Experimental data supporting lower valence halides of scandium were not found in the literature. Our investigation was of the phase diagram of the ScCl3-Sc system, and also the vapor pressure-composition isotherm (at 960 degree) for this system. Investigation of the ScCl3-Sc system presented particular difficulties in comparison with analogous systems for rare earth elements in that ScCl3 is highly volatile (boiling pt. = 967 degree); according to our data the vapor pressure is 512 mm Hg measured at 960 degree C. Furthermore, ScCl3 and its vapors react vigorously with quartz. Because of the mentioned extent of reaction in a quartz ampule, the inside was covered with a solid layer of metallic molybdenum for use with relatively large batches of ScCl3.