High-temperature mass spectrometry was used to determine the Gibbs energies, activities, and chemical potentials of SrO and SiO₂ in glasses and melts of the SrO-SiO₂ system in the temperature range 1840-1970 K. Negative deviations from the ideal behavior were revealed in the system. The standard enthalpies of formation and atomization of gaseous SrSiO₂ and SrSiO₃ were determined.