We have investigated the dissociation rates of nonstoichiometric semiconductors Ag2±δX (X=S, Se) to the vacuum by means of solid-state electrochemical technique. The values of chalcogen fluxes from the sample’s surface were measured versus compound’s composition and temperature. There has been obtained experimental evidence of the surface reconstruction of silver chalcogenides when the exact phase composition δcr.(T) is reached. This critical value δcr. correlates with the order-disorder transition in the silver sublattice for the Ag2±δX/vacuum interface.