Decomposition of Mg(HSeO3)2•3H2O and Mg(HSeO3)2, IR spectroscopic and thermoanalytical investigations

By crystallization from aqueous Mg(HSeO3)(2) solutions, single crystals of Mg(HSeO3)(2) .3H2O, Mg(HSeO3)(2), and MgSe2O5 could be obtained. The compounds have been characterized by means of IR spectroscopy. The dehydration mechanisms of Mg(HSeO3)(2) . 3H(2)O and Mg(HSeO3)(2) have been studied using TG, DTA and high-temperature Raman techniques. DTA and TG measurements indicate that the thermal decomposition of Mg(HSeO3)(2) . 3H(2)O results in the direct formation of the diselenite MgSe2O5. High-temperature Raman experiments under quasi static conditions (heating rate < 5 K/h, isothermal intervals of similar to 1h) show that Mg(HSeO3)(2) . 3H(2)O decomposes in two steps under the intermediate formation of the anhydrous hydrogenselenite Mg(HSeO3)(2).