An amino acid ionic liquid, [C2mim][Val] (1-ethyl-3-methylimidazolium α-aminoisovaleric acid salt), was prepared by the neutralization method. Using the solution-reaction isoperibol calorimeter, the molar solution enthalpies of ionic liquid [C2mim][Val], ?solHm(w), with known initial mass fractions of water, w2, and with different molalities were determined at 298.15 ±0.01 K. In terms of standard addition method (SAM) and Archer’s method, the standard molar enthalpy of solution for [C2mim][Val] without water, ΔsolHmθ, was obtained. The combustion energy of the ionic liquid was determined using an RB-II type the rotating-bomb combustion calorimeter. The standard molar enthalpy of combustion, ΔcHmθ, and the standard molar enthalpy of formation, ΔfHmθ, were calculated. In terms of standard molar enthalpy of solution, ΔsHmθ, and the standard molar enthalpy of formation for cation of [C2mim]+, the standard molar enthalpy of formation for anion of [Val]? in water solution were calculated. Using an RD496-III heat conduction microcalorimeter, the molar enthalpies of dilution, ΔDHm(mi→mf), of aqueous [C2mim][Val] with various molalities were measured. The values of apparent relative molar enthalpy, φL, were calculated using extended Debye-Hückel equation, which are in good agreement with that calculated using Pitzer’s ion-interaction model.

Key words: valine, ionic liquid, enthalpy of solution, enthalpy of combustion, enthalpy of dilution