kwpooh
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Disposal of a solution of silver nitrate / ammonia
Anyone know how to deal with old silver nitrate ammonia solution?? I really do not want any explosion....
Edit: Changed title to something more descriptive...
[Edited on 21-2-2005 by chemoleo]
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kwpooh
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silver azide
anybody familiar with silver azide? how to deal with it without explosion???
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chemoleo
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If it is still a solution, with no precipitate you have nothing to fear, as the Ag nitride (not azide) is insoluble.
EDIT: STOP CROSSPOSTING!
[Edited on 21-2-2005 by chemoleo]
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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kwpooh
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oh yeah?
so it should be okay that I drop some HCl to remove the silver ??
I am really scared to touch those 'bombs'.
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chemoleo
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IF there is no black precipitate (or any precipitate for that matter) it should be pretty safe.
I'd always test it with a small amount first, regardless.
I'd rather use NaOH though and precipitate it as Ag2O, which can be reused more easily I suppose.
[Edited on 21-2-2005 by chemoleo]
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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kwpooh
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well, what do you guys do with the waste? can i just discard throw the drain or i have to use HCl and collect the waste.
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JohnWW
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Because of the value of Ag, if it is a large quantity, you should look at possible ways of recovery of the Ag, e.g. by either electrolysis, or
precipitation as Ag Cl.
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neutrino
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You can’t drop the silver out of solution with the chloride ion if there’s ammonia present. Iodide would work and I’m pretty sure that bromide
would, too.
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kwpooh
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actually, i did use HCl for the fresh prepared silver nitrate ammonia solution, and precipitated AgCl. But I am not sure if I can use it for the old
solutions...
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unionised
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In the presence of excess HCl there isn't any ammonia present, it gets protonated.
Silver chloride isn't difficult to smelt back to silver.
I'm pretty sure that NaOH wouldn't work. I have made solutions like this starting with silver oxide, and dissolving it in an amine.
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neutrino
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That’s right, acids tend to protonate ligands. Sorry about that.
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tgenade
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Hello,
I've been a very silly chemist and just very nearly got my head blown off by a silver nitrate/ammonia solution.
KOH precipitation does definitely not work. It did drive off some of the ammonia though which is what I was hoping...
I had tried this to reclaim the silver and had managed to get a lot of precipitate which I am already drying (which has me very worried) but probably
has a lot of of the Ag nitride in the mix. I also have a lot more of the solution in the fume hood (which is now a god-awful mess).
1. Can I add dilute KI to the solution to precipitate the silver?
2. Can I submerge the dried silver salts into KI solution?
Thanks
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The WiZard is In
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Quote: Originally posted by kwpooh  | | Anyone know how to deal with old silver nitrate ammonia solution?? I really do not want any explosion.... |
Anyone know?
The analogue guy knows (of a reference).
Fair use ... or “The Morality of Convenience” (If it’s convenient ... it’s moral!)
From: Mirrors: A Guide to Manufacture of Mirrors and Reflecting Surfaces
Dr. Bruno Schweig
Pelham Books - London 1973
Danger of Explosions
Unexpected explosions have frequently occurred in silvering shops, to the surprise of the
operators and their employers. The people concerned were rarely in a position to account
for the cause. The present author was repeatedly asked in court cases to explain what
happened, and why. On one occasion an experienced silverer received severe eye
injuries, on another the silvering equipment was destroyed by a night-time explosion, and
on a third a schoolboy lost the sight of one eye when he to make a mirror for his physics
teacher. In all these cases fulminating silver was formed.
Fulminating Silver and its formation was first detected and named after the French chemist
Count Claude Berthollet in about 1770. Crell describes Berthollet's experience in 1788 in
Annalen, der Chemie Pharmacie 2, p. 390. F. Raschig, in Liebig's Ann., 1886 (233), p. 93 e
a full study of it. Dr. W. Friedel in Centralzeitungfor Optik und hanik, March 20th, 1928,
published a good report on the dangers xplosions when silvering, and concluded that the
danger of formation of fulminating silver only exists if concentrated solutions of silver nitrate
and ammonia come together, and that the probability that fulminating silver precipitates is
greatly enhanced by the presence of strong sodium or potassium hydroxide solutions.
These observations tally to a great extent with those of the present author. As far as his
experiences go, over a period of thirty-five years, there was never an explosion from
fulminating silver when silver nitrate and ammonia alone were mixed, independent of their
strength. He has, however, read that such explosions occurred when the mixture was
heated on a water bath.
But fulminating silver was formed and explosions took place when strong alkali
hydroxides were present, or when the solution became concentrated through evaporation.
A similar conclusion was reached by the Pittsburgh Plate Glass Co. of U.S.A. in 1955, i.e.
that:
(1) Explosions are not produced by adding concentrated ammonium hydroxide (ammonia)
to solid silver nitrate.
(2) Addition of sodium or potassium hydroxide to the silver-ammonia complex definitely
increases the tendency to form explosive material. The action of the alkali hydroxides is not
quite clear, but may be explained by their tendency to displace ammonia.
(3) A very high alkalinity of pH 15 appears to favour formation of explosive. The pH of
usual silvering solutions is about 13-4. The dangerous pH region starts at about 14-5.
(4) Although the concentrated silver-ammonia complex appears not to form fulminating
silver, it is recommended to dissolve silver nitrate in water before adding ammonia.
(5) Therefore, silvering solutions should not be stored, and under no circumstances over
longer periods such as weekends.
Dr. Eduard Lohmann had already expressed the same opinion in 1931, in the Journal
Diamant, No. 33. And the British Ministry of Labour Factory Department is even more
cautious. It postulates that the silver ammonia solution must not contain more than 6%
silver nitrate.
Fulminating silver is a black precipitate. It consists mainly of silver nitride (Ag3N) and
silver imide (Ag2NH) and possibly also of silver amide (AgNH2). It is often mixed with
metallic silver. When left alone for a few months, it tends to lose its nitrogen component
and to change completely into harmless silver powder. Fulminating silver can be regarded
as an ammonia whose hydrogen is wholly or partially replaced by silver. It is not silver
azide (AgN3) a white precipitate which is also explosive; it forms under different
circumstances to this.
The danger of bringing these exploisves substances to a weighing machine makes their
analysis difficult. According to Dr. W. Friedel, Centralzeitung fur Optik und Mechanik,
Berlin, March 3rd, 1928, the formation of fulminating silver from silver nitrate and ammonia
may take place in this fashion, as earlier formulated by F. Raschig in 1886 (Liebigs
Annalen, 233, p. 93).
3 Ag(NH3)2-NO3 = Ag3N + 3NH4NO3 + 2NH3
Silver Ammonia Silver Ammonium Ammonia
Nitrate Nitride Nitrate
and
2 Ag(NH3)2-NO3 = Ag2NH + 2NH4-NO3 + NH3
Silver Ammonia Silver Ammonium Ammonia
Nitrate Imide Nitrate
and
Ag(NH3)2-NO3 = AgNH2 + NH4-NO3
Silver Ammonia Silver Ammonium
Nitrate Amide Nitrate
To conclude, it may be pointed out once more that diluted solutions of silver nitrate with
ammonia and alkali hydroxides are harmless, but they must not be allowed to become
concentrated. They no longer present a danger when the reducer is added and the silver is
precipitated as a mirror or as silver powder.
The black precipitate of fulminating silver must not be confused with the harmless
dark-brown-to-black silver oxide [Ag2O] which forms when insufficient ammonia is added to
the silver nitrate solution.
If, however, any suspicion of the presence of fulminating silver is aroused, extreme
caution is imperative. Under no circumstances must the vessel be moved or shaken.
Fulminating silver, whether dry or wet, explodes at the slightest touch.
In order to eliminate the danger, diluted hydrochloric acid should be added until the
solution becomes acidic, and the fulminating silver is converted into silver chloride. The
operator should approach the suspected vessel behind a screen of thick glass, protect his
eyes and hands, and add the acid carefully. It is better to destroy and discard the ful-
minating silver than to run an often underestimated risk.
[Edited on 6-5-2011 by The WiZard is In]
[Edited on 6-5-2011 by The WiZard is In]
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