I am trying to purify my silver nitrate. The impurity is copper. I would wash it with alcoholic ammonia, but I've heard bad things about the
safety and stability of AgNO<sub>3</sub>/NH<sub>3</sub> solutions.The_Davster - 9-4-2005 at 16:34
Possibly...
Add NaCl to precipitate AgCl, and filter it out. CuCl2 is soluble so you are just left with AgCl. Wash it well. Dissolve it in nitric acid and
evaporate to get AgNO3 crystals.HNO3 - 9-4-2005 at 17:23
I'd rather not have to try a thermit. I'm afraid with your method the chloride won't leave, and I'll be left with a nitric
acid/silver chloride solution. I dunno.The_Davster - 9-4-2005 at 17:41
Hmm, now that I think about it, the equilibrium would favour the nitric acid/silver chloride solution instead of silver nitrate and HCl. You could
electrolyse the solution with carbon electrodes, the silver would plate out first on the cathode. Problem is that if you run the electrolysis for too
long copper would plate out ontop of the silver. Actually, this is not so much of a problem, just continue the electrolysis untill copper starts
plating out on top of the silver, then place this electrode in dilute nitric acid to dissolve the layer of copper. You are left with silver on a
carbon electrode, which can be dissolved off using hot concentrated nitric acid, leaving you with a solution of pure silver nitrate(and possibly some
carbon particles which can be filtered out).neutrino - 9-4-2005 at 18:34
There's a very simple solution: crystallize and wash with EtOH. The copper nitrate will wash off with a little silver, but you'll still have
the bulk of your silver left. If you really want that last little bit of silver, add some copper, separate the silver crystals, and redissolve in
acid.
P.S. Silver nitrate stain are almost impossible to wash out (you should see my countertop), so be careful. Just because it doesn’t seem to be there
doesn’t mean it isn’t.
[Edited on 10-4-2005 by neutrino]azaleaemerson - 12-4-2005 at 05:50
I can't find it for Cu nitrate, but Ag nitrate is soluble at (in 100mL % ethanol):
4g at cold 95%
10g at cold 80%
18g at hot 95%
42g at hot 80%
azaleaunionised - 12-4-2005 at 10:59
A straightforward recrystalisation from water should work. Water/alcohol would be easier to work with but beware that AgNO3/ organic trash can explode
on heating.
"If you really want that last little bit of silver, add some copper, separate the silver crystals, and redissolve in acid.
"
I wonder how close that is to why he has some silver nitrate conaminated with copper in the first place.Tacho - 12-4-2005 at 11:13
Dissolve the nitrate and boil away most of the water. White cristals will form. Filter away the blue solution (copper ions).Esplosivo - 12-4-2005 at 11:25
I have done the following many times now, although on a small scale. Place a pure copper wire (use the ones from wires) in the solution. Leave the
copper immersed in the mixture for some time (I usually leave it for a couple of days, even a week). Preferabbly use more than one wire. A silver
'tree' will form which can easily be sraped from the copper wire. Redissolve this silver by adding conc. nitric acid (pure) and crystallize.
Viola... you've got very very pure silver nitrate. Hope this helps.neutrino - 12-4-2005 at 13:00
Copper (II) nitrate is much more soluble in EtOH than silver nitrate. I don’t remember the exact figures, but I think it was somewhere around 10x.HNO3 - 12-4-2005 at 14:27
Quote:
"If you really want that last little bit of silver, add some copper, separate the silver crystals, and redissolve in acid.
"
I wonder how close that is to why he has some silver nitrate conaminated with copper in the first place.
Actually, my first copper contaminated silver nitrate came from United Nuclear's "99.999% pure silver". After that I went to a silver
coin. No, my nitric acid is not contaminated with copper.
