Adiabatic Calorimetry of Organic Salts: Tetra-n-hexylammonium Perchlorate

Abstract

We have measured the heat capacity of a zone refined sample of tetra-n-hexylammonium perchlorate (99.94 % pure, by analysis of the fusion curve). Values of the transition temperatures, enthalpies and entropies are: fusion 379.18 K, 16 350 J mol-1, 43.10 J K-1 mol-1; transition (1) 367.51, 2658, 7.24; transition (2) 355.91, 5839, 16.42; transition (3) 333.57, 22 990, 68.93. We interpret fusion and transition (3) as being due, respectively, to ionic melting (break down of the lattice) and “ melting ” of the hexyl groups. Transitions (1) and (2) are explained by re-orientation of the perchlorate anions.