The refractive indexes of three ionic liquids, glutamic acid tetrafluoroborate ([GA]BF₄), glutamic acid double trifluoromethyl sulfonyl amine salts ([GA]TF₂N), glutamic acid hexafluorophosphate ([GA]PF), with ethanol and/or Water systems under 10~35 °C were studied. The excessive refractive index of the systems and the relationship between the refractive index and the constituent molar fraction at 20 °C, and the empirical relationship between the excess refractive rate and the constituent mole fraction were established. The experimental results show that the excess refractive index is positive in the measured concentration range, and the refractive index of ethanol+Water with the increase in the composition appears maximum and the refractive index of ethanol/Water+ [GA]BF₄, ethanol/Water+[GA]PF, ethanol/Water+[GA]TF₂N system is increased with the increase in composition. By using the Redlich-Kister equation to correlate the binary system and the excess refractive index of ternary system, the fitting results show that the refractive index of ternary system can be estimated using the refractive index of the polynomial equation of binary system.
