Metastability in solid solution growth

Crystallization of binary mixtures of 1,4-dichlorobenzene and 1,4-dibromobenzene is examined in an adiabatic calorimeter. First heated to 380 K under adiabatic conditions and thus transformed into a binary melt, the mixture was slowly cooled to 250 K. The experimental cooling curves (the recorded change of mixture's temperature with time) obtained for the various compositions of the issued mixture, served for the specification of enthalpy change of the mixture during crystallization. In order to demonstrate the importance of the kinetics during an even slow crystallization process, the experimental data will be interpreted in terms of a kinetic model as opposed to the traditionally used equilibrium approach. We will show that kinetic model can serve for the derivation of excess parameters that characterize the degree of mixing in the phases.