Abstract:When titanium, zirconium, cerium and other rare metals were directly extracted by calciothermic reactions, rise of molten salt viscosity often led to difficulties in stirring, energy consumption and slow reaction. In order to find out the factors affecting viscosity of CaCl2 molten salt, viscosity of different compositions of molten salt in temperature range from 1 073 K to 1 373 K was measured. According to experimental results, viscosity-temperature curves of four molten salt systems of CaCl2, CaCl2-CaF2, CaCl2-CaO, and CaCl2-CaF2-CaO were drawn. The results show that viscosity value is mostly 2.0~10.0 mPa?s within test temperature range, viscosity of four molten salt systems rises with decreasing of temperature. Viscosity of molten salt drops with addition of CaF2 and rises with addition of CaO.