Abstract
The molecular properties of benzoic acid, ethyl p-aminobenzoate and benzophenone mixed with porous glass powder were investigated by differential scanning calorimetry (DSC), powder X-ray diffraction, and gas adsorption measurements. The mixtures had anomalous properties as compared with the mixtures with glass beads, that is, (1) a low concentration mixture (about 5%) did not show the melting heat and X-ray diffraction peaks associated with the medicinal crystals, (2) a high concentration mixture (about 20%) showed only a broad endothermic peak at a lower temperature than the melting point, and (3) a higher concentration mixture (more than 40%) showed an endothermic heat effect at the melting point together with the broad peak at a lower temperature. The peak area at the melting point increased with an increase of drug concentration while the broad peak area remained unchanged. Mixing with medicinals caused a decrease of surface area and a change of pore diameter distribution of the porous glass. From these results it was concluded that the medicinals took three phases in the mixture ; phase 1 (crystal structure), phase 2 (disordered structure) and phase 3 (probably adsorbed on the pore walls). The amounts of these phases were calculated from DSC curves.
