Differential drop calorimetry for the determination of enthalpy of fusion

Drop calorimetry was modified in order to adapt it to the measurement of the enthalpy of fusion of materials with above-ambient fusion temperatures, T_F, such as salt hydrates suitable as phase change materials. In the modified form, differential drop calorimetry, the energy delivered to the molten sample at temperatures above T_F and by the crystalline sample at temperatures below T_F are extrapolated to T_F to give the enthalpy of freezing. The calorimetric system was calibrated electrically and with acetamide (T_F = 353.3 K) and applied to the congruently melting magnesium nitrate hexahydrate, cadmium nitrate tertrahydrate, ammonium alum, and several hydrated salt mixtures.