Silver Electrolytic Cell Volume

[Oz]

If you are trying to produce .999+ silver crystal I would keep hydrochloric acid out of the process. You are already casting anodes, just clean out the cell and recast the silver.

As to cementing your used electrolyte on copper, that is how I handle it. I do everything I can to limit the amount of silver chloride I need to process.

 

[rbramsey]

I am now attempting to refine my silver with a electrolytic cell. I have a couple of questions?

GSP stated that you can run 92.5 silver through the cell but it was harder to do. I can concur. The crystals are very small, and very slow to form. The temperature started at 40 F ( I used 12V to begin with to help raise the temperature of the electrolyte). The results were not good. After letting the cell run for about 30 minutes at 12V ( the electrolyte was warm to the touch, I switched to 6V, and let the cell run for another 2 hours. The current draw was estimated at 2A (needle barely moved on the meter). The volume of crystals was very little. I estimate less than 10ml. Also, there were two distinct colors of crystals. One was bright white (silver) the other was darker with a tint of brown ( copper I presume). I assume this was caused by me running the cell at 12V.

Tonight I adapted a computer PS to run the cell tomorrow. I will use the 3.3V rail. It is rated at 20A. What parameters do I need to watch out for when refining sterling? How the temperature of the electrolyte factor into the cell. How critical is the anode to cathode area ratio? The anode bars I cast are 1-3/8" diameter. The cathode is 1.5 x 2.5. So the ratio is 2.5:1.

Also, kadiver stated that his crystals didn't dissolve in the electrolyte after leaving them in there over night. Mine dissolved. I guess this means I have too much nitric in the solution. Should there be any free nitric in the electrolyte?

I will setup again tomorrow to run another batch.
Richard

 

[goldsilverpro]

I am now attempting to refine my silver with a electrolytic cell. I have a couple of questions?

GSP stated that you can run 92.5 silver through the cell but it was harder to do. I can concur. The crystals are very small, and very slow to form. The temperature started at 40 F ( I used 12V to begin with to help raise the temperature of the electrolyte). The results were not good. After letting the cell run for about 30 minutes at 12V ( the electrolyte was warm to the touch, I switched to 6V, and let the cell run for another 2 hours. The current draw was estimated at 2A (needle barely moved on the meter). The volume of crystals was very little. I estimate less than 10ml. Also, there were two distinct colors of crystals. One was bright white (silver) the other was darker with a tint of brown ( copper I presume). I assume this was caused by me running the cell at 12V.

Tonight I adapted a computer PS to run the cell tomorrow. I will use the 3.3V rail. It is rated at 20A. What parameters do I need to watch out for when refining sterling? How the temperature of the electrolyte factor into the cell. How critical is the anode to cathode area ratio? The anode bars I cast are 1-3/8" diameter. The cathode is 1.5 x 2.5. So the ratio is 2.5:1.

Also, kadiver stated that his crystals didn't dissolve in the electrolyte after leaving them in there over night. Mine dissolved. I guess this means I have too much nitric in the solution. Should there be any free nitric in the electrolyte?

I will setup again tomorrow to run another batch.
Richard

Excess nitric will definitely redissolve crystal and is probably the reason the crystal is forming slowly. As the solution warms, it will dissolve the crystal at a faster rate. To avoid the excess, use a little less nitric than it would take to dissolve all of the silver being used to make up the solution. In other words, there should be a little undissolved silver left over when all the nitric has completely reacted. Theoretically, it takes 1.22 ml of nitric to dissolve 1g of silver and it will take 4.2 ml to dissolve 1g of copper. If you're dissolving sterling to make up the solution, it takes about 1.44ml/gram [(1.22 x .925) + (4.2 x .075)]. In practice, use about 95% of the total nitric you calculate to be required.

When the silver in solution gets too low, it can be increased by adding a known quantity of nitric. This will dissolve about 1g of crystal for each 1.22 ml added.

For your 3.75 sq.in. of cathode area, I would use from .65 to 1.3 amps at 3 to 4 volts. If you go much higher, you will get poor crystal and possibly will deposit some copper.

 

[elfixx]

I have a question for you guys, as you know, the voltage(shown on the rectifier) of a silver cell lower with the electrolyte resistance. I have always ran my cell setting the voltage first to 3v and then let the resistance set, my question is should I keep on running the cell this way or could I set the volatge to 3v once it is running whitout risking contaminating the final product? Perhaps my question isn't nicely formulated, pardon my poor english.

Thank you

 

[DNIndustry]

Been awhile. Thought I would throw My 2 cents in. I'm sure that we all have computer power supplies lying around. I saw on instructables and other places Directions for making your own laboratory power source.
There are both. 3.3 v & 5 lines. Pending on the units each baby anywhere from 15 up to 50A.
This would give you a much closer setup parameters.

 

[DNIndustry]

I should have read. Already posted.

 

[metatp]

Yes, be sure to maintain a 4" anode to cathode spacing. Also the cathode should be no more than twice the area of the anode

Can you tell me the significance of the cathode to anode area ratio? What happens when the anode is larger than the cathode?

Thanks,
Tom

 

[kadriver]

Hello:

I have been running my silver cell now for a good bit with good results.

The crystals are much easier to work with over cemented silver.

I have cleaned the cell filter bags several times. I usually remove the filter assembly from the cell to another container, then remove undissolved anodes and filter bags (I use double filter bags to ensure no junk gets in my silver).

I wash the slimes into a container, and then treat with dilute nitric acid (50/50 mix of distilled H2O and 70% nitric acid). Then I filter off the residual and add the filtered silver laden liquid to a silver cementing container.

Here is my question: What is this red stuff left over after treating with nitric acid?

I have treated some of the filters that have this red material with aqua regia and got some gold (about .5 grams last time).

I will just continue to save these filters in a plastic bag until I get some info on what this red material is and how to process it.

Thanks to all - kadriver

 

[goldsilverpro]

kadriver,

Looks like a little colloidal gold to me.

 

[kadriver]

Thank you - i will just continue to treat this with AR and get the gold out.

kadriver

 

[nickvc]

I always keep all my filter papers and leave them to dry in a plastic open container and then incinerate them when I have a reasonable amount and recover any pms present. You might find that you have PGMs as well as gold from your silver cell sludges in time especially if your running cemented silver from inquarting,test your AR with stannous before discarding.

 

[kadriver]

I am still new to this business of refining silver.

Somehow I got the impression that I could make up an electrolytic silver cell and then cast anode bars from silver jewelry or sterling flateware and dishes and just throw these bars in the anode basket to refine them.

I found that the cell quickly becomes contaminated with impurities and that weird things start happening in the cell.

For example, I assembled a cell with electrolyte and anodes, but did not connect the electrical leads. I was called away and when I returned about 2 hours later, silver crystals had begun to grow in and around the anode bag and the solution had begun to turn blue!

I was dumbfounded and in my inexperience just decided to hook up the electric leads and go with it.

Big mistake as some i could immediately see some contamination floating around in my electrolyte.

So I disassembled the cell and cleaned everything. Then I put it all back together and got it running fine.

That evening I was leaving the shop so I just turned off the poweer supply to the cell as I have always done.

To my befuddlement, the same problem appeared the next morning - silver crystals had begun to grow in and around the anode bag again.

This time I disassembled the cell and cleaned everthing up before restarting.

I only got about 8 troy ounces from this cell before I took it apart and recovered the silver.

During the last part of operation, a blob of brownish yellow pudding-looking material began to grow on top of one of the crystal formations that had grown to within 2 inches of the anode bag. I have had crystals get this close before, but have never seen this blob form.

As a result of all this, i am now using only cemented silver anode bars in the cell, and i am keeping a close watch to ensure that the crystals do not get too close to the anode basket.

I also remove the anode basket from the cell for overnight storage and reinstall the next morning before startup.

Is it possilbe that there was a weak current going throught the electrolyte even with no power to the cell?

Any input that would help explain these strange results would be greatly appreciated.

Thank you - kadriver

 

[lazersteve]

It's simply cementation happening from the impurities in your anode.

Steve

 

[Goldfinger4]

It is quite normal that your electrolyte turns blue, that happens through copper impurities but should not excite you. If your silver concentration is high enough and the current is not too high only silver should crystallize.

When leaving your raw silver in the silver nitrate solution, the copper is dissolved and silver crystallizes on the raw material.

Ag+ + Cu --> Ag + Cu+

You should inform yourself about electro chemistry: https://secure.wikimedia.org/wikipedia/en/wiki/Electrochemical_series

 

[kadriver]

I removed the battery charger and replaced it with a PC power supply using the 3.3 volt rail. The crystals are nice and beefy and the cell is working perfectly.

I will do some study on electroysis to get familiar with the processes in the cell.

The silver did not look like cemented silver that I am used to seeing. The silver that was forming on the filter bag looked exactly like the silver crystals growing on the cell.

I will just make a practice of removing the anode bag when the cell is not in operation.

Thanks for all your input - kadriver

 

[ORCB]

Hi all,

I see there's discussion of lasersteve's DVD on this thread, so I hope this is the right place to ask some more technical questions about it. I just got the DVD, good vid.

I'm wondering why the copper ions from the sterling are not reduced at the cathode, so why are only the silver ions reduced? Also, what's the function of the basket, is that somehow selectively trapping the base metals from going into solution? Yet, I know some copper ions get into the solution, if there's copper in your silver, cause in the video, eventually the electrolyte will go blue.

Thanks!

 

[ORCB]

Hi all,

I see there's discussion of lasersteve's DVD on this thread, so I hope this is the right place to ask some more technical questions about it. I just got the DVD, good vid.

I'm wondering why the copper ions from the sterling are not reduced at the cathode, so why are only the silver ions reduced? Also, what's the function of the basket, is that somehow selectively trapping the base metals from going into solution? Yet, I know some copper ions get into the solution, if there's copper in your silver, cause in the video, eventually the electrolyte will go blue.

Thanks!

Sorry to double post. Is it cause the electrolyte is saturated? Even still, I don't see how that would select the oxidized silver ions to replace the reducing ions in the solution over copper ions. Hmmm. Looking forward to answer.

 

[lazersteve]

In the video I start off with cemented silver (98%+ purity) so there I very little copper present. As the electrolyte builds up copper you have to change the electrolyte to prevent the copper from co-depositing.

Keeping the volts around 3 to 4V will also keep the copper out of the crystals.

Lastly, copper tends to want to remain in the solution more so than the silver (think cementation reaction) . The silver is more reactive, therefore it's the first to deposit at the low voltage.

Maybe some of the other members will post their theories why the copper doesn't co-deposit?

The basket is there to catch the insoluble slimes that are in the silver. These slimes are gold and other metals that are not readily soluble in nitric acid. Without the basket you end up with black specks of gold and other metals in your clean silver crystals.

Steve

 

[metatp]

I just tried a new cathode I created made of stainless steel. I tested it first in nitric acid for hours to make sure it didn't start to dissolve. The "arm" of the cathode going up the side of the beaker is about a half inch wide sheet of the same stainless sheet. I coated it with plastic that was a dip coating used for applications like coating pliers handles. This is what happened:

Before I started the cell, I dissolve 100g of cemented silver powder in only enough nitric acid to dissolve the silver (150ml of distilled water).

I used heat to assist in dissolving the silver (I may have left it on the heat a bit too long and the solution was at a slight boil enough after the silver was dissolved.

I let the solution cool and added enough distilled water to fill the cell.

All seemed fine with the solution have a slight blue tint.

When I started the power at 3V and about 1Amp, silver started growing right away and faster than I am used to seeing. They grew like grass more than crystals. It was darker than the normal crystals. This was weird, but it got weirder. silver started plating on the coated "arm" and crystal started growing from there as well. I even a a small area on the glass beaker than looked plated.

Any speculation to why the crystal grow was this way? Cemented silver should have been incinerated? Coating on "arm" not thick enough? Could the silver nitrate be supersaturated since it was boiling for some time after the nitric acid was used up? It is a little perplexing.

Also, the anodes are cemented silver that was melted into ingots.

I am starting over with my graphite cathode for now.

Thanks,
Tom

 

[Barren Realms 007]

I'v seen that coating be porus. This would allow your crystals to grow thru it.