A colorless and transparent ionic liquid EMIInCl₄ was prepared by mixing 1-ethyl- 3-methylimidazolium chloride (EMIC) with InCl₃ in a glove box filled with dry argon. The molar dissolution enthalpies (Δ_sH_m) of EMIC and EMIInCl₄ in water with various molalities were determined by a solution-reaction isoperibol calorimeter at 298.15 K. In terms of Pitzer electrolyte solution theory, the molar dissolution enthalpy of EMIC and EMIInCl₄ at infinite dilution (Δ_sH_m⁰) and Pitzer parameters (β_MX^(0)L, β_MX^(1)L and C_MX^ФL) were obtained, respectively. Using values of the dissolution enthalpies and the hydration heat, the dissociation heat of InCl₄^－ (Δ_dH_m) and the enthalpy change (Δ_rH_m) for the reaction of EMIC＋InCl₃→EMIInCl₄ were estimated respectively. The result, Δ_rH_m＝(－60.37±1.8) kJ•mol^－1, was in agreement with exothermic phenomenon observed while the ionic liquid was synthesized.

Key words: isoperibol calorimeter, dissolution enthalpy, Pitzer’s theory, ionic liquid