Low-temperature heat capacity and derived thermodynamic properties for 1-methyl-3-propylimidazolium bromide and 1-butyl-3-methylimidazolium iodide

•Thermodynamic properties of two ionic liquids were determined from calorimetric measurements.•Heat capacities of liquid [C4mim]Hal are independent of the halide.•Residual entropies of glassy [C4mim]Hal are independent of the halide.

Heat capacity in the temperature range (5 to 370) K and parameters of fusion and the glass transition were determined for 1-methyl-3-propylimidazolium bromide and 1-butyl-3-methylimidazolium iodide. Thermodynamic properties of the compounds in the condensed state in a range of temperatures (0 to 370) K were calculated from the obtained data. It was demonstrated that heat capacities of liquid 1-butyl-3-methylimidazolium halides coincide within the experimental uncertainties, similar consistency is observed for residual entropy of the glassy compounds.

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