# Silver cell economy



## amesametrita (Feb 4, 2013)

<omited>


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## butcher (Feb 8, 2013)

GSP gave some equations on running a silver cell using sterling as the anode, it show about how long the cell could be run before it was contaminated with copper (at the current the cell was operated) and would need replaced 

Add KNO3 or NaNO3 or Cu(NO3)2 to bust up amperage (I do not understand this statement).

I can follow your math down the page a way's only because I recognize where the numbers come from and what they are referring to.

But after half way down the page I am lost, and lose interest, I lose where the numbers come from or what they are referring to doing, If I am the one doing the math I know in my head where I am going and what I am looking for, but when your doing the math I need to know where your going what your looking for or where and why you picked those numbers.

I would need some explanation.


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## amesametrita (Feb 9, 2013)

Let's assume we have 90/10 sterling silver.
Initially somehow we produce 37.5g of cemented silver.
And take 100g of sterling
Dissolving in HNO3 (10*4.15ml + (90+37.5)*1.22ml = 197ml)
Dilute to 1.5 liter
Ag 85g/l Cu 5g/l
Add KNO3 or NaNO3 or Cu(NO3)2 to boost up amperage
Critical amount <25g/l Ag
Till 25g/l Ag we can remove 60 g/l
And introduce 60/3.4=17.6 g/l Cu
To introduce 17.6 g/l we can refine 176g/l of sterling in the cell
176*1.5l = 264g - refined
60*1.5 = 90g - depleted
264*0.9+90=327.6 harvested
Plus we have 37.5g Ag in solution which we cement with only 37.5/3.4=11g Cu
And start over.

Total:
327.6g of pure Ag using 197ml of HNO3 and 11g Cu

Normal method even not counting electrolyte (price is divided by ~10 refinings):
327.6g pure Ag -> 364g sterling
To dissolve 327.6*1.22+32.7*4.15 = 535.3ml HNO3
To cement 327.6/3.4=96.3g Cu
Counting electrolyte is even bigger


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## butcher (Feb 9, 2013)

amesametrita,
Thanks, the math was much easier to follow, and the few added words in your description give me a much better Idea of what you are describing making it easier for me to follow the math and the discussion, I need SLOW :lol: (I cannt follow fast without getting left behind).

You have discussed only 1.5 liters of electrolyte and a few ounces of silver, the smaller the cell the faster it would contaminate, the more trouble having to monitor and replace electrolyte, easier to get contaminated silver crystals, and you discuss going to the trouble of setting up and running this cell for a very short period of time, only doing a very small lot of silver, and then calculate your nitric savings.

In the long run for larger lots, and considering quality of product, time and trouble of running this type of cell, I am still not convinced you would save that much nitric acid, as copper still consumes the nitric acid, although I still remain sitting on the fence of this subject, not really sure, which side of this fence the grass is greener.

To make a gallon of the electrolyte would use almost as much silver in your whole equation (for a bigger cell), (copper would consume a portion of that electrolyte), you could run the silver cell silver for a little while before it was consumed by the copper and would need replaced, the more you ran the cell the less saving in nitric you will have. 

We have members who do use this method of running sterling silver in a cell and it has been discussed several times. 

GSP has given the math before complete with details and the problems involved, as well as many details of how to run the cells.

For the first few ounces you did show less nitric used, but as copper in the electrolyte solution loaded the purity of the silver crystals also would decrease in purity, if you were just doing a little bit of silver and was going to go to all of the trouble to set up the cell to do a small run, you may save a little nitric, but if you were going to the trouble to set up a silver cell and run a lot of silver, eventually the more sterling you ran you would get to a point that your nitric consumption was using about the same amount as you would if you dissolved the copper from the sterling before running the silver in the cell, either way the copper will consume the nitric, and either method you would be having to spend time and work dealing with dissolving or removing the copper, in the sterling silver cell by monitoring and replacing electrolyte as copper contaminated system (taking chances of a less pure silver crystal product).

I have not tried it, Have been thinking of trying it, but I have also been thinking of trying it a little different, once I collect enough silver, my thought was to take my cemented silver and melt it with sterling to raise the percentage of silver in the anodes lowering the copper content, so I would have less copper in the silver anode to foul the silver product, and possibly be able to run the cell longer without having to replace the electrolyte so often.

From the way I understand it it may save a little nitric but in the long run you will still be using almost the same amount of nitric acid, as the copper consumes the nitric acid, the first few ounces you show doing you may get by with using less nitric acid, but then more nitric will be needed to replace the nitric in the electrolyte.

Another option, some members have discussed running the silver twice through the silver cell, to remove silver that co-deposited with the silver crystals in the first run, this also may lower nitric usage some, but here again we after talking trading time and trouble for a small amount of saving from using a little less HNO3.

Laser Steve has showed how he removes silver from the copper loaded electrolyte to reuse the electrolyte, using a graphite anode which may help in saving some nitric, but even this would trade labor for some saving and also some of the nitric is lost as gases.

All in all I suppose you could save some on the nitric acid, trading time and trouble of operating the cell, and also taking a chance of getting less pure silver crystals, for a little less in consumption of acid.

Although I could also make and distill nitric acid and use to process silver to high grade and to also run the cells, which could save me on the cost of nitric acid.

I have not heard of adding a nitrate salt like KNO3 or NaNO3 to bust up the amperage (I suppose you mean to boost up the amperage through the circuit by lowering cells resistance) I do not see where this would be needed where you already have so much metal in the electrolyte solution, and it is also fairly loaded with copper nitrate, what good would it do to add the reactive metals of sodium or potassium to the cell?

Thanks for reposting the math with more description, maybe discussing this more can get me off the fence and help me decide which side of the fence the grass is greener, although I do have time to decide while I collect my silver.


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## mikeinkaty (Feb 9, 2013)

"If you want to electro refine faster, you have to lower the resistance of the solution. Add KNO3 or NaNO3 or Cu(NO3)2 to bust up amperage. Forum prefers Cu(NO3)2, me KNO3"

Oh! Bust = Boost, or, to refine faster increase the amperage.

But why add anything? Why not just increase the voltage until you get the amperage you desire???? The Cu(NO3)2 concentration will increase by itself as you make more crystals.

Mike


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## amesametrita (Feb 9, 2013)

CORRECTION: in my posts bust up = boost up


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## amesametrita (Feb 9, 2013)

mikeinkaty said:


> But why add anything? Why not just increase the voltage until you get the amperage you desire???? The Cu(NO3)2 concentration will increase by itself as you make more crystals.



If you increase voltage you can achieve cathode potential enough to start depositing copper from the solution.


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## butcher (Feb 9, 2013)

From the way I understand it, the copper in the cell is to grow crystals differently, and is not necessarily needed, as far as cell resistance, but helps to change the type of crystal growth, you could also change that by not diluting silver electrolyte so much with water giving more silver in solution, which would also effect conductivity as silver is a great conductor of electrons, copper in solution may help here also, but as Mike says in the sterling cell you are soon going to have much more copper than you need, in fact so much copper you will push silver out of solution, so why worry about adding any other metal salt.


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## amesametrita (Feb 9, 2013)

Too low concentration. To low current. Too slow production. Need Additives.


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## amesametrita (Feb 9, 2013)

They don't depend on copper.


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## butcher (Feb 9, 2013)

“Initial concentration in my calc: 85g/l Ag, 7g/l Cu.
Final: 25g/l Ag, 18g/l Cu.
Too low concentration. To low current. Too slow production. Need Additives.”

So you do not have an impure sterling silver anode, dissolving more silver / copper into solution at a rate of 90/10 into solution replacing silver, but as more copper is dissolved into solution the electrolyte is eventually replaced by copper and the longer the cell ran the lower silver to copper ratio would become?

What are you doing pushing silver out of solution with a graphite inert anode, because you are showing where metals ions are depleted from solution, you do show an slight increase in copper, and as we have learned one gram of copper will displace 3.4g silver from a nitrate solution, you started with 7g/l and ended with 18g/l, (18gCu -7gCu =11gCu), then this 11 grams of copper will displace silver from the electrolyte, 11 grams which would push out silver, 11gCu x 3.4 NO3 = 37.4g silver replaced from electrolyte), since the added 11g copper in solution replaced 37.4 g of silver, it looks like you depleted the metals in solution somehow, with 37.4g of silver replaced by copper, plus the 25g you say you end up with gives 37.4 + 25 = 62.4g , you originally had 85g silver in this liter 85-62.4=how did you push out 22.6grams of silver without replacing it with copper or silver from the anode, or is the anode inert?


I understand current voltage temperature size of electrodes and distance as well as electrolyte concentration circulation in the cell has an effect on how the crystal grow, as well as additives are sometimes used like metals, acids or even organics, I have heard that the crystal growth of the silver cell and its operation can be improved by a little copper in the cell to begin with (within limits of course).
I just have not heard of adding potassium or sodium salts as an additive I am not saying it would not work, I just have not heard of it and do not see the benefit that could not be achieved by another means without the additive.

Need more current lower water content or move electrode spacing or change size of the electrodes, even temperature has some effect, voltage can also be adjusted within limits as you and mike pointed out.

But as I stated above I have very little experience in this area, and am repeating what I believe I have heard that those with experience a lot of experience have stated, as well as relying on my limited experience in this area.


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## Lou (Feb 9, 2013)

What do you mean crystals don't depend on copper?


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## amesametrita (Feb 10, 2013)

Acidity and Tellurium are not about copper as well.


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## amesametrita (Feb 10, 2013)

From 85g/t of Ag to 25g/l of Ag we have to remove from solution 60g/l.


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## goldsilverpro (Feb 10, 2013)

The copper concentration definitely has something to do with the crystal characteristics. I know this from experience as well as the literature. For removal and filtering ease, short dense crystal is desirable.



Butts and Coxe said:


> The variations in silver and copper nitrate and the ratio of one to the other are based on certain objectives, such as:
> (a) Efficient anode reaction.
> *(b) Type of deposit desired for removal routine.*
> (c) Consideration of anode impurities.
> (d) Maximum conductivity with minimum silver tie-up.



If you want to increase the [NO3-] in the solution, there are only 2 things you can add safely: silver nitrate or nitric acid. Nitric acid will decrease the cathode efficiency temporarily. Adding KNO3 will likely poison the cell, in time. Adding copper nitrate will reduce the life of the cell.

The cell should contain nothing more than Ag+, Cu++, H+, and NO3-. The only exception I can think of is that some refineries add small amounts of tartaric acid to make the crystals even more shorter and denser.


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## amesametrita (Feb 10, 2013)

Variation of the Ag/Cu ratio influence the quoted goals.


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## butcher (Feb 10, 2013)

amesametrita,

You sound very educated in your posts on these subjects.
I am just a backyard refiner, learning this, with little experience.
Can I ask you where your experience comes from on this subject?

From your last post I feel you misunderstood what GSP has said, and with his experience in this field of work, I doubt he has to quote any book to prove his point, with his years of observations and practical work experience in this field.

I am still confused On why you suggest adding a potassium nitrate if you need more NO3- in the electrolyte when the HNO3 in slight excess would proving this in the beginning (until the reaction with metals, consumed any free NO3 as AgNO3 or Cu(NO3)2). Would not the metal sodium or potassium being a positive Cation possibly move to cathode and have undesirable effects On the cells reaction or crystal growth.

I do think the sterling cell would be much different than a pure metal and solution, in its actions and crystal growth, but adding one more variable like a reactive salt KNO3, does it help or hurt, improve or contaminate, and how or why.

Also we need to be careful that our minor disagreements in theory, do not get out of hand, and our discussions do not become some kind of ppsssing contest, but that we can all share and learn from each other, even if we do not agree with each other’s theories.

I do like the disscussion so far and think we may both learn something from it if we do not let it get out of hand.


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## Palladium (Feb 10, 2013)

I think all GSP's quotes come from real life experience and not literature though he can quote that for you to. I question what you are saying as well. Even though i don't have a chemistry background and can't break it all down for you i know from personal observation that copper does play a role in the silver cell. As we all know the difference between literature and what really happens in a chemical system is like the difference between day and night. I do enjoy this discussion and topic.


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## amesametrita (Feb 10, 2013)

Dear friends,
The original post was not about additives.


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## amesametrita (Feb 10, 2013)

Has to be checked for miscalcs.


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## g_axelsson (Feb 10, 2013)

For those that don't have access to it already :
The principles of applied electrochemistry. by A.J.Allmand (1912 edition)

Göran


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## butcher (Feb 10, 2013)

amesametrita, 
Thank you for the tip on the book I will keep my eye out for it.

"The principles of applied electrochemistry" by A.J.Allmand is as valuable in electrorefining "

If you wish to continue the cell you can read up on the forum, Laser Steve has posted, of how he push's copper out of solution with an inert graphite anode to reuse some of the electrolyte.

I guess for a short run and a small lot of silver there is a saving in HNO3 used, but in the long run if cell was continued to run, for larger batches of sterling, I still feel you would come to a point where just as much nitric was consumed, as would be the case if you removed most of the copper from the silver before making anodes of it, my thinking is bottom line the copper consumes HNO3.
at least these are my thoughts so far, maybe after I play with it a while I will see things differently.

P.S, no need to add copper nitrate additives, you will get plenty of that from the sterling silver.

Speaking of the book Looks like Goran found it for me.


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## Palladium (Feb 10, 2013)

Here's a good read i had earlier.


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## g_axelsson (Feb 10, 2013)

butcher said:


> You have discussed only 1.5 liters of electrolyte and a few ounces of silver, the smaller the cell the faster it would contaminate, the more trouble having to monitor and replace electrolyte, easier to get contaminated silver crystals, and you discuss going to the trouble of setting up and running this cell for a very short period of time, only doing a very small lot of silver, and then calculate your nitric savings.


You don't need to sample and monitor the electrolyte if you are running a known alloy as sterling silver. You can scale the cell and volume of electrolyte so you run it after the clock. If you know what you feed the cell you can calculate at which current a batch has to run for example 23 hours before needing to change the electrolyte. Then it is a simple task draining the old electrolyte and fill it up with pre mixed electrolyte and you are up and running again.
The silver from the old electrolyte is recovered by cementation with copper and used for preparation of new electrolyte.
New electrolyte is made up of dissolved sterling and recovered silver from the old electrolyte.



butcher said:


> In the long run for larger lots, and considering quality of product, time and trouble of running this type of cell, I am still not convinced you would save that much nitric acid, as copper still consumes the nitric acid, although I still remain sitting on the fence of this subject, not really sure, which side of this fence the grass is greener.


The saving in nitric is that you don't need to dissolve the silver in the feedstock. Nitric is still needed but the amount is much less than if you dissolve the sterling in nitric, then cementing on copper before going to the silver cell.



butcher said:


> To make a gallon of the electrolyte would use almost as much silver in your whole equation (for a bigger cell), (copper would consume a portion of that electrolyte), you could run the silver cell silver for a little while before it was consumed by the copper and would need replaced, the more you ran the cell the less saving in nitric you will have.


I think you are missing the bigger picture here. It will take just as much nitric to make the electrolyte for the cell which ever method you are using, it is silver and copper nitrate and you can't change that fact. But the saving is in the feedstock. Any nitric that is used up in the initial make of the electrolyte is "reused" when copper from the sterling electrode is dissolved and silver is deposited. The silver that is dissolved into silver nitrate is balanced by the silver deposited on the cathode.

Compare the two cases in an ideal world :
1. Sterling -> Dissolving -> cementation -> silver cell
and
2. Sterling -> silver cell

In the first case we dissolve everything and cementing, effectively every two atoms of silver is replaced by a copper atom in the cementing stage. This will decide the amount of nitric used in the long run as ideally the silver cell will run with a perfect feedstock and could be run as long as we have materials to run.
But every two silver atoms will create a copper nitrate molecule as waste and the nitrate comes from nitric acid.

In the second case we don't use cementation and the cell needs to be restarted repeatedly. But all silver nitrate in the make up of the electrolyte will be transformed into copper nitrate in the cell until the level of silver in the electrolyte forces us to shut down the cell and restart it. The rest of the silver in the electrolyte is recovered by cementation.
The silver that we run through the cell doesn't add to the waste stream and neither does the silver we used up from the electrolyte. The waste stream here is copper nitrate from the sterling and the copper nitrate produced when we recover silver from the depleted electrolyte.

Comparing the two cases we see that the copper in the sterling is converted into copper nitrate in both cases and that is the part we can't affect. But all the silver that goes through the first case is creating a copper nitrate waste stream while in the second case only the silver we recover from the electrolyte is creating the copper nitrate waste stream.



butcher said:


> We have members who do use this method of running sterling silver in a cell and it has been discussed several times.
> 
> GSP has given the math before complete with details and the problems involved, as well as many details of how to run the cells.


I have a large backlog before I have read all the discussion on the forum so I might be missing something. I haven't run a silver cell for 20 years, and then it was just a few experiments in my kitchen. Real life has a way of crushing even the best of theories. :lol: 



butcher said:


> For the first few ounces you did show less nitric used, but as copper in the electrolyte solution loaded the purity of the silver crystals also would decrease in purity, if you were just doing a little bit of silver and was going to go to all of the trouble to set up the cell to do a small run, you may save a little nitric, but if you were going to the trouble to set up a silver cell and run a lot of silver, eventually the more sterling you ran you would get to a point that your nitric consumption was using about the same amount as you would if you dissolved the copper from the sterling before running the silver in the cell, either way the copper will consume the nitric, and either method you would be having to spend time and work dealing with dissolving or removing the copper, in the sterling silver cell by monitoring and replacing electrolyte as copper contaminated system (taking chances of a less pure silver crystal product).


That is wrong, just because the electrolyte is getting depleted faster doesn't mean that you get an inferior product. If you make one long run you spend just as much time with a bad electrolyte as if you run ten or more shorter runs to the same electrolyte quality. If the quality of the electrolyte is the same in the end then the time it takes to reach it doesn't matter. As for monitoring you can just time it from the weight of the anode or the time if running with constant current.



butcher said:


> I have not tried it, Have been thinking of trying it, but I have also been thinking of trying it a little different, once I collect enough silver, my thought was to take my cemented silver and melt it with sterling to raise the percentage of silver in the anodes lowering the copper content, so I would have less copper in the silver anode to foul the silver product, and possibly be able to run the cell longer without having to replace the electrolyte so often.


Why not running the fine silver first and then the sterling? In the end it would make no difference except the first run will be longer. You would need to replace the electrolyte just as ofter in the both cases.



butcher said:


> From the way I understand it it may save a little nitric but in the long run you will still be using almost the same amount of nitric acid, as the copper consumes the nitric acid, the first few ounces you show doing you may get by with using less nitric acid, but then more nitric will be needed to replace the nitric in the electrolyte.


That is a good point, I didn't count the nitric mixed in the electrolyte. How much is that and what does it end up as? Will it mostly be used up to dissolve the anode or is it still left in the electrolyte when the silver is depleted? This would add to the waste stream too but I don't know in which way. If it goes through without reacting with the anode or cathode then it is wasted, but if it dissolves the metal then it is in the end turned into copper nitrate by copper in the sterling and not wasted.



butcher said:


> Another option, some members have discussed running the silver twice through the silver cell, to remove silver that co-deposited with the silver crystals in the first run, this also may lower nitric usage some, but here again we after talking trading time and trouble for a small amount of saving from using a little less HNO3.
> 
> Laser Steve has showed how he removes silver from the copper loaded electrolyte to reuse the electrolyte, using a graphite anode which may help in saving some nitric, but even this would trade labor for some saving and also some of the nitric is lost as gases.
> 
> ...



We meet again in an interesting discussion. 8) 

Göran

edit: corrected a mixup between anode and cathode...


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## goldsilverpro (Feb 10, 2013)

Here's the 1920 edition. Click on the gear icon on the top right and download the pdf.
http://books.google.com/books?id=1YJPAAAAMAAJ&printsec=frontcover&dq=intitle:electrochemistry+inauthor:allmand&hl=en&sa=X&ei=wV0YUeDuAsfQqAGe-YGIDw&ved=0CDAQ6AEwAA#v=onepage&q&f=false


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## butcher (Feb 10, 2013)

Göran,
I read what you stated I did not see anything to discuss, I still believe my statements were valid points, and I read your statements which I also believe are valid points.
but always willing to discuss something with you.
Do you have a certain point you would like to discuss?


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## Lou (Feb 10, 2013)

The thing no body mentions when they talk about recycling old electrolyte is how they remove the palladium and nickel that co-deposit with them onto copper. Formate doesn't remove either of them. 

I have treated it successfully with HCl and rinsed the silver chloride in a 24" Buchner but it makes too much solution. Very tedious for even one 45 gallon cell and you're breaking the "silver" rule in silver refining: do not make AgCl (rule #2: don't let it get dry) in the refinery unless there is no other choice.

Solvent extraction also makes a lot of solution, or so I'd imagine--never tried it out of nitrate medium.

DMG is even less practical. Making black mass of the electrolyte (Pd et all turn to oxides) might work the best but it's a scary process.


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## butcher (Feb 11, 2013)

Never thought about it Lou, good question.

If you had an electrolyte loaded with copper, some silver, nickel, and a little palladium as nitrate solution.

Why not just use a copper metal buss bar to cement silver and palladium.

Before using the electricity and pushing copper and nickel out of the electrolyte with a graphite inert anode.

Although not having tried recovering nitric from the cell, I do not know which would be best to try recover the nitric from this used electrolyte solution, or if it would really be worth it in the long run, with either electrolysis or distillation and evaporating the copper nitrate to salts and driving Nitric out of the salts with heat, bubbling the NOx gas through water.

Could just use the spent electrolyte to remove base metals above copper from my stockpot, or evaporate and save the copper nitrate for some other project.

In a way it almost seems as simple to just make up a batch of home made nitric and distill it. Than to try and recover the little bit of nitric the electrolyte would contain.


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## amesametrita (Feb 11, 2013)

g_axelsson said:


> I think you are missing the bigger picture here. It will take just as much nitric to make the electrolyte for the cell which ever method you are using, it is silver and copper nitrate and you can't change that fact. But the saving is in the feedstock. Any nitric that is used up in the initial make of the electrolyte is "reused" when copper from the sterling electrode is dissolved and silver is deposited. The silver that is dissolved into silver nitrate is balanced by the silver deposited on the cathode.
> 
> Compare the two cases in an ideal world :
> 1. Sterling -> Dissolving -> cementation -> silver cell
> ...



Thank you, Göran


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## amesametrita (Feb 11, 2013)

Good acid choice is tartaric


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## amesametrita (Feb 11, 2013)

And remember you build up tellurium, tin, antimony, lead...


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## butcher (Feb 11, 2013)

> g_axelsson wrote:
> I think you are missing the bigger picture here. It will take just as much nitric to make the electrolyte for the cell which ever method you are using, it is silver and copper nitrate and you can't change that fact. But the saving is in the feedstock. Any nitric that is used up in the initial make of the electrolyte is "reused" when copper from the sterling electrode is dissolved and silver is deposited. The silver that is dissolved into silver nitrate is balanced by the silver deposited on the cathode.
> 
> Compare the two cases in an ideal world :
> ...




Nope I do not see where I missed that picture, I thought I have seen it clearly.

I agree if you are going to set up a cell and run just a couple of ounces I see where you could save some nitric.

But I am also discussing not just going to all of the trouble to set up and run a little bit and quit, If I set up I would want to continue, to run enough to make setting up worth it, so what I was also discussing is continued operation, with larger batches of silver (sterling in this case) and the longer you run the cell, that saving of nitric is also used up the more sterling silver you run, eventually the copper begins to consume most of the savings, you are trading saving a little solution for much more work and possible contamination by running the cell with too much copper.

I am not disputing you could save a little nitric, or that it may be worth it to try to.

Although I am still on the fence trying to decide if it is truly worth it in the long run as a continued operation, to remove copper from a large batch of sterling silver.

Running the silver cells as they are normally run with fairly pure anodes seems trouble enough.

The sterling cell just seems like a lot of trouble to deal with the copper in the cell, for a tiny bit of saved nitric solution.
Either way you are still consuming nitric acid to get rid of the copper either way you approach it.

Recovering the electrolyte as Laser Steve did with the graphite anode may help some also. But even with that option I still am not sure it would be worth the trouble in the long run.

I do not dispute some saving in nitric acid that would be a fact, but I also do not doubt that no matter which method you choose the copper consumes nitric acid.

With larger batches and with constant removal of the copper loaded electrolyte, a portion of silver is also removed, when you recover the silver from this electrolyte solution you could also consume more nitric depending on how you recovered the silver or reused the electrolyte or dealt with it, then we need also more nitric or silver nitrate to replace the solution removed to continue operation.

Just my view from sitting on the fence and my opinion, which I seem stuck with it at this point.

One of these days I will have enough silver saved up, and I can then try both ways, maybe then I will see it differently and more clearly.


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## butcher (Feb 11, 2013)

amesametrita said:


> butcher said:
> 
> 
> > If you wish to continue the cell you can read up on the forum, Laser Steve has posted, of how he push's copper out of solution with an inert graphite anode to reuse some of the electrolyte.
> ...



Sounds like your now begining see my point :lol: 

I do not see How your recovering and reusing the electrolyte, using pH, and how that would be very effective,or would save on nitric usage, can you refer me to a study on this so I could look it over.


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## amesametrita (Feb 11, 2013)

butcher said:


> I do not see How your recovering and reusing the electrolyte, using pH, and how that would be very effective



Why do you need old technology then I have just shown the modern and most economical method?


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## Lou (Feb 11, 2013)

I think for running costs and ease, a Thum cell is the way to go. 

I run my cells from 40-60 g/L Ag but let the other metals accumulate no higher than 4-6 g/L.


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## amesametrita (Feb 11, 2013)

Moebius with scrappers and agitation 0.3kW per 1 kg of Ag


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## goldsilverpro (Feb 11, 2013)

This is a crazy confusing thread. I've read it several times and still don't understand its purpose or see that anything has been accomplished. 

I've run sterling in 3 different ways:
(1) Melt sterling into anodes and run them directly in the cell.
(2) Dissolve sterling in nitric, cement with copper, and run the resulting bars of approx. 99% in the cell.
(3) Have 2 cells. The first as a break-down cell to upgrade the silver purity and the second to purify it.

In all 3, the amount of overall nitric used will ultimately be the same. I prefer (2) because there are fewer steps and you can run the cell 10 times longer than in (1) - 1% copper vs 10% copper.

_________________________________________

amesametrita,

I know of no case on the forum where copper nitrate was used to increase the NO3- in solution. It wouldn't work anyway, since that wouldn't result in any free NO3-. The same with any other nitrate compound such as KNO3. The only way to increase the free NO3- would be to add HNO3. This would form H+ and NO3-. The H+ would soon be eliminated as H2 gas at the cathode or by neutralization from the OH- resulting from water splitting at the inefficient anode, resulting in more free NO3-. With more free NO3-, the silver in solution would increase. Of course, all this doesn't occur in discrete steps. There are several things going on at the same time.

In any solution, the total electrical charges (positive and negative) of the ions must balance. There are several positive ions (H+, Ag+, Cu++) and only one negative ion (NO3-). Therefore, the total amount of positive ions (Ag+) cannot increase without an increase in the NO3-. The addition of KNO3 would not increase the free NO3-, since there would be a equal amount of K+ to offset it.

The figures you gave concerning the power consumption differences of the Thum vs the Moebius cells are meaningless. For the Thum cell, 1.5KW/kg of silver is about $.006/oz and the Moebius is a little over $.001/oz. Why quibble over pennies? In both cases, the power costs are negligible. Lou is running both types of cells on a fairly large scale and prefers the Thum. I agree with Lou. About the only advantage of the Moebius cell over the Thum cell is that it takes less floor space. Disadvantages of the Moebius are that the crystal is more difficult to gather and about 15% of the anodes must be remelted.

You say we can't see the big picture. Maybe you should try to do a better job of explaining what it is. I don't think you truly understand the process. Prove me wrong. You seem to be just riding the coat tail of that book you mentioned. I read the silver section of the book (1920 edition) several times and see nothing new there (see attachment). There were several newer editions written that may contain different information, but I don't have access to them.

By the way, if you are going to blatantly tell me I'm wrong about something, give me a detailed technical explanation of why you think this. Otherwise, I will take it as an insult. Keep this in mind if you want to stay on the forum.

Chris


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## Auful (Feb 11, 2013)

Thanks Palladium and GSP for the links to the book!

Matt


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## amesametrita (Feb 11, 2013)

goldsilverpro said:


> By the way, if you are going to blatantly tell me I'm wrong about something, give me a detailed technical explanation of why you think this. Otherwise, I will take it as an insult.


Sorry in advance. It was not my intention.


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## amesametrita (Feb 11, 2013)

Unfortunately I can't find any modern silver electrorefining books in public domain in ENGLISH.
The good book in Russian is "МЕТАЛЛУРГИЯ БЛАГОРОДНЫХ МЕТАЛЛОВ"
Good Slovak paper "ELEKTROLYTICKÁ RAFINÁCIA STRIEBRA Z METALICKÝCH ODPADOV"
Chinese libraries are the best but you need registration there.


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## goldsilverpro (Feb 11, 2013)

You are right. There is no such thing as "free" nitrate ion. I should have use the term "available" instead. In order to increase the [Ag+], you must somehow make more NO3- available. The only way I know to do this to add nitric. To make more available NO3- for the silver, the H+ from the nitric must be eliminated. The OH- coming from the anode reaction and/or, the extra nitric dissolving silver crystal, is probably what eliminates it. I erred on the water splitting at the cathode. A guy I worked for ran 12, 30 gallon Thum cells. He routinely added some nitric when the silver content got too low.

I did print out and read the silver section of the book and didn't think much of it. I have a hard copy of Liddell's Handbook of Non-Ferrous Metallurgy, Volume 2, 1926, and feel it gives a better discussion on silver. Also, I feel the Butts and Coxe book is better on this subject.

You mentioned earlier that you had an improved modern way of doing this. Can you detail your process, practically, step by step, without the theory. To me, theory is about 10% of the learning curve. How to successfully apply it is the other 90%.

Can you give us your background in this field and where you live? Have you ever run a silver cell? If so, what size, how many, and how much silver did you produce daily?


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## amesametrita (Feb 11, 2013)

goldsilverpro said:


> Can you give us your background in this field and where you live? Have you ever run a silver cell? If so, what size, how many, and how much silver did you produce daily?


I have a reason not to disclosure this info.


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## amesametrita (Feb 11, 2013)

The difference between "I copy that somebody did and it works" and "I understand the process and can improve and finetune it" is huge.


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## Palladium (Feb 11, 2013)

I'm starting to think this thread needs to end.


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## Lou (Feb 11, 2013)

You're right that electrochemistry doesn't depend on how many cells of what type you run. However, your qualifications for practical implementation is what was questioned.

Theory is great. You're right that nitrogen oxides are produced, not hydrogen in this application.
You're right about several things.

As for my preference for Thum cell? I prefer it in the context of small lots. It's easy to dump a bunch of shot in the Thum cell or keep stacking anodes. It's more continuous than a standard Moebius, which I find more batch wise as it needs emptied once a day--you can empty the Thum cells every couple hours if cash flow demands. No moving parts either!

I prefer Moebius for

1.) speed of production--as there is double anode surface area
2.) efficiency of resources (less electric consumption is trivial)--lower voltage means more cells can be run off a single power supply
3.) accountability on gold for individual bagged, numbered anodes

The higher current density and lower voltage make deposit purity a wash.


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## butcher (Feb 11, 2013)

I do not see any valid point being made here on this thread.
I do see it degrading to nothing but trouble.

Most everything being discussed here, has been discussed several times, and more intelligently in several other threads.

Where much of any of this here is to help anyone who wishes to recover or refine silver, or learn more facts.

When facts are brought to the surface they seem to be argued against for the sake of argument.

Statements are made with nothing to back them up except hot air.

So far this whole thread seems to be just a waste of time and resources, leading nowhere but trouble.

Trouble we do not need, and will not put up with.

We are not here to argue or get into arguments.

We can have intelligent discussion that gets somewhere, but at this point this is going nowhere.

We will have no Pssn contest on this forum, which prove nothing and serve no purpose, have no point except to disrupt order on the forum.


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## amesametrita (Feb 11, 2013)

Lou said:


> 2.) efficiency of resources (less electric consumption is trivial)--lower voltage means more cells can be run off a single power supply



I meant exactly that then compared power consumption.
High ampere rectifiers are very expensive for atmosphere heating, more then 4 cells in series are troublesome.


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## g_axelsson (Feb 11, 2013)

Palladium said:


> I'm starting to think this thread needs to end.


I disagree.

Please, don't stop this thread. There is a real saving in nitric acid if the cell is run as amesametrita suggests.



amesametrita said:


> You use 2.7 times less HNO3 and 8.7 times less copper.
> Every day, every batch of sterling you process.



What I see is a language and cultural barrier between amesametrita who apparently seems to be Russian, and a number of American members. This is breeding frustration and some one could easily take that as disrespect and questioning of ones experience.
It doesn't get better as there are three different things discussed in this thread, savings in nitric, the use of KNO3 and power requirements of the cell.
If you feel frustrated when answering a thread, take a deep breath, fetch a cup of coffee/tea/vodka/beer/wine/ or orange juice and then read through your rsponse before posting it.

Me? I'm just sitting here in the middle in Sweden. :mrgreen: 

(Getting a cup of tea...)

I can see a real saving in nitric between the cementation before the cell and batch wise running sterling directly in the cell. The amount of nitric used may not be a big issue for those with a big refinery and buying nitric by the barrel, but the home refiner who pays hazmat fees and buys by the liter it could mean a lot.

I have no practical experience yet but when I will set up my cell for running 5-10 kg of material I've collected then I know I will use this method. For me it isn't the nitric that is the problem. It is the NOx gases that is a problem. Small batches I can run at home but anything bigger and I need to relocate.

I tried to give an explanation in my reply to butcher but it seems no one is seeing what I see. I don't know how to explain it better, amesametrita have given equations with numbers and I tried to give an alternative view.
I can't set up a cell today and run it to give practical numbers so I'm almost out of ideas on how to describe what I see. I know what I will do with my cell but I feel it is sad that some other members could be missing a better way for them to run their cells.

Göran


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## butcher (Feb 11, 2013)

g_axelsson,
I agree there will be some nitric saving on a small batch, and for a small lot of silver it can be done, 

Laser steve Has proved that in his thread Processing silver without nitric acid.

I also agree there are several small details we seem to dissagree on, or just do not completely understand what the other is trying to say, too many points in the discussion and such a wide subject.

I just do not want to see this get out of hand.

I too have a hard time explaining what I see and what I am trying to say.

I do not think this thread should go away.

But I also do not think it should continue to go the way it has.


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## Lou (Feb 12, 2013)

Reading it over, the poor guy is just advocating running the sterling in the cell rather than dissolving it up in nitric and cementing it and _then_ putting it into the cell. Using the cell requires much less nitric acid. The biggest issue people will have here is that they have no means to remove Pd/Ni from their electrolytes unless AgCl is precipitated and re-converted. 

He did his math correctly. I've attached a (somewhat redacted) photo of what I use. There is no need to add soluble nitrate of any sort to the cell above and beyond copper and silver nitrate--it doesn't increase efficiency all that much. If you're running sterling, you need not add any copper at all (it will build rapidly enough to not cause too much dense druse formation). 

On a semi-related note, it is completely possible to digest silver sub-stoichiometrically with nitric acid and skip the NOx altogether. In fact, it works very, very well.

It's quite nice because on a mass basis, 1 kg of silver requires 600 mL of 42Be nitric acid to digest (1 g to 0.6 mL HNO3). It has gone unmentioned here because it is largely out of the reach of the private individual, and probably out of their comfort zone. It is now being employed by the more highly technical refineries as there is no cash inventory lockup in electrolyte. I like it for sterling, but the PPOP is higher and it comes with its own set of issues and liabilities. I've used it for rhenium, silver, copper, and several other metals. I particularly like it for high grade rhenium (as that dissolution is very consuming of nitric acid). I may make the switch one day soon...


EDIT: still can't attach files...


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## g_axelsson (Feb 12, 2013)

Thanks butcher, I'll look that up. I've been away from the forum for two years and I haven't had time to catch up on all subjects yet.... working on it. 8)

I will do a calculation on how much nitric is used in the both cases but I'll have to do that later. Gotta run off to work now... no, I haven't quit my daytime job yet. :lol: 

Göran


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## butcher (Feb 13, 2013)

I read the document GSP posted, Very interesting, Dates on this document seem to suggest late 1895 to early 1911, I found it very interesting, they were running Moebius and Balbach-thum cells with higher copper electrolyte content, it also seems to indicate current density and stirring of the electrolyte can be very important, for controlling copper reduction with the silver crystals, I was also under the impression the were recovery cells, not necessarily trying for High purity silver, but recover silver at a reasonably pure state as well as recover other valuable metals in the slimes. 

What I found most interesting in the document was the Dietsel cell with rotating drum cathodes were copper is deposited from solution, the impure silver anode dissolves into the electrolyte solution, which when saturated with silver and depleted of copper is drained, the silver cemented out of solution with copper metal, the copper nitrate returned to the cell, to pick up more silver into solution and deposit more copper.

The Dietsel cell I think would be interesting to experiment with and to try to run sterling similar using a similar method, at the same time maybe reuse or process some copper nitrate waste from my refining operation.

One of the questions I have about the Dietsel cell is it looks like the copper drums are exposed to air as they rotate, I am curious if they oxidize the copper or are they kept wet enough with acid to keep oxidation to a minimum.

Now to find a cheap source for the platinum wire basket used in the cell.


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## amesametrita (Feb 13, 2013)

My explanations are coming


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