ИСТИНА

There is a constantly growing interest in iron(VI) compounds mainly due to their potential in water treatment. A number of publications on ferrates increase year by year. But they are generally devoted to the application problems. Meanwhile there are many open questions in ferrate chemistry and physics. The answers are necessary for synthesis, identification and literate usage of these compounds. The first question is simple: what ferrates(VI) have been synthesized? But it is not simple to give an answer. For good identification it is desirable at least to perform a structural analysis of the sample, to know the content of elements in it and to have a confirmation of oxidation state of iron because Fe6+ is unstable. But it is difficult to meet such studies in the literature. Mossbauer spectroscopy is a powerful technique for ferrate analysis. It allows us to determine relative content of iron(VI) in the substance and also to identify the ferrate. For identification isomer shift can be used. But isomer shifts of ferrates(VI) are almost equal ( 0.87 ÷ –0.91) mm/s-1 relative to alfa-Fe). Recent detection of quadrupole splitting for some ferrates [1] allows us to achieve better selectivity. In this work we calculated quadrupole splittings for several ferrates(VI) in terms of point charge approach and compared them with known experimental data. Quadrupole splittings for potassium, rubidium and cesium ferrates(VI) have not yet been experimentally observed. The calculated values are relatively low. Experimental spectrum of barium ferrate is a resolved doublet, but for strontium salt the splitting is smaller and two doublet lines are not resolved. It is indicative that relation between calculated and experimental values for barium compound is almost the same as for strontium ferrate. The calculated splitting for mixed potassium-sodium ferrate is close to the values of other ferrates of alkali metals, but very far from experimentally observed one. Reference: 1. S.K.Dedushenko, Yu.D.Perfiliev, M.G.Goldfeld and A.I.Tsapin, Hyperfine Interactions, 136/137(2001), 373