Standard state thermodynamic properties for aqueous sodium perrhenate at temperature in the range of (298.15 to 598.15) K and at p(sat) were determined by high dilution solution calorimetry down to 10(-4) M. Standard state partial molar heat capacities, C-p,2(o), of aqueous sodium perrhenate calculated from present study are compared to literature values up to T = 398.15 K. The differences between C-p,2(o) of ReO4-(aq) and Cl-(aq) at lower temperature is much greater than that due to their internal molecular motions. Consequently, the perrhenate ion appears to have an ionic incomplete primary hydration shell as compared to the chloride ion. The ReO4-/Cl- difference in thermodynamic functions has now been well defined up to T = 598.15 K for other important high temperature calculations. (C) 2009 Elsevier Ltd. All rights reserved.