Thermophysics of thallium alkanoates IV. Heat capacity and thermodynamic functions of thallium(I) n-dodecanoate from 7 to 470 K,

Abstract

The thermal behavior of thallium(I) n-dodecanoate was studied by adiabatic calorimetry from 6 to 350 K and by d.s.c. from 230 through 470 K. The agreement between the results (temperature and thermal functions of transitions and heat capacity) from both methods was within the experimental error over the common temperature range. Several phases were observed in the sample. Four of the five solid-to-solid transitions appeared in the common temperature range of both techniques. The two lowest-temperature transitions appear as a bifurcated pair (at 282.65 and 284.8 K) with (Cp,m/R) [approximate] 250 and 450, respectively. The third and fourth occur at 293.1 and 312.1 K with (Cpm/R) [approximate] 250 and 14000. Above 350 K three more transitions were measured by d.s.c.: solid-to-solid, solid-to-mesophase, and mesophase, and mesophase-to-isotropic-liquid transformations at 356.6, 400.1, and 471.5 K. The corresponding values of [Delta]trsSmo/R for the seven transitionswere 0.910, 1.111, 0.710, 2.075, 0.69, 1.64, and 0.50. Smoothed thermodynamic values are tabulated at selected temperatures through the "clearing" point.