Moessbauer study of the photolysis of alkali tris(oxalato)ferrate(III) complexes

The photolysis of alkali tris(oxalato)ferrate(III) complexes (Li, Na, K, Cs, NH4) was performed in acidic aqueous medium in the visible region using radiations from a medium pressure mercury lamp. The products were precipitated from solution with the addition of methanol. The Moessbauer spectra of the products show the formation of iron(II) oxalates. The rate of photoreduction is higher for sodium-, potassium- and ammonium tris(oxalato)ferrate(III) complexes. Precipitation appeared after 8 min of irradiation (intensity of the mercury lamp being 7.07x1017 quanta/sec). The Moessbauer spectra of the precipitates show the formatiom of ferrous oxalate. The precipitation appeared after 16 min in case of lithium-, and caesium tris(oxalato)ferrate(III) complexes. The rate of photodecomposition of these complexes is in the following order: Sodium-, potassium-, ammonium tris(oxalato)ferrate(III) > lithium-, caesium tris(oxalato)ferrate(III). (author)