Blogfast25:
I’m having a bit of silver trouble right now with fairly freshly precipitated AgCl that seems resistant to dissolution in (> 25 w% ammonia. I would have thought it would dissolve in that solvent effortlessly but
part of it resists the ammonia. Any thoughts, anyone? I’m loathe to heat it because the ammonia stench would be unbearable…
Quote: |
If it won't dissolve in ammonia, then it is lead (II) chloride. This can be removed by boiling in hot water, or else just smelting the silver with
sodium nitrate, sodium carbonate, and silica (2:1:0.5).
We run sterling electrolytically. Every 10,000 t oz there is between 4-5 t oz gold, 0.2 t oz Pt, 0.5-1 t oz Pd, usually some rhodium if it has been
plated, and always a hefty proportion of lead oxides that stay in the anode bag.
Silver metal doesn't really have a visible oxide in air nor one while melting it.
Its oxide is useful if you start from silver chloride and need to cast anodes, other than that, stay away from AgCl.
Much more convenient to do for high purity silver from sterling is to use a saturated solution of sodium formate at 60-70 Centigrade and pH 3 (it'll
raise the pH). This gives a heavy silver sand of high fineness. Before adding the formate, be sure to add a few mL sulfuric acid and then filter it
and the gold out. The residues should be retained until there is enough to merit processing.
| |