September 18th, 2014, 08:01 AM
what would cause a black precipitate to form when a titration of silver nitrate takes place.
the only chemicals involved are sodium hypochlorite (NaClO), water (H2O) and silver nitrate (AgNO3)
the only thing I can think of that would cause a black precipitate is silver sulphide (Ag2S) but since there is no sulphur in the reaction I can't think what else could be forming to create this black precipitate.
thank you for any help
Could it be silver oxide?
More than likely silver oxide.
ah yes. I think it is. I didn't realize silver oxide was black until just now. this makes sense
I would guess that is the same stuff that makes silver jewelry turn black?
Actually tarnish on silver is both sulphides and oxides.
The suphides are easier to remove than the oxides are.
If you dip your jewelry into bleach you get that hard to remove oxide tarnish because bleach (sodium hypochlorite) is such a powerful oxidizer, even when diluted to the levels used around the house or in water supplies.
(Silver oxide can be reduced to metalic silver again with hydrogen peroxide)
If you want to remove silver sulphide tarnish here is a set of instructions for a hands free method.
Finishing Techniques in Metalwork
(Edit: I should point out that almost all of the tarnish commonly on silver is silver sulphide instead of the oxide.)
Last edited by dan hunter; September 21st, 2014 at 10:51 AM.
Thats good to know. THanks!
There are several references around to this reaction forming a mixture of silver peroxide and silver chloride. The reference is A comprehensive treatise on inorganic and theoretical chemistry, Volume 2 By Joseph William Mellor. p271
Thistext is available online. I took the time to look up the reference and it further says that the remaining solution decomposes to give further silver chloride.You can see the original text here:https://archive.org/stream/comprehen...e/270/mode/2up
I mean you can do this with mixing silver nitrate and any hydroxide... Add some silver nitrate to water and sodium hydroxide you will have insoluble silveroxide at the bottom.Originally Posted by Warron
The reaction in question is between silver nitrate and sodium hypochlorite, not sodium hydroxide.I mean you can do this with mixing silver nitrate and any hydroxide... Add some silver nitrate to water and sodium hydroxide you will have insoluble silveroxide at the bottom.
Yes I can read, I was just putting out another method of silver-oxide.The reaction in question is between silver nitrate and sodium hypochlorite, not sodium hydroxide.I mean you can do this with mixing silver nitrate and any hydroxide... Add some silver nitrate to water and sodium hydroxide you will have insoluble silveroxide at the bottom.
Then I don't know why you quoted my post, which references the formation of silver peroxide, not silver oxide.Yes I can read, I was just putting out another method of silver-oxide.The reaction in question is between silver nitrate and sodium hypochlorite, not sodium hydroxide.I mean you can do this with mixing silver nitrate and any hydroxide... Add some silver nitrate to water and sodium hydroxide you will have insoluble silveroxide at the bottom.
Silver Nitrate is just much more common in precipitating halides (inorganic) and alkyl halides (in organic chemistry) than Silver Peroxide. I guess if you were trying to synthesis it from Silver Chloride you would need to use Silver Peroxide but.. The most common is Silvernitrate + a hydroxide. Though in the OPs reaction.. sodium hypochlorite + Silver Nitrate titration would produce Silver Oxide as by product.The reaction in question is between silver nitrate and sodium hypochlorite, not sodium hydroxide.I mean you can do this with mixing silver nitrate and any hydroxide... Add some silver nitrate to water and sodium hydroxide you will have insoluble silveroxide at the bottom.
Last edited by AndresKiani; September 26th, 2014 at 07:12 AM.
This is getting too bizarre for me.
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