HNO3
Hazard to Others
Posts: 211
Registered: 10-11-2004
Location: America
Member Is Offline
Mood: No Mood
|
|
Purification of silver nitrate
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.
\"In the beginning, God...\" Wait a minute, God doesn\'t exist!!!!!!!!!! \"OK, in the beginning, ummm, hydrogen...\" Wait a minute, what about the
laws of thermodynamics? \"OK, in the beginning, ummm.....UMMMMM, what\'s left to choose from?
|
|
|
The_Davster
A pnictogen
Posts: 2861
Registered: 18-11-2003
Member Is Offline
Mood: .
|
|
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
Hazard to Others
Posts: 211
Registered: 10-11-2004
Location: America
Member Is Offline
Mood: No Mood
|
|
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.
\"In the beginning, God...\" Wait a minute, God doesn\'t exist!!!!!!!!!! \"OK, in the beginning, ummm, hydrogen...\" Wait a minute, what about the
laws of thermodynamics? \"OK, in the beginning, ummm.....UMMMMM, what\'s left to choose from?
|
|
|
The_Davster
A pnictogen
Posts: 2861
Registered: 18-11-2003
Member Is Offline
Mood: .
|
|
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
International Hazard
Posts: 1583
Registered: 20-8-2004
Location: USA
Member Is Offline
Mood: oscillating
|
|
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
Harmless
Posts: 27
Registered: 8-4-2005
Location: AR
Member Is Offline
Mood: No Mood
|
|
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%
azalea
azalea
|
|
|
unionised
International Hazard
Posts: 5128
Registered: 1-11-2003
Location: UK
Member Is Offline
Mood: No Mood
|
|
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
National Hazard
Posts: 582
Registered: 5-12-2003
Member Is Offline
Mood: No Mood
|
|
Recrystalization from water! Check this.
Dissolve the nitrate and boil away most of the water. White cristals will form. Filter away the blue solution (copper ions).
|
|
|
Esplosivo
Hazard to Others
Posts: 491
Registered: 7-2-2004
Location: Mediterranean
Member Is Offline
Mood: Quantized
|
|
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.
Theory guides, experiment decides.
|
|
|
neutrino
International Hazard
Posts: 1583
Registered: 20-8-2004
Location: USA
Member Is Offline
Mood: oscillating
|
|
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
Hazard to Others
Posts: 211
Registered: 10-11-2004
Location: America
Member Is Offline
Mood: No Mood
|
|
| 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.
\"In the beginning, God...\" Wait a minute, God doesn\'t exist!!!!!!!!!! \"OK, in the beginning, ummm, hydrogen...\" Wait a minute, what about the
laws of thermodynamics? \"OK, in the beginning, ummm.....UMMMMM, what\'s left to choose from?
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
