The thermodynamic equilibrium of the bimolecular dehydration of 1-butanol to di-n-butyl ether (DNBE) and water in the liquid phase was studied. Equilibrium experiments were performed at 4 MPa and in the temperature range of 413-463 K over the ion exchange resin Amberlyst-70. The thermodynamic equilibrium for the side reactions (dehydration to 1-butene, olefins isomerization, olefins hydration and branched ether formation) was also studied. The equilibrium constant for the dehydration reaction of 1-butanol to di-n-butyl ether and water was found to be independent on the operating temperature, within the limits of the experimental error ( 5.2%). The experimental equilibrium constants at 413-463 K allows to estimate the standard enthalpy change of reaction (ΔrH0(l) = -0.3 ± 2.9 kJ¿mol-1) and the standard entropy change of reaction (ΔrS0(l) = 26.8 ± 6.7 J¿mol-1¿K-1). From these values the standard formation enthalpy (ΔfH0DNBE,(l)) and the molar entropy of DNBE (S0DNBE,(l)) at 298.15 K were computed to be -370.5 ± 10.9 kJ¿mol-1 and 408.3 ± 6.8 J¿mol-1¿K-1 respectively