silonyl - 21-2-2006 at 08:15
I am looking for a quick and simple method for the quantification of nitrite in solution (or solid), if one exists. What I want is essentially a way
to check the purity of a sample of bulk material, which most likely contains only nitrite and water. Dehydration would be acceptible, although I'd
prefer a chemical method for didactic reasons.
Since the material is thought to be primarily nitrite, with water as a primary contaminant, quick tests that quantitate nitrate+nitrite would probably
be acceptible as well.
Thanks!
garage chemist - 21-2-2006 at 09:45
Addition of an excess of ammonium salt (e.g. NH4Cl) and heating under stirring until evolution of gas (nitrogen) stops.
The amount of nitrogen evolved is directly proportional to the amount of nitrite contained in the sample.
If (at 0°C) 22,4 L (or 24L at 25°C) of nitrogen are evolved, the test substance contained 1 mol of nitrite ion.
silonyl - 21-2-2006 at 10:17
Interesting, although I'm not so much in the mood to set up a gas collection tube unless I have to.
What kind of temperature is needed for this reaction to proceed? Is there a possibility of titrating unknown nitrite with known concentration of NH4Cl
or a primary ammonium salt? Or possibly acidifying the nitrite to form HONO and then titrating with ammonia/amine?
The GRIESS reagent system
Lambda - 21-2-2006 at 14:29
The easiest tests that I know for Nitrite Ion determination are based an the formation of the "Azo" compound of a reagent (which often turn red in
color). The famous "GRIESS" test is one example of a very specific and sensitive Nitrite determination test, using Sulfanilamide. This is then
measured via a Photo Spectrometer. Fishery and Aquarium stores sell similar kits for under $10. Some are even based on the same principle as Litmus
Acid/Base test strips, which are compared to a reference color match chart. It can't get much simpler than this, can it.
An example can be found here (AquaTru® Nitrite Test Kit):
http://www.novalek.com/kpd45.htm
And for the "GRIESS" reagent system:
http://www.promega.com/tbs/tb229/tb229.pdf
I have often used the Nitrite determination test by means of the "GRIESS" principle, and it's one of the most sensitive and best I know of to get the
job done right.
[Edited on 21-2-2006 by Lambda]
Microtek - 22-2-2006 at 07:08
You could titrate with acidified KMnO4 if you have a sample of pure nitrite ( or other reducing agent ) to act as primary standard. In acidic solution
MnO4- is reduced all the way to colorless Mn2+.