Thermodynamics of thallium alkanoates III. Heat capacity and thermodynamic functions of thallium(I) n-tetradecanoate from 7 to 450 K

Abstract

The heat capacity of thallium(I) n-tetradecanoate was measured by adiabatic calorimetry to 350 K and by d.s.c. from 235 through 460 K. Good agreement between the methods was obtained within the common temperature range. Several phases were observed in the sample. Two solid-to-solid transitions were found, a very sharp one at 318.5 K (Cp, m/R for the maximum is about 104; enthalpy (ΔtrsHm/R) increments are 1913.5 K and 6.00, respectively) and the other at 378.0 K: [ΔtrsHm/R = 346 K, ΔtrsSm/R = 0.92. Between these transitions there is a broad diffuse hump whose maximum is at about 360 K. The sample melts into a liquid-crystal phase at 396.3 K: ΔtrsHm/R = 754 K, ΔtrsSm/R = 1.9. Finally, "clearing" occurs at 460.7 K: ΔtrsHm/R = 201 K, ΔtrsSm/R = 0.44. Smoothed thermophysical properties are tabulated through "clearing".