Schleimsäure
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Silver sulfate
I got some 250g of reagent grade silver sulfate once in a deal. It's from the late 70's but looks as new, well sealed in brown glass.
It seems to be very expensive like all silver salts (like 300 EUR for 250g).
But I don't see any use with it. Is it possible to form another silver compound from it which is more useful, like silver nitrate?
Or is it best to reduce it to elemental silver?
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blogfast25
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Quote: Originally posted by Schleimsäure  | But I don't see any use with it. Is it possible to form another silver compound from it which is more useful, like silver nitrate?
Or is it best to reduce it to elemental silver?
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It should be possible to convert it to silver nitrate by displacement with barium nitrate, because barium sulphate is far less soluble than silver
sulphate. Digest over several hours to reduce occlusion by the barium sulphate. Filter off silver nitrate solution. Purify the silver nitrate by
recrystallization(s). Whether that's really worth doing is another matter.
Reduction to elemental silver may be better.
[Edited on 9-4-2015 by blogfast25]
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Schleimsäure
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Well, thank you. Maybe I will give it a try.
Or I let it just sit in the shelf, bolstering the chemicals collection.
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Praxichys
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Convert half to the nitrate so you can include both on your collection list! 
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Schleimsäure
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Ja, maybe the best. I've got only barium carbonate and barium chloride so far, but it's easy to make barium nitrate from the carbonate with HNO3 I
guess.
[Edited on 9-4-2015 by Schleimsäure]
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DraconicAcid
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I wouldn't use barium nitrate to convert it to the nitrate. Better to precipitate it as the oxide or carbonate, and then dissolve that in nitric
acid.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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AJKOER
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I suspect the reason the Silver sulfate is so valuable is due to its purity, not the Silver per se.
To preserve the purity and in line with DraconicAcid recommendation, I would pass ammonia gas into an aqueous solution of Ag2SO4 to form Ag2O, but
don't over do it as a soluble complex will form (see, for example, https://sites.google.com/a/hollandchristian.org/ap-chem-lab-... ).
Then, I would try to treat the Ag2O (which has been well washed to remove any traces of the sulfate with pure water) with an excess of NO2 gas ([Edit]
with added oxygen also based upon further research) as to quote Wikipedia on NO2 ( link: http://en.m.wikipedia.org/wiki/Nitrogen_dioxide ):
"NO2 is used to generate anhydrous metal nitrates from the oxides:[8]
MO + 3 NO2 → M(NO3)2 + NO "
[Edit] I found a reference supporting this reaction for Ag2O, at least in the presence of oxygen, which interestingly, would be the reverse of the
thermal decomposition reaction of AgNO3. Per "Interaction of Silver with a NO/O2 Mixture: A Combined X-ray Photoelectron Spectroscopy and Scanning
Electron Microscopy Study" by D.Y.Zemlyanov, et al., to quote from the abstract:
"whereas AgNO3 resulted from the subsequent reaction of Ag2O with NO2 in the gas phase."
Link: https://www.google.com/url?sa=t&source=web&rct=j&...
And, in the presence of moisture, I would expect more than just a surface reaction as:
4 NO2 + O2 + 2 H2O = 4 HNO3
But, this does assume the complete oxidation of the intermediate HNO2 (otherwise possible nitrite contamination) which could be mitigated by the use
of a large excess of oxygen (in which case, I would recommend working with NO not NO2 with the added bonus of generating it from dilute Nitric acid
and copper).
So, try and performed carefully with clean glassware and pure gases, and you may actually obtain reagent grade Silver nitrate (or close to it).
[Edited on 10-4-2015 by AJKOER]
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woelen
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I would do like DraconicAcid said, or try to reduce it to metallic silver, but only for a small amount, e.g. 10 grams. If this fails or leads to
unsatisfying results, then at least you did not spoil all of your precious material.
Keep in mind that you have to work with very dilute solutions when using Ag2SO4. This material is only very sparingly soluble. For dissolving 10 grams
you will need 1.5 liters of water and it will take a long time to dissolve all. Precipitating Ag2O will not be easy from such dilute solutions. You
probably get very very fine particles in this dilute solution (opalescent, not really visible particles) and you may need centrifuging to get the
precipitate down in reasonable time.
Silver sulfate probably dissolves better in moderately concentrated sulphuric acid, as silver bisulfate, but please try that on a test tube scale
first with 100 mg or so of the solid, added to 30% H2SO4. If this indeed is the case, then you could use that for making precipitates.
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blogfast25
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| Quote: Originally posted by woelen | | Keep in mind that you have to work with very dilute solutions when using Ag2SO4. This material is only very sparingly soluble.
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If you're going to convert to oxide/hydroxide or carbonate, you can directly treat a silver sulphate slurry with hydroxide or carbonate and allow
sufficient time and stirring for complete conversion.
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AJKOER
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[Edit] Per Wikipeda on Silver Sulfate, it is much more soluble in Sulfuric acid than water (for example, 31.56 g/100 g H2O in 0.1 mole H2SO4 at 24.5
C). Link: http://en.m.wikipedia.org/wiki/Silver_sulfate
Even AgCl is apparently soluble in strong HCl, and lacking pure 6 M Hydrochloric acid, wet AgCl and Cl2 may even form a soluble ligand. And, for those
who like to experiment, without (or not desiring to employ) their high purity H2SO4, perhaps even SO2 on an aqueous suspension of Ag2SO4 may suffice
(forming perhaps a soluble sulfite and bisulfate, which I would proceed to neutralize with NH3 gas to obtain Ag2O).
For possible educational purposes, I leave my prior comments below.
---------------------------------------------------------------------
Woelen may be right on the need for working with very dilute solutions here, but there are examples of reactions involving fine suspensions of weakly
soluble reagents. For example, the acid/base reaction of passing Cl2 into a very fine (lots of surface area and freshly precipitated possibly as well)
suspension of CaCO3 in water. This is a cited and long known preparation of HOCl from Watts as the formed HCl via:
Cl2 + H2O = HCl + HOCl
is neutralized by the carbonate leaving the Hypochlorous acid which can be distilled off.
So, in the case of your Ag2SO4 if it produces a fine suspension that good news, but its age is a negative, and you may indeed have to try to dissolve
it, but only in very pure H2SO4! If you do not have it, I would recommend the following possible reaction (in the hypothetical special case of a
Silver salt which are a bit unique), a version of which (employing Na2SO4 and not Ag2SO4) is cited in Watts also as a path to HOCl:
Ag2SO4 + Cl2 + H2O = AgCl (s) + AgHSO4 + HOCl
The AgCl could be recovered and recycled, limiting the loss of Silver. The solution should be promptly heated to remove the volatile Hypochlorous acid
before it largely decomposes into HCl (which occurs more so in concentrated solutions). The logic is if Ag2SO4 is soluble in Sulfuric acid,
Hydrochloric acid should work also and the formation of the precipitate should move the reaction to the right. The amount of Chlorine must be limited
as otherwise just AgCl and H2SO4 are produced (which could react with added Ag2SO4 to form the bisulfate or not if the created Sulfuric acid is too
dilute, so consider limiting the amount of H2O as well).
[Edit] A Watts reference link that may work for some is https://play.google.com/books/reader?id=ijnPAAAAMAAJ&pri...
[Edited on 10-4-2015 by AJKOER]
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Schleimsäure
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Now these are many roads. Will try first with small amounts like suggested. On versuchschemie.de someone also suggested to just use NaCl solution in
large excess to get the chloride.
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blogfast25
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That wouldn't even need an excess but AgCl is a bit... well, useless really.
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Sulaiman
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If I had lots of silver sulfate I would give a thick silver plate to as many of the surfaces that I come in daily contact with as practical.
Silver is my present 'favourite element'
(dabbling with electrochemical cells, photochemistry, chemistry, etc.)
I now have a simple ionic/colloidal silver 'generator' in use as I have come to believe in the anti-'germ' power of silver,
time will tell and it's cheap and non-toxic so no harm if I'm wrong.
(unless I've completely mis-calculated and I turn blue, forever. http://en.wikipedia.org/wiki/Argyria
I can't think of any atmospheric pollutants that would significantly reduce the silver purity
so I guess recovering the pure silver is logical.
I have not purified silver to my own satisfaction yet, my aim is non light sensitive silver nitrate crystals.
so I have not enough experience to suggest the path.
edit: changed 'experimenting' to 'dabbling' as my level of experimenting in silver is an insult to science !
[Edited on 11-4-2015 by Sulaiman]
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AJKOER
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| Quote: Originally posted by Sulaiman | ...
I can't think of any atmospheric pollutants that would significantly reduce the silver purity
so I guess recovering the pure silver is logical.
I have not purified silver to my own satisfaction yet, my aim is non light sensitive silver nitrate crystals.
so I have not enough experience to suggest the path....
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With my largely gaseous exercise to promote purity and which hopefully should reduce the unwanted presence of certain metals, there still may be a
non-metal of concern. I am referring to Sulfur and in particular, H2S which commonly tarnishes Silver in the presence of copper, oxygen, moisture, and
salt (serving as an electrolyte).
This is, in my assessment, actually an example of galvanic corrosion (that is, there is an electrochemical basis to the act of tarnishing itself).
Here is an extract from one reference noting that for gold jewelry, where the acid H2S is replaced by human fatty acids (link: http://www.jewelrygenius.com/tarnish.html ):
"Pure gold, 24K, itself will not corrode but is too soft for many kinds of jewelry and therefore is alloyed with proportions of base metals, usually
silver or copper to make it harder. The composition of 14 karat gold is 14/24 pure gold and 10/24 alloys. Only the base metal used for alloying
corrodes, leaving the gold untouched. The chemical compounds of silver and copper which are formed turn very dark even when slightly corroded.This
corrosion occurs under moist or wet conditions.
Our skin on which the jewelry lies, is provided with thousands of perspiration glands. Chemically the perspiration is mostly fat and fatty acids.
These essentially mild chemicals are enough to cause corrosion of 14 karat gold especially when aided by warmth and free access of air. ...
Rings containing copper and silver alloys, particularly sterling silver, corrode readily on the skin if enough salt is present. Simply exposing the
hands to salted nuts, crackers, or popcorn can cause such corrosion and discolor the skin. "
On the topic of sterling silver, the author further notes:
"The main cause of tarnishing of silver is a trace of hydrogen sulfide gas in the air. This gas is particularly present in smoke from burnt raw fuel,
such as coal or oil; in some strong smelling foodstuffs, such as eggs and onions; in some fish or shellfish; and in polluted air...The tarnish may
turn the jewelry black and may also be rubbed off on the skin or clothing."
My take on the likely main side and half reactions (and ignoring the catalytic roles of other metals like copper):
4 H2S + 4 H2O <---> 4 HS- + 4 H3O+
8 Ag + 4 HS- <---> 4 Ag2S (s) + 2 H2 (g) + 4 e-
02 + 2 H2O + 4 e- <---> 4 OH-
4 H3O+ + 4 OH- <---> 8 H2O
Net:
4 H2S + 8 Ag + O2 ---> 4 Ag2S (s) + 2 H2 (g) + 2 H2O
Reference: See http://www.vam.ac.uk/content/journals/conservation-journal/i...
This source (see http://nautarch.tamu.edu/CRL/conservationmanual/File13.htm ) notes that in oxygen rich salt water environments, Ag2S may just be one of several
possible silver salts formed. Hence, one may see a net corrosion reaction specified excluding and sometimes including oxygen, which is not incorrect
per se, but perhaps incomplete in specifying reaction conditions and other possible products.
[Edited on 12-4-2015 by AJKOER]
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bolbol
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I havent worked with the sulfate of silver at all but if you want to reduce it to the metal think of a way to make the carbonate of it as it is very
easy to turn it into metal just be heating it with a propane torch. Same goes for silver oxide but that material is very gooey and sticks to
everything way way easier than the carbonate.
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Schleimsäure
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I'll try different routes, but by no way will convert the whole 250g. At last I found a good use in organic synthesis.
AgSO4 is used in conjunction with iodine in MeOH for some selective iodinations.
| Quote: |
Suzuki–Miyaura Cross-Coupling Aryl borate 3a, the second component required for Suzuki–Miyaura cross-coupling, was prepared starting from
l-tyrosine (Scheme 4). Methyl ester formation, as shown, followed by protection of the amino group as its Cbz derivative under standard conditions
afforded phenol 17 in quantitative yield. Subsequent O-methylation of 17 with Me2SO4 in the presence of LiOH in THF provided 18 in 86% yield.17
Selective iodination of 18 at the 3-position, ortho to the methoxy group, was accomplished in high yield with I2/AgSO4 in methanol
(see compound 19).18 The required aryl borate 3a was obtained from 19 in 95% yield following Miyaura’s protocol.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2507741/
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AndrewCampbell
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Reading the forum makes we think that I should start looking at how I can get a bit scientific with my business! Perhaps I can start looking at other
compounds to improve my range of silver jewellery haha! Anybody here have any ideas?
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