Heat capacities of aqueous binary and ternary mixtures (with piperazine) of N-(2-aminoethyl)-piperazine and N,N,N′-trimethylethylenediamine at temperatures (303.2–353.2) K

• Heat capacities of aqueous mixtures (with piperazine) of two polyamines were measured.
• Two polyamines are N-(2-aminoethyl)piperazine and N,N,N′-trimethylethylenediamine.
• The measured data were reported as functions of temperature and composition.
• The measured data were represented satisfactorily by the applied correlations.

A new set of values for the molar heat capacities of N-(2-aminoethyl)piperazine (AEP) and N,N,N′-trimethylethylenediamine (tMEDA) and their aqueous mixtures over the whole range of compositions are reported in the present work. Molar heat capacities of ternary mixtures of each polyamine with piperazine (PZ): (AEP + PZ + H2O) and (tMEDA + PZ + H2O) were also measured. Measurements were done over the temperature range T = (303.2–353.2) K and p = 101.3 kPa by the differential scanning calorimetry technique. Excess molar heat capacities of aqueous binary mixtures were correlated with composition and temperature using a Redlich–Kister relation, which was then used to correlate molar heat capacities of the mixtures at different temperatures and compositions. The equation fit the results with the average absolute deviation (AAD) of 2.1% and 0.2% for the excess molar heat capacity and molar heat capacity, respectively. A modified Söhnel and Novotný equation was applied to represent the composition and temperature dependence of the molar heat capacity of aqueous ternary mixtures at AAD between the correlated and the experimental data of about 0.1%. The correlations proposed here are of acceptable accuracy for application in process design and engineering.