interest when you and GSP had discussed the addition of copper to starting electrolyte. I will start without adding Cu to mine the first time for the experience, if it gives me difficulty it will be easy to clean my cathode with nitric and start over after adding a known quantity of Cu. It will also extend the useful life of my electrolyte if I can avoid it.

I had planned on testing my silver precipitate for palladium by dissolving a small amount in nitric then testing with DMG, this will give me the opportunity to see copper and nickel contamination as well. 

As to my PGM values being too great to allow the silver to shed, I can’t imagine they are that high knowing the original feed but I sure wouldn’t complain with the extra labor.

Thanks again for great information.


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## Harold_V (Jan 19, 2009)

Platdigger said:


> could you tell us how you proceeded with the stock pot to get to the point of "dore" that you
> parted in your cell? Did you just cement everything to iron and then melt it?


The contents of my stock pot, which was cleaned out on an irregular basis, were simply incinerated and placed in storage, right along with filter papers and other material that contained traces, but were not worthy of being processed individually. 

The doré of which I spoke was the result of all of the waste materials that were extracted by furnace reduction. Keep in mind, I purposely allowed silver chloride to accumulate in the waste material, expecting it to act as a collector of the greater values. It was an excellent decision, proven by an assay of the flux after the fact. I achieved well over 99% recovery. 

It is important for you to understand that I did NOT part the doré in the silver cell. That would not work. The material contained a huge amount of gold---roughly 30%----which, alone, would have stopped the cell from working. It was also quite high in copper. 

The doré was cornflaked and parted with nitric. That separated all of the gold, most of the platinum and the vast majority of the palladium from the material, leaving a solution heavily laden with silver, traces of platinum and heavy with palladium, along with the included copper. The values were then recovered on copper, which is the source of the exceedingly high level of concentration of platinum metals that were troublesome in the silver parting cell. 

Had I known what I know now, I'd have blended the recovered cement silver and platinum metals with other silver that was low or absent any greater values. That would have made parting in the silver cell a much easier chore. 

As for the contents of the stock pot, I'd remove any pieces of iron, then allow the particulates to settle well. Siphon off the majority of the barren liquid, then, using an inexpensive but fairly retentive filter paper, filter the balance, collecting all of the solids. Anything that was not desirable (sulfur, from SO2, or even paint specks from scrap steel that might have been used) would be eliminated in incineration. 

You can easily skip the furnace process, assuming you keet silver chloride out of the mix. Incinerate the collected values from the stock pot, then process chemically. The problem is, any washes you perform just create more values that need to be processed, which is why I used the furnace. 

After incineration, if you wash the stock pot contents with HCl, you'll dissolve palladium oxides. If you wash the contents with nitric, you'll dissolve palladium -----so I chose to not do the waste chemically. That need not be your case. 

Harold


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## Harold_V (Jan 19, 2009)

Oz said:


> It is nice to know that the palladium seemed to indicate by a visible brown before you had co-deposition. I have not tested a known purity of Pd in nitric for a reference but I have found that even US mint .999 silver can give me a trace of green from copper.


That may not be copper. If you dissolve pure silver in nitric, it will have a green cast. Given a boil, it expels what must be NO2, eventually yielding what is nearly a colorless solution. I experienced that every time I made electrolyte. My experience indicates that silver nitrate will have a hint of yellow, but not green. The hint of yellow is VERY subtle. 



> I had read with interest when you and GSP had discussed the addition of copper to starting electrolyte. I will start without adding Cu to mine the first time for the experience, if it gives me difficulty it will be easy to clean my cathode with nitric and start over after adding a known quantity of Cu. It will also extend the useful life of my electrolyte if I can avoid it.


There is no doubt in my mind, copper is not essential to parting. It is used to increase conductivity of electrolyte, and obviously to create softer crystals, but is otherwise not useful. You are correct in your thinking-you will get greater use from your electrolyte without adding any. 

When you start your cell for the first time, if it is absent copper, and your anode is made from cemented silver, you'll notice the color of the electrolyte changes almost immediately. It assumes a hint of light green, then continues getting darker. Expect it to be more green than blue, a function of the presence of silver. Any traces of palladium will also shift the color away from blue. 



> I had planned on testing my silver precipitate for palladium by dissolving a small amount in nitric then testing with DMG, this will give me the opportunity to see copper and nickel contamination as well.


In that case, I'd likely precipitate the silver with a drop of HCl, then test accordingly. DMG is very sensitive to minute traces of palladium, but you'd do well to separate the remaining solution from the silver chloride before testing. The use of a spot plate is also very wise--you can examine the reactions closely, often seeing any flocculence that might come from DMG. I used spot plates routinely, preferring them over other methods. I'm not suggesting they are better, but they were my custom. 



> As to my PGM values being too great to allow the silver to shed, I can’t imagine they are that high knowing the original feed but I sure wouldn’t complain with the extra labor.


Yep---I wasn't exactly unhappy with the large amount I recovered, but to make life easier, it's really nice when you pick up the anode and all of the slimes slip right off. That happens when they're in low levels of concentration. 

So you understand, you can expect a high percentage of silver particles in your slimes. That's the nature of the beast. Major refiners used to boil the material in cast iron vessels, using concentrated sulfuric, which would remove the silver. I simply did a nitric acid process, then recovered all the values on copper once again. It really concentrated the palladium, but it worked. 

Harold


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## Platdigger (Jan 20, 2009)

Still trying to understand this part Harold...

"The contents of my stock pot, which was cleaned out on an irregular basis, were simply incinerated "

Do you mean, just boiled down and incinerated? 
Or....... cemented first?
Randy


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## Oz (Jan 20, 2009)

Harold_V said:


> So you understand, you can expect a high percentage of silver particles in your slimes. That's the nature of the beast. Major refiners used to boil the material in cast iron vessels, using concentrated sulfuric, which would remove the silver. I simply did a nitric acid process, then recovered all the values on copper once again. It really concentrated the palladium, but it worked.



Maybe I am missing something here but if you have a nitric solution containing silver and palladium could you not add sodium chloride to drop the silver and leave the palladium in solution? Just a guess on my part based on palladium solutions I have worked with.


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## Harold_V (Jan 20, 2009)

That was the method I pursued towards the end, but the volume of silver chloride makes it almost impossible to separate all of the palladium from the silver. I used all of the procedures, slowly isolating the values. Well rinsed silver chloride was converted to elemental silver, using aluminum, washed well after conversion, then melted and cast as an anode, and parted once again. The resulting solution was evaporated to reduce volume, then the palladium was recovered. The residue, now much smaller in volume, would then be processed again. Eventually all of it is recycled and separated. 

I did not use salt, not wanting to add anything that might be troublesome. I used HCl only in the process. Excess salt could have complicated the processing of palladium once the solution was concentrated (growing crystals). I didn't want to risk that problem. 

Harold


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## goldsilverpro (Jan 21, 2009)

Harold,



> There is no doubt in my mind, copper is not essential to parting. It is used to increase conductivity of electrolyte, and obviously to create softer crystals, but is otherwise not useful. You are correct in your thinking-you will get greater use from your electrolyte without adding any.



When I started running silver cells, I did a lot of research to determine the bath make-up and found that, without exception, all the formulas added copper nitrate to the cell solution. The copper concentrations ranged from 30 gm/l to 80 gm/l. I treated this data with reverence and, like you with Hoke, I followed it to a tee and started my solutions at about 30 gm/l Cu.

Recently, I reread my books to try and find out why they added the copper and didn't have much luck. Only in Rose's, "Metallurgy of Gold", 7th edition, page 481, did I find any comments. To quote:"Mulligan states that an increase in the copper content of the electrolyte from 55 to 75 gm/l resulted in a better production of silver." Don't ask me what that means. It may be because of better conductivity and, therefore, lower voltage. It may mean that the silver was purer or that it rinsed easier.

In the classic book, "Silver" by Butts and Coxe (yes, Folks, that's their real names), the several formulas, used by the big companies, all added copper to the cells.

One of the best discussions on silver cells is in the last article in IPMI's, "Symposium on Recovery, Reclamation, and Refining of Precious Metals." The title is "Silver Refining at The Torreon Smelter." I know that you also have this book. In it, they only say that they don't let the copper exceed 60 gm/l, but they obviously maintain copper in the cell.

Silver cells were originally designed to part silver from gold in dore' bars and, in all these references, that's what they were used for. These dore' bars had very little copper in them. It was in the order of ppms. For example, at the Torreon Smelter, they only had to bail out 1% (1 liter) of the solution each day to maintain the copper at the desired level. The day-to-day anode makeup in all of these smelters was very consistent and it was easy to maintain the solution at the desired copper/silver levels. However, every reference I've found uses copper in the cell. Therefore, I must assume that it is desirable to do so.

We are doing something that the cells weren't designed for, in that our anode compositions vary all over the map. So, each of us are on our own to make it work for our particular application. For example, I ran tons of sterling through the cells. This isn't easy, and you're not supposed to be able to do that, but I made it work.

It is possible to start a cell with only distilled water and a measured amount of nitric acid. The silver crystals produced re-dissolve until the free nitric gets down to about 1% and the silver in the solution is at a desired level. When I did this, I found the crystals were harder to rinse unless I also had a certain amount of copper in the cell. For this reason, I used some sterling as my anodes when I did this.

I am convinced that some copper is good and I will continue to use it. Just how much I should use is still up in the air. I know that some copper gives better conductivity and I have proven, at least to myself, that I could rinse the crystals with fewer rinses, due to the character of the crystals. I always checked my final rinses with ammonia. To me, fewer rinses required meant that there was a smaller chance of retaining copper solution in the crystal.

Most of my silver was used to make stamped 10 oz and 100 oz bars, for sale to the public. I stamped them at 999.5 Fine. I guaranteed this and therefore followed the procedures of the big guys to help assure it.

I think I remember you saying that all of your silver was used exclusively for inquarting gold. I assume that, after inquarting, you cemented out the silver on copper. If so, why bother with the silver cell? Cemented silver is about 99% and about the only impurity is copper. Why couldn't you add this directly to the gold without purifying the silver first? I can't see how a little extra copper would affect the inquartation. There's a lot of copper in the karat gold, anyway.

Your friend,

Chris


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## Harold_V (Jan 21, 2009)

goldsilverpro said:


> I think I remember you saying that all of your silver was used exclusively for inquarting gold. I assume that, after inquarting, you cemented out the silver on copper. If so, why bother with the silver cell?


You've lost sight of the material I processed. While some lots that were refined were just gold, the majority of my lots contained at least traces of platinum or palladium. I processed a fair amount of dental material, and many of my customers also worked with platinum, although not all of them did. My cemented silver always contained traces of these metals, so to not part them would have been a foolish decision. Remember, by its nature, silver automatically becomes the carrier of the platinum group of metals. I took advantage of that fact to make the recovery. There was method to my madness, and it paid handsome dividends. 

I also did not recycle my silver to be used more than once in inquartation. That invited problems in parting in the silver cell due to the increase in platinum group metals. Many of my anodes were less than willing to shed the slimes as it was. To have added to the percentage of contaminants would not have been in my best interest. 

I was fortunate to have silver come in at about the same rate as it was consumed, so I rarely lacked silver for inquartation. Considering it's relatively low value, I'd simply weigh it in, then credit the owner with the value, minus my refining fee. I was not concerned if I gave away a few cents in value in the case where items marked sterling might not be. I processed silver only because it was a necessity. 

As for copper in the silver cell, I have the Butts & Coxe book, too, and I'm quite sure it is in that book that the key to the use of copper was made clear. It is to provide conductivity, which, in turn, would obviously enhance the rate of transfer. My logic, which did NOT fail me, was to eliminate the copper at the outset, because it accumulated at a rather fast rate. It is absolutely NOT necessary for a cell to operate. I parted silver crystals that had traces of copper within, at times as much as 200 ounces. They parted perfectly well---leaving behind so little copper that the color of my electrolyte would be, at best, a very light pea green. Copper is absolutely NOT an essential in electrolyte, and is, indeed, the sole contributor to limited life of electrolyte. 

I had to change electrolyte after running each anode, roughly 200 troy ounces, because of copper co-deposition, which was the source of the problem with the crystals I'd re-run on occasion. I finally learned to stop before it was too late----using the crystal growth as an indicator. The silver would start growing fine threads instead of coarse crystals. That was the point where I cut off the cell and replaced the electrolyte. 

Copper is used by the "big boys" because they have hundreds, if not thousands, of ounces of silver in their electrolyte. They can keep the volume to a minimum by the controlled addition of copper. If you are not parting material with high copper content, maybe that makes sense, but parting either sterling, or silver recovered on copper, copper is added to the cell at a high rate, so starting with copper makes no sense. 

My method worked, and never yielded a problem that I could identify, the only negative being that electrolyte with no copper alters the deposition, a point I made perfectly clear. The first few hours of operation often yielded a full covering of silver that was tightly bonded to the cell. I used a fiber glass scraper to remove the layer, which I'd leave until the cell started growing crystals. That was when the copper level increased, but when it was well below a critical level. 

Anyone that parts silver that has been recovered on copper is wise to start without copper in their electrolyte. They will part far more silver before they must change their electrolyte, otherwise they will produce silver that has copper content. 

That copper may be used to create sterling isn't a point to consider unless the silver is used in-house. If an ingot is stamped with a level of purity, it should be no lower in quality than the stamp. That's part of building a reputation for honesty, and helps others in knowing when they can use an ingot for a given purpose. I tried, to the very best of my ability, to be honest in my operation, never stealing from my customers, nor giving them misleading information. Either of those can lead to rapid failure of a refining business.

Harold


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## goldsilverpro (Jan 22, 2009)

Harold,

I really wasn't trying to start an argument. We've been on this subject before. You did it your way, I did it my way, and both ways worked. I understand your reasoning. It looks like I'll be running tons of silver in the near future. I just wanted to kick this around a bit to come up with some answers as to the copper content. I'm more interested in how I WILL do it rather than how I used to do it.

In Butts/Coxe, page 89, they list several variables that are controlled by the silver/copper ratio, only one of which is conductivity:
(a) Efficient anode reaction
(b) Type of deposit required for removal routine.
(c) Consideration of anode impurities.
(d) Maximum conductivity with minimum silver tie-up.



> the only negative being that electrolyte with no copper alters the deposition, a point I made perfectly clear. The first few hours of operation often yielded a full covering of silver that was tightly bonded to the cell. I used a fiber glass scraper to remove the layer, which I'd leave until the cell started growing crystals. That was when the copper level increased, but when it was well below a critical level.



I have also had the cathode completely plate and I didn't like the aggravation one bit. I didn't like the ordeal of scraping it and I didn't like dealing with the scrapings mixed with the crystal in the filter. For no other reason than that, I would think that it would be better to start with at least a small amount of copper in the solution, maybe 1/2 to 1 oz/gal. This would not, very much, alter the time that the cell could be run before having to deal with it.

Chris


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## Harold_V (Jan 22, 2009)

Platdigger said:


> Do you mean, just boiled down and incinerated?
> Or....... cemented first?


Yes, cemented first. I'd add fluids to my stock pot on a daily basis. After everything (including copper) had cemented, I'd siphon off the solution and allow it to settle well. Any traces of solids would be returned to the stock pot so nothing was discarded with the now barren solution. When there was a fairly large accumulation of cemented material in the bottom, I'd remove all pieces of scrap steel and recover the cemented materials, which is what got incinerated. 

Harold


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## Harold_V (Jan 22, 2009)

goldsilverpro said:


> I really wasn't trying to start an argument.


Nor do I, Chris. I simply think it's important for readers to understand that adding copper to their electrolyte when parting silver that has been recovered with copper will drastically limit their electrolyte lifespan. 

The first time you part silver with a single batch of electrolyte, where it isn't constantly replenished, this will probably make a lot more sense. 

The features mentioned were all proven by me when I ran my cell. I would also include temperature. It's hard to say whether it is cause for alteration of crystal growth, because by the time my cell achieved ambient temperature, it also had accumulated a noticeable amount of copper, so it could well be that temperature may play no role in the nature of the deposit. I know for certain, copper is one of the controlling factors in how the silver develops----whether it grows crystals that are easy to harvest, or not. 

I did not like scraping my cell when it grew a sheet of silver, but I found it would come out fairly easily if I could get under a corner. I generally used the chunks for making electrolyte because they were a general PITA to handle. 

You may recall, my customers were pretty good about accepting crystal in settlement, so I didn't melt my silver. Fact is, I still have a great deal of it, stored in a couple 5 gallon buckets. Haven't laid eyes on it in years, so I don't have a clue if it is still bright and shiny, or not. 



> It looks like I'll be running tons of silver in the near future. I just wanted to kick this around a bit to come up with some answers as to the copper content. I'm more interested in how I WILL do it rather than how I used to do it.


It will be interesting for me to see if you find it to your benefit to avoid adding copper. For me, it was a no-brainer. 

If you do intend to add copper, I'd strongly advise a chemical wash of the cement silver, to minimize the amount of copper carried into the process. I used to rinse my cement silver in a buchner, until the rinse water was clear, then I'd melt with a generous flux cover to absorb oxidation. The lot was poured to a cone mold, then well cleaned before the resulting button was re-melted to be cast as an anode. The anode was always bright, but there was enough residual copper to quickly contaminate the electrolyte. I expect you won't have a different result unless you alter the process significantly. In retrospect, I wonder if a wash of the cemented silver in HCl might have been a good idea. 



> I would think that it would be better to start with at least a small amount of copper in the solution, maybe 1/2 to 1 oz/gal. This would not, very much, alter the time that the cell could be run before having to deal with it.


My opinion? You'll lose more than 50% of the useful life of the electrolyte. It will be interesting to see the results you get. 

Don't get me wrong, Chris. I'm not trying to win a contest here----I'm simply relating my experiences. I read the book and made decisions in keeping with my objective of running batch lots instead of constantly trying to balance my electrolyte by partial replacement for continuous operation. That was well beyond my capability, not understanding the testing techniques, but fully understanding the ramifications of allowing the electrolyte to become overly concentrated with copper. The harsh reality is that copper accumulates rapidly----so any you can eliminate is to your benefit, assuming you're willing to tolerate the short interval where the cell grows a solid film. The time taken to remove the film is small compared to the time you spend changing the electrolyte. It also minimizes the amount of silver you must recycle. 

Harold


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## goldsilverpro (Jan 22, 2009)

> Quote:
> It looks like I'll be running tons of silver in the near future. I just wanted to kick this around a bit to come up with some answers as to the copper content. I'm more interested in how I WILL do it rather than how I used to do it.
> 
> It will be interesting for me to see if you find it to your benefit to avoid adding copper. For me, it was a no-brainer.



In this case, I will be running dore' type bars, with very little copper. Therefore, I will definitely start the cells with quite a bit of copper. To me, that is a no-brainer.



> Quote:
> I would think that it would be better to start with at least a small amount of copper in the solution, maybe 1/2 to 1 oz/gal. This would not, very much, alter the time that the cell could be run before having to deal with it.
> 
> My opinion? You'll lose more than 50% of the useful life of the electrolyte. It will be interesting to see the results you get.



I always kept track of the silver and copper in the bath by analysis. A long time ago, I experimented to determine how much copper it took to affect the silver purity. I dissolved some crystal and ran it for copper on the AA. I came up with about 12 oz/gal as the critical limit for copper in solution. Even at 10 oz/gal, I would only lose 5% of the life of the bath, if I started with .5 oz/gal copper. I would lose 10% at 1 oz/gal.

BTW, I read in one of the books that you must have 10 times more Au than Pd in the bar, in order to prevent the Pd from dissolving and entering the solution. If the Pd goes into the solution, it will co-deposit with the silver. Other problem metals are Pb, Se, Te, and Bi.

Chris


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## Oz (Jan 22, 2009)

Every time you 2 debate this I pick up a gem or more.

I have wondered about at what concentration Pd would start to precipitate with the silver as I expected most of it to go into solution instead of staying in the anode basket. Do you expect any Pd in solution to precipitate as readily as the Ag? If not at what concentration would you expect it to?



goldsilverpro said:


> BTW, I read in one of the books that you must have 10 times more Au than Pd in the bar, in order to prevent the Pd from entering the solution. If the Pd goes into the solution, it will co-deposit with the silver. Other problem metals are Pb, Se, Te, and Bi.



I am surprised to hear that gold will limit this as I expected gold to stay elemental in the basket. Do you have any insights as to why gold would affect it?


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## goldsilverpro (Jan 22, 2009)

> Every time you 2 debate this I pick up a gem or more.


Me too!

goldsilverpro wrote:


> BTW, I read in one of the books that you must have 10 times more Au than Pd in the bar, in order to prevent the Pd from entering the solution. If the Pd goes into the solution, it will co-deposit with the silver. Other problem metals are Pb, Se, Te, and Bi.


Reading further, I find that, in order for this to work, the Au content of the bars has to be less than 4.5%. This is because, as the Au increases, the anode efficiency (rate of dissolving per amp) decreases. As the anode efficiency decreases, the more likely the Pd will dissolve.



> I am surprised to hear that gold will limit this as I expected gold to stay elemental in the basket. Do you have any insights as to why gold would affect it?


None whatsoever. Maybe a Au/Pd alloy forms that is insoluble in these conditions.


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## Oz (Jan 22, 2009)

goldsilverpro said:


> Reading further, I find that, in order for this to work, the Au content of the bars has to be less than 4.5%. This is because, as the Au increases, the anode efficiency (rate of dissolving per amp) decreases. As the anode efficiency decreases, the more likely the Pd will dissolve.



If you need 10 times more Au than Pd and the gold content has to be less than 4.5% then you can’t exceed .45% Pd, that’s not much. As my silver is from inquartation I am sure I would exceed that in Pd even if I added a bit of gold to limit its dissolution. In the material you are getting ready to run I can see it may work out to your advantage depending on your gold percentage.

I still am left with trying to figure out if Pd precipitation will be a constant problem at any concentration or if there is a threshold as in Cu. In the absence of any other information I will find out by testing my crystal silver by re-dissolving some and testing with DMG. If there is a threshold I could make a habit of testing my electrolyte concentration the same way to assure high purity Ag.

I welcome any other input.


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## Harold_V (Jan 23, 2009)

goldsilverpro said:


> As the anode efficiency decreases, the more likely the Pd will dissolve.


That was my experience. I commented earlier that an abundance of other elements in the anode can be troublesome. 

I can recall only one instance where I had palladium show in my electrolyte. The anode had a serious amount of other elements present, requiring the anode to be scraped. Even then the slimes were difficult to remove. It was that experience that depleted my electrolyte. 

If palladium is being dissolved in the cell, it won't go unnoticed visually. The color of the electrolyte will shift to dark green. 

Take note that I made mention of dissolving silver from the cell to make the next batch of electrolyte. My routine was to dissolve the needed 30 ounces from the most recently harvested batch, which was generally around 200 ounces. If the silver was contaminated with copper or palladium, it would show in the dissolved silver. That was the indicator to me to either accept the balance of the crystals as being pure, or to return them to the silver cell, where they were parted a second time. No melting, just placing them in the basket and covering them with an anode was sufficient. 

Testing of electrolyte after parting will indicate the presence of dissolved palladium. I don't recall it being a problem unless too much was present. When an anode was cast that was low in other values, it parted cleanly, leaving slimes free in the filter bag. When the anode was lifted, it would be a dull light tan color-----and the slimes would rinse off easily with a wash bottle. In such cases, I do not recall ever having any problems with palladium going in to solution. My slimes were exceedingly heavy with them, a sure sign that they did not dissolve in the cell. In my opinion, it's a non-issue unless the percentage is too high. 

Harold

edit: I should make note-----my silver contained very little gold. Only what little managed to slip past me when siphoning solutions. I recovered very little gold from my silver cell, so gold did not play a significant role in preventing palladium from dissolving.


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## Oz (Jan 25, 2009)

Thanks for that Harold. I had waited to reply in the hope GSP would weigh in on it. What you wrote helps much in what I should expect as to Pd.


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