Information about the state of Sulfur in silicate melts and glasses is important in both earth sciences and materials sciences. Because of its variety of valence states from S2- (sulfide) to S6+ (Sulfate). the speciation of sulfur dissolved in silicate melts and glasses is expected to be highly dependent on the oxygen fugacity. To place new constraint on this issue, we have synthesized sulfur-bearing sodium silicate glasses (quenched melts) front starting materials containing sulfur of different valence states (Na2SO4, Na2SO3, Na2S2O3 and native S) using an internally heated gas pressure vessel, and have applied electron-induced SKalpha X-ray fluorescence, micro-Raman and NMR spectroscopic techniques to probe their structure. The wavelength shift of SKa X-rays revealed that the differences in the valence state of sulfur in the starting compounds are largely retained in the synthesized sulfur-bearing glasses, with a small reduction for more oxidized samples. The Si-29 MAS NMR spectra of all the glasses contain no peaks attributable to the SiO4-nSn (with n > 0) linkages. The Raman spectra are consistent with the coexistence of sodium sulfate (Na2SO4) species and one or more types of more reduced sulfur species containing S-S linkages in all the sulfur-bearing silicate glasses, with the former dominant in glasses produced from Na2SO4-doped starting materials, and the latter more abundant in more reduced glasses. The 29Si MAS MAR and Raman spectra also revealed changes in the silicate network Structure of the sulfur-bearing glasses, which can be interpreted in terms of change:, in the chemical composition and sulfur speciation. Copyright (C) 2004 Elsevier Ltd.