The molar heat capacities of the room temperature ionic liquid 1-ethyl-3-methytimidazolium ethyl sulfate (EMIES) were measured by an adiabatic calorimeter in temperature range from 78 to 390 K. The dependence of the molar heat capacity on temperature was given as a function of the reduced temperature X by polynomial equations, C-p,C-m (J K-1 mol(-1)) = 178.6 + 50.28X + 2.886X(2) - 1.362X(3) + 0.6616X(4) + 7.155X(5) [X= (T - 132.5)/54.5] for the solid phase (78-187 K) and C-p,C-m (J K-1 mol(-1)) = 376.2 + 25.94X - 3.397X(2) - 0.6407X(3) + 0.8091 X-4 + 0.9869X(5) [X= (T - 292.5)/97.5] for the liquid phase (195-390 ), respectively. According to the polynomial equations and thermodynamic relationship, the values of thermodynamic function of the EMIES relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass translation of EMIES was observed at 192.85 K. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of EMIES was determined to be Delta H-c(m)o -5152.6 +/- kJ mol(-1). The standard molar enthalpy of formation of EMIES was evaluated to be Delta(f) H-m(o) = -79.13 +/-0.15 kJ mol(-1) at T = 298.150 +/- 0.001 K. (C) 2006 Elsevier B.V. All rights reserved.