The isochoric heat capacity of mixtures of n-heptane + water with compositions of 3.0 wt.% and 11.50 wt.% of water is investigated in liquid-liquid-vapor, liquid-vapor and homogeneous states using high-temperature adiabatic calorimeter. The density of the azeotropic state was determined from the C-V measurements. (C) 1998 Elsevier Science B.V. All rights reserved.