ON CALCIUM BROMATES AND IODATES - CRYSTAL-STRUCTURE, X-RAY, IR AND RAMAN SPECTROSCOPICAL AND THERMOANALYTICAL INVESTIGATIONS

The phase relationships (and both decomposition and disproportionation) of bromates and iodates of alkaline earth metals are studied by means of thermal analyses (DTA, DSC, TG) and (high-temperature) X-ray, IR-, and (high-temperature) Raman spectroscopic measurements. The following compounds have been established: Ca(IO3)2 . 6H2O oF216, the isotypic Ca(BrO3)2 . H2O and Ca(IO3)2 . H2O mP48, Ca(IO3)2 I (lautarite) mP36, Ca(IO3)2 II, and Ca(BrO3)2. The crystal structure of Ca(IO3)2 . H2O (bruggenite) (space group P2(1)/c, Z = 4) has been determined by single crystal X-ray diffraction (MoK-alpha). The final R value for 3 888 reflections with I(o) > 3-sigma(I) is 0.0487. The structures of bromates and iodates of alkaline earth metals known so far are discussed with respect to the energetic (mode frequencies) and geometric (bond lengths) distortion of the XO3--ions as well as the strengths of H-bonds present in the respective hydrates.