Abstract:

A novel compound—monohydrated zinc nicotinate was prepared via room temperature solid phase synthesis and ball grinding. FTIR, chemical and elemental analyses and X-ray powder diffraction technique were applied to characterizing the structure and composition of the complex. Low-temperature heat capacities of the solid coordination compound were measured by a precision automated adiabatic calorimeter over a temperature range from 77 to 400 K. A solid-solid phase transition process occurred in a temperature range of 321―342 K inferred according to the heat capacity curve, and the peak temperature, molar enthalpy and entropy of the phase transition of monohydrated zinc nicotinate were determined to be T_trs=(340.584±0.829) K, ?_trsH_m=(12.682±0.041) kJ/mol and ?_trsS_m= (37.235±0.101) J/(K?mol). The experimental values of the molar heat capacities in the temperature regions of 77―321 K and 342―400 K were, respectively, fitted to two polynomial equations. In addition, the polynomial fitted values of the molar heat capacities and fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were calculated and tabulated at intervals of 5 K.

Key words: Zinc nicotinate; Adiabatic calorimeter; Heat capacity; Phase transition; Thermodynamic function