# Big bad silver deplater



## SapunovDmitry (Jul 25, 2014)

Allright folks. It's brainstorming time.
What would i do without our forum.  
The problem:
It is about stripping silver out of stainless steel (66% Fe, 33% Ni).
The solution i have used is the following:
1 liter of about 55% nitric acid + 10 liters of tap water.
I put the piece of stainless steel(4,5 kg) in the solution for 2 days.
After 2 days stainless steel is completely stripped of the silver and ready for further recycling. It is the good news.
The bad news is that i have a 11 L solution with 4.5 gr/liter of Ag and i want to cement it out badly (other metals are Cu - 5 gr/l, Fe - 3 gr/l, Ni - 2 gr/l, Pb - 0.75 gr/l).
So i do what i have to do. I put copper bar in the solution.
And i wait, and i wait, and i wait (for 3 days).
Guess what?
Nothing happens, but copper bar thins.
I wait another week and guess what?
Right! 
Nothing happens, but bar thins.
So it took me a week to understand that i have excessive nitric in the solution.
Great!
Now the question is: 
Can i use Soda (Na2CO3) to get rid of the excessive nitric.
And more important when do i stop if i can?
Should i continue cementing out silver with copper? (It takes too long to cement out silver using this approach as i suspect (I hope i am wrong))
I DO NOT want to use silver chloride method in this case.
I think maybe precipitation of silver as carbonate using controlled pH could go good.
I am really stuck.....
If anyone could give some advice i would be very grateful.
Thanks in advance.


----------



## nickvc (Jul 25, 2014)

Is this a one off or for continual processing of these silver plated stainless plates?
With such a small amount of silver if you can just keep using the solution until it ceases to work and reclaim the silver later, turning it into a chloride would be easiest and in small quantities not too hard to handle.


----------



## goldsilverpro (Jul 25, 2014)

SapunovDmitry said:


> Allright folks. It's brainstorming time.
> What would i do without our forum.
> The problem:
> It is about stripping silver out of stainless steel (66% Fe, 33% Ni).
> ...


If this is a one-batch deal, I would precipitate the silver with a chloride and then use Karo (corn) syrup/sodium hydroxide to convert the AgCl to Ag. I have given the complete procedure several times on the forum.

If this is on-going and there are more batches of the same material to be run, you can use the same solution and make proper nitric additions when needed. When all has been run, drop the silver as AgCl.

I usually avoid AgCl but it's absolutely the best way to go in this case.

Nick,

I wasn't trying to rain on your parade. Before seeing your post, I had already written mine. Looks like great minds think alike. :lol:


----------



## solar_plasma (Jul 25, 2014)

Why don't you want to make silver chloride? In this case it is the cheapest and most direct way to get the silver. If you precipitate by pH control, you will co-precipitate some base metals. If you go on using copper in your large excess of extremely diluted nitric it will take very long time - weeks at least I would assume. And you will have to dissolve a lot of good copper.

Of course cement silver or silver oxides are easier to handle, but in this special case the silver chloride route is the way of choice. I am curious, what others will say.

EDIT: Oh well, GSP has been faster than me :lol: Since I am a little bit proud of having been close to a master's advice, I post it anyway. 8)

EDIT2: ....wow, even two seniors! :lol:


----------



## SapunovDmitry (Jul 25, 2014)

Oh boy.... Guess i will have to use chloride route. I am not against it. I just don't want it because you need to boil silver chloride precipitate for it to coagulate and fall down properly and completely. Has anyone any experience in coagulating silver chloride from dilluted solutions? What can speed it up except for heat?


----------



## solar_plasma (Jul 25, 2014)

I have never counted the time, but it is not that bad. I know for sure, after a week the solution is clear, but I guess most often it takes only a day for the last mg. Most of it will be down after an hour.

No big deal, it's more that silver chloride takes its time to get filtered (best with vaccuum and buchner funnel) and washed, ten cycles or more are surely usual, until all copper is gone. Much worse than gold, much better than any nasty hydroxides.


----------



## kurtak (Jul 26, 2014)

evaporate your 11 liters down to 2 liters - add a drop of HCL - if the drop of HCL doesn't make a nice heavy Ag/CL curd - evaporate down to 1 liter

the more concentrated the solution the heaver the precipitate - the more dilute the solution the finer the precipitate

Kurt


----------



## goldsilverpro (Jul 26, 2014)

I see no reason to evaporate. The AgCl will settle. With 11 liters, I would stir it first and then let it settle in a bucket, on a bench, tilted toward me with a piece of 2x4 underneath the back of it. When settled, I would then syphon off the solution. Shouldn't take more than 2 days, at the outside. Not meaning to get religion into it but my main mentor always advised (at least daily), "Let God (gravity) do it".


----------



## SapunovDmitry (Jul 26, 2014)

Allright. Today I tried Chloride in a test bucket and it failed. Yes, the solution was white and Yes, it settled down, but just a bit (say 80%, and that's bad). It settled only in presence of excess nitric and silver ions. I think it didn't settle because concentration was not good enough.
(Since I have less than 1gr/liter of lead it couldn't be lead chloride since it has 10 gr/liter solubility in water.)
You know, i didn't gave up and started to raise pH of the solution with Na2CO3 (Actually it was a washing powder called "Calcinated soda"). When pH was about 2,5-3,2 i put copper bar in the solution and it happened.
Copper bar was black and muddy. At first I saw with my own eyes how silver dropped out of the solution on the bar and then dissolved at the bottom of the jar and after a while dissolution stopped, but dropping out continued. 
So now i am a happy owner of a jar of olive-light brown liquid and black/metallic/a bit of dark brown precipitate.
I will let it settle for a day and then smelt it with borax, quartz and soda to remove copper and iron oxides from the bar. I hope to bring you photos of the process on tuesday, maybe wednessday.

Dmitry


----------



## solar_plasma (Jul 26, 2014)

Test the left over liquid for silver. I guess it will take some time to cement all silver.

Silver chloride doesn't fail. As I said, most of it will settle within an hour, the rest may take days, but not more.


----------



## Geo (Jul 30, 2014)

I see no reason you can't use sulfamic acid to neutralize the free nitric. Warm the solution and add small amounts of sulfamic acid dissolved into distilled water until there is no more reaction. The byproducts are NO gas and sulfuric acid in solution. This should make it possible to cement the silver out using copper.


----------

