Physical chemistry of binary organic eutectic and monotectic alloys; durene-pyrogallol system

The phase-diagram of durene-pyrogallol system, determined by the thaw-melt method, shows the formation of a eutectic at 79.6 degreesC and a monotectic at 127.7 degreesC containing 0.95 and 0.05 mol fractions of durene, respec tively. Growth data for the pure components, the eutectic and the monotecti c, determined by measuring the rate of movement of solid-liquid interface i n a capillary at different undercoolings (DeltaT) suggest the applicability of Hillig-Turnbull equation, nu = u(DeltaT)(n), where u and n are constant s depending on the nature of materials involved. The values of enthalpy of fusion of the pure components, the eutectic and the monotectic were determi ned and from these values, the enthalpy of mixing, size of the critical nuc leus, interfacial energy and excess thermodynamic functions were calculated . While optical microphotographs of the pure components showed a faceted mi crostructure, those of eutectic and monotectic show their characteristic fe atures. (C) 2000 Elsevier Science B.V. All rights reserved.