Phase transitions in crystalline [M(H2O)(6)](ClO4)(2) (M=Mg, Mn, Fe, Co, Ni, Cu, Zn, Cd and Hg)

The results of DSC measurements in the temperature range 140-370 K on nine crystalline compounds of the type [M(H2O)(6)](ClO4)(2), where M=Mg, Mn, Fe, Co, Ni, Cu, Zn, Cd and Hg, are discussed. Anomalies detected in the DSC cu rves are related to the existence of solid-solid phase transitions and/or t o the melting points of these compounds. In consequence of two different hy pothetical structural modifications of [Fe(H2O)(6)](ClO4)(2), two DSC curve s are obtained. For the compounds with M=Fe, Cd and Hg, new phase transitio ns have been discovered. The transition temperatures of the other phase tra nsitions are in good agreement with literature data obtained by adiabatic c alorimetry. For the compounds with M=Mg, Ni and Cd, DTA measurements were a lso carried out and the melting points of theses compounds were established .