CRYSTAL-STRUCTURE, THERMOANALYTICAL PROPERTIES AND INFRARED-SPECTRA OF DOUBLE MAGNESIUM SELENATES

Magnesium selenates double salts K2Mg(SeO4)(2).6 H2O, Rb2Mg(SeO4)(2).6 H2O, Cs2Mg(SeO4)(2) . 6 H2O, and (NH4)(2)Mg(Se0(4))(2).6 H2O have bee n studied by means of X-ray diffraction methods, thermoanalytical meth ods, and infrared spectroscopy. The basic building units of these comp ounds are slightly deformed tetrahedra of selenate anions and octahedr a of hexaaquamagnesium(II) cations interconnected by a system of hydro gen bonds. The investigation of IR spectra has been used in the discus sion of X-ray diffraction results in the field of description of the h ydrogen bond system and deformation of the basic polyhedra of selenate anion and hexaaquamagnesium cation. The thermoanalytical studies are used in evaluating the effects of hydrogen bonds and polarization infl uence of M(+) cations on thermal stability of the compounds studied.