Chapter 23: Measurement of Heat Capacity and Phase Transition Enthalpy for Condensed Materials by Precision Adiabatic Calorimetry

A fully automated adiabatic calorimeter used for heat capacity measurements from 80 K to 400 K was constructed. The reliability of the calorimeter was verified by measuring the heat capacities of Standard Reference Material 720. The deviation of the data obtained by this calorimeter from NIST was within ±0.1%. The heat capacity of ionic liquid 1-ethyl-3-methylimidazolium tetracyanoborate was measured from 78 K to 370 K by the calorimeter. The dependence of heat capacity on the temperature was put forward. The melting temperature, enthalpy and entropy were determined. The thermodynamic functions [H$T0$−H$298.150$] and [S$T0$−S$298.150$] were derived.