Testing Iron Ions in Oxygen Absorbers

[chris_yau]

how to test the component inside oxygen absorber in food??

we guess that there may be iron(II) or iron(III) ion.
we use reducing agent or oxidzing agent to test it ?
however, if both of them exist in the oxygen absorber, how can we distinguish them??

 

[chris_yau]

If we add dil. HCl to dissolve the oxygen absorber and then add NaOH.
Green ppt. will ba formed if there are iron(II) ion and brown ppt. for iron(III) ion. However, if the oxygen absorber contains both iron(II)and iron(III) ion, how can we test it??

 

[mrjeffy321]

If you think the Oxygen absorber is Iron Oxide you then basically have 3 situations to test...it could be either Iron (III) Oxide - Fe2O3, Iron (II) Oxide - FeO, or Iron (II, III) Oxide - Fe3O4.
Iron (II) Oxide and Iron (II, III) Oxide is back while Fe2O3 is reddish-brown. Fe3O4 has both Fe+2 and Fe+3 ions in the compound while the others are either only contain Fe+2 or only Fe+3 cations.

What you can do is dissolve the Iron Oxide in an acid, preferably Sulfuric acid, to place the Iron ions in solution. What you can then do is try to oxidize all the ions to Fe+3 using the Permanganate ion, MnO4-, from Potassium Permanganate. KMnO4 is a powerful oxidizer and is also especially useful in a situation like this since it has an easily detectable color (purple) in solution, so it can be used as its own indicator to tell when the reaction is complete.
You can titrate your Iron ion solution with a KMnO4 solution. Measure how much KMnO4 is required to oxidize all the Iron ions to Fe+3...the end point should come as the solution turns from clear to purple.

If your solution contained entirely Fe+3 ions, it shouldn’t take any KMnO4 to oxidize it.
If your solution contained entirely Fe+2 ions or mixture of Fe+3 and Fe+2 (in a 2:1 ratio), you should be able to calculate out the amount of KMnO4 required to oxidize it all to Fe+3.
Compare your actual measurements with the theoretical values for the three types of Iron Oxides to determine which type you originally had.

 

[GCT]

Not quite sure what you're question pertains to, however, if you want to determine the composition Fe II and Fe III, that is the ratio of their concentrations, one way to do it is to isolate the iron oxides and perform a redox titration with a simple potentiostat.

 

[scottmulia]

Hi I am confuse what really contain in an oxygen absorber? does it contain Fe that is electrolically charge particle and sodium chloride? Does it also contain other material?