Solution of silver ions turning amber

In summary, when silver ions are added to a solution, they form a colorless or light-amber compound. If the solution is left for a few days, the compound turns darker. It is possible that the compound is formed from silver oxides, which are then reduced back to silver nanoparticles.
  • #1
cnidocyte
36
0
I've been making solutions of silver ions by hooking 20-30V up to 2 silver electrodes in distilled water and noticed something interesting. The solution starts off as clear and by adding a bit of NaCl, AgCl precipitates out so there's definitely Ag+ ions in there. If I leave the solution for a few days it turns amber coloured. This is the colour
IMAG0177.jpg

whats going on here? I haven't bothered to retest for Ag+ ions but the only theory I've come up with is that the Ag+ ions have been reduced somehow and neutral Ag atoms absorb some light.
 
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  • #2
Hmm, I'm not sure, but it's likely that it is related to the formation of silver oxides. Add some base and see if the color deepens.
 
  • #3
Photochemical reduction of the AgCl back to nanoparticles of silver, maybe?
 
  • #4
Acut: I added NaOH but no color change at all.

minerva: Solutions with no AgCl turn amber.

Oxidation to Ag2O is the best theory so far IMO. I did read that silver nano particles absorb some wavelengths of light and the result is an amber color though so I wonder if the cations could be getting reduced somehow. Does that kinda thing occur? Spontaneous reduction of cations. Enough theorizing though I'll just add some NaCl and look for AgCl precipitate.
 
  • #5
Hm, I think it's not Ag2O.
Addition of strong base to Ag+ solutions produces silver hydroxide, which, in turn, reacts with oxygen from the air to form the oxide. So addition of silver hydroxide would either deepen the collor or produce more of this amber-collored compound.

I'm not a silver expert, however.
 
  • #6
Acut said:
Addition of strong base to Ag+ solutions produces silver hydroxide, which, in turn, reacts with oxygen from the air to form the oxide.

Try to write reaction equation.
 
  • #7
I'd guess this,

2Ag(OH) + O2 -> Ag2O + 2OH-

But I've only read its description, never saw its chemical equation.
 
  • #8
So you are electrolyzing in distilled water, eh? Not very efficient, at least at first. It is likely that CO2 is being absorbed into the solution and you are making small amounts of silver carbonate.
At 20 to 30 V you are certainly hydrolyzing water as well so your solution and your silver electrodes have oxygen present as well as the reducing hydrogen gas. Hydrogen gas can react with silver to produce silver hydride which can be a variety of colors from red to black.
 
  • #9
Acut said:
I'd guess this,

2Ag(OH) + O2 -> Ag2O + 2OH-

Check if it can be balanced.
 
  • #10
@Borek: Hm, I never realized that!

But I'm sure I read about this reaction.

It's amazing how much I learn with your posts!
 
  • #11
In short - Ag+ was already oxidized, it doesn't change its oxidation state, so it doesn't need oxidizer.

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1. What causes silver ions to turn amber?

Silver ions turn amber when they react with certain chemicals or compounds in their environment. This reaction is known as a reduction reaction, where the silver ions lose electrons and become a different color.

2. Is the color change of silver ions to amber permanent?

No, the color change of silver ions to amber is not permanent. It can be reversed by adding an oxidizing agent, which will cause the silver ions to regain their electrons and return to their original color.

3. Can silver ions be turned back to amber after they have been reduced?

Yes, silver ions can be turned back to amber after they have been reduced. This can be done by adding an oxidizing agent, such as hydrogen peroxide or nitric acid, which will cause the silver ions to regain their electrons and return to their original color.

4. What is the significance of silver ions turning amber in a scientific experiment?

The color change of silver ions to amber is often used as an indicator in chemical reactions. It can help scientists determine the presence of certain compounds or the progress of a reaction. It can also be used to study the kinetics of reduction reactions.

5. Are there any health concerns associated with silver ions turning amber?

No, there are no known health concerns associated with silver ions turning amber. However, it is important to handle all chemicals and compounds safely and follow proper disposal procedures to prevent any potential hazards.

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