The mechanochemical transformation of ?Ñalfa-realgar As4S4 to its high temperature polymorph ?"beta- form has been studied. The size dependance of this transformation was elucidated for particle size 25-62 nm. The mechanochemical transformation is hindered by agglomeration effects in this case. The identified phenomena - polymorphous transformation, new surface area formation and preparation of realgar particles in nanosize - are expected to have good impact on solubility as well as bioavailability of realgar as a potential new pharmaceutical drug for leukemia treatment.
