Heat-capacity measurements by adiabatic calorimetry at temperature T = 5 K to 350 K were supplemented by differential-scanning calorimetry (d.s.c.) into the liquid region on thallium(I) propanoate and pentanoate. Apparent phase transitions were noted for the propanoate for the crystal III-to-crystal II transition with DELTA(trans)S(m)-degrees = (1.473 +/- 0.001) R at T = (277.7 +/- 0.1) K adiabatic calorimetry and for the crystal II-to-crystal I transition at (0.10 +/- 0.01) R at T = (268.4 +/- 0.4) K by d.s.c. and for the crystal I-to-liquid transition with DELTA(trans)S(m)-degrees = (2.70 +/- 0.09) R at T = (468.0 +/- 0.4) K. For the VI-to-V and V-to-IV transitions of the pentanoate by adiabatic calorimetry the corresponding values are (0.359 +/- 0.002) R and (235.1 +/- 0.1) K, (1.511 +/- 0.003) and (219.(3) +/- 1) K. For the IV-to-III, III-to-II, II-to-I, plus crystal 1-to-mesophase and mesophase-to-isotropic liquid for the same compound the pairs of values by d.s.c. (only) are : (0.26 +/- 0.02) R and (234.6 +/- 0.4) K; (1.00 +/- 0.04) R and (284.5 +/- 0.4) K; (0.72 +/- 0.03) R and (353.0 +/- 0.4) K; (1.50 +/- 0.05) R and (455.0 +/- 0.5) K; and (0.75 +/- 0.04) R and (488.0 +/- 0.8) K. Like thallium(I) butanoate, the propanoate does not show a meso-tropic liquid phase.