A residue of 10 μg is dissolved in 5 μL of water and 5 μL of reagent is added to it. 3,4- MDPV forms two types of crystals with aqueous gold chloride reagent 1) sheaves of short rods that are bright under crossed polars 2) tight clusters of plates and with angled edges. These features are better defined under crossed polars. The microcrystals that are clusters of thick plates offer good maneuverability for infrared spectroscopy and the resulting transmission spectra exhibit spectral features that are a match for the pure substance.