This manuscript presents thermodynamic analysis of some binary organic eutectic systems, which reveals the interactions between unlike phase molecules in the miscibility phenomenon. Computation of excess thermodynamic functions from experimentally investigated solidus-liquidus equilibrium data of a binary organic eutectic system in the condensed phase, comprehensively yields quantitative analysis of molecular interactions considered to be the cause of deviations from the molten state of the system over the entire mole fraction composition range. The excess functions are reliable, since all the parameters involved in their computation are experimentally determined. The obedience of spontaneity criteria, and Planck formulation, S = k ln w (k and w, respectively, being the Boltzmann constant and the complexion number of constituent phase molecules) by an eutectic system throughout its diagram of state accessible to it, authenticates the reliability of the functions. The application of Guggenheim lattice theory to the eutectic mixture at its liquidus temperature offers supporting evidence to the essence of molecular interactions. The aesthetics and motivation of the present work is that the excess thermodynamic functions, computed from experimentally determined enthalpies of fusion and consequently, from activity coefficients of eutectic phases, by variation in a mole fraction composition range provide an alternative tool to predict a schematic diagram of solidus-liquidus equilibrium curve of a binary system, particularly capable of forming eutectic mixture. (C) 2004 Elsevier B.V. All rights reserved.