•The results with both trifluoperazine di-HCl and clonidine HCl provide strong evidence for dissociative adsorption of water on organic hydrochloride salts. •This strongly bound water may act as nuclei for further moisture uptake and cause stability problems for moisture-labile salts. •Future work will investigate: • Role of surface chemistry and defect density of various faces of clonidine HCl single crystals on the extent of dissociation • Comparison between clonidine HCl, clonidine HBr and clonidine free bas
