Na(NTO)(H2O) was prepared by mixing an aqueous solution of 3-nitro- 1,2,4-triazol-5-one (NTO) and that of sodium hydroxide. The crystal structure of Na(NTO)(H2O) was determined by single crystal diffraction analysis. The crystal is monoclinic, space group P21/c with crystal parameters of a=0.6303(1)nm, b=0.8285(1)nm, c=1.1574(2) nm, β=103.85(1)°, V=0.5868(2) nm^3, Dc=1.925g/cm^3, Z=4, F(000)=344, μ=0.238 mm^-1, R=0.0259. By measurement of the solution enthalpy of Na(NTO)(H2O) in water at 298.15 K, the standard enthalpy of formation, lattice energy, and lattice enthalpy have been calculated.

Key words: SODIUM HYDROXIDE, CRYSTAL STRUCTURE, THERMODYNAMIC PROPERTIES, X-RAY DIFFRACTION ANALYSIS, NITRO COMPOUNDS, TRIADIMEFON