Marquis reagent

Marquis reagent is used as a simple spot-test to presumptively identify alkaloids as well as other compounds.

It is composed of a mixture of formaldehyde and concentrated sulfuric acid, which is dripped onto the substance being tested.

Methanol may be added to slow down the reaction process to allow better observation of the colour change.

[citation needed] Marquis reagent was first discovered in 1896[2] and described by the Russian (Estonian) pharmacologist, Eduard Markus (1871–1944) (Russian: Эдуард Маркус)[3] in his magister dissertation in 1896;[4] and named after him,[5] and was tested for the first time at the University of Dorpat.

The test is performed by scraping off a small amount of the substance and adding a drop of the reagent (which is initially clear and colorless).