Processing Sterling Silver without nitric acid

[nickton]

So what's the basic high school chemistry for producing copper nitrate?

Sorry in advance for being so dumb. :mrgreen:

I think I'LL LOOK IT UP.

 

[ION 47]

You might look in to carbon arc electrodes. Traditionally these are just copper plated graphite.

Obviously this was posted earlier by Butcher. To make this post worthwhile since I can't delete it....

I have read through the forum in relation to selective refining via voltage variation. It is my understanding that at higher voltages, you have a greater chance of copper deposition, whereas at the lower voltage the nitrate only reacts with the silver atoms.

With that, there was at least one patent which placed a third electrode in the solution, close to the anode, as you can then measure the voltage drop over the solution, as well as the voltage drop right at the transition. This effectively reduces the variation in cell design, but would also allow one to set up a simple PID controller to vary power supply output to match the potential needed to only drop silver. Has anyone on the board played around with such a beast?

The device is called a "potentiostat". I use it to process photographic solutions and extract silver. when little silver remains in solution, it is impossible to ensure the selectivity of the deposition.

 

[lazersteve]

Hi folks. Here is an update with images from my experiments. I have not been able to grow copper out of the cell. I tried using a copper tube for the cathode while using stainless steel for the anode, and it didn't grow red copper onto the tube. It doesn't really mater since I have been able to grow very pure silver crystals anyways. The title of this topic is misleading since you do need nitric acid in the whole process. I realized this is essentially a silver cell.

I tried using straight sterling for an anode, and as it dissolved the silver did not crystalize onto the cathode, but instead it turned into a grey powder ( just like LS's test ). So far I have been reusing the electrolyte solution and it seems to be holding up. I had processed some sterling in nitric acid, and simply poured the solution without cementing into the cell and nice silver crystals grew on the cathode. I also made some cemented silver anodes and replaced them as they dissolved in the cell. I did notice that eventually the electrolyte does tap out, and I can tell when it happens because crystals stop growing, and the solution becomes a crystal clear blue solution. Also the smell of nitric acid goes away, and it's hard for a new anode to dissolve in the solution. So I simply added some new ( silver cemented out ) copper nitrate solution into the cell, with a fresh new anode, and the process picked right back up again. Sometimes you can actually see the silver in solution as very tiny little specks of silver reflect light off of them. When you cant see them anymore it's about time to replenish the solution.

I am using a stainless steal spatula that I removed the wooden handle and bent into shape. It provides a lot of surface area for silver to grow off of. I put a 10 amp fuse on the cathode just in case of a short since I leave it on 24/7. The circuit pulls around 4 amps at 3v with a PC power supply. I am using a plastic bottle for an anode slime trap, and it seems to be working well. It also shields the anode from any potential short.

Copper nitrate solution can be formed without using silver via

Copper sulfate + calcium nitrate = Copper nitrate (aq) + calcium sulfate(s)

CuSO4 + Ca(NO3)2 --> Cu(NO3)2 + CaSO4

After filtration and evaporation to 6M use this Copper nitrate solution in kick starting the Cell without the need for nitric proper.

I have detailed the closed loop nitric process as I have called it elsewhere on the forum.

Steve
Edited Ca(NO3)2 correction

 

[BGDOCK]

Hello I like this concept of reusing copper nitrate and running a silver cell. I copied your post/notes looking for the graphite cathode now.
Did you ever make a video of this ?
Thank you

 

[lazersteve]

I have not.

Steve

 

[BGDOCK]

I started the copper nitrate cell tonight . I had used Sterling silver that was poured into shot in my anode bag. It’s been running for a few hours now and the copper sheen on the shot is gone ( into solution)
My first cathode was a piece of stainless it had plated copper on it. I realized my mistake and switched it out for a graphite cathode .
Running 2 VDC .4 A
It looks like I’m dropping silver out like cement not crystals like you see on the cathode of a silver cell.

 

[BGDOCK]

Top View the Sterling silver shot in basket looks like the copper is stripped off already ?