The Mandelin reagent is used as a simple spot-test to presumptively identify alkaloids as well as other compounds.
It is composed of a mixture of ammonium metavanadate and concentrated sulfuric acid.
Its primary use is for the detection of ketamine and PMA[1] Unlike the most common reagent test chemicals, it has a deep red colour that changes to yellow if there is no alkaloid, which occurs within about 48 hours of mixing.
[2] The United States Department of Justice method for producing the reagent is the addition of 100 mL of concentrated (95–98%) sulfuric acid to 0.5[3]-1 g of ammonium metavanadate.
[4] This reagent was invented by the German pharmacologist, Karl Friedrich Mandelin (1854–1906) at the University of Dorpat.