ИСТИНА

The scientific literature has accumulated a large amount of data on the physicochemical properties of ionic liquids. To optimize technological processes, as well as expluatation conditions, it is necessary to have data on the thermodynamic properties of these substances. Despite the fact that ionic liquids have been the subject of research for several decades, in the scientific literature and international databases the thermodynamic properties of ionic liquids are presented fragmentarily. The object of this work is 1-ethyl-3- methylimidazolium methanesulfonate (EmimMS). The aim of the work is to determine the low-temperature heat capacity over a wide temperature range and to calculate the standard thermodynamic functions of the EmimMS formation in the crystal and liquid states. The isobaric heat capacity of the crystal and liquid phases of EmimMS was determined in the temperature range from 80 to 380 K by the vacuum adiabatic calorimetry. Two phase transitions were observed: G-type at 203.3±0.5 K and melting at 313.01 ± 0.2 K (Figure 1). Melting parameters were also refined by DSC. At temperatures from 5 to 80 K the heat capacity of EmimMS was assessed by the Kelly method. The temperature dependencies of EmimMS main thermodynamic functions have been determined in the temperature range from 5 to 380 K (isobaric heat capacity Cp,m(T), standard entropy S 0m(T), heat content H 0 (T) ‒ H 0 (0), Gibbs energy content G 0 (T) ‒ H 0 (0)). In the present study the standard entropies and Gibbs energies of EmimMS formation in the crystal and liquid state at 298.15 K were calculated from the experimental data of adiabatic calorimetry in conjunction with dissolution calorimetry data [1]. Comparison of the obtained thermodynamic characteristics with the literature data was carried out. [1] L.A. Tiflova, D.A. Kalinyuk , A.I. Druzhinina, Book of abstracts of XXIII International Conference on Chemical Thermodynamics in Russia, 2022, 86. Investigation was supported by the Program “Chemical Thermodynamics and Theoretical Material Science” (AAA-1210313000391) and by the Federal Project "Growth of Advanced Infrastructure for Research and Development in the Russian Federation" of the national project "Science and Universities" (updating of equipment for scientific research).