Silver Stalemate

[Mingo]

Hello all;
I have just precipitated 4 oz of silver ?chloride? using the method Noxx outlined for photo-grade silver. I started with Sterling from some old Sterling flatware and various necklaces (the hallmarks were in place and stannous tests affirmed same) I followed the procedure closely, washed with hot water 5 times to rid as much lead as was possible, also added 10 ml H2SO4. I treated with industrial strength ammonium hydroxide to digest, added HcL to break the bond, filtered, washed as was required and then treated with KoH to proceed to the oxide.
I now have a nice uniform light gray powder. When I ran a test melt, all I get is a reddish slag. I tried this several times and decided to start over. I added the 50-50 mixture of 70% nitric and water and absolutely nothing will react with this powder. Why? I am now using the copper cementation method with good success, but I need to save these 4+oz''s.
Any help is always appreciated. This is my first real run with silver.
Regards, Tim

 

[lazersteve]

Tim,

Red slag and lots of smoke is a sign of silver chloride. This means you are not getting the chloride converted to oxide.

Steve

 

[Mingo]

What do you suggest sir? I have tried KoH.....should I try sodium carbonate and baking?

 

[lazersteve]

If you still have the bulk of the moist brown powder then you can finish the conversion by adding more water and hydroxide followed by cane sugar and lots of stirring, then rinse/settle throughly several times.

If it's all been melted then remelting with soda ash may convert some of the silver/slag to silver metal.

Be very careful of the white fumes when melting silver!

Steve

 

[Mingo]

Thank you LazerSteve! I did manage to save this silver using (sodium) hydroxide instead of the (potassium) hydroxide.......I don't understand the chemistry of that (I am trying to learn the chemistry of all these reactions) , but after the conversion I melted with lots of Borax and Bicarbonate of Soda and got a very nice, clean result.......although I did lose some values in the process.
"The proof is in the pudding"............truer words never spoken :wink:
-Regards, Mingo-