My first silver refining attempt, help needed.

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erling66

Member
Joined
Mar 25, 2018
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20
Hi, first a short summary, I dissolved 830 scrap silver with nitric and distilled water, the precipitated out the silver with copper, washed the cement several time, and melted it to shots. Made electrolyte and anode from the shots. And started a silver cell, 7 liter glass bowl with a stainless 316 plate cathode. 2volt and 1.2 ampere. I use one layer of cotton filter and a coffee filter. But the the thing that grows looks like trees and they are very soft and flexible. The cell has been running for 18 hours now and they are already 4cm long and has a dull grey color, So any idea what I am doing wrong? I was hoping for slow growing crystals.IMG_20220127_082830.jpgIMG_20220127_082800.jpgIMG_20220127_082436.jpg
 
What is your solution concentration?
I see a problem with anode to cathode surface area as well as anode to cathode spacing. Use a stainless bowl for the cathode.
 
What is your solution concentration?
I see a problem with anode to cathode surface area as well as anode to cathode spacing. Use a stainless bowl for the cathode.
the solution is 100gram silver pr liter. I have a 5 liter stainless boiler I can use, but maybe it will be better to buy a bowl because of the shape?
 
Looks similar to my silver cell, i run a conceentration of 175 g/ liter. Also the cathode seems like its to far away, try to keep in in the 4 inch range.
 
Hello if you want to get to 999, what you have done seems to me good, the stainless steel is good and especially if you have done well, and we can recover the precious in the anode base, for me two things here:

1) yes you can use a stainless steel receptacle as said above and it will be distributed more homogeneously.
2) if you want to grow your metals and make them larger, denser, you have to reduce your voltage because that's what will determine the growth of the silver.
3) So the slower the growth, the bigger the crystals you will have.
4) you can recover the pgms in the sludge on the anode.
If your nitric is well diluted, you will not dissolve the palladium.
5) you should not have any in your base solution of palladium ions if you start from Ag 999 to make your electrolysis.
some pictures to illustrate what I say
 

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A few quick thoughts, your cathode and anode are a bit too far apart. ~4 inches is what you're looking for. Also, 100g/liter is a little low on the concentration, I usually use 250g/liter. Remember as your cell runs, you're going to lose free nitrate from the silver to make copper nitrate which stays in solution. Some people recommend adding a little bit of nitric acid as the cell runs to introduce more nitrate. I also run my cell at 3.5volts measured at the anode/cathode with a multi-meter.

As for an anode basket filter, for about five dollars you can get a dacron cloth filter made for a shop-vac. I buy mine from Lowes. I've found they work really well.

https://www.amazon.com/Shop-Vac-901-15-00-Performance-Dacron/dp/B0000CBJIH
It's a good start though, so keep engineering/experimenting with it until you get a yield you are happy with. I've gone from a stainless steel bowl cell to a three liter mobius cell design for better control of spacing, surface area, and to be able to circulate electrolyte.

Elemental
 
Thanks for advise. I will change to a stainless steel bowl, change anode cathode distance, add more silver to the solution and report back .
 
With the stainless steel bowl design i have seen different characteristics of crystal formations verses the plate designs. You have one side facing the anode and one away from the anode 50/50. Seems to cause an imbalance in crystal formation on the side facing away. Voltage has to rise to get more amps into the cell. With the bowl design every bit of the cathode surface is facing the anode with pretty much the same direction and distance. You can create more current density this way. This will lower the voltage while increasing the amps. On the Anode side we can help with the current density by increasing its surface which leads to Higher amps and lower volts. That's why the shot method was chosen as the most efficient method of efficiency for this design. More surface are on the anode means higher current density. with bars you get less surface area and less current density. You get about the maximum efficiency and crystal density while minimizing other metals that might be in the solution from plating with you silver and contaminating you crystals in the bowl design. We work too dam hard for those things. The next thing to cover is the filter or membrane barrier. You want the weave to be just tight enough to catch the debris, but not so tight it restricts flow of electrons. This would cause a rise in voltage to maintain the amperage at the same level. This can lead to stretched crystals. Then there is 2 or 3 other things that happens in the solution i won't go into. If you want denser crystal formations you can run it till the bowl frosts up then lower you voltage after that happens. You can get some good current at low voltage wile still having maximum impact. Once that frost starts the surface area of the cathode can be calculated as the surface area of the crystal surface times god knows how much. The surface area of the crystal in the reference of cathode to anode surface area is over whelming in favor of the cathode. Might even throw a kicker of Tartaric acid in there for favor. Increase your solution strength. Set that voltage about 1.5 and step away for 30 days.
 

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Your crystal structure is very long and stringy, that is not what I see when my cell is running. I'm curious what your volts are set to and how many amps are being pushed. (I would recommend measuring with a multi-meter, instead of looking at what is on your power supply). When my cell is running the stainless bowl would get a frost of small crystals all over it, then larger crystals would grow. I might end up with a tree or two for the shortest distance that I would have to knock down.

Elemental
 
My new cell, 9 liter 200gram silver/liter. 4.5 inch spacing all directions. But still making the same tree like crystals. The photo of the crystals are after 24 hours. Can it be the power supply? It is only able to put out 1.5 amp
 
Doesn't look like you basket is in the solution deep enough. You won't get good current density that way. Get a smaller bowl to where you can fill it with solution almost to the top leaving about 1/2 inch from the rim. Show us both connections for power and take a picture of your power supply so we know what you are using. Take a picture of the bottom of the basket also. You will get there in a minute.
 
Here is another good article for this thread.
 

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I am still growing the same tree like crystals after making lots of changes. Now I have ordered a new powersupply that will arrive today, I believe I need more amps so we will see. I made some bars and I think they became quite nice. With more experience, I think they will become even nicer.
 

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Nice pouring :)
Curious why you cannot achieve better crystal growth. Maybe there is some trace impurity which cause crystals to grow less dense. However, purity is probably unaffected, so most likely it is just aesthetic "issue".
Many times this happen when some organics are accidentaly mixed in, or some specific ionic impurity is in solution. Many times slight change in pH make huge difference.
 
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