Mixtures of d- and l-carvone .1. Differential scanning calorimetry and solid-liquid phase diagram

Pure l-carvone and mixtures of d- and l-carvone have been studied by differential scanning calorimetry. The obtained curves of heat flow against temperature show the glass transition of the samples, followed by two crystallisation events and, finally, the melting of the carvone mixtures. The measured temperature of melting of pure l-carvone is (247.7 +/- 0.5) K and the heat of fusion (11.55 +/- 0.05) kJ mol(-1). Five precrystallised samples with compositions ranging from equal amounts of d- and l-carvone up to pure l-carvone have been studied. The carvone system shows mixed crystals at all compositions corresponding to a phase diagram with a minimum at equimolar composition. The data obtained by computer calculations agree with the experimental values, thus showing the thermodynamic consistency of the obtained phase diagram.