It was found that, in air as well as in an inert atmosphere, beta-Ag6S3O4 melts incongruently at 390 degrees C. Solid product of the incogruent melting of beta-Ag6S3O4 is beta-Ag8S4O4, the second phase existing in the Ag2SO4-Ag2S system. beta-Ag8S4O4 melts at 400 degrees C. At this temperature and in air the liquid obtained after melting starts decomposing to give metallic silver. In an inert atmosphere or at reduced pressure the liquid starts decomposing: at 530 degrees C and the final solid products of this decomposition are silver sulfide and metallic silver, gaseous product is SO2.