The phase stabilities of three pseudopolymorphs of DN-9693 were studied by using thermogravimetry and differential thermal
analysis. The thermal dehydration of DN-9693·2HCl·H2O proceeds by the mechanism of two-dimensional growth of nuclei. The thermal dehydration of 0.5 mol of H2O per mol of DN-9693·2HCl·2H2O, and that of 2 mol of H2O per mol of DN-9693·2HCl·3H2O, proceed by the mechanisms of three-dimensional diffusion and three-dimensional phase boundary reaction, respectively, but
the dehydration followed overlaps with the thermal elimination of HCl. The half-lives for the dehydration at 25°C show that
DN-9693·2HCl·H2O is the most stable form.