When the DSC analysis of different samples of terpin hydrate is carried out, a non identified small endotherm is observed at about 100°C, just before the melting endotherm. This phenomenon is detected whatever the experimental conditions are.After some trials, this endotherm was identified as an eutectic formed with terpin hydrate and desolvated terpin (17/83).The importance of the experimental conditions is preponderant. In an open pan, the desolvation occurs and the melting endotherm of the anhydrous form can be observed at 105°C. In a closed pan, no desolvation is detected and the melting endotherm at 120°C is that of the terpin hydrate.The eutectic exhibits a good compression ability and a fast dissolution. Its stability is correct. Its use in therapeutic tablets can be envisaged.The eutectic structure could be, more generally, favourable to compression owing to the isotropic texture of this particular solid state.
The polymorphic forms II and III of paracetamol were obtained by melting the marketed form I. Under the melting and cooling conditions used, it was possible to obtain forms I, II and III. The recrystallization conditions and the physical properties of forms II and III were investigated by means of various techniques: thermomicroscopy, DSC analysis, infrared microspectrometry and X-ray powder diffraction at room temperature and as a function of temperature. Form III was found to be very unstable. However, its formation seems to be an important intermediate step in the preparation of form II.