ULTRAVIOLET VISIBLE ABSORPTION-SPECTRA OF EQUILIBRIUM SULFUR VAPOR - MOLAR ABSORPTIVITY SPECTRA OF S-3 AND S-4

Ultraviolet-visible absorption spectra of equilibrium sulfur vapor were measured at various allotropic concentrations. This was achieved by using a two-temperature cell having sulful liquid in equilibrium with sulfur vapor. Independent variation of either temperature changes the vapor composition and, therefore, the absorption spectrum. Factor analysis techniques were applied to these vapor-phase mixtures to determine the identity and spectrum of each allotropic component. Our results show S3 and S4 to be two of the components which absorb in the spectral region between 350 and 600 nm. Quantitative, pure-component spectra of S3 and S4 were determined and used to calculate the partial pressures present in each mixture. DELTA-H-degrees(rxn) and DELTA-S-degrees(rxn) for the reaction 3S4 half-arrow-pointing-left-and-right 4S3 were determined to be 77.65 kJ/mol and 28.1 J/(mol K), respectively, at 810 K.