Heat Capacities and Thermodynamic Properties of Two Tetramethylammonium Halides

Abstract

Heat capacities of tetramethylammonium chloride and bromide were determined by low-temperature adiabatic calorimetry from 5° to 350°K. Derived thermodynamic properties were then calculated. Two transitions were found in the chloride: a sharp, apparently first-order transition occurs at 75.76°K with an entropy of transition of 0.37 cal mole—1 °K—1 and a lambda-shaped transition at 184.85°K with an entropy increment of 0.14 cal mole—1 °K—1. No anomaly has been observed in the bromide. Molal values of heat capacity, entropy, and free energy function at 298.15°K for the chloride and the bromide are: 37.51, 38.64, 45.58, 47.99, and —23.36, —25.36 cal mole—1 °K—1, respectively.