Thermal stability and related thermodynamic properties of N-ethylthiourea

Abstract

The enthalpy and entropy of sublimation of N-ethylthiourea were obtained from the temperature dependence of its vapour pressure measured by both the torsion–effusion and the Knudsen effusion method in the temperature range 360–380 K. The compound undergoes no solid-to-solid phase transition or decomposition below 380 K. The pressure against reciprocal temperature resulted in lg( p, kPa) = (13.40 ± 0.27) − (6067 ± 102) / T(K). The molar sublimation enthalpy and entropy at the mid interval temperature were Δ sub H m(370 K) = (116.1 ± 2.0) kJ mol −1 and Δ sub S m(370 K) = (218.0 ± 5.2) J mol −1 K −1, respectively. The same quantities derived at 298.15 K were (118.8 ± 2.1) kJ mol −1 and (226.1 ± 5.5) J mol −1 K −1, respectively.