Solidification Behavior of the Benzamide plus O-Chlorobenzoic Acid Eutectic System

The phase diagram of the benzamide + o-chlorobenzoic acid system has been studied by the thaw-melt method, and results show the formation of a simple eutectic mixture. Values of enthalpies of fusion of pure components-and the eutectic mixture were determined from DSC studies. Excess Gibb's energy (G (E)), excess enthalpy (H-E), and excess entropy (S-E) of mixing of pre-, post-, and the eutectic mixture were also calculated using activity coefficient data. Linear velocities of solidification of pure components and the eutectic mixture were determined at different undercooling rates. The values of the excess thermodynamic functions, linear velocity of crystallization, and ab initio calculations indicate the nonideal nature of the eutectic mixture in the melt. The anisotropic and instantaneous crystallizations of benzamide, o-chlorobenzoic acid, and the eutectic mixture were studied. The flexural strengths of the pure components and the eutectic mixture were also measured.