mewrox99
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Diaminesilver complexes
I'm thinking of playing with some [Ag(NH3)2]+ClO4- and some [Ag(NH3)2]+NO3-
Does diaminesilver share the same explosive properties as tetraminecopper?
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woelen
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It is much more dangerous. The danger is not in the anionic species (be it nitrate, perchlorate or whatever ion), but in the silver-ammine complex
itself. Ammoniacal silver tends to form so-called "fulminating silver", which most likely is (very impure) silver nitride. Fulminating silver is a
dark brown solid, which is EXTREMELY sensitive to mechanical agitation. E.g. if a small crystal of this breaks in two parts, or two crystals touch
each other accidentally, then this may cause an explosion.
Fulminating silver is formed slowly, when an aqueous solution, containing the [Ag(NH3)2](+) ion is allowed to stand for a while. For this reason, one
never may prepare Tollen's reagent (which is an ammoniacal silver solution) a long time before it is used.
Fulminating silver must not be confused with silver fulminate (a well-characterized white crystalline solid with formula AgONC, which also is
explosive).
[Edited on 7-6-10 by woelen]
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The WiZard is In
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Quote: Originally posted by mewrox99  | I'm thinking of playing with some [Ag(NH3)2]+ClO4- and some [Ag(NH3)2]+NO3-
Does diaminesilver share the same explosive properties as tetraminecopper? |
---------
Fair use ... or The Morality of Convenience. (If it’s convenient ... it’s moral!)
Extracted 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 (A93N) 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.
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The WiZard is In
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| Quote: Originally posted by mewrox99 | I'm thinking of playing with some [Ag(NH3)2]+ClO4- and some [Ag(NH3)2]+NO3-
Does diaminesilver share the same explosive properties as tetraminecopper? |
-----
Something to do with your fulminating silver.
Endless Amusement :
A COLLECTION OF NEARLY 400 ENTERTAINING EXPERIMENTS
IN VARIOUS BRANCHES OF SCIENCE; INCLUDING
ACOUSTICS, ELECTRICITY, MAGNETISM, ARITHMETIC,
HYDRAULICS, MECHANICS, CHEMISTRY, HYDROSTATICS,
OPTICS; WONDERS OF THE AIR-PUMP; ALL THE POPULAR
TRICKS AND CHANGES OF THE CARDS, &c., &c
TO WHICH IS ADDED, A COMPLETE SYSTEM OF PYROTECHNY; OF
THE ART OF MAKING FIRE-WORKS.
THE WHOLE SO CLEARLY EXPLAINED AS TO BE WITHIN THE
REACH OF THE MOST LIMITED CAPACITY.
PROM THE SEVENTH LONDON EDITION.
PHILADELPHIA:
LEA AND BLANCHARD.
1847.
http://tinyurl.com/25foj3x 1821 ed.
http://tinyurl.com/2d38s95 1847 ed.
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AJKOER
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OK, I have a slightly different take on the formation of Ag3N from the decomposition of diamine Silver complex. My contention is that a high
concentration of NH3 is a not a promoting factor, but instead a stoichiometric excess of Ag2O relative to NH3.
My argument follows upon first noting the dissolving of Silver oxide does require an excess of aqueous NH3:
Ag2O(s) + 4NH3 (g) + 4H2O <---> 2 [Ag(NH3)2]OH + 3H2O [1]
Note, I have written this reaction as reversible (see as a source, "Second year college chemistry" by William Henry Chapin, page 255):
"As might be expected, the silver-ammonium complex dissociates slightly into its constituents as indicated by the equation
Ag(NH3)2+ <==> Ag+ + 2 NH3 [2]
This is a reversible reaction, very much like the ionization of a very weak acid or base." I suspect that by making the environment less prone for
the retention of NH3 (for example, by applying heat or adding NaOH or alcohol) would move equation [2] to the right, that is, reversing equation [1].
Continuing the argument, the equation for the creation of Silver Nitride can be written for one mole of Ag2O as:
2/3 NH4OH (aq) + Ag2O (s) --> 2/3 Ag3N (s) + 5/3 H2O [3]
which interestingly implies that less NH3 (not more) is required to form the Silver nitride. Or, one could argue, when there is a stoichiometric
excess of Ag2O relative to NH3, then equation [3] moves to the right and forms Silver nitride. See the following Youtube clip apparently employing
close to or more Ag2O then needed (also, this reaction did not rely on a more reactive a fresh precipitate of Ag2O with, nevertheless, a successfully
formation of Ag3N):
http://www.youtube.com/watch?v=4k7QItV__Hs
Per "Comprehensive Inorganic Chemistry Series", Silver Nitride can be prepared by adding Ag2O to concentrated ammonia and letting stand in air,
heating in a hot water bath (or, one can precipitate it with the addition of alcohol).
Now, my speculation as to the mechanism of Ag3N formation is that by applying heat promotes the removal of NH3 and the reverse of Equation [1]
(remember the Ag3N preparation calls for standing in air, or heating in water bath or adding alcohol), and the loss of water (promoted upon
evaporation and also in the presence of NaOH, KOH or alcohol) moving equation [3] to the right. Also the formation of Ag3N, I suspect, is endothermic
so heat and/or the possible presence of a strong alkali like NaOH (which would consume water and simultaneously warm the solution) would speed up the
formation of Silver nitride.
As such, for safety when working with Ag2O and ammonia, my opinion is working with fresh solutions (as Silver complexes breakdown with time with the
natural loss of NH3 and water), cold storing (if need be) and having tighly sealed containers are the most important points.
[Edited on 18-9-2011 by AJKOER]
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blogfast25
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AJKOER:
You are, in a rather longwinded way, stating the blindingly obvious here.
The video makes it very hard to estimate the relative quantities of NH3 and Ag2O used, especially as these substances have wildly different molecular
weights. The experiment shows only that a shock sensitive substance forms over time, when silver (I) oxide and strong ammonia solution are left in
contact with each other. We assume that it is Ag3N (a reasonable assumption).
Regards, ‘[,,,] and having tighly sealed containers […]’, that may not be the best advice because in case of an accidental detonation
your container will act as a bomb (a shell as it were); there’s a big difference between fast development of gas in non-contained conditions and the
same thing in a bomb, shell or any sealed container. This particular UToober could have had a more spectacular result by sealing off his vial prior to
dropping it, in short…
Storing this stuff for prolonged periods of time is probably a strict no-no in the best of conditions…
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annaandherdad
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silvering mirrors
My daughter and I have been silvering glass objects for fun, mostly jelly jars (round ones work best) and flat pieces of glass for ordinary mirrors.
I've been following instructions on the Brashear method for silvering mirrors, developed in the 19th century and explained in detail in an Amateur
Astronomer book that I found on Google (I'll look up the exact reference). The recipe calls for aqueous AgNO3 plus ammonia, first creating a black
precipitate (Ag2OH I guess), which with further ammonia is dissolved. Then one adds NaOH solution, which causes a further precipitate. Then more
ammonia until this is just *not quite* dissolved.
This is then poured over the mirror, and a solution of dextrose, alcohol and NaOH is added and mixed. The silver deposition occurs almost
immediately. Temperature must be between 60 and 70 degrees F.
So I see from reading this thread that the mixture (AgNO3+NH4OH+NaOH is exactly what is needed to make explosives. My reference warns about this, and
says the silvering process should be done within 2 hours. Actually, it takes about 10 minutes max. Afterwards, the book says, you defuse the danger
of explosion by acidifying the mixture with HCl (which causes some AgCl to precipitate, although some Ag is already precipitated in metal form).
The book warns severely that the surfaces must be absolutely clean for the silvering to work. This means: wash first in tap water and soap, then
distilled water, then rub down with acetone, then rinse with distilled water again, then rub down with a cotton ball soaked in nitric acid, then rinse
in distilled water again and don't let it dry before you do the silvering.
Anyway, we've created some nice mirrors. I've covered the silver surface with polyurethane to prevent tarnishing, we'll see how well that works in
the long run.
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AJKOER
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Blogfast25:
In short, my argument is that the loss of NH3 and water are likely factors in the formation of Ag3N, and hence the recommendation for a closed system.
However, I suspect that aqueous Silver salts may breakdown even in closed containers as I believe I read in an old chemistry text on the observed
hydrolysis of Silver acetate with time (the salt being normally soluble and stable in an acidic environment).
Others with any such observations please comment, or kindly supply a reference, or more interestingly, an explanation of the mechanics in a closed
system.
As such, my sealed container recommendation, I agree, may not be supportable apart from your argument.
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blogfast25
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| Quote: Originally posted by AJKOER | [...]water are likely factors in the formation of Ag3N, and hence the recommendation for a closed system.
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The reactions aren’t likely to be affected much by whether the system is closed or open. Especially when one starts from the diammonia Ag(I)
complex, for instance by adding the required amount of ammonia solution to a dissolved silver salt:
2 NH<sub>3</sub> (aq) + Ag<sup>+</sup> (aq) < === > Ag(NH<sub>3</sub> <sub>2</sub><sup>+</sup> (aq) has quite a high complexation constant (formation constant
K<sub>f</sub>. This is evidenced by the fact that the complex forms
even when ammonia is added to an ‘insoluble' Ag (I) salt like Ag<sub>2</sub>O. Little ‘free’ ammonia then exists in solution and the
vapour pressure of it is small, unless an excess of ammonia was used (and a small amount of the ‘free’ ammonia is protonated to
NH<sub>4</sub><sup>+</sup>.
But even with an excess of ammonia present, open or closed won’t make much difference because the complexation is so near-complete. The factor that
influences the rate of silver nitride formation the most is most likely to be the actual silver ammonia complex concentration,
[Ag(NH<sub>3</sub><sub>2</sub><sup>+</sup>].
That, in turn, will depend on initial silver ion concentration and is roughly equal to it (if you make it completely from solutions) or the ammonia
concentration (if you make it from a solid silver (I) source and ammonia solution).
[Edited on 19-9-2011 by blogfast25]
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AJKOER
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Blogfast25:
I found your comments interesting and valuable.
I do believe I have left out a possibly important, but potentially overlooked, point in avoiding the creation of Ag3N. Now, per wikipedia, the
standard free energy of Silver nitride is about +315 kJ/mol, confirming its endothermic nature. As obviously the formation of Ag3N proceeds on
standing in the presence of bright light in about an hour (see the video), the potential promoting role of light/radiation (the photo-reactivity of
many Silver salts being well known) should be noted. Thus, the use of dark containers should be recommended when handling/storing diammine Silver
complex, and also avoid working (for example, in a mirroring project) in the presence of bright light.
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blogfast25
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+ 315 kJ/mol of Standard Free Energy for Ag3N? That's rather a lot...
Light sensitivity is a plausible assumption.
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