Thermodynamic properties of calcium-ammonium nitrate decahydrate

The functions of formation at T = 298.15 K of calcium-ammonium nitrate decahydrate, 5Ca(NO3)2·NH4NO3·10H2O, have been computed on the basis of experimental results obtained in this work. Single-phase crystalline calcium-ammonium nitrate decahydrate has been synthesized and checked by chemical analysis, thermogravimetry, differential scanning calorimetry, powder X-ray diffraction, and infrared spectroscopy. The enthalpy of dissolution of the decahydrate in water at T = 298.15 K was measured in a sealed swinging calorimeter with an isothermal jacked. The low-temperature heat capacity of the solid has been measured by vacuum adiabatic calorimetry in the temperature range (7 to 338) K. The temperature, enthalpy, and entropy of fusion of the crystalline hydrate have been determined via differential scanning calorimetry at high pressure. A second-order solid-solid transition for the substance in the temperature range (300 to 330) K has been detected by methods of adiabatic calorimetry and differential scanning calorimetry.