SFA

Re: Carbonates treatment for silver cyanide solutions

I remember a conversation with my good friend Dr. Kushner where he said something along the lines of the fact that these potassium carbonates can be removed from your silver bath by treating it with any of the following chemicals: calcium nitrate, barium cyanide, calcium sulfate, calcium hydroxide, calcium cyanide.  As far as the actual procedure goes, maybe one of the other members here can help with that.

I would suggest, that as you would with any other plating tank changes, you test this with a small sample before you go at the tank, and make sure you have a proper analysis before you do anything.  And also don’t forget to look for what is causing this problem so you can attempt to minimize it in the future.  A couple of places that you can look at towards minimizing it in the future would include to not using a return dragout tank, and maintaining a tank temp of 70F, fine silver anodes, and by bagging your anodes. 

Good luck!

jimtrottier

Re: Carbonates treatment for silver cyanide solutions

Removal of carbonate can be accomplished by crystallizing at low temptures ( known as" freezing out") or precipitation with calcium or barium salts followed by careful and thorough filtration.

This is a quote from the finishing bible.

   Jim

SFA

Re: Carbonates treatment for silver cyanide solutions

Hey Jim, I'm a big fan of the Metal Finishing Guidebook and Directory (MF Bible) too...and have not reached for it yet... but I thought that potassium carbonates was a different animal??

jimtrottier

Re: Carbonates treatment for silver cyanide solutions

   Potassium carbonate is a main component of this bath and is only added at bath make up, the potassium cyanide when oxidized produces potassium carbonate whitch grows in this bath over time even when the bath is idle.

   Jim

DustinGebhardt

Re: Carbonates treatment for silver cyanide solutions

I agree with Jim on the freeze out method.  Although depending on the level of the carbonates, you may be better off making up a new bath after reclaiming the silver.

-Dustin Gebhardt, CEF

Advanced Manufacturing/Finishing Engineer

Moen

Sanford, NC