DECOMPOSITION OF MG(HSEO3)(2)CENTER-DOT-3H(2)O AND MG(HSEO3)(2), IR SPECTROSCOPIC AND THERMOANALYTICAL INVESTIGATIONS

By crystallization from aqueous Mg(HSeO3)(2) solutions, single crystal s 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(HSe O3)(2) . 3H(2)O results in the direct formation of the diselenite MgSe 2O5. High-temperature Raman experiments under quasi static conditions (heating rate < 5 K/h, isothermal intervals of similar to 1h) show tha t Mg(HSeO3)(2) . 3H(2)O decomposes in two steps under the intermediate formation of the anhydrous hydrogenselenite Mg(HSeO3)(2).