K NUDSEN measurements of the sublimation and the Heat of Formation of GeSe

K NUDSEN effusion studies of the sublimation of polycrystalline GeSe have been performed employing mass spectrometry in a temperature range of about 530–730°K and vacuum microbalance techniques in the temperature range 601–796°K and at pressures ranging from about 10 −6 –10 −4 atm. The results are concordant and demonstrate that GeSe vaporizes congruently under present experimental conditions according to the reaction GeSe(s) = GeSe(g). The mean values for the third law heat and second law entropy of reaction based on direct mass‐loss data are ΔH   298 0= 42.0 ± 1.5 kcal/mole and ΔS   298 0= 42.3 ± 1.6 eu. From these data the standard heat of formation and absolute entropy of GeSe(s) were calculated to be −10.1 ± 2.0 kcal/mole and 16.9 ± 2.0 eu, respectively.