Chalcogenide glasses of special purpose that contain rare-earth oxides are transparent to infrared rays, absorb ultraviolet rays, and are resistant to different types of radiation. A special composition of rare-earth oxide glasses absorbing neutrons has been designed recently. The purpose of this work was to determine the boundaries of the glass formation region in the Ga 2 S 3 -Eu 2 O 3 system and to investigate the physicochemical properties of the samples prepared. The physicochemical properties of a red glass were studied. This glass was synthesized by incongruent melting of a compound in the Ga 2 S 3 -Eu 2 O 3 system. The initial compound was melted in an electric arc furnace with subsequent cooling in an inert gas flow [1,2].Glass samples were synthesized from the initial compounds β -Eu 2 O 3 and β -Ga 2 S 3 . The synthesis was performed under pressure in sulfur vapors at a temperature of 1475 K in a glassy carbon crucible placed in a reactor fabricated from fused silica. The synthesis duration was 2 h. After the synthesis, the samples taken at 1475 K were quenched into a room-temperature water. The alloys thus prepared were studied using differential thermal analysis, differential thermal gravimetry, and X-ray powder diffraction analysis.It was established that glasses containing 16-21 mol % Eu 2 O 3 are transparent and stable against crystallization. An increase in the Eu 2 O 3 content to 21.0-22.5 mol % results in the formation of opaque glasses. The opacity of the glasses is associated with the formation of crystals, which was confirmed by the X-ray powder diffraction analysis. As the Eu 2 O 3 content increases, the color of the glasses changes from orange to red. The thermal decomposition of the (Ga 2 S 3 ) 0.80 · (Eu 2 O 3 ) 0.20 glass