Cementing Silver

[g_axelsson]

To get rid of excess nitric. If too much nitric in the mix you would dissolve extra copper and cement your silver from a dirtier solution, increasing drag down of copper. He also claims that higher pH (less free nitric) creates bigger crystals that is easier to clean and by crystallization also pushes contaminants out. (Compare to repeat crystallization as a refining method)

Göran

 

[amesametrita]

Good advice

 

[kjt124]

I had to jump in on this because I had what I thought to be a fluke happen a second time. Sorry for being somewhat off topic, but at least in an appropriate threat...

I've been using the copper strapping you would use to hang plumbing in your basement (happens to be what was on hand). After an embarrassing first attempt I figured out pretty quickly to burn off the lacquer coating from them before cementation.

Anyway, the last 2 cementation attempts I did were from rather concentrated solutions, roughly 80% of saturation. I took some advice from amesametrita and held the pH right around 3 or so with a few drops of nitric a couple times and got absolutely beautiful silver crystals that were dense, well formed, non-adherent, rinsed very easily, and melted like butter.

However, about half way through (half the expected silver dropped) the copper strapping got silver plated. It was a very nice looking very shiny, almost polished looking solver plate on copper. Of course it stopped cementing any additional Silver.

Obviously I can hit it with nitric and get my little bit of silver back. Also, I was in a hurry and hit the rest of the solution with HCl (in retrospect I should have heeded the warning of many on here and avoid Silver Chloride at any cost).

Can anyone tell me what happened in this solution? The feed stock was a bit of dirty cemented silver (too much copper) and some silver nitrate crystals so I can't imagine there was much in the way of foreign contaminants. The only thing I can think of was too high a concentration in solution. The only other possibility I can come up with is that it is quite cold where I have it set up, but it can't be below 45-50 F.

Thoughts?

 

[jonn]

The copper plumbing strap is Not copper all the way through. Usually those are copper plated steel or an alloy of steel. Something to be mindful of.

 

[kjt124]

Looking closer at them (in better light) I was starting to suspect that what I was looking at was not actually silver plate, but another metal entirely. It wasn't making much sense in my head that you would copper plate something like that, but I would suppose if there is a few pennies to be saved by making it mostly out of steel then that's how it would happen.

Thanks for the heads up / confirmation. I'll keep an eye out for better (free, hopefully) copper stock.

 

[bgp_scrap]

Hey, if it hasn't been said yet. Drop your silver with table salt, (nacl) to precipitate agcl. Then evaporate your cl's off, or use sulfic acid, as stated in hokes book.
Hope this helps a little more than the copper cementing.

 

[Smack]

Hey, if it hasn't been said yet. Drop your silver with table salt, (nacl) to precipitate agcl. Then evaporate your cl's off, or use sulfic acid, as stated in hokes book.
Hope this helps a little more than the copper cementing.

I disagree, making silver chloride is not as desirable for the simple fact it creates more steps to get the same results.

 

[Palladium]

And waste ! What do you mean evaporate the chlorides off. I think you may have a couple of things confused.