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Richard F. Dallinger Wabash College, Crawfordsville, IN 47933
We have adopted the potassium tris(oxalato)ferrate(III) trihydrate (K sub 3 Fe(C sub 2 0 sub 4 ) sub 3 x 3H sub 2 O, potassium ferrioxalate) empirical formula experiment (1) for our general chemistry laboratory and find it, as advertised, to be an excellent integrative experience in synthesis and characterization for the students. The synthesis and recrystallization of the title compound proceed smoothly, and we follow the prescribed methods for the analytical determination of oxalate (by KMnO sub 4 titration) and waters of hydration (by gravimetry). However, we have introduced a fast and accurate spectrophotometric method for the determination of iron in the product that takes the place of the photochemical-gravimetric procedure described in Reference 1. Besides the pedagogic interest of bringing three different types of chemical analysis (titrimetric, gravimetric, spectrophotometric) to bear on one compound, the new iron determination allows us to complete the experiment (with students working in pairs) in two three-hour laboratory periods rather than the five periods allotted in Reference 1.
The iron content of the potassium ferrioxalate product is determined by making the tris(bipyridine)iron(II) complex ion directly from the
Fe(C sub 2 0 sub 4 ) sub 3
sup 3-complex ion and measuring the absorbance of the resulting
Fe(bpy) sub 3
sup 2+ solution. Approximately 0.15 g...