Excess heat capacities of (binary + ternary) mixtures containing [emim][BF4] and organic liquids

•The CPE and CPEijk data have been measured over entire composition range at four temperatures.•The observed data have been fitted to Redlich–Kister equation.•The observed data have been analyzed in terms of Graph theory.•The values determined by Graph theory compare well with experimental values.

The excess heat capacities, CPE and CPEijk (calculated from the measured molar heat capacities, Cp data) of binary 1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyrrolidin-2-one or 1-methylpyrrolidin-2-one or pyridine (j); pyrrolidin-2-one (i) + pyridine (j) and ternary 1-ethyl-3-methylimidazolium tetrafluoroborate (i) + pyrrolidin-2-one or 1-methylpyrrolidin-2-one (j) + pyridine (k) mixtures have been measured as a function of composition at T = (293.15, 298.15, 303.15 and 308.15) K and 0.1 MPa using micro differential scanning calorimeter. The CPEijk values for the present ternary mixtures are positive over entire range of composition. The CPE and CPEijk data have been fitted to Redlich–Kister equation to compute binary and ternary adjustable parameters along with their standard deviations. The topology of the constituent molecules (Graph theory) has been utilized to obtain the expressions that describe well the CPE and CPEijk data of the present mixtures. It has been observed that Graph theory describes well the CPE and CPEijk data of the binary as well as ternary mixtures.