The equilibrium pressure over the phase mixture (Li2NH + LiNH2 + LiH) was measured from 343 to 683 K by static manometric method. The plot of In (p(eq)/p(0)) versus (1/T) showed three distinct temperature regions with different slopes. Analysis of the equilibrium gas composition in each temperature regions revealed that the equilibrium gas is a mixture of H-2, NH3 and N-2 below 443 K whereas above 443 K, the equilibrium gas is mainly H-2. The enthalpy and entropy of the reaction of H-2 with Li2NH to form LiNH2 and LiH are found to be -55.0 +/- 1.3 kJ.mol(-1) and -86 +/- 2 J.K-1.mol(-1), respectively at 523 K, where LiNH2 exists in the solid state and -18.5 +/- 0.5 kJ.mol(-1) and -26 +/- 1 J.K-1.mol(-1), respectively at 658 K, where LiNH2 exists in the liquid state. The enthalpy and entropy of melting of solid LiNH2 are calculated as 36.5 +/- 1.4 kJ.mol(-1) and 60 + +/- 2J.K-1.mol(-1), respectively. Copyright (C) 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.