Abstract:On the basis of reinvestigation of related binary systems, the phase diagram of system LaCl₃ BaCl₂ NaCl was determined by DTA. There are 5 liquid surfaces corresponding to LaCl₃, NaCl, α BaCl₂, β BaCl₂ and Ba₂ LaCl₇ respectively and 6 univariant curves corresponding to the secondary crystallization and eutectic point E(69.0% LaCl₃, 2.0% BaCl₂, 29.0% NaCl, 509 ℃) and peritectic point  P  (52.0% LaCl₃, 22.0% BaCl₂, 26.0% NaCl, 550 ℃).

Key words: phase diagram LaCl₃ BaCl₂ NaCl LaCl₃