yankeex
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Making silver nitrate - impure silver
Ok I have got some old scrap silver which is anywhere between .500 to .925 so it contains more or less amounts of copper. If I just dump them into
HNO3, would this ruin the silver nitrate obtaining process or is there any way to remove the impurities in any feasible way?
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weiming1998
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You can remove the copper+other metal impurities by first dissolving the silver in nitric acid, then boiling/evaporating the solution of
AgNO3/Cu(NO3)2 dry, then heat very strongly in a ventilated place.
According to Wikipedia(http://en.wikipedia.org/wiki/Copper(II)_nitrate), copper nitrate decomposes to CuO at 180 degrees Celsius.
Silver nitrate decomposes into elemental silver though, when heated(http://en.wikipedia.org/wiki/Silver_nitrate) because silver oxide's decomposition temperature is lower than silver nitrate's. The silver/copper
oxide/oxides mix can then be separated with the addition of some non-oxidizing acid, like cold H2SO4, which removes the oxides and leaves you with
almost pure silver.
Another way to extract silver is to first dissolve the impure silver, then putting waste copper into the solution. Silver as pure crystals will
crystallize out.
Also, this probably belongs in the Beginnings, not Organic Chemistry.
[Edited on 10-4-2012 by weiming1998]
[Edited on 10-4-2012 by weiming1998]
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cyanureeves
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i like to add salt to the dissolved sterling and make the curd like silver chloride because the copper remains in solution as a blue liquid that is
visible so you can decant it. the silver chloride can then be washed again and again with plain water until no more hint of blue remains as silver
chloride is insoluble in water.then i like to add hcl acid and water to the silver chloride and drop zinc pennies rid of their copper shell. you can
see the displacement take place before you as the silver chloride turns black like a thunder cloud passing over the earth. the black stuff is silver
metal mud that can be washed also again and again with water to rid it of zinc chloride or you can just melt the pure silver and digest it again with
nitric. dropping a clean piece of copper in your blue solution of dissolved silver alloy will also displace the silver which will grow around the
copper like a crystal fungus.just make sure your blue solution is diluted with water when you do the copper displacement method.
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ScienceSquirrel
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Thread Moved
10-4-2012 at 00:53 |
MrHomeScientist
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Here's the process I'd try:
First, dissolve the sterling silver in HNO<sub>3</sub> to form silver and copper nitrates in solution. Then, add a source of chloride ions
to the solution (NaCl solution seems most convenient) to precipitate out AgCl as a white solid. Filter this off, rinse a few times with water, and
then dissolve the precipitate in ammonia solution. Filter off any remaining impurities that appear as insoluble residue. Finally, add nitric acid
again to convert to silver nitrate.
You'll have some ammonium nitrate impurities though, and now that I look at it this might be difficult to separate. Ammonium and silver nitrates have
similar solubilities in water. Hmm.
P.S. I haven't tried the ammonia dissolution step myself - I found it referenced in "Handbook of Inorganic Chemicals", Patnaik, p.839
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annaandherdad
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I've done some of this in the last year or so and have tried various methods. Sterling silver is about 93% silver and 7% copper---I found
quantitatively that this was close to the mark in a sample I had.
The best way I found was to dissolve the impure silver in nitric acid. Weigh the (impure) silver first so you have an upper bound on the amount of
silver. Then add NaCl---the amount I added was based on the weight of the impure silver, so that I had an excess of NaCl but not too much. I don't
know if a large excess of NaCl would be harmful (eg., causing some of the AgCl to go back into solution) but I wasn't taking any chances. AgCl is
highly insoluble in H20 but you will also have HNO3, NaCl, Na2NO3, and various copper compounds present (plus maybe some other metal nitrates).
Anyway, filter and wash the AgCl.
This can be reduced to metallic Ag by boiling in a solution of NaOH plus dextrose. I followed a recipe in an article I found in the chemistry
literature---I don't have the reference handy but I'll look it up for you and post again. The silver can then be filtered and washed (both water and
acetone, the latter to get rid of any organic materials left from the sugar and its decomposition).
If you want AgNO3, you can redissolve the silver in HNO3, and crystallize. I did this in a desiccation chamber with NaOH to absorb the H2O and HNO3
vapors. Got some nice, clear AgNO3 crystals that way, but it took a long time.
Another method I tried that didn't work well was to insert copper after getting the solution of silver and copper nitrates after the first dissolution
in HNO3. One does get beautiful silver crystals forming, but I found that when I would shake them off the copper and filter them out, that little
bits of copper were sticking to the silver. So, when I redissolved in HNO3, I still had some copper contaminating the solution. The route through
AgCl and reduction worked better.
Any other SF Bay chemists?
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cyanureeves
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i think its better to melt the silver because all other impurities will remain in solution or in their salts and will not withstand the heat enough to
go back to metallic state.
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nezza
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weiming is right. Copper nitrate decomposes at a much lower temperature than silver nitrate. I have made pure silver nitrate from sterling silver by
this route :-
1. Dissolve silver/copper alloy in HNO3
2. Evaporate to dryness
3. Heat gently - the Copper nitrate decomposes before the silver nitrate
4. Extract with water - a colourless solution of silver nitrate is obtained. This can be evaporated and crystallised or just filtered an used as is.
Note that if there are other metals in the alloy apart from copper this will not work.
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froot
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A retired metallurgist once told me that they used to purify gold from old jewellry and concentrate using the aqua regia method but with a twist. He
would dissolve the metals in aqua regia and afterwards neutralise by adding urea. The silver would drop out and be filtered off. Not sure what sort of
complex this would create or weather the copper complex would have different solubility to the silver. If I was doing this I would try dissolving a
sample in HNO3 after which I would add urea to see if the same would happen.
We salute the improvement of the human genome by honoring those who remove themselves from it.
Of necessity, this honor is generally bestowed posthumously. - www.darwinawards.com |
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bolbol
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I made some Silver Nitrate yesterday with a troy ounce of silver advertised as 99.99%. I used 25 mls of distilled water and 30 mls of conc nitric acid
for this. After it all dissolved and cooled down, I got silver nitrate crystalizing at the bottom and i got a liquid solution that has a blue tint to
it... Is this normal for a 99.99% stuff
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cyanureeves
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bolbol i dont think .01 impurity would make a blue tint of any kind. i have dissolved 99% silver and have gotten no blue tint, but how blue is it?dark
blue as in a lot of copper or just a light blue tint?i think you got dirty bullion because i ordered a troy once from china that i suspected to be
adulterated because it weighed less than 31 grams.the bullion did not turn blue as copper does but maybe does have zinc or something that doesnt
tinge.i never weighed the pure silver either but it was alot so it was good enough for me i guess. the loss was minimal to me but i know it will add
up if the seller does this by kilograms.
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bolbol
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It was like 31.18 grams if i remember correctly.. and its just a very light blue tint but still noticeable when you look at it. I was hoping I'd get
pure silver nitrate now I think I should throw in some copper and get all the silver out and redissolve the silver powders in nitric acid again.
Unless there is an easier way?
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unionised
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Adding copper to get rid of copper isn't a brilliant idea.
You can precipitate silver as the acetate, (essentially all other acetates are soluble) then heat it to get silver. (Be careful, the reaction can get
violent
Or- probably easier, you can precipitate the silver as the chloride by adding salt or hydrochloric acid, then wash the AgCl with lots of water to
remove the Cu.
Then heat the chloride with an excess of sodium carbonate to get sliver metal.
On the other hand, if the silver was anything like 99.99% pure then you should be able to get practically pure AgNO3 by recrystallisation from hot
water.
http://en.wikipedia.org/wiki/Recrystallization_%28chemistry%...
[Edited on 8-2-15 by unionised]
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bolbol
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Well if it was 99.99% pure I don't think I'd get that blue tint. Even through videos ive seen on youtube every solution after the reaction is over
turns into clear colorless solutions.
I like the silver acetate idea but my goal is to get silver nitrate not silver metal. Would vinegar work if I added it to a silver nitrate solution
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unionised
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Really, I'd recommend recrystallising it before I tried anything else- it is by far the easiest route.
Vinegar wouldn't work unless you also added some alkaline material to strip out all the excess acid.
You can see the blue colour of solutions of copper salts down to a few tens of parts per million.
Once you get the silver pure, you can redissolve it in nitric acid.
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bolbol
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I will recrystalize it and the rest that remains in solution ill redo with copper I guess.. I just dont want the recrystalized stuff to have a blue
tint to it...
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bolbol
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I'd like to know if anyone ever made AgNO3 with 99.9% purity silver bullion american or not and didn't get a blue tinted solution after the reaction
was over and the NO2 color was out of solution.
I switched to Canadian silver which is 99.99% and no more copper presence is detected but I have seen some good priced silver online that is 99.9% and
before buying I'd like to know others experience
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morganbw
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Quote: Originally posted by bolbol  | I'd like to know if anyone ever made AgNO3 with 99.9% purity silver bullion american or not and didn't get a blue tinted solution after the reaction
was over and the NO2 color was out of solution.
I switched to Canadian silver which is 99.99% and no more copper presence is detected but I have seen some good priced silver online that is 99.9% and
before buying I'd like to know others experience |
It has been maybe 30 years ago, but yes -> no blue.
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Sulaiman
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I made silver nitrate with a US 99.9% 1oz. eagle a couple of months ago, just the tiniest hint of blue/green
BUT
the silver nitrate produced was light sensitive
which it should not be if perfectly pure.
I intend to do a recrystallization some time soon ......
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bolbol
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I've never successfully been able to recrystallize Silver nitrate. The crystals barely drain and the remaining solution when dried still leaves a
colored tint that is apparent when compared to something like more pure AgNO3
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AndrewCampbell
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I have never thought that I could possibly perform my own science experiment in the comfort of my own home to successfully separate silver from
copper. However, with advices from experienced enthusiasts like you people, nothing is ever impossible if we are determined to achieve them.
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