The heat capacity of (n-C12H25NH3)2CdCl4 was measured from 280 to 500 K by using a automated adiabatic calorimeter. A solid-solid phase transition was found with the max. temperature at 332.4 ?0.1 K. The enthalpy and entropy of the transition were determine to be 48.35 kJ/mol and 145.5 J/K.mol, resp. G. F. Needham (1984) reported two solid-solid phase transitions for the virgin sample of the compound, a minor transition at 332 K preceding the main transition at 334 K; the minor transition disappeared in the DSC experiment for the reheated sample. By combining with the data for the corresponding Mn and Zn compounds, the influence of central atoms on the phase transitions of series of compounds (n-CnH2n+1NH3)2MCl4 was discussed on the basis of the different structures of [MCl4]2- (M = Mn, Zn Cd).

Key words: THERMODYNAMIC PROPERTIES, PHASE TRANSFORMATION, ENTROPY, ENTHALPY, SPECIFIC HEAT, C12 COMPOUNDS, CADMIUM CHLORIDE, AMMONIUM