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Design experiment to reduce Fe3+ to Fe2+

I just need some help to get started on designing an experiment for a quantitative colorimetric iron assay. We're allowed to use the following items:

deionized water
0.02 M feCl3
filter paper
test tubes and test tube racks
volumetric flasks
digested soil samples
undigested soil samples

Are solutions with Fe3+ ions a different color than Fe2+ solutions? What colors are they? How can I figure out the molecular formulas of 1,10-phenanthroline & ferrozine? What does the soil add to the equation?

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Let me give you some background to some of the issue involved. That might get you started.


The reduction of Fe3+ to Fe2+ is an important assay when it comes to determining the levels of Fe3+ in mine water, reservoirs, soil samples, etc. It is a typical quantitative test conducted by environmental chemists quite a bit in fact. The reduction process itself is often employed when total iron levels need to be calculated. Since Fe2+ complexes well with ferrozine (and with phenanthroline for that matter), all the Fe3+ in a sample needs to be reduced to Fe2+ so that the Fet (total iron) can be determined. (Generally speaking Fe3+ doesn't complex well with ...

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This solution helps provide assistance with designing an experiment to reduce Fe3+ to Fe2+.