phlogiston
International Hazard
Posts: 1376
Registered: 26-4-2008
Location: Neon Thorium Erbium Lanthanum Neodymium Sulphur
Member Is Offline
Mood: pyrophoric
|
|
identifying ammonium persulfate
Hi guys and gals,
I was given an unlabeled bottle of a white powder which is most likely ammonium persulfate.
However, I would like to confirm this unambiguously before I add it to my collection of chemicals.
Do any of you know a (preferably simple) reaction that is highly specific for persulfates?
I know it can be used for etching copper circuit boards and as an initiator for polyacrylamide gels, both of which I can try, but in both cases I can
see there are possibly other compounds that can give similar results, ie they are not conclusive tests.
[Edited on 21-4-2013 by phlogiston]
-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
|
|
AndersHoveland
Hazard to Other Members, due to repeated speculation and posting of untested highly dangerous procedures!
Posts: 1986
Registered: 2-3-2011
Member Is Offline
Mood: No Mood
|
|
with heating, persulfate can oxidize AgNO3 solution to brown Ag2O2... not sure if the ammonium ion would interfere
you could also try heating it to decomposition and see if any residue is left. If it is ammonium persulfate, there should not be any residue. (be sure
to heat extra hot to decompose any ammonium sulfate that may be left)
this thread really belongs in the beginnings section
[Edited on 21-4-2013 by AndersHoveland]
|
|
|
woelen
Super Administrator
Posts: 7987
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
Mix some solid NaOH and some of the salt and add a drop of water. Only use small quantities, e.g. a small spatula of chemicals.
If there is ammonium in the salt, then you can smell the ammonia from this reaction.
If the compound is a persulfate, then a very peculiar reaction occurs when NaOH and a drop of water are added. You get a transient yellow or even
slightly orange color, which fairly quickly disappears again. With normal sulfate or other white ammonium salts you do not get this yellow or orange
color.
Other confirmations of persulfate:
- Prepare a precipitate of Ni(OH)2 (which is pale green) by adding an excess amount of a solution of NaOH to a solution of a soluble nickel(II) salt.
To the liquid with the pale green precipitate add a solution of your supposed persulfate. If it indeed is persulfate, then the precipitate turns black
at once.
- Dissolve a tiny amount (just a few cubic mm) of AgNO3 in one or two drops of water. Add a few ml of conc. HNO3 to this. This gives a clear and
colorless solution of AgNO3 in HNO3. Now dissolve some of your supposed ammonium persulfate in a very small amount of water. Add a few drops of this
to the solution of AgNO3 in conc. HNO3. If there indeed is persulfate, then the solution turns deep brown. This is a very sensitive test.
|
|
|
Fantasma4500
International Hazard
Posts: 1681
Registered: 12-12-2012
Location: Dysrope (aka europe)
Member Is Offline
Mood: dangerously practical
|
|
also add NH4OH to the stuff
it should turn the solution dark blue due to tetraammine.. you should get TACPS by this if im not mistaken (:
interesting exotic primary, not very strong tho
|
|
|
woelen
Super Administrator
Posts: 7987
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
Quote: Originally posted by Antiswat  | also add NH4OH to the stuff
it should turn the solution dark blue due to tetraammine.. you should get TACPS by this if im not mistaken (:
interesting exotic primary, not very strong tho |
No, you're wrong. Adding ammonia to it does nothing. What
you are referring to is adding ammonia AND a copper salt to it, or even better, ammonia and cuprous hydroxide.
The royal blue color is due to formation of the complex [Cu(NH3)4](2+) and this has nothing to do with persulfate. This is the first three letters of
the acronym TACPS, which stands for Tetra Ammine Copper Peroxo Sulfate. Other similar salts exists, ike TACN (the nitrate) and TACP (the perchlorate).
For testing whether a compound is a persulfate, this thing with copper has no value. Use one of the other suggested methods to check for persulfate.
|
|
|
Fantasma4500
International Hazard
Posts: 1681
Registered: 12-12-2012
Location: Dysrope (aka europe)
Member Is Offline
Mood: dangerously practical
|
|
| Quote: Originally posted by woelen | | Quote: Originally posted by Antiswat | also add NH4OH to the stuff
it should turn the solution dark blue due to tetraammine.. you should get TACPS by this if im not mistaken (:
interesting exotic primary, not very strong tho |
No, you're wrong. Adding ammonia to it does nothing. What
you are referring to is adding ammonia AND a copper salt to it, or even better, ammonia and cuprous hydroxide.
The royal blue color is due to formation of the complex [Cu(NH3)4](2+) and this has nothing to do with persulfate. This is the first three letters of
the acronym TACPS, which stands for Tetra Ammine Copper Peroxo Sulfate. Other similar salts exists, ike TACN (the nitrate) and TACP (the perchlorate).
For testing whether a compound is a persulfate, this thing with copper has no value. Use one of the other suggested methods to check for persulfate.
|
oh.. sorry.. just remember the synth of tacps as in needing to go through CuSO4 + NH4OH if youre using alkali persulfates, but more straightforward
with ammonium persulfate.. :s
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
