Low-temperature heat capacities of the compound Na(C4H7O5)center dot H2O(s) have been measured with an automated adiabatic calorimeter. A solid-solid phase transition and dehydration occur at 290-318 K and 367-373 K, respectively. The enthalpy and entropy of the solid-solid transition are Delta H-trans(m) = (5.75 +/- 0.01) kJ mol(-1) and Delta S-trans(m) = (18.47 +/- 0.02) J K-1 mol(-1). The enthalpy and entropy of the dehydration are Delta H-d(m) = (15.35 +/- 0.03) kJ mol(-1) and Delta S-d(m) = (41.35 +/- 0.08) J K-1 mol(-1). Experimental values of heat capacities for the solids (I and II) and the solid-liquid mixture (111) have been fitted to polynomial equations. (c) 2006 Elsevier B.V. All rights reserved.