Iron(III) selenite is an inorganic compound with the chemical formula Fe2(SeO3)3. It exists in anhydrous form and as various hydrates.
Structure The pentahydrate has the structure of Fe2(OH)3(H2O)2(HSeO3)3.Maldagalieva, R. A.; Shokanov, A. K. Infrared spectroscopic study of the state of water molecules in crystal hydrates of transition metal selenites. Trudy Khimiko-Metallurgicheskogo Instituta, Akademiya Nauk Kazakhskoi SSR, 1973. 22: 16-20. ISSN: 0516-0324. Single-crystal X-ray diffraction of the trihydrate shows that its structure consists of two independent FeO6 octahedrons and SeO32− with a tetrahedral geometry.
Preparation The heptahydrate is produced by the reaction of ferric chloride and selenous acid (or sodium selenite) at a pH of 1.05.Pinaev, G. F.; Volkova, V. P. Preparation and some properties of iron(III) selenite. Obshchaya i Prikladnaya Khimiya, 1970. 3: 33-39. ISSN: 0369-7045.
Reactions The anhydrous salt decomposes into Fe2O3·2SeO2 at 534 °C, generates 4Fe2O3·SeO2 at 608 °C, and finally obtains Fe2O3 at 649 °C.Bakeeva, S. S.; Muldagalieva, R. A.; Buketov, E. A.; Pashinkin, A. S. Thermal stability of neutral iron selenite. Trudy Khimiko-Metallurgicheskogo Instituta, Akademiya Nauk Kazakhskoi SSR, 1970. 15: 88-92. ISSN: 0516-0324.
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