The sub-ambient heat capacity of thallium(I) n-heptanoate is characterized by two sets of transitions between 262 and 301 K. The lowest transition (at 262.8 K) has a maximum Cp, m/R ~ 700. Next, a bifurcated pair (at 267.8 and 271.7 K) has (Cp, m/R)'s ~ 200, and the highest bifurcated pair (at 297.2 and 300.9 K) has maximum (Cp, m/R)'s ~ 450 and ~ 16000. The corresponding values of ΔtrsSmo/R for the two sets are about 1.935 and 2.215. The heat capacities are in fair accord with the d.s.c. values of Fernandez-Martin, Lopez de la Fuente, and Cheda over the common range of superambient values. At 298.15 K the values of {Smo(T)-Smo(0)}/R, {Hmo(T)-Hmo(0)}/R, and -{Gmo(T)-Hmo(0)}/RT are 38.58, 5514.7 K, and 20.30. Smoothed thermodynamic values are tabulated at selected temperatures through melting.This research was supported in part by the Structural Chemistry and Chemical Thermodynamics Program of the Chemistry Section of the National Science Foundation under grant CHE-7710049.Peer reviewed