Tacho
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Silver nitrate from silver and acid - a writeup
If I ever had to do a quick set of chemistry demonstrations, I would use silver nitrate. It easily makes mirrors, explosives, photo-sensitive stuff,
grows silver crystals on copper and makes beautiful precipitates. Besides, it teaches you a lesson about being careful with chemicals: even if you
think you were careful, the black spots in your fingers in the next day make you wonder "what if that was a more dangerous compound..."
Silver nitrate is quite expensive, and one can save some money using pieces of commercial silver and nitric acid.
I’ll report MY experience and MY (maybe wrong) conclusions:
1- The reaction between silver and the acid may not be immediate, may require some heating. Diluted acid seem to work best.
2- Poisonous brown fumes evolve, make sure you stay away from them.
3- When the reaction is over (silver no longer fizzes the brown fumes) don’t assume your acid is depleted. In my reaction, the solution would no
longer attack silver, but would attack copper violently. I presume it’s because it was saturated with silver nitrate as I’ll explain later.
4- The solution is blue, because commercial silver has copper in it. To obtain pure white silver nitrate, I decided to distill away about 70% of it.
Edit1: That is: boil away most of the solution so that it gets over saturated and the silver nitrate crystalizes as it cools.
5- Due to a failure in my heating device, I could only distill about 10% of it in the first day. Even then, next morning, lots of white crystals were
in the cooled flask. Hence my conclusion that the solution was saturated.
6- During the final moments of distillation, after turning off the heat, lots of brown fumes formed in the flask and, when opened, steam-like acid
fumes evolved. Be careful!
7- The white crystals are big, beautiful and easy to separate. I filtered them with fritted glass filter, but decanting may be an option. I tried to
filter the hot solution with paper filter and it dissolved away.
8- The distillate (the liquid that condenses) is a solution of nitric acid. The blue liquid that’s left is a mixture of acid and copper nitrate.
9- Poisonous fumes; hot strong acid maybe concentrated; silver nitrate is also not very nice to the skin and definitely not nice to your eyes... So:
you can easily hurt yourself, and it’s very likely that you go blind if you don’t protect your eyes. THIS IS NOT A CASUAL EXPERIMENT!!!
In retrospect, the whole thing was quite successful. I got lots of relatively pure silver nitrate.
It seems I used too much acid though.
[Edited on 21-5-2004 by Tacho]
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JDP
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hmm, I've never heard of heating the AgNO3 to distill anything off of it; were you just trying to get the excess HNO3 out of it? Wouldn't
heating the AgNO3 lead to decomposition?
Whenever I go about making AgNO3 I just go to the local coin shop and buy some .999 silver. Then I just dissolve it in an adequate amount of HNO3, let
it cool, once all the mixture has come to an ambient temperature, just spread the crystals out in a Polypropylene container and let the extra HNO3
vapor off naturally.
Edit: Worded it a bit poorly - Sorry.
[Edited on 21-5-2004 by JDP]
~JDP
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Tacho
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(sniped by edit)I edited the text to make it more clear.
Your method is, no doubt, better.
The whole idea is save money using old cheap silver scrap you don't want anymore.
This post was edited many times.
I didn't want to be rude... well, I wanted to be rude, but I changed my mind, ok?.
[Edited on 21-5-2004 by Tacho]
[Edited on 21-5-2004 by Tacho]
[Edited on 21-5-2004 by Tacho]
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I am a fish
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Silver(I) nitrate is more soluble that copper(II) nitrate. Therefore, it is likely that your blue solution still contains a significant amount of
silver.
If you add sodium chloride solution, silver(I) chloride will precipitate out. (Make sure that your solution is sufficiently dilute, otherwise
copper(II) chloride will also precipitate). This precipitate can then be dissolved in ammonia solution to give a solution of diamminesilver(I)
chloride. This can be reduced by an aldehyde (such as glucose), causing pure elemental silver to precipitate out.
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