Molar heat capacities, (C-P)(123) and (C-P)(mix), have been measured for the ternary o-chlorotoluene (1) + tetrahydropyran (2) + benzene or toluene or o-xylene (3) and their binaries tetrahydropyran (1) + benzene or toluene or o-xylene (2) at 298.15, 303.15 and 308.151< and atmospheric pressure. From the experimental results, excess heat capacities, C-P(E), and (C-P(F))(123) values were calculated and fitted to Redlich-Kister equation to determine binary and ternary adjustable parameters along with standard deviations. The observed C-P(E) and (C-P(E))(123) data have been analyzed by utilizing topology of the constituent molecules (Graph theory). The estimated C-P(E) and (C-P(E))(123) values from Graph theory are in agreement with experimental values. The interaction parameters, chi* and chi(12)' for binary mixtures (simulated by Graph theory) have been discussed to obtain information about molecular interactions in mixtures. (C) 2014 Elsevier B.V. All rights reserved.