Seperating Copper nitrate and silver nitrate solution.

[eamonn58]

I am experimenting on a problem. I have dissolved a silver coin (50% silver 50% copper) in nitric acid. and after filtering I have a nice clear blue solution.
I am interested if there is a way to selective remove the copper leaving me with silver nitrate (or a silver solution that I can precipitate elemental silver.
I am familliar with dropping silver chloride with salt soln but that would require a lot of extra processing to get back to a silver solution.
I did think of adding calcium/sodium flouride as silver flouride is soluble and copper flouride,not so much.
I dont know if I can use my process on the silver flouride to get the type of fine silver i need.
But I thought I would ask here first before I buy some flouride salt.

Any thoughts greatly appreciated.

Cheers
Eamonn

 

[canedane]

If you want the silver , just put a clean copper wire in your solution, and the silver will drop. Then you will have a copper nitrate solution.

 

[butcher]

Copper being more reactive than silver makes removing copper and leaving silver in solution very difficult.
Consider:
Adding a bar of copper cement your silver, now you are left with primarily a copper nitrate solution.

Now that you have elemental silver you can put back into solution if that is what you wish, or refine it further or melt it...
From here you have a solution of copper nitrate you can recover elemental copper from, or you can convert it to other useful reagents of copper salts such as copper sulfate, or you can use to make nitric acid...

 

[g_axelsson]

One way you can separate the two nitrate salts are by crystallization. Copper and silver nitrate will form crystals of one salt only, then you could just pick the crystals off and manually sort them. Slow crystallization forms larger crystals.

This is the separation I managed to do over some time (months). Copper nitrate to the left and silver nitrate to the right. Yes, there is concentrated silver nitrate solution in the evaporating dish to the right.



This method is tedious and takes long time, but it is possible to do it in several steps to get quite pure material. Mechanical drag down (inclusion) will make it far from ideal but over time it will work.

I've done it once out of curiosity, but now I cement all my silver nitrate on copper, it's easy and fast.

Göran

 

[butcher]

Recrystallization will make a purer product.

Wow, Goran,

Now that is cool, I have recovered salts using crystallization methods but those salts or solutions were much simpler to separate and took a lot less time and trouble, I never even thought of trying it with copper and silver...

I

 

[eamonn58]

Thanks for the advice guys.
I knew about cementing the silver but I want to reduce the steps to get back to pure silver nitrate.
I will try to crystalise and seperate the crystals then i might be able to recrystalise with more concentrated impure silver nitrate and get it really pure. It might be more work than it worth seperating those crystals but Ill give it a go.
Thanks
Eamonn

 

[goldenchild]

Are you trying to make silver nitrate in aqueous form or crystal form? Either way you're better off dropping the silver out with elemental copper first. You'll then perform good washings to remove the copper chloride and then react the now elemental silver again. I wouldn't waste time trying to remove aqueous copper from aqueous silver. If that's even possible.