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 It is unusual among reagent tests that it has a very strong yellow colour prior to being used for testing, which forms within about 48 hours of mixing.
The United States Department of Justice method for producing the reagent is the addition of 100 mL of concentrated (95–98%) sulfuric acid to 0.5-1 g of ammonium vanadate.
This reagent was invented by the German Pharmacologist, Karl Friedrich Mandelin (1854–1906) at the University of Dorpat.
References
Mandelin reagent Wikipedia(Text) CC BY-SA