K obtained from mass spectrometric investigations

No experimental information is available about the entropy and heat capacity of Se4(g). All published values are based on estimates made by comparison with gaseous sulphur and other selenium molecules. 

The values in [70KEL] and [74MIL] seem to be based on the same set of molecular parameters although those in [74MIL] are undocumented. Although not decisive, the second law entropies are in favour of the lower of the values calculated from molecular data. The entropy value in [84PUP/RUS] is selected, 

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Table V-6 Re-evaluated second and third law values of the enthalpy of formation of Se3(g) at 298.15 K obtained from mass spectrometric investigations. Determinations that yield too large Se (g) concentrations result in too low enthalpies of formation.

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